draft-ietf-ipo-framework-02.txt   draft-ietf-ipo-framework-03.txt 
Bala Rajagopalan Bala Rajagopalan
Internet Draft Tellium, Inc. Internet Draft Tellium, Inc.
draft-ietf-ipo-framework-03.txt James Luciani
draft-ietf-ipo-framework-02.txt James Luciani Expires on: 7/13/2003 Consultant
Expires on: 12/10/2002 Crescent Networks
Daniel Awduche Daniel Awduche
Movaz Networks Isocore
Brad Cain
Cereva Networks
Bilel Jamoussi
Nortel Networks
Debanjan Saha
Tellium, Inc.
IP over Optical Networks: A Framework IP over Optical Networks: A Framework
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet Drafts are working documents of the Internet Engineering Internet Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
skipping to change at line 38 skipping to change at line 31
documents at any time. It is inappropriate to use Internet- Drafts documents at any time. It is inappropriate to use Internet- Drafts
as reference material or to cite them other than as "work in as reference material or to cite them other than as "work in
progress." progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
1. Abstract Abstract
The Internet transport infrastructure is moving towards a model of The Internet transport infrastructure is moving towards a model of
high-speed routers interconnected by optical core networks. The high-speed routers interconnected by optical core networks. The
architectural choices for the interaction between IP and optical architectural choices for the interaction between IP and optical
network layers, specifically, the routing and signaling aspects, are network layers, specifically, the routing and signaling aspects, are
maturing. At the same time, a consensus has emerged in the industry maturing. At the same time, a consensus has emerged in the industry
on utilizing IP-based protocols for the optical control plane. This on utilizing IP-based protocols for the optical control plane. This
document defines a framework for IP over Optical networks, document defines a framework for IP over Optical networks,
considering both the IP-based control plane for optical networks as considering both the IP-based control plane for optical networks as
well as IP-optical network interactions (together referred to as "IP well as IP-optical network interactions (together referred to as "IP
over optical networks"). over optical networks").
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Table of Contents Table of Contents
----------------- -----------------
1. Abstract...........................................................1 Abstract..............................................................1
2. Introduction.......................................................3 1. Introduction.......................................................3
3. Terminology and Concepts...........................................4 2. Terminology and Concepts...........................................4
4. The Network Model..................................................8 3. The Network Model..................................................8
4.1 Network Interconnection........................................8 3.1 Network Interconnection.......................................8
4.2 Control Structure.............................................10 3.2 Control Structure............................................10
5. IP over Optical Service Models and Requirements...................12 4. IP over Optical Service Models and Requirements...................12
5.1 Domain Services Model.........................................12 4.1 Domain Services Model........................................12
5.2 Unified Service Model.........................................13 4.2 Unified Service Model........................................13
5.3 Which Service Model?..........................................14 4.3 Which Service Model?.........................................14
5.4 What are the Possible Services?................................14 4.4 What are the Possible Services?...............................14
6. IP transport over Optical Networks................................15 5. IP transport over Optical Networks................................15
6.1 Interconnection Models.........................................15 5.1 Interconnection Models........................................15
6.2 Routing Approaches.............................................16 5.2 Routing Approaches............................................16
6.3 Signaling-Related..............................................19 5.3 Signaling-Related.............................................19
6.4 End-to-End Protection Models..................................20 5.4 End-to-End Protection Models.................................21
7. IP-based Optical Control Plane Issues.............................22 6. IP-based Optical Control Plane Issues.............................23
7.1 Addressing....................................................23 6.1 Addressing...................................................23
7.2 Neighbor Discovery............................................24 6.2 Neighbor Discovery...........................................24
7.3 Topology Discovery............................................25 6.3 Topology Discovery...........................................25
7.4 Restoration Models............................................26 6.4 Restoration Models...........................................26
7.5 Route Computation.............................................27 6.5 Route Computation............................................27
7.6 Signaling Issues..............................................29 6.6 Signaling Issues.............................................29
7.7 Optical Internetworking.......................................31 6.7 Optical Internetworking......................................31
8. Other Issues......................................................32 7. Other Issues......................................................32
8.1 WDM and TDM in the Same Network..............................32 7.1 WDM and TDM in the Same Network.............................32
8.2 Wavelength Conversion........................................32 7.2 Wavelength Conversion.......................................32
8.3 Service Provider Peering Points..............................32 7.3 Service Provider Peering Points.............................33
8.4 Rate of Lightpath Set-Up.....................................33 7.4 Rate of Lightpath Set-Up....................................33
8.5 Distributed vs. Centralized Provisioning.....................34 7.5 Distributed vs. Centralized Provisioning....................34
8.6 Optical Networks with Additional Configurable Components.....34 7.6 Optical Networks with Additional Configurable Components....35
8.7 Optical Networks with Limited Wavelength Conversion Capability35 7.7 Optical Networks with Ltd Wavelength Conversion Capability..35
9. Evolution Path for IP over Optical Architecture..................35 8. Evolution Path for IP over Optical Architecture..................35
10. Security Considerations..........................................37 9. Security Considerations...........................................37
10.1 General security aspects......................................38 9.1 General security aspects......................................38
10.2 Protocol Mechanisms...........................................39 9.2 Protocol Mechanisms...........................................39
11. Summary and Conclusions..........................................39 10. Summary and Conclusions...........................................39
12. References.......................................................39 11. References........................................................39
13. Acknowledgments..................................................40 12. Acknowledgments...................................................40
14. Author's Addresses...............................................41 13. Contributors......................................................41
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2. Introduction 1. Introduction
Optical network technologies are evolving rapidly in terms of Optical network technologies are evolving rapidly in terms of
functions and capabilities. The increasing importance of optical functions and capabilities. The increasing importance of optical
networks is evidenced by the copious amount of attention focused on networks is evidenced by the copious amount of attention focused on
IP over optical networks and related photonic and electronic IP over optical networks and related photonic and electronic
interworking issues by all the major network service providers, interworking issues by all the major network service providers,
telecommunications equipment vendors, and standards organizations. telecommunications equipment vendors, and standards organizations.
In this regard, the term "optical network" is used generically in In this regard, the term "optical network" is used generically in
practice to refer to both SONET/SDH-based transport networks, as practice to refer to both SONET/SDH-based transport networks, as
well as transparent all-optical networks. well as transparent all-optical networks.
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optical networks is the capability to instantiate and route optical optical networks is the capability to instantiate and route optical
layer connections in real-time or near real-time, and to provide layer connections in real-time or near real-time, and to provide
capabilities that enhance network survivability. Furthermore, there capabilities that enhance network survivability. Furthermore, there
is a need for multi-vendor optical network interoperability, when an is a need for multi-vendor optical network interoperability, when an
optical network may consist of interconnected vendor-specific optical network may consist of interconnected vendor-specific
optical sub-networks. optical sub-networks.
The optical network must also be versatile because some service The optical network must also be versatile because some service
providers may offer generic optical layer services that may not be providers may offer generic optical layer services that may not be
client-specific. It would therefore be necessary to have an optical client-specific. It would therefore be necessary to have an optical
network control layer that can handle such generic optical services. network control plane that can handle such generic optical services.
There is general consensus in the industry that the optical network There is general consensus in the industry that the optical network
control plane should utilize IP-based protocols for dynamic control plane should utilize IP-based protocols for dynamic
provisioning and restoration of lightpaths within and across optical provisioning and restoration of lightpaths within and across optical
sub-networks. This is based on the practical view that signaling and sub-networks. This is based on the practical view that signaling and
routing mechanisms developed for IP traffic engineering applications routing mechanisms developed for IP traffic engineering applications
could be re-used in optical networks. Nevertheless, the issues and could be re-used in optical networks. Nevertheless, the issues and
requirements that are specific to optical networking must be requirements that are specific to optical networking must be
understood to suitably adopt the IP-based protocols. This is understood to suitably adopt and adapt the IP-based protocols. This
especially the case for restoration. Also, there are different is especially the case for restoration, and for routing and
views on the model for interaction between the optical network and signaling in all-optical networks. Also, there are different views
client networks, such as IP networks. Reasonable architectural on the model for interaction between the optical network and client
alternatives in this regard must be supported, with an understanding networks, such as IP networks. Reasonable architectural alternatives
of their pros and cons. in this regard must be supported, with an understanding of their
relative merits.
Thus, there are two fundamental issues related to IP over optical Thus, there are two fundamental issues related to IP over optical
networks. The first is the adaptation and reuse of IP control plane networks. The first is the adaptation and reuse of IP control plane
protocols within the optical network control plane, irrespective of protocols within the optical network control plane, irrespective of
the types of digital clients that utilize the optical network. The the types of digital clients that utilize the optical network. The
second is the transport of IP traffic through an optical network second is the transport of IP traffic through an optical network
together with the control and coordination issues that arise together with the control and coordination issues that arise
therefrom. therefrom.
draft-ietf-ipo-framework-02.txt
This document defines a framework for IP over optical networks This document defines a framework for IP over optical networks
covering the requirements and mechanisms for establishing an IP- covering the requirements and mechanisms for establishing an IP-
draft-ietf-ipo-framework-03.txt
centric optical control plane, and the architectural aspects of IP centric optical control plane, and the architectural aspects of IP
transport over optical networks. In this regard, it is recognized transport over optical networks. In this regard, it is recognized
that the specific capabilities required for IP over optical networks that the specific capabilities required for IP over optical networks
would depend on the services expected at the IP-optical interface as would depend on the services expected at the IP-optical interface as
well as the optical sub-network interfaces. Depending on the well as the optical sub-network interfaces. Depending on the
specific operational requirements, a progression of capabilities is specific operational requirements, a progression of capabilities is
possible, reflecting increasingly sophisticated interactions at possible, reflecting increasingly sophisticated interactions at
these interfaces. This document therefore advocates the definition these interfaces. This document therefore advocates the definition
of "capability sets" that define the evolution of functionality at of "capability sets" that define the evolution of functionality at
the interfaces as more sophisticated operational requirements arise. the interfaces as more sophisticated operational requirements arise.
This document is organized as follows. In the next section, This document is organized as follows. In the next section,
terminology covering certain concepts related to this framework are terminology covering some basic concepts related to this framework
described. In Section 4, the network model pertinent to this are described. The definitions are specific to this framework and
framework is described. The service model and requirements for IP- may have other connotations elsewhere. In Section 3, the network
optical, and multi-vendor optical internetworking are described in model pertinent to this framework is described. The service model
Section 5. This section presently considers certain general and requirements for IP-optical, and multi-vendor optical
requirements. Specific operational requirements may be accommodated internetworking are described in Section 4. This section also
in this section as they arise. Section 6 considers the considers some general requirements. Section 5 considers the
architectural models for IP-optical interworking, describing the architectural models for IP-optical interworking, describing the
pros and cons of each model. It should be noted that it is not the pros and cons of each model. It should be noted that it is not the
intent of this document to promote any particular model over the intent of this document to promote any particular model over the
others. However, particular aspects of the models that may make one others. However, particular aspects of the models that may make one
approach more appropriate than another in certain circumstances are approach more appropriate than another in certain circumstances are
described. Section 7 describes IP-centric control plane mechanisms described. Section 6 describes IP-centric control plane mechanisms
for optical networks, covering signaling and routing issues in for optical networks, covering signaling and routing issues in
support of provisioning and restoration. Section 8 describes certain support of provisioning and restoration. Section 7 describes a
specialized issues in relation to IP over optical networks. The number of specialized issues in relation to IP over optical
approaches described in Section 7 and 8 range from the relatively networks. The approaches described in Section 5 and 6 range from
simple to the sophisticated. Section 9 describes a possible the relatively simple to the sophisticated. Section 8 describes a
evolution path for IP over optical networking capabilities in terms possible evolution path for IP over optical networking capabilities
of increasingly sophisticated functionality supported. Section 10 in terms of increasingly sophisticated functionality that may be
considers security aspects. Finally, summary and conclusion are supported. Section 9 considers security issues pertinent to this
presented in Section 11. framework. Finally, the summary and conclusion are presented in
Section 10.
3. Terminology and Concepts 2. Terminology and Concepts
This section introduces the terminology pertinent to this framework This section introduces terminology pertinent to this framework and
and some related concepts. some related concepts. The definitions are specific to this
framework and may have other interpretations elsewhere.
WDM WDM
--- ---
Wavelength Division Multiplexing (WDM) is a technology that allows Wavelength Division Multiplexing (WDM) is a technology that allows
multiple optical signals operating at different wavelengths to be multiple optical signals operating at different wavelengths to be
multiplexed onto a single fiber so that they can be transported in multiplexed onto a single optical fiber and transported in parallel
parallel through the fiber. In general, each optical wavelength may through the fiber. In general, each optical wavelength may carry
carry digital client payloads at a different data rate (e.g., OC-3c, digital client payloads at a different data rate (e.g., OC-3c, OC-
OC-12c, OC- 48c, OC-192c, etc.) and in a different format (SONET, 12c, OC- 48c, OC-192c, etc.) and in a different format (SONET,
draft-ietf-ipo-framework-02.txt draft-ietf-ipo-framework-03.txt
Ethernet, ATM, etc.) For example, there are many commercial WDM Ethernet, ATM, etc.) For example, there are many commercial WDM
networks in existence today that support a mix of SONET signals networks in existence today that support a mix of SONET signals
operating at OC-48c (approximately 2.5 Gbps) and OC-192 operating at OC-48c (approximately 2.5 Gbps) and OC-192
(approximately 10 Gbps) over a single optical fiber. An optical (approximately 10 Gbps) over a single optical fiber. An optical
system with WDM capability can achieve parallel transmission of system with WDM capability can achieve parallel transmission of
multiple wavelengths gracefully while maintaining high system multiple wavelengths gracefully while maintaining high system
performance and reliability. In the near future, commercial WDM performance and reliability. In the near future, commercial dense
systems are expected to concurrently carry more than 160 WDM systems are expected to concurrently carry more than 160
wavelengths at data rates of OC-192c and above, for a total of 1.6 wavelengths at data rates of OC-192c and above, for a total of 1.6
Tbps or more. The term WDM will be used in this document to refer Tbps or more. The term WDM will be used in this document to refer
to both WDM and DWDM (Dense WDM). to both WDM and DWDM (Dense WDM).
In general, it is worth noting that WDM links are affected by the In general, it is worth noting that WDM links are affected by the
following factors, which may introduce impairments into the optical following factors, which may introduce impairments into the optical
signal path: signal path:
1. The number of wavelengths on a single fiber. 1. The number of wavelengths on a single fiber.
2. The serial bit rate per wavelength. 2. The serial bit rate per wavelength.
3. The type of fiber. 3. The type of fiber.
4. The amplification mechanism. 4. The amplification mechanism.
5. The number of nodes through which the signal passes before 5. The number of nodes through which the signal passes before
it reaches the egress node or before regeneration. it reaches the egress node or before regeneration.
All these factors and others not mentioned here constitute domain All these factors (and others not mentioned here) constitute domain
specific features of optical transport networks. As noted in [1], specific features of optical transport networks. As noted in [1],
these features should be taken into account in developing standards these features should be taken into account in developing standards
based solutions for IP over optical networks. based solutions for IP over optical networks.
Optical cross-connect (OXC) Optical cross-connect (OXC)
--------------------------- ---------------------------
An OXC is a space-division switch that can switch an optical data An OXC is a space-division switch that can switch an optical data
stream on an input port to a output port. Such a switch may have stream from an input port to a output port. Such a switch may
optical-electrical conversion at the input port and electrical- utilize optical-electrical conversion at the input port and
optical conversion at the output port, or it can be all-optical. An electrical-optical conversion at the output port, or it may be all-
OXC is assumed to have a control-plane processor that implements optical. An OXC is assumed to have a control-plane processor that
signaling and routing protocols necessary for realizing an optical implements the signaling and routing protocols necessary for
network. computing and instantiating connectivity in the optical domain.
Optical channel trail or Lightpath Optical channel trail or Lightpath
---------------------------------- ----------------------------------
An optical channel trail is a point-to-point optical layer An optical channel trail is a point-to-point optical layer
connection between two access points in an optical network. In this connection between two access points in an optical network. In this
document, the term "lightpath" is used interchangeably with optical document, the term "lightpath" is used interchangeably with optical
channel trail. channel trail.
Optical mesh sub-network Optical mesh sub-network
------------------------ ------------------------
An optical sub-network, as discussed in this framework, is a network An optical sub-network, as used in this framework, is a network of
of OXCs that supports end-to-end networking of optical channel OXCs that supports end-to-end networking of optical channel trails
trails providing functionality like routing, monitoring, grooming, providing functionality like routing, monitoring, grooming, and
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and protection and restoration of optical channels. The protection and restoration of optical channels. The interconnection
interconnection of OXCs in this network can be based on a general of OXCs in this network can be based on a general mesh topology.
topology (also called "mesh" topology) Underlying this network could The following may underlie this network:
be the following:
(a) An optical multiplex section (OMS) layer network : The optical (a) An optical multiplex section (OMS) layer network : The optical
multiplex section layer provides the transport of the optical multiplex section layer provides transport for the optical
channels. The information contained in this layer is a data channels. The information contained in this layer is a data
stream comprising a set of optical channels, which have a stream comprising a set of optical channels, which may have a
defined aggregate bandwidth. defined aggregate bandwidth.
(b) An optical transmission section (OTS) layer network : This (b) An optical transmission section (OTS) layer network : This layer
provides functionality for transmission of the optical signal on provides functionality for transmission of optical signals
optical media of different types. through different types of optical media.
This framework does not address the interaction between the optical This framework does not address the interaction between the optical
sub-network and the OMS, or between the OMS and OTS layer networks. sub-network and the OMS, or between the OMS and OTS layer networks.
Mesh optical network (or simply, "optical network") Mesh optical network (or simply, "optical network")
--------------------------------------------------- ---------------------------------------------------
A mesh optical network, as considered in document, is a mesh- A mesh optical network, as used in document, is a topologically
connected connected collection of optical sub-networks whose node degree may
collection of optical sub-networks. Such an optical network is exceed 2. Such an optical network is assumed to be under the purview
assumed to be under a single administration. It is also possible to of a single administrative entity. It is also possible to conceive
conceive of a large scale global mesh optical network consisting of of a large scale global mesh optical network consisting of the
the voluntary interconnection of autonomous optical networks, each voluntary interconnection of autonomous optical networks, each of
of which is owned and administered by an independent entity. In this which is owned and administered by an independent entity. In such an
circumstance, abstraction can be used to hide the internal details environment, abstraction can be used to hide the internal details of
of each autonomous optical cloud from the remainder of the network. each autonomous optical cloud from external clouds in the remainder
of the network.
Optical internetwork Optical internetwork
-------------------- --------------------
An optical internetwork is a mesh-connected collection of optical An optical internetwork is a mesh-connected collection of optical
networks. Each of these networks may be under different networks. Each of these networks may be under a different
administration. administration.
Wavelength continuity property Wavelength continuity property
------------------------------ ------------------------------
A lightpath is said to satisfy the wavelength continuity property if A lightpath is said to satisfy the wavelength continuity property if
it is transported over the same wavelength end-to-end. Wavelength it is transported over the same wavelength end-to-end. Wavelength
continuity is required in optical networks with no wavelength continuity is required in optical networks with no wavelength
conversion feature. conversion feature.
Wavelength path Wavelength path
--------------- ---------------
A lightpath that satisfies the wavelength continuity property is A lightpath that satisfies the wavelength continuity property is
called a wavelength path. called a wavelength path.
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Opaque vs. transparent optical networks Opaque vs. transparent optical networks
--------------------------------------- ---------------------------------------
A transparent optical network is an optical network in which each A transparent optical network is an optical network in which optical
transit node along a path passes optical transmission without using signals traverse from transmitter to receiver across intermediate
transducers to convert the optical signal into an electrical signal nodes in the optical domain without OEO conversion. More generally,
and back again to an optical signal. More generally, all all intermediate nodes in a transparent optical network will pass
intermediate nodes in a transparent optical network will pass
optical signals without performing retiming and reshaping and thus optical signals without performing retiming and reshaping and thus
such nodes are unaware of many characteristics of the carried such nodes are unaware of the characteristics of the payload carried
signals. One could, for example, carry analog signals together with by the optical signals.
digital signals (potentially of varying bit rate) on different
wavelengths over such a network.
Note that amplification of signals at transit nodes is Note that amplification of signals at transit nodes is
permitted in transparent optical networks. This is a result of the permitted in transparent optical networks (e.g. using Erbium Doped
availability of all optical amplification devices such as Erbium Fiber Amplifiers EDFAs).
Doped Fiber Amplifiers (EDFAs).
In opaque optical networks, by comparison, transit nodes will On the other hand, in opaque optical networks, transit nodes may
manipulate the optical signals as the signals traverse through manipulate optical signals traversing through them. An example of
them. An example of such manipulation would be 3R (reshaping, such manipulation would be OEO conversion which may involve 3R
retiming, regeneration/amplification). operations (reshaping, retiming, regeneration/amplification).
Trust domain Trust domain
------------ ------------
A trust domain is a network under a single technical administration A trust domain is a network under a single technical administration
in which most nodes in the network are considered to be secure or in which adequate security measures are establish to prevent
trusted in some fashion. An example of a trust domain is a campus unauthorized intrusion from outside the domain. Hence, most nodes in
or corporate network in which all routing protocol packets are the domain are deemed to be secure or trusted in some fashion.
considered to be authentic, without the need for additional security Generally, the rule for "single" administrative control over a trust
schemes to prevent unauthorized access to the network domain may be relaxed in practice if a set of administrative
infrastructure. Generally, the "single" administrative control rule entities agree to trust one another to form an enlarged
may be relaxed in practice if a set of administrative entities agree heterogeneous trust domain. However, to simplify the discussions in
to trust one another to form an enlarged heterogeneous trust domain. this document, it will be assumed, without loss of generality, that
However, to simplify the discussions in this document, it will be the term trust domain applies to a single administrative entity with
assumed, without loss of generality, that the term trust domain appropriate security policies. It should be noted that within a
applies to a single administrative entity. trust domain, any subverted node can send control messages which can
compromise the entire network.
Flow Flow
---- ----
For the purpose of this document, the term flow will be used to For purposes of this document, the term flow will be used to
represent the smallest non-separable stream of data, as seen by an signify the smallest non-separable stream of data, from the point of
endpoint (source or destination node). It is to be noted that the view of endpoint or termination point (source or destination node).
term flow is heavily overloaded in the networking literature. Within The reader should note that the term flow is heavily overloaded in
the context of this document, it may be convenient to consider a contemporary networking literature. Therefore, within the context of
wavelength as a flow under certain circumstances. However, if there this document, it may be convenient to consider a wavelength as a
flow under certain circumstances. However, if there
is a method to partition the bandwidth of the wavelength, then each is a method to partition the bandwidth of the wavelength, then each
partition may be considered a flow, for example by quantizing time partition may be considered a flow, for example by using time
into some nicely manageable intervals, it may be feasible to division multiplexing (RDM) to quantize time into time slots, it may
consider each quanta of time within a given wavelength as a flow. be feasible to consider each quanta of time within a given
wavelength as a flow.
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Traffic Trunk Traffic Trunk
------------- -------------
A traffic trunk is an abstraction of traffic flow that follows the A traffic trunk is an abstraction of traffic flow that follows the
same path between two access points which allows some same path between two access points which allows some
characteristics and attributes of the traffic to be parameterized. characteristics and attributes of the traffic to be parameterized.
4. The Network Model 3. The Network Model
4.1 Network Interconnection 3.1 Network Interconnection
The network model considered in this memo consists of IP routers The network model considered in this memo consists of IP routers
attached to an optical core internetwork, and connected to their attached to an optical core internetwork, and connected to their
peers over dynamically established switched lightpaths. The optical peers over dynamically established switched optical channels. The
core itself is assumed to be incapable of processing individual IP optical core itself is assumed to be incapable of processing
packets in the data plane. individual IP packets in the data plane.
The optical internetwork is assumed to consist of multiple optical The optical internetwork is assumed to consist of multiple optical
networks, each may possibly be administered by a different entity. networks, each of which may possibly be administered by a different
Each optical network consists of sub-networks interconnected by entity. Each optical network consists of sub-networks interconnected
optical links in a general topology (referred to as an optical mesh by optical fiber links in a general topology (referred to as an
network). This network may contain re-configurable optical equipment optical mesh network). This network may contain re-configurable
from a single vendor or from multiple vendors. In the near term, it optical equipment from a single vendor or from multiple vendors. In
may be expected that each sub-network will consist of a single the near term, it may be expected that each sub-network will consist
vendor switches. In the future, as standardization efforts mature, of switches from a single vendor. In the future, as standardization
each optical sub-network may in fact contain optical switches from efforts mature, each optical sub-network may in fact contain optical
different vendors. In any case, each sub-network itself is assumed switches from different vendors. In any case, each sub-network
to be mesh-connected internally. In general, it can be expected that itself is assumed to be mesh-connected internally. In general, it
topologically adjacent OXCs in an optical mesh network will be can be expected that topologically adjacent OXCs in an optical mesh
connected via multiple, parallel (bi-directional) optical links. network will be connected via multiple, parallel (bi-directional)
This network model is shown in Figure 1. optical links. This network model is shown in Figure 1.
Here, an optical sub-network may consist entirely of all-optical in this environment, an optical sub-network may consist entirely of
OXCs or OXCs with optical-electrical-optical (OEO) conversion. all-optical OXCs or OXCs with optical-electrical-optical (OEO)
Interconnection between sub-networks is assumed to be through conversion. Interconnection between sub-networks is assumed to be
compatible physical interfaces, with suitable optical-electrical implemented through compatible physical interfaces, with suitable
conversions where necessary. The routers that have direct physical optical-electrical conversions where necessary. The routers that
connectivity with the optical network are referred to as "edge have direct physical connectivity with the optical network are
routers". As shown in the figure, other client networks (e.g., ATM) referred to as "edge routers" with respect to the optical network.
may connect to the optical network. As shown in Figure 1, other client networks (e.g., ATM) may also
connect to the optical network.
The switching function in an OXC is controlled by appropriately The switching function in an OXC is controlled by appropriately
configuring the cross-connect fabric. Conceptually, this may be configuring the cross-connect fabric. Conceptually, this may be
viewed as setting up a cross-connect table whose entries are of the viewed as setting up a cross-connect table whose entries are of the
form <input port i, output port j>, indicating that the data stream form <input port i, output port j>, indicating that the data stream
entering input port i will be switched to output port j. In the entering input port i will be switched to output port j. In the
context of a wavelength selective cross-connect (generally referred context of a wavelength selective cross-connect (generally referred
to as a WXC), the cross-connect tables may also indicate the input to as a WXC), the cross-connect tables may also indicate the input
and output wavelengths along with the input and output ports. A and output wavelengths along with the input and output ports. A
lightpath from an ingress port in an OXC to an egress port in a lightpath from an ingress port in an OXC to an egress port in a
remote OXC is established by setting up suitable cross-connects in remote OXC is established by setting up suitable cross-connects in
the ingress, the egress and a set of intermediate OXCs such that a the ingress, the egress and a set of intermediate OXCs such that a
draft-ietf-ipo-framework-02.txt draft-ietf-ipo-framework-03.txt
continuous physical path exists from the ingress to the egress port. continuous physical path exists from the ingress to the egress port.
Optical paths tend to be bi-directional, i.e., the return path from Optical paths tend to be bi-directional, i.e., the return path from
the egress port to the ingress port is typically routed along the the egress port to the ingress port is typically routed along the
same set of intermediate ports as the forward path, but this may not same set of intermediate ports as the forward path, but this may not
be the case under all circumstances. be the case under all circumstances.
Optical Network Optical Network
+----------------------------------------+ +----------------------------------------+
| | | |
skipping to change at line 474 skipping to change at line 471
| (e.g., ATM) | | | | (e.g., ATM) | | |
+--------------+ +------------+ +--------------+ +------------+
Figure 1: Optical Internetwork Model Figure 1: Optical Internetwork Model
Multiple data streams output from an OXC may be multiplexed onto an Multiple data streams output from an OXC may be multiplexed onto an
optical link using WDM technology. The WDM functionality may exist optical link using WDM technology. The WDM functionality may exist
outside of the OXC, and be transparent to the OXC. Or, this function outside of the OXC, and be transparent to the OXC. Or, this function
may be built into the OXC. In the later case, the cross-connect may be built into the OXC. In the later case, the cross-connect
table (conceptually) consists of pairs of the form, <{input port table (conceptually) consists of pairs of the form, <{input port
draft-ietf-ipo-framework-02.txt draft-ietf-ipo-framework-03.txt
i, Lambda(j)}, {output port k, Lambda(l)}>. This indicates that the i, Lambda(j)}, {output port k, Lambda(l)}>. This indicates that the
data stream received on wavelength Lambda(j) over input port i is data stream received on wavelength Lambda(j) over input port i is
switched to output port k on Lambda(l). Automated establishment of switched to output port k on Lambda(l). Automated establishment of
lightpaths involves setting up the cross-connect table entries in lightpaths involves setting up the cross-connect table entries in
the appropriate OXCs in a coordinated manner such that the desired the appropriate OXCs in a coordinated manner such that the desired
physical path is realized. physical path is realized.
Under this network model, a switched lightpath must be established Under this network model, a switched lightpath must be established
between a pair of IP routers before they can communicate. This between a pair of IP routers before they can communicate. This
lightpath might traverse multiple optical networks and be subject to lightpath might traverse multiple optical networks and be subject to
different provisioning and restoration procedures in each different provisioning and restoration procedures in each
network. The IP-based control plane issue is that of designing network.
standard signaling and routing protocols for coherent end-to-end
provisioning and restoration of lightpaths across multiple optical The IP-based control plane issue is that of designing
standard signaling and routing protocols for provisioning and
restoration of lightpaths across multiple optical
networks. Similarly, IP transport over such an optical network networks. Similarly, IP transport over such an optical network
involves determining IP reachability and seamless establishment of involves determining IP reachability and seamlessly establishing
paths from one IP endpoint to another over an optical core paths from one IP endpoint to another over an optical network.
internetwork.
4.2 Control Structure 3.2 Control Structure
There are three logical control interfaces identified in Figure 1. There are three logical control interfaces identified in Figure 1.
These are the client-optical internetwork interface, the internal These are the client-optical internetwork interface, the internal
node-to-node interface within a network (between OXCs in different node-to-node interface within an optical network (between OXCs in
sub-networks), and the external node-to-node interface between nodes different sub-networks), and the external node-to-node interface
in different networks. These interfaces are also referred to as the between nodes in different optical networks. These interfaces are
User-Network Interface (UNI), the internal NNI (INNI), and the also referred to as the User-Network Interface (UNI), the internal
external NNI, respectively. The distinction between these interfaces NNI (INNI), and the external NNI, respectively.
arises out of the type and amount of control information flow across
them. The UNI represents a service boundary between the client and
optical networks. The client and server are essentially two
different roles: the client role requests a service connection from
a server; the server role establishes the connection to fulfill the
service request -- provided all relevant admission control
conditions are satisfied. Thus, the control flow across the UNI is
dependent on the set of services defined across it and the manner
in which the services may be accessed. The service models are
described in Section 7. The NNIs represent vendor-independent
standardized control flow between nodes. The distinction between the
INNI and the ENNI is that the former is an interface within a given
network under a single technical administration, while the later
indicates an interface at the administrative boundary between
networks. The INNI and ENNI may thus differ in the policies that
restrict control flow between nodes. Security, scalability,
stability, and information hiding are important considerations in
the specification of the ENNI. It is possible in principle to
harmonize the control flow across the UNI and the NNI and eliminate
the distinction between them. On the other hand, it may be required
to minimize control flow information, especially routing-related
information, over the UNI; and even over the ENNI. In this case,
UNI and NNIs may look different in some respects. In this document,
these interfaces are treated as distinct.
draft-ietf-ipo-framework-02.txt The distinction between these interfaces arises out of the type and
amount of control information flow across them. The client-optical
internetwork interface (UNI) represents a service boundary between
the client and optical networks. The client and server are
essentially two different roles: the client role requests a service
connection from a server; the server role establishes the connection
to fulfill the service request -- provided all relevant admission
control conditions are satisfied.
The UNI can be categorized as public or private depending upon Thus, the control flow across the client-optical internetwork
context and service models. Routing information (ie, topology state interface is dependent on the set of services defined across it
information) can be exchanged across a private UNI. On the other and the manner in which the services may be accessed. The service
hand, such information is not exchanged across a public UNI, or such models are described in Section 4. The NNIs represent vendor-
information may be exchanged with very explicit restrictions independent standardized control flow between nodes. The distinction
(including for example abstraction, filtration, etc). Thus, between the INNI and the ENNI is that the former is an interface
different relationships (e.g., peer or over-lay, Section 7) may within a given network under a single technical administration,
occur across private and public logical interfaces. while the later indicates an interface at the administrative
boundary between networks. The INNI and ENNI may thus differ in the
policies that restrict control flow between nodes.
Security, scalability, stability, and information hiding are
important considerations in the specification of the ENNI. It is
draft-ietf-ipo-framework-03.txt
possible in principle to harmonize the control flow across the UNI
and the NNI and eliminate the distinction between them. On the other
hand, it may be required to minimize control flow information,
especially routing-related information, over the UNI; and even over
the ENNI. In this case, UNI and NNIs may look different in some
respects. In this document, these interfaces are treated as
distinct.
The client-optical internetwork interface can be categorized as
public or private depending upon context and service models. Routing
information (ie, topology state information) can be exchanged across
a private client-optical internetwork interface. On the other hand,
such information is not exchanged across a public client-optical
internetwork interface, or such information may be exchanged with
very explicit restrictions (including, for example abstraction,
filtration, etc). Thus, different relationships (e.g., peer or over-
lay, Section 5) may occur across private and public logical
interfaces.
The physical control structure used to realize these logical The physical control structure used to realize these logical
interfaces may vary. For instance, for the UNI, some of the interfaces may vary. For instance, for the client-optical
possibilities are: internetwork interface, some of the possibilities are:
1. Direct interface: An in-band or out-of-band IP control channel 1. Direct interface: An in-band or out-of-band IP control channel
(IPCC) may be implemented between an edge router and each OXC (IPCC) may be implemented between an edge router and each OXC
to which it is connected. This control channel is used for to which it is connected. This control channel is used for
exchanging signaling and routing messages between the router and exchanging signaling and routing messages between the router and
the OXC. With a direct interface, the edge router and the OXC it the OXC. With a direct interface, the edge router and the OXC it
connects to are peers in the control plane. This is shown in connects to are peers with respect to the control plane. This
Figure 2. The type of routing and signaling information exchanged situation is shown in Figure 2. The type of routing and signaling
across the direct interface would vary depending on the service information exchanged across the direct interface may vary
definition. This issue is dealt with in the next section. Some depending on the service definition. This issue is addressed in
choices for the routing protocol are OSPF/ISIS (with traffic the next section. Some choices for the routing protocol are OSPF
engineering Extensions and additional extensions to deal with the or ISIS (with traffic engineering extensions and additional
peculiar characteristics of optical networks) or BGP, or some enhancements to deal with the peculiar characteristics of optical
other protocol. Other directory-based routing information networks) or BGP, or some other protocol. Other directory-based
exchanges are also possible. Some of the signaling protocol routing information exchanges are also possible. Some of the
choices are adaptations of RSVP-TE or CR-LDP. The details of how signaling protocol choices are adaptations of RSVP-TE or CR-LDP.
the IP control channel is realized is outside the scope of this The details of how the IP control channel is realized is outside
document. the scope of this document.
2. Indirect interface: An out-of-band IP control channel may be 2. Indirect interface: An out-of-band IP control channel may be
implemented between the client and a device in the optical network implemented between the client and a device in the optical network
to signal service requests and responses. For instance, a to signal service requests and responses. For instance, a
management system or a server in the optical network may receive management system or a server in the optical network may receive
service requests from clients. Similarly, out-of-band signaling service requests from clients. Similarly, out-of-band signaling
may be used between management systems in client and optical may be used between management systems in client and optical
networks to signal service requests. In these cases, there is no networks to signal service requests. In these cases, there is no
direct control interaction between clients and respective direct control interaction between clients and respective
OXCs. One reason to have an indirect interface would be that the OXCs. One reason to have an indirect interface would be that the
OXCs and/or clients do not support a direct signaling interface. OXCs and/or clients do not support a direct signaling interface.
draft-ietf-ipo-framework-02.txt draft-ietf-ipo-framework-03.txt
+-----------------------------+ +-----------------------------+ +-----------------------------+ +-----------------------------+
| | | | | | | |
| +---------+ +---------+ | | +---------+ +---------+ | | +---------+ +---------+ | | +---------+ +---------+ |
| | | | | | | | | | | | | | | | | | | | | | | |
| | Routing | |Signaling| | | | Routing | |Signaling| | | | Routing | |Signaling| | | | Routing | |Signaling| |
| | Protocol| |Protocol | | | | Protocol| |Protocol | | | | Protocol| |Protocol | | | | Protocol| |Protocol | |
| | | | | | | | | | | | | | | | | | | | | | | |
| +-----+---+ +---+-----+ | | +-----+---+ +---+-----+ | | +-----+---+ +---+-----+ | | +-----+---+ +---+-----+ |
| | | | | | | | | | | | | | | |
skipping to change at line 604 skipping to change at line 610
Figure 2: Direct Interface Figure 2: Direct Interface
3. Provisioned interface: In this case, the optical network services 3. Provisioned interface: In this case, the optical network services
are manually provisioned and there is no control interactions are manually provisioned and there is no control interactions
between the client and the optical network. between the client and the optical network.
Although different control structures are possible, further Although different control structures are possible, further
descriptions in this framework assume direct interfaces for IP- descriptions in this framework assume direct interfaces for IP-
optical and optical sub-network control interactions. optical and optical sub-network control interactions.
5. IP over Optical Service Models and Requirements 4. IP over Optical Service Models and Requirements
In this section, the service models and requirements at the UNI and In this section, the service models and requirements at the UNI and
the NNIs are considered. Two general models have emerged for the the NNIs are considered. Two general models have emerged for the
services at the UNI (which can also be applied at the NNIs). These services at the UNI (which can also be applied at the NNIs). These
models are as follows. models are as follows.
5.1 Domain Services Model 4.1 Domain Services Model
Under the domain services model, the optical network primarily Under the domain services model, the optical network primarily
offers high bandwidth connectivity in the form of lightpaths. offers high bandwidth connectivity in the form of lightpaths.
Standardized signaling across the UNI (Figure 1) is used to invoke Standardized signaling across the UNI (Figure 1) is used to invoke
the following the following
services: services:
1. Lightpath creation: This service allows a lightpath with the 1. Lightpath creation: This service allows a lightpath with the
specified attributes to be created between a pair of termination specified attributes to be created between a pair of termination
points in the optical network. Lightpath creation may be subject points in the optical network. Lightpath creation may be subject
to network-defined policies (e.g., connectivity restrictions) and to network-defined policies (e.g., connectivity restrictions) and
security procedures. security procedures.
draft-ietf-ipo-framework-02.txt draft-ietf-ipo-framework-03.txt
2. Lightpath deletion: This service allows an existing lightpath to 2. Lightpath deletion: This service allows an existing lightpath to
be deleted. be deleted.
3. Lightpath modification: This service allows certain parameters of 3. Lightpath modification: This service allows certain parameters of
the lightpath to be modified. the lightpath to be modified.
4. Lightpath status enquiry: This service allows the status of 4. Lightpath status enquiry: This service allows the status of
certain parameters of the lightpath (referenced by its ID) to be certain parameters of the lightpath (referenced by its ID) to be
queried by the router that created the lightpath. queried by the router that created the lightpath.
skipping to change at line 660 skipping to change at line 666
certain attributes in a point-to-point manner between the router and certain attributes in a point-to-point manner between the router and
the optical network. Such a protocol may be based on RSVP-TE or LDP, the optical network. Such a protocol may be based on RSVP-TE or LDP,
for example. for example.
The optical domain services model does not deal with the type and The optical domain services model does not deal with the type and
nature of routing protocols within and across optical networks. nature of routing protocols within and across optical networks.
The optical domain services model would result in the establishment The optical domain services model would result in the establishment
of a lightpath topology between routers at the edge of the optical of a lightpath topology between routers at the edge of the optical
network. The resulting overlay model for IP over optical networks network. The resulting overlay model for IP over optical networks
is discussed in Section 7. is discussed in Section 5.
5.2 Unified Service Model 4.2 Unified Service Model
Under this model, the IP and optical networks are treated together Under this model, the IP and optical networks are treated together
as a single integrated network from a control plane point of view. as a single integrated network from a control plane point of view.
In this regard, the OXCs are treated just like any other router as In this regard, the OXCs are treated just like any other router as
far as the control plane is considered. Thus, in principle, there is far as the control plane is considered. Thus, in principle, there is
no distinction between the UNI, NNIs and any other router-to-router no distinction between the UNI, NNIs and any other router-to-router
interface from a routing and signaling point of view. It is assumed interface from a routing and signaling point of view. It is assumed
that this control plane is MPLS-based, as described in [1]. The that this control plane is MPLS-based, as described in [1]. The
unified service model has so far been discussed only in the context unified service model has so far been discussed only in the context
of a single administrative domain. A unified control plane is of a single administrative domain. A unified control plane is
possible even when there are administrative boundaries within an possible even when there are administrative boundaries within an
optical internetwork, but some of the integrated routing optical internetwork, but some of the integrated routing
capabilities may not be practically attractive or even feasible in capabilities may not be practically attractive or even feasible in
this case (see Section 7). this case (see Section 5).
Under the unified service model, optical network services are Under the unified service model and within the context of an MPLS or
obtained implicitly during end-to-end MPLS signaling. Specifically, GMPLS network, optical network services are obtained implicitly
draft-ietf-ipo-framework-02.txt draft-ietf-ipo-framework-03.txt
an edge router can create a lightpath with specified attributes, or during end-to-end GMPLS signaling. Specifically, an edge router can
delete and modify lightpaths as it creates MPLS label-switched paths create a lightpath with specified attributes, or delete and modify
(LSPs). In this regard, the services obtained from the optical lightpaths as it creates GMPLS label-switched paths (LSPs). In this
network are similar to the domain services model. These services, regard, the services obtained from the optical network are similar
however, may be invoked in a more seamless manner as compared to the to the domain services model. These services, however, may be
domain services model. For instance, when routers are attached to a invoked in a more seamless manner as compared to the domain services
single optical network (i.e., there are no ENNIs), a remote router model. For instance, when routers are attached to a single optical
could compute an end-to-end path across the optical internetwork. It network (i.e., there are no ENNIs), a remote router could compute an
can then establish an LSP across the optical internetwork. But the end-to-end path across the optical internetwork. It can then
edge routers must still recognize that an LSP across the optical establish an LSP across the optical internetwork. But the edge
internetwork is a lightpath, or a conduit for multiple LSPs. The routers must still recognize that an LSP across the optical
concept of "forwarding adjacency" can be used to specify virtual internetwork is a lightpath, or a conduit for multiple LSPs.
The concept of "forwarding adjacency" can be used to specify virtual
links across optical internetworks in routing protocols such as OSPF links across optical internetworks in routing protocols such as OSPF
[3]. In essence, once a lightpath is established across an optical [3]. In essence, once a lightpath is established across an optical
internetwork between two edge routers, it can be advertised as a internetwork between two edge routers, the lightpath can be
forwarding adjacency (a virtual link) between these routers. Thus, advertised as a forwarding adjacency (a virtual link) between these
from a data plane point of view, the lightpaths result in a virtual routers. Thus, from a data plane point of view, the lightpaths
overlay between edge routers. The decisions as to when to create result in a virtual overlay between edge routers. The decisions as
such lightpaths, and the bandwidth management for these lightpaths to when to create such lightpaths, and the bandwidth management for
is identical in both the domain services model and the unified these lightpaths is identical in both the domain services model and
service model. The routing and signaling models for unified services the unified service model. The routing and signaling models for
is described in Section 7. unified services is described in Sections 5 and 6.
5.3 Which Service Model? 4.3 Which Service Model?
The pros and cons of the above service models can be debated at The pros and cons of the above service models can be debated at
length, but the approach recommended in this framework is to define length, but the approach recommended in this framework is to define
routing and signaling mechanisms in support of both. As pointed out routing and signaling mechanisms in support of both models. As noted
above, signaling for service request can be unified to cover both above, signaling for service requests can be unified to cover both
models. The developments in GMPLS signaling [4] for the unified models. The developments in GMPLS signaling [4] for the unified
service model and its adoption for UNI signaling [5, 6] under the service model and its adoption for UNI signaling [5, 6] under the
domain services model essentially supports this view. The domain services model essentially supports this view. The
significant difference between the service models, however, is in significant difference between the service models, however, is in
routing protocols, as described in Section 7. routing protocols, as described in Sections 5 and 6.
5.4 What are the Possible Services? 4.4 What are the Possible Services?
Specialized services may be built atop the point-to-point Specialized services may be built atop the point-to-point
connectivity service offered by the optical network. For example, connectivity service offered by the optical network. For example,
optical virtual private networks and bandwidth on demand are some of
the services that can be envisioned.
5.4.1 Virtual Private Networks (VPNs) 4.4.1 Optical Virtual Private Networks (OVPNs)
Given that the data plane between IP routers over an optical network Given that the data plane between IP routers over an optical network
amounts to a virtual topology which is an overlay over the optical amounts to a virtual topology which is an overlay over the optical
network, it is easy to imagine a virtual private network of network, it is easy to envision a virtual private network of
lightpaths that interconnect routers (or any other set of clients). lightpaths that interconnect routers (or any other set of clients)
Indeed, in the case where the optical network provides connectivity belonging to a single entity or a group of related entities across a
for multiple sets of external client networks, there has to be a public optical network. Indeed, in the case where the optical
way to enforce routing policies that ensure routing separation network provides connectivity for multiple sets of external client
between different sets of clients (i.e., VPN service). draft-ietf-ipo-framework-03.txt
draft-ietf-ipo-framework-02.txt networks, there has to be a way to enforce routing policies that
ensure routing separation between different sets of client networks
(i.e., VPN service).
6. IP transport over Optical Networks 5. IP transport over Optical Networks
To examine the architectural alternatives for IP over optical To examine the architectural alternatives for IP over optical
networks, it is important to distinguish between the data and networks, it is important to distinguish between the data and
control planes over the UNI. As described in Section 6, the optical control planes over the UNI. The optical network provides a service
network provides a service to external entities in the form of fixed to external entities in the form of fixed bandwidth transport pipes
bandwidth transport pipes (optical paths). IP routers at the edge of (optical paths). IP routers at the edge of the optical networks must
the optical networks must necessarily have such paths established necessarily have such paths established between them before
between them before communication at the IP layer can commence. communication at the IP layer can commence. Thus, the IP data plane
Thus, the IP data plane over optical networks is realized over a over optical networks is realized over a virtual topology of optical
virtual topology of optical paths. On the other hand, IP routers and paths. On the other hand, IP routers and OXCs can have a peer
OXCs can have a peer relation on the control plane, especially for relation with respect to the control plane, especially for routing
the implementation of a routing protocol that allows dynamic protocols that permit the dynamic discovery of IP endpoints attached
discovery of IP endpoints attached to the optical network. The IP to the optical network.
over optical network architecture is defined essentially by the
organization of the control plane. The assumption in this framework
is that an MPLS-based control plane [1] is used. Depending on the
service model(Section 6), however, the control planes in the IP and
optical networks can be loosely or tightly coupled. This coupling
determines
o the details of the topology and routing information advertised by The IP over optical network architecture is defined essentially by
the optical network across UNI; the organization of the control plane. The assumption in this
framework is that an IP-based control plane [1] is used, such as
GMPLS. Depending on the service model(Section 4), however, the
control planes in the IP and optical networks can be loosely or
tightly coupled. This coupling determines the following
characteristics:
o Level of control that IP routers can exercise in selecting o The details of the topology and routing information advertised by
specific paths for connections across the optical network; and the optical network across the client interface;
o The level of control that IP routers can exercise in selecting
explicit paths for connections across the optical network;
o Policies regarding the dynamic provisioning of optical paths o Policies regarding the dynamic provisioning of optical paths
between routers. This includes access control, accounting and between routers. These include access control, accounting and
security issues. security issues.
The following interconnection models are then possible: The following interconnection models are then possible:
6.1 Interconnection Models 5.1 Interconnection Models
6.1.1 The Peer Model 5.1.1 The Peer Model
Under the peer model, the IP/MPLS layers act as peers of the optical Under the peer model, the IP control plane acts as a peer of the
transport network, such that a single control plane runs optical transport network control. This implies that a single
over both the IP/MPLS and optical domains. When there is a single instance of the control plane is deployed over the IP and optical
optical network involved, presumably a common IGP domains. When there is a single optical network involved and the IP
and optical domains belong to the same entity, then a common IGP
such as OSPF or IS-IS, with appropriate extensions, can be used to such as OSPF or IS-IS, with appropriate extensions, can be used to
distribute topology information [7] over the integrated IP-optical distribute topology information [7] over the integrated IP-optical
network. In the case of OSPF, opaque LSAs can be used to advertise network. In the case of OSPF, opaque LSAs can be used to advertise
topology state information. In the case of IS-IS, extended TLVs will topology state information. In the case of IS-IS, extended TLVs will
have to be defined to propagate topology state information. When an draft-ietf-ipo-framework-03.txt
optical internetwork with multiple optical networks is involved
(that spans different administrative boundaries), a single instance
of an intra-domain routing protocol is not practically attractive or
even feasible. In this case, inter-domain routing and signaling are
needed. In either case, a tacit assumption is that a common
addressing scheme will be used for the optical and IP networks. A
draft-ietf-ipo-framework-02.txt
common address space can be trivially realized by using IP addresses have to be defined to propagate topology state information. Many of
in both IP and optical domains. Thus, the optical network elements these extensions are occurring within the context of GMPLS.
become IP addressable entities as noted in [1].
6.1.2 The Overlay Model When an optical internetwork with multiple optical networks is
involved (e.g., spanning different administrative domains), a
single instance of an intra-domain routing protocol is not
attractive or even realistic. In this case, inter-domain routing and
signaling protocols are needed. In either case, a tacit assumption
is that a common addressing scheme will be used for the optical and
IP networks. A common address space can be trivially realized by
using IP addresses in both IP and optical domains. Thus, the optical
network elements become IP addressable entities as noted in [1].
Under the overlay model, the IP/MPLS routing, topology distribution, 5.1.2 The Overlay Model
and signaling protocols are independent of the routing, topology
distribution, and signaling protocols at the optical layer. This Under the overlay model, the IP routing, topology distribution, and
model is conceptually similar to the classical IP over ATM or MPOA signaling protocols are independent of the routing, topology
models, but applied to an optical internetwork directly. In the distribution, and signaling protocols within the optical domain.
This model is conceptually similar to the classical IP over ATM or
MPOA models, but applied to an optical internetwork instead. In the
overlay model, topology distribution, path computation and signaling overlay model, topology distribution, path computation and signaling
protocols would have to be defined for the optical domain. In protocols would have to be defined for the optical domain,
certain circumstances, it may also be feasible to statically independently of what exists in the IP domain. In certain
configure the optical channels that provide connectivity in the circumstances, it may also be feasible to statically configure the
overlay model through network management. Static configuration is, optical channels that provide connectivity in the overlay model
however, unlikely to scale in very large networks, nor support the through network management functions. Static configuration is,
rapid connection provisioning required in todays competitive however, unlikely to scale in very large networks, and will not
networking environment. support the rapid connection provisioning required in existing and
future competitive networking environments.
6.1.3 The Augmented Model 5.1.3 The Augmented Model
Under the augmented model, there are actually separate routing Under the augmented model, there are separate routing instances in
instances in the IP and optical domains, but information from one the IP and optical domains, but certain types of information from
routing instance is passed through the other routing instance. For one routing instance can be passed through to the other routing
example, external IP addresses could be carried within the optical instance. For example, external IP addresses could be carried within
routing protocols to allow reachability information to be passed to the optical routing protocols to allow reachability information to
IP clients. be passed to IP clients.
The routing approaches corresponding to these interconnection models The routing approaches corresponding to these interconnection models
are described below. are described below.
6.2 Routing Approaches 5.2 Routing Approaches
6.2.1 Integrated Routing 5.2.1 Integrated Routing
This routing approach supports the peer model within an This routing approach supports the peer model within a single
administrative domain. Under this approach, the IP and optical administrative domain. Under this approach, the IP and optical
networks are assumed to run the same instance of an IP routing networks are assumed to run the same instance of an IP routing
protocol, e.g., OSPF with suitable "optical" extensions. These protocol, e.g., OSPF with suitable "optical" extensions. These
extensions must capture optical link parameters, and any constraints extensions must capture optical link parameters, and any constraints
that are specific to optical networks. The topology and link state that are specific to optical networks. The topology and link state
information maintained by all nodes (OXCs and routers) is identical. information maintained by all nodes (OXCs and routers) may be
This permits a router to compute an end-to-end path to another draft-ietf-ipo-framework-03.txt
router across the optical network. Suppose the path computation is
triggered by the need to route a label switched path (LSP). Such an
LSP can be established using MPLS signaling, e.g., RSVP-TE or CR-
LDP. When the LSP is routed over the optical network, a lightpath
must be established between two edge routers. This lightpath is in
essence a tunnel across the optical network, and may have capacity
much larger than that required to route the first LSP. Thus, it is
essential that other routers in the network realize the availability
of resources in the lightpath for other LSPs to be routed over it.
draft-ietf-ipo-framework-02.txt
The lightpath may therefore be advertised as a virtual link in the identical, but not necessarily. This approach permits a router to
topology. compute an end-to-end path to another router across the optical
network. Suppose the path computation is triggered by the need to
route a label switched path (LSP) in a GMPLS environment. Such an
LSP can be established using GMPLS signaling, e.g., RSVP-TE or CR-
LDP with appropriate extensions. In this case, the signaling
protocol will establish a ightpath between two edge routers. This
lightpath is in essence a tunnel across the optical network, and may
have capacity much larger than the bandwidth required to support the
first LSP. Thus, it is essential that other routers in the network
realize the availability of excess capacity within the lightpath so
that subsequent LSPs between the routers can use it rather
instantiating a new lightpath. The lightpath may therefore be
advertised as a virtual link in the topology as a means to address
this issue.
The notion of "forwarding adjacency" (FA) described in [3] is The notion of "forwarding adjacency" (FA) described in [3] is
essential in propagating existing lightpath information to other essential in propagating existing lightpath information to other
routers. An FA is essentially a virtual link advertised into a link routers. An FA is essentially a virtual link advertised into a link
state routing protocol. Thus, an FA could be described by the same state routing protocol. Thus, an FA could be described by the same
parameters that define resources in any regular link. While it is parameters that define resources in any regular link. While it is
necessary to specify the mechanism for creating an FA, it is not necessary to specify the mechanism for creating an FA, it is not
necessary to specify how an FA is used by the routing scheme. Once necessary to specify how an FA is used by the routing scheme. Once
an FA is advertised in a link state protocol, its usage for routing an FA is advertised in a link state protocol, its usage for routing
LSPs is defined by the route computation and traffic engineering LSPs is defined by the route computation and traffic engineering
skipping to change at line 884 skipping to change at line 904
network of FAs. The above scheme is one way to tackle the problem. network of FAs. The above scheme is one way to tackle the problem.
Another approach is to associate appropriate dynamic attributes with Another approach is to associate appropriate dynamic attributes with
link state information, so that a link that cannot be used to link state information, so that a link that cannot be used to
establish a particular type of connection will be appropriately establish a particular type of connection will be appropriately
tagged. Generally, however, there is a great deal of similarity tagged. Generally, however, there is a great deal of similarity
between integrated routing and domain-specific routing (described between integrated routing and domain-specific routing (described
next). Both ultimately deal with the creation of a virtual next). Both ultimately deal with the creation of a virtual
lightpath topology (which is overlaid over the optical network) to lightpath topology (which is overlaid over the optical network) to
meet certain traffic engineering objectives. meet certain traffic engineering objectives.
6.2.2 Domain-Specific Routing draft-ietf-ipo-framework-03.txt
5.2.2 Domain-Specific Routing
The domain-specific routing approach supports the augmented The domain-specific routing approach supports the augmented
interconnection model. Under this approach, routing within the interconnection model. Under this approach, routing within the
optical and IP domains are separated, with a standard routing optical and IP domains are separated, with a standard routing
protocol running between domains. This is similar to the IP inter- protocol running between domains. This is similar to the IP inter-
domain routing model. A specific approach for this is considered domain routing model. A specific approach for this is considered
next. It is to be noted that other approaches are equally possible. next. It is to be noted that other approaches are equally possible.
6.2.2.1 Domain-Specific Routing using BGP 5.2.2.1 Domain-Specific Routing using BGP
The inter-domain IP routing protocol, BGP [8], may be adapted for The inter-domain IP routing protocol, BGP [8], may be adapted for
exchanging routing information between IP and optical domains. This exchanging routing information between IP and optical domains. This
draft-ietf-ipo-framework-02.txt
would allow the routers to advertise IP address prefixes within would allow the routers to advertise IP address prefixes within
their network to the optical internetwork and to receive external their network to the optical internetwork and to receive external
IP address prefixes from the optical internetwork. The optical IP address prefixes from the optical internetwork. The optical
internetwork transports the reachability information from one IP internetwork transports the reachability information from one IP
network to others. For instance, edge routers and OXCs can run network to others. For instance, edge routers and OXCs can run
exterior BGP (EBGP). Within the optical internetwork, interior BGP exterior BGP (EBGP). Within the optical internetwork, interior BGP
(IBGP) is used between border OXCs within the same network, and EBGP (IBGP) is used between border OXCs within the same network, and EBGP
is used between networks (over ENNI, Figure 1). is used between networks (over ENNI, Figure 1).
Under this scheme, it is necessary to identify the egress points in Under this scheme, it is necessary to identify the egress points in
skipping to change at line 934 skipping to change at line 954
other border OXCs or edge routers. An edge router receiving this other border OXCs or edge routers. An edge router receiving this
information need not propagate the egress address further, but it information need not propagate the egress address further, but it
must keep the association between external IP addresses and egress must keep the association between external IP addresses and egress
OXC addresses. Specific BGP mechanisms for propagating egress OXC OXC addresses. Specific BGP mechanisms for propagating egress OXC
addresses are to be determined, considering prior examples addresses are to be determined, considering prior examples
described in [9]. When VPNs are implemented, the address prefixes described in [9]. When VPNs are implemented, the address prefixes
advertised by the border OXCs may be accompanied by some VPN advertised by the border OXCs may be accompanied by some VPN
identification (for example, VPN IPv4 addresses, as defined in [9], identification (for example, VPN IPv4 addresses, as defined in [9],
may be used). may be used).
6.2.3 Overlay Routing 5.2.3 Overlay Routing
The overlay routing approach supports the overlay interconnection The overlay routing approach supports the overlay interconnection
model.Under this approach, an overlay mechanism that allows edge model.Under this approach, an overlay mechanism that allows edge
routers toregister and query for external addresses is implemented. routers toregister and query for external addresses is implemented.
draft-ietf-ipo-framework-03.txt
This is conceptually similar to the address resolution mechanism This is conceptually similar to the address resolution mechanism
used for IP over ATM. Under this approach, the optical network could used for IP over ATM. Under this approach, the optical network could
implement a registry that allows edge routers to register IP implement a registry that allows edge routers to register IP
addresses and VPN identifiers. An edge router may be allowed to addresses and VPN identifiers. An edge router may be allowed to
query for external addresses belonging to the same set of VPNs it query for external addresses belonging to the same set of VPNs it
belongs to. A successful query would return the address of the belongs to. A successful query would return the address of the
egress optical port through which the external destination can be egress optical port through which the external destination can be
reached. reached.
Because IP-optical interface connectivity is limited, the Because IP-optical interface connectivity is limited, the
determination of how many lightpaths must be established and to what determination of how many lightpaths must be established and to what
endpoints are traffic engineering decisions. Furthermore, after an endpoints are traffic engineering decisions. Furthermore, after an
draft-ietf-ipo-framework-02.txt
initial set of such lightpaths are established, these may be used as initial set of such lightpaths are established, these may be used as
adjacencies within VPNs for a VPN-wide routing scheme, for example, adjacencies within VPNs for a VPN-wide routing scheme, for example,
OSPF. With this approach, an edge router could first determine other OSPF. With this approach, an edge router could first determine other
edge routers of interest by querying the registry. After it obtains edge routers of interest by querying the registry. After it obtains
the appropriate addresses, an initial overlay lightpath topology may the appropriate addresses, an initial overlay lightpath topology may
be formed. Routing adjacencies may then be established across the be formed. Routing adjacencies may then be established across the
lightpaths and further routing information may be exchanged to lightpaths and further routing information may be exchanged to
establish VPN-wide routing. establish VPN-wide routing.
6.3 Signaling-Related 5.3 Signaling-Related
6.3.1 The Role of MPLS 5.3.1 The Role of MPLS
It is possible to model wavelengths, and potentially TDM channels It is possible to model wavelengths, and potentially TDM channels
within a wavelength as "labels". This concept was proposed in [1], within a wavelength as "labels". This concept was proposed in [1],
and "generalized" MPLS (GMPLS) mechanisms for realizing this are and "generalized" MPLS (GMPLS) mechanisms for realizing this are
described in [4]. MPLS signaling protocols with traffic engineering described in [4]. MPLS signaling protocols with traffic engineering
extensions, such as RSVP-TE and CR-LDP can be used for signaling extensions, such as RSVP-TE and CR-LDP can be used for signaling
lightpath requests. In the case of the domain services model, these lightpath requests. In the case of the domain services model, these
protocols can be adapted for UNI signaling as well [5, 6]. In the protocols can be adapted for UNI signaling as well [5, 6]. In the
case of the unified services model, lightpath establishment occurs case of the unified services model, lightpath establishment occurs
to support end-to-end LSP establishment using these protocols (with to support end-to-end LSP establishment using these protocols (with
suitable GMPLS enhancements [10, 11]). suitable GMPLS enhancements [10, 11]).
6.3.2 Signaling Models 5.3.2 Signaling Models
With the domain-services model, the signaling control plane in the With the domain-services model, the signaling control plane in the
IP and optical network are completely separate as shown in Figure 3 IP and optical network are completely separate as shown in Figure 3
below. This separation also implies the separation of IP and optical below. This separation also implies the separation of IP and optical
address spaces (even though the optical network would be using address spaces (even though the optical network would be using
internal IP addressing). While RSVP-TE and LDP can be adapted for internal IP addressing). While RSVP-TE and LDP can be adapted for
UNI signaling, the full functionality of these protocols will not be UNI signaling, the full functionality of these protocols will not be
used. For example, UNI signaling does not require the specification used. For example, UNI signaling does not require the specification
of explicit routes. On the other hand, based on the service of explicit routes. On the other hand, based on the service
attributes, new objects need to be signaled using these protocols as attributes, new objects need to be signaled using these protocols as
described in [5, 6]. described in [5, 6].
draft-ietf-ipo-framework-03.txt
MPLS Signaling UNI Signaling MPLS or other signaling MPLS Signaling UNI Signaling MPLS or other signaling
| |
+-----------------------------+ | +-----------------------------+ +-----------------------------+ | +-----------------------------+
| IP Network | | | Optical Internetwork | | IP Network | | | Optical Internetwork |
| +---------+ +---------+ | | | +---------+ +---------+ | | +---------+ +---------+ | | | +---------+ +---------+ |
| | | | | | | | | | | | | | | | | | | | | | | | | |
| | Router +---+ Router +-----+------+ OXC +---+ OXC | | | | Router +---+ Router +-----+------+ OXC +---+ OXC | |
| | | | | | | | | | | | | | | | | | | | | | | | | |
| +-----+---+ +---+-----+ | | | +-----+---+ +---+-----+ | | +-----+---+ +---+-----+ | | | +-----+---+ +---+-----+ |
+-----------------------------+ | +-----------------------------+ +-----------------------------+ | +-----------------------------+
| |
| |
Completely Separated Addressing and Control Planes Completely Separated Addressing and Control Planes
Figure 3: Domain Services Signaling Model Figure 3: Domain Services Signaling Model
draft-ietf-ipo-framework-02.txt
With the unified services model, the addressing is common in the IP With the unified services model, the addressing is common in the IP
network and optical internetwork and the respective signaling network and optical internetwork and the respective signaling
control are related, as shown in Figure 4. It is understood that control are related, as shown in Figure 4. It is understood that
GMPLS signaling is implemented in the IP and optical domains, using GMPLS signaling is implemented in the IP and optical domains, using
suitably enhanced RSVP-TE or CR-LDP protocols. But the semantics of suitably enhanced RSVP-TE or CR-LDP protocols. But the semantics of
services within the optical internetwork may be different from that services within the optical internetwork may be different from that
in the IP network. As an example, the protection services offered in in the IP network. As an example, the protection services offered in
the optical internetwork may be different from the end-to-end the optical internetwork may be different from the end-to-end
protection services offered by the IP network. Another example is protection services offered by the IP network. Another example is
skipping to change at line 1040 skipping to change at line 1062
| | | |
+--------+ +--------+ | +-------+ +-------+ | +--------+ +--------+ +--------+ | +-------+ +-------+ | +--------+
| | | | | | | | | | | | | | | | | | | | | | | |
| IP LSR +--+ IP LSR +--+--+Optical+--+Optical+-+--+ IP LSR +--- | IP LSR +--+ IP LSR +--+--+Optical+--+Optical+-+--+ IP LSR +---
| | | | | | LSR | | LSR | | | | | | | | | | LSR | | LSR | | | |
+-----+--+ +---+----+ | +-----+-+ +---+---+ | +--------+ +-----+--+ +---+----+ | +-----+-+ +---+---+ | +--------+
Common Address Space, Service Translation Common Address Space, Service Translation
Figure 4: Unified Services Signaling Model Figure 4: Unified Services Signaling Model
draft-ietf-ipo-framework-03.txt
Thus, as illustrated in Figure 4, the signaling in the case of Thus, as illustrated in Figure 4, the signaling in the case of
unified services is actually multi-layered. The layering is based on unified services is actually multi-layered. The layering is based on
the technology and functionality. As an example, the specific the technology and functionality. As an example, the specific
adaptations of GMPLS signaling for SONET layer (whose functionality adaptations of GMPLS signaling for SONET layer (whose functionality
is transport) are described in [12]. is transport) are described in [12].
6.4 End-to-End Protection Models 5.4 End-to-End Protection Models
Suppose an LSP is established from an ingress IP router to an egress Suppose an LSP is established from an ingress IP router to an egress
router across an ingress IP network, a transit optical internetwork router across an ingress IP network, a transit optical internetwork
and an egress IP network. If this LSP is to be afforded protection and an egress IP network. If this LSP is to be afforded protection
in the IP layer, how is the service coordinated between the IP and in the IP layer, how is the service coordinated between the IP and
optical layers? optical layers?
Under this scenario, there are two approaches to end-to-end Under this scenario, there are two approaches to end-to-end
protection: protection:
draft-ietf-ipo-framework-02.txt 5.4.1 Segment-Wise Protection
6.4.1 Segment-Wise Protection
The protection services in the IP layer could utilize optical layer The protection services in the IP layer could utilize optical layer
protection services for the LSP segment that traverses the optical protection services for the LSP segment that traverses the optical
internetwork. Thus, the end-to-end LSP would be treated as a internetwork. Thus, the end-to-end LSP would be treated as a
concatenation of three LSP segments from the protection point of concatenation of three LSP segments from the protection point of
view: a segment in the ingress IP network, a segment in the optical view: a segment in the ingress IP network, a segment in the optical
internetwork and a segment in the egress IP network. The protection internetwork and a segment in the egress IP network. The protection
services at the IP layer for an end-to-end LSP must be mapped onto services at the IP layer for an end-to-end LSP must be mapped onto
suitable protection services offered by the optical internetwork. suitable protection services offered by the optical internetwork.
Suppose that 1+1 protection is offered to LSPs at the IP layer, Suppose that 1+1 protection is offered to LSPs at the IP layer,
skipping to change at line 1088 skipping to change at line 1109
this path be as shown in Figure 5, traversing router interface B this path be as shown in Figure 5, traversing router interface B
in the ingress network, optical ports C (ingress) and D (egress), in the ingress network, optical ports C (ingress) and D (egress),
and router interface E in the egress network. Next, 1+1 protection and router interface E in the egress network. Next, 1+1 protection
is realized separately in each network by establishing a protection is realized separately in each network by establishing a protection
path between points A and B, C and D and E and F. Furthermore, the path between points A and B, C and D and E and F. Furthermore, the
segments B-C and D-E must themselves be 1+1 protected, using drop- segments B-C and D-E must themselves be 1+1 protected, using drop-
side protection. For the segment between C and D, the optical side protection. For the segment between C and D, the optical
internetwork must offer a 1+1 service similar to that offered in the internetwork must offer a 1+1 service similar to that offered in the
IP networks. IP networks.
draft-ietf-ipo-framework-03.txt
+----------------+ +------------------+ +---------------+ +----------------+ +------------------+ +---------------+
| | | | | | | | | | | |
A Ingress IP Net B----C Optical Internet D----E Egress IP Net F A Ingress IP Net B----C Optical Internet D----E Egress IP Net F
| | | | | | | | | | | |
+----------------+ +------------------+ +---------------+ +----------------+ +------------------+ +---------------+
Figure 5: End-to-End Protection Example Figure 5: End-to-End Protection Example
6.4.2 Single-Layer Protection 5.4.2 Single-Layer Protection
Under this model, the protection services in the IP layer do not Under this model, the protection services in the IP layer do not
rely on any protection services offered in the optical internetwork. rely on any protection services offered in the optical internetwork.
Thus, with reference to Figure 5, two SRLG-disjoint LSPs are Thus, with reference to Figure 5, two SRLG-disjoint LSPs are
established between A and F. The corresponding segments in the established between A and F. The corresponding segments in the
optical internetwork are treated as independent lightpaths in the optical internetwork are treated as independent lightpaths in the
optical internetwork. These lightpaths may be unprotected in the optical internetwork. These lightpaths may be unprotected in the
optical internetwork. optical internetwork.
6.4.3 Differences 5.4.3 Differences
A distinction between these two choices is as follows. Under the A distinction between these two choices is as follows. Under the
first choice, the optical internetwork is actively involved in end- first choice, the optical internetwork is actively involved in end-
to-end protection, whereas under the second choice, any protection to-end protection, whereas under the second choice, any protection
draft-ietf-ipo-framework-02.txt
service offered in the optical internetwork is not utilized directly service offered in the optical internetwork is not utilized directly
by client IP network. Also, under the first choice, the protection by client IP network. Also, under the first choice, the protection
in the optical internetwork may apply collectively to a number of IP in the optical internetwork may apply collectively to a number of IP
LSPs. That is, with reference to Figure 5, many LSPs may be LSPs. That is, with reference to Figure 5, many LSPs may be
aggregated into a single lightpath between C and D. The optical aggregated into a single lightpath between C and D. The optical
internetwork protection may then be applied to all of them at once internetwork protection may then be applied to all of them at once
leading to some gain in scalability. Under the second choice, each leading to some gain in scalability. Under the second choice, each
IP LSP must be separately protected. Finally, the first choice IP LSP must be separately protected. Finally, the first choice
allows different restoration signaling to be implemented in the IP allows different restoration signaling to be implemented in the IP
and optical internetwork. These restoration protocols are "patched and optical internetwork. These restoration protocols are "patched
skipping to change at line 1143 skipping to change at line 1164
restoration protocols in the IP layer must run transparently over restoration protocols in the IP layer must run transparently over
the optical internetwork in the overlay mode. IP based recovery the optical internetwork in the overlay mode. IP based recovery
techniques may however be more resource efficient, as it may be techniques may however be more resource efficient, as it may be
possible to convey traffic through the redundant capacity under possible to convey traffic through the redundant capacity under
fault-free scenarios. In particular, it may be possible to utilize fault-free scenarios. In particular, it may be possible to utilize
classification, scheduling, and concepts of forwarding equivalence classification, scheduling, and concepts of forwarding equivalence
class to route lower class traffic over protect facilities and then class to route lower class traffic over protect facilities and then
possibly preempt them to make way for high priority traffic when possibly preempt them to make way for high priority traffic when
faults occur. faults occur.
7. IP-based Optical Control Plane Issues draft-ietf-ipo-framework-03.txt
6. IP-based Optical Control Plane Issues
Provisioning and restoring lightpaths end-to-end between IP networks Provisioning and restoring lightpaths end-to-end between IP networks
requires protocol and signaling support within optical sub-networks, requires protocol and signaling support within optical sub-networks,
and across the INNI and ENNI. In this regard, a distinction is made and across the INNI and ENNI. In this regard, a distinction is made
between control procedures within an optical sub-network (Figure 1), between control procedures within an optical sub-network (Figure 1),
between sub-networks, and between networks. The general guideline between sub-networks, and between networks. The general guideline
followed in this framework is to separate these cases, and allow the followed in this framework is to separate these cases, and allow the
possibility that different control procedures are followed inside possibility that different control procedures are followed inside
different sub-networks, while a common set of procedures are different sub-networks, while a common set of procedures are
followed across sub-networks and networks. followed across sub-networks and networks.
The control plane procedures within a single vendor sub-network need The control plane procedures within a single vendor sub-network need
not be defined since these can be proprietary. Clearly, it is not be defined since these can be proprietary. Clearly, it is
possible to follow the same control procedures inside a sub-network possible to follow the same control procedures inside a sub-network
as defined for control across sub-networks. But this is left as a and across sub-networks. But this is simply a recommendation within
recommendation even choice within this framework document, this framework document, rather than an imperative requirement.
rather than as an imperative requirement. Thus, in the following, Thus, in the following, signaling and routing across sub-networks is
signaling and routing across sub-networks is considered first, considered first, followed by a discussion of similar issues across
followed by a discussion of similar issues across networks. networks.
draft-ietf-ipo-framework-02.txt
7.1 Addressing 6.1 Addressing
For interoperability across optical sub-networks using an IP-centric For interoperability across optical sub-networks using an IP-centric
control plane, the fundamental issue is that of addressing. What control plane, the fundamental issue is that of addressing. What
entities should be identifiable from a signaling and routing point entities should be identifiable from a signaling and routing point
of view? How should they be addressed? This section presents some of view? How should they be addressed? This section presents some
guidelines on this issue. guidelines on this issue.
Identifiable entities in optical networks includes OXCs, optical Identifiable entities in optical networks includes OXCs, optical
links, optical channels and sub-channels, Shared Risk Link Groups links, optical channels and sub-channels, Shared Risk Link Groups
(SRLGs), etc. An issue here is how granular the identification (SRLGs), etc. An issue here is how granular the identification
skipping to change at line 1196 skipping to change at line 1217
does not depend on the precise termination point information, but does not depend on the precise termination point information, but
rather only on the terminating OXC. Thus, finer granularity rather only on the terminating OXC. Thus, finer granularity
identification of termination points is of relevance only to the identification of termination points is of relevance only to the
terminating OXC and not to intermediate OXCs (of course, resource terminating OXC and not to intermediate OXCs (of course, resource
allocation at each intermediate point would depend on the allocation at each intermediate point would depend on the
granularity of resources requested). This suggests an identification granularity of resources requested). This suggests an identification
scheme whereby OXCs are identified by a unique IP address and a scheme whereby OXCs are identified by a unique IP address and a
"selector" identifies further fine-grain information of relevance at "selector" identifies further fine-grain information of relevance at
an OXC. This, of course, does not preclude the identification of an OXC. This, of course, does not preclude the identification of
these termination points directly with IP addresses(with a null these termination points directly with IP addresses(with a null
draft-ietf-ipo-framework-03.txt
selector). The selector can be formatted to have adequate number of selector). The selector can be formatted to have adequate number of
bits and a structure that expresses port, channel, sub-channel, etc, bits and a structure that expresses port, channel, sub-channel, etc,
identification. identification.
Within the optical network, the establishment of trail segments Within the optical network, the establishment of trail segments
between adjacent OXCs require the identification of specific port, between adjacent OXCs require the identification of specific port,
channel, sub-channel, etc. With a GMPLS control plane, a label channel, sub-channel, etc. With a GMPLS control plane, a label
serves this function. The structure of the label must be such that serves this function. The structure of the label must be such that
it can encode the required information [12]. it can encode the required information [12].
skipping to change at line 1220 skipping to change at line 1243
fibers routed over a conduit could belong to the same SRLG. The fibers routed over a conduit could belong to the same SRLG. The
notable characteristic of SRLGs is that a given link could belong to notable characteristic of SRLGs is that a given link could belong to
more than one SRLG, and two links belonging to a given SRLG may more than one SRLG, and two links belonging to a given SRLG may
individually belong to two other SRLGs. This is illustrated in individually belong to two other SRLGs. This is illustrated in
Figure 6. Here, the links 1,2,3 and 4 may belong to SRLG 1, links Figure 6. Here, the links 1,2,3 and 4 may belong to SRLG 1, links
1,2 and 3 could belong to SRLG 2 and link 4 could belong to SRLG 3. 1,2 and 3 could belong to SRLG 2 and link 4 could belong to SRLG 3.
Similarly, links 5 and 6 could belong to SRLG 1, and links 7 and 8 Similarly, links 5 and 6 could belong to SRLG 1, and links 7 and 8
could belong to SRLG 4. (In this example, the same SRLG, i.e., 1, could belong to SRLG 4. (In this example, the same SRLG, i.e., 1,
contains links from two different adjacencies). contains links from two different adjacencies).
draft-ietf-ipo-framework-02.txt
While the classification of physical resources into SRLGs is a While the classification of physical resources into SRLGs is a
manual operation, the assignment of unique identifiers to these manual operation, the assignment of unique identifiers to these
SRLGs within an optical network is essential to ensure correct SRLGs within an optical network is essential to ensure correct
SRLG-disjoint path computation for protection. SRLGs could be SRLG-disjoint path computation for protection. SRLGs could be
identified with a flat identifier (e.g., 32 bit integer). identified with a flat identifier (e.g., 32 bit integer).
Finally, optical links between adjacent OXCs may be bundled for Finally, optical links between adjacent OXCs may be bundled for
advertisement into a link state protocol [14]. A bundled interface advertisement into a link state protocol [14]. A bundled interface
may be numbered or unnumbered. In either case, the component links may be numbered or unnumbered. In either case, the component links
within the bundle must be identifiable. In concert with SRLG within the bundle must be identifiable. In concert with SRLG
identification, this information is necessary for correct path identification, this information is necessary for correct path
computation. computation.
7.2 Neighbor Discovery 6.2 Neighbor Discovery
Routing within the optical network relies on knowledge of network Routing within the optical network relies on knowledge of network
topology and resource availability. This information may be gathered topology and resource availability. This information may be gathered
and used by a centralized system, or by a distributed link state and used by a centralized system, or by a distributed link state
routing protocol. In either case, the first step towards network- routing protocol. In either case, the first step towards network-
wide link state determination is the discovery of the status of wide link state determination is the discovery of the status of
local links to all neighbors by each OXC. Specifically, each OXC local links to all neighbors by each OXC. Specifically, each OXC
must determine the up/down status of each optical link, the must determine the up/down status of each optical link, the
bandwidth and other parameters of the link, and the identity of the bandwidth and other parameters of the link, and the identity of the
remote end of the link (e.g., remote port number). The last piece of remote end of the link (e.g., remote port number). The last piece of
information is used to specify an appropriate label when signaling information is used to specify an appropriate label when signaling
for lightpath provisioning. The determination of these parameters for lightpath provisioning. The determination of these parameters
could be based on a combination of manual configuration and an could be based on a combination of manual configuration and an
automated protocol running between adjacent OXCs. The automated protocol running between adjacent OXCs. The
draft-ietf-ipo-framework-03.txt
characteristics of such a protocol would depend on the type of OXCs characteristics of such a protocol would depend on the type of OXCs
that are adjacent (e.g., transparent or opaque). that are adjacent (e.g., transparent or opaque).
Neighbor discovery would typically require in-band communication on Neighbor discovery would typically require in-band communication on
the bearer channels to determine local connectivity and link status. the bearer channels to determine local connectivity and link status.
In the case of opaque OXCs with SONET termination, one instance of a In the case of opaque OXCs with SONET termination, one instance of a
neighbor discovery protocol (e.g., LMP [2]) would run on each OXC neighbor discovery protocol (e.g., LMP [2]) would run on each OXC
port, communicating with the corresponding protocol instance at the port, communicating with the corresponding protocol instance at the
neighboring OXC. The protocol would utilize the SONET overhead bytes neighboring OXC. The protocol would utilize the SONET overhead bytes
to transmit the (configured) local attributes periodically to the to transmit the (configured) local attributes periodically to the
neighbor. Thus, two neighboring switches can automatically determine neighbor. Thus, two neighboring switches can automatically determine
the identities of each other and the local connectivity, and also the identities of each other and the local connectivity, and also
keep track of the up/down status of local links. Neighbor discovery keep track of the up/down status of local links. Neighbor discovery
with transparent OXCs is described in [2]. with transparent OXCs is described in [2].
draft-ietf-ipo-framework-02.txt
+--------------+ +------------+ +------------+ +--------------+ +------------+ +------------+
| +-1:OC48---+ +-5:OC192-+ | | +-1:OC48---+ +-5:OC192-+ |
| +-2:OC48---+ +-6:OC192-+ | | +-2:OC48---+ +-6:OC192-+ |
| OXC1 +-3:OC48---+ OXC2 +-7:OC48--+ OXC3 | | OXC1 +-3:OC48---+ OXC2 +-7:OC48--+ OXC3 |
| +-4:OC192--+ +-8:OC48--+ | | +-4:OC192--+ +-8:OC48--+ |
| | | | +------+ | | | | | +------+ |
+--------------+ +----+-+-----+ | +----+------+-----+ +--------------+ +----+-+-----+ | +----+------+-----+
| | | | | | | | | |
| | | | | | | | | |
+--------------+ | | | | | +--------------+ | | | | |
| | +----+-+-----+ | | +------+-----+ | | +----+-+-----+ | | +------+-----+
| +----------+ +--+ | | | | +----------+ +--+ | | |
| OXC4 +----------+ +----+ | | | OXC4 +----------+ +----+ | |
| +----------+ OXC5 +--------+ OXC6 | | +----------+ OXC5 +--------+ OXC6 |
| | | +--------+ | | | | +--------+ |
+--------------+ | | | | +--------------+ | | | |
+------+-----+ +------+-----+ +------+-----+ +------+-----+
Figure 6: Mesh Optical Network with SRLGs Figure 6: Mesh Optical Network with SRLGs
7.3 Topology Discovery 6.3 Topology Discovery
Topology discovery is the procedure by which the topology and Topology discovery is the procedure by which the topology and
resource state of all the links in a network are determined. This resource state of all the links in a network are determined. This
procedure may be done as part of a link state routing protocol procedure may be done as part of a link state routing protocol
(e.g., OSPF, ISIS), or it can be done via the management plane (in (e.g., OSPF, ISIS), or it can be done via the management plane (in
the case of centralized path computation). The implementation of a the case of centralized path computation). The implementation of a
link state protocol within a network (i.e., across sub-network link state protocol within a network (i.e., across sub-network
boundaries) means that the same protocol runs in OXCs in every sub- boundaries) means that the same protocol runs in OXCs in every sub-
network. If this assumption does not hold then interworking of network. If this assumption does not hold then interworking of
routing between sub-networks is required. This is similar to inter- routing between sub-networks is required. This is similar to inter-
network routing discussed in Section 8.7. The focus in the following network routing discussed in Section 6.7. The focus in the following
is therefore on standardized link state routing. is therefore on standardized link state routing.
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In general, most of the link state routing functionality is In general, most of the link state routing functionality is
maintained when applied to optical networks. However, the maintained when applied to optical networks. However, the
representation of optical links, as well as some link parameters, representation of optical links, as well as some link parameters,
are changed in this setting. Specifically, are changed in this setting. Specifically,
o The link state information may consist of link bundles [14]. o The link state information may consist of link bundles [14].
Each link bundle is represented as an abstract link in the network Each link bundle is represented as an abstract link in the network
topology. Different bundling representations are possible. For topology. Different bundling representations are possible. For
instance, the parameters of the abstract link may include the instance, the parameters of the abstract link may include the
number, bandwidth and the type of optical links contained in the number, bandwidth and the type of optical links contained in the
underlying link bundle [14]. Also, the SRLGs corresponding to each underlying link bundle [14]. Also, the SRLGs corresponding to each
optical link in the bundle may be included as a parameter. optical link in the bundle may be included as a parameter.
o The link state information should capture restoration-related o The link state information should capture restoration-related
parameters for optical links. Specifically, with shared protection parameters for optical links. Specifically, with shared protection
(Section 8.5), the link state updates must have information that (Section 6.5), the link state updates must have information that
allows the computation of shared protection paths. allows the computation of shared protection paths.
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o A single routing adjacency could be maintained between neighbors o A single routing adjacency could be maintained between neighbors
which may have multiple optical links (or even multiple link which may have multiple optical links (or even multiple link
bundles) between them. This reduces the protocol messaging bundles) between them. This reduces the protocol messaging
overhead. overhead.
o Since link availability information changes dynamically, a o Since link availability information changes dynamically, a
flexible policy for triggering link state updates based on flexible policy for triggering link state updates based on
availability thresholds may be implemented. For instance, changes availability thresholds may be implemented. For instance, changes
in availability of links of a given bandwidth (e.g., OC-48) may in availability of links of a given bandwidth (e.g., OC-48) may
trigger updates only after the availability figure changes by a trigger updates only after the availability figure changes by a
certain percentage. certain percentage.
These concepts are relatively well-understood. On the other hand, These concepts are relatively well-understood. On the other hand,
the resource representation models and the topology discovery the resource representation models and the topology discovery
process for hierarchical routing (e.g., OSPF with multiple areas) process for hierarchical routing (e.g., OSPF with multiple areas)
are areas that need further work. are areas that need further work.
7.4 Restoration Models 6.4 Restoration Models
Automatic restoration of lightpaths is a service offered by optical Automatic restoration of lightpaths is a service offered by optical
networks. There could be local and end-to-end mechanisms for networks. There could be local and end-to-end mechanisms for
restoration of lightpaths within a network (across the INNI). Local restoration of lightpaths within a network (across the INNI). Local
mechanisms are used to select an alternate link between two adjacent mechanisms are used to select an alternate link between two adjacent
OXCs across the INNI when a failure affects the primary link over OXCs across the INNI when a failure affects the primary link over
which the (protected) lightpath is being routed. Local restoration which the (protected) lightpath is being routed. Local restoration
does not affect the end-to-end route of the lightpath. When local does not affect the end-to-end route of the lightpath. When local
restoration is not possible (e.g., no alternate link is available restoration is not possible (e.g., no alternate link is available
between the adjacent OXCs in question), end-to-end restoration may between the adjacent OXCs in question), end-to-end restoration may
be performed. With this, the affected lightpath may be rerouted over be performed. With this, the affected lightpath may be rerouted over
an alternate path that completely avoids the OXCs or the link an alternate path that completely avoids the OXCs or the link
segment where the failure occurred. For end-to-end restoration, segment where the failure occurred. For end-to-end restoration,
alternate paths are typically pre-computed. Such back-up paths may alternate paths are typically pre-computed. Such back-up paths may
have to be physically diverse from the corresponding primary paths. have to be physically diverse from the corresponding primary paths.
End-to-end restoration may be based on two types of protection End-to-end restoration may be based on two types of protection
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schemes; "1 + 1" protection or shared protection. Under 1 + 1 schemes; "1 + 1" protection or shared protection. Under 1 + 1
protection, a back-up path is established for the protected primary protection, a back-up path is established for the protected primary
path along a physically diverse route. Both paths are active and the path along a physically diverse route. Both paths are active and the
failure along the primary path results in an immediate switch-over failure along the primary path results in an immediate switch-over
to the back-up path. Under shared protection, back-up paths to the back-up path. Under shared protection, back-up paths
corresponding to physically diverse primary paths may share the same corresponding to physically diverse primary paths may share the same
network resources. When a failure affects a primary path, it is network resources. When a failure affects a primary path, it is
assumed that the same failure will not affect the other primary assumed that the same failure will not affect the other primary
paths whose back-ups share resources. paths whose back-ups share resources.
It is possible that different restoration schemes may be implemented It is possible that different restoration schemes may be implemented
within optical sub-networks. It is therefore necessary to consider a within optical sub-networks. It is therefore necessary to consider a
two-level restoration mechanism. Path failures within an optical two-level restoration mechanism. Path failures within an optical
sub-network could be handled using procedures specific to the sub-network could be handled using procedures specific to the
sub-network. If this fails, end-to-end restoration across sub- sub-network. If this fails, end-to-end restoration across sub-
networks could be invoked. The border OXC that is the ingress to a networks could be invoked. The border OXC that is the ingress to a
sub-network can act as the source for restoration procedures within sub-network can act as the source for restoration procedures within
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a sub-network. The signaling for invoking end-to-end restoration a sub-network. The signaling for invoking end-to-end restoration
across the INNI is described in Section 8.6.3. The computation of across the INNI is described in Section 6.6.3. The computation of
the back-up path for end-to-end restoration may be based on various the back-up path for end-to-end restoration may be based on various
criteria. It is assumed that the back-up path is computed by the criteria. It is assumed that the back-up path is computed by the
source OXC, and signaled using standard methods. source OXC, and signaled using standard methods.
7.5 Route Computation 6.5 Route Computation
The computation of a primary route for a lightpath within an optical The computation of a primary route for a lightpath within an optical
network is essentially a constraint-based routing problem. The network is essentially a constraint-based routing problem. The
constraint is typically the bandwidth required for the lightpath, constraint is typically the bandwidth required for the lightpath,
perhaps along with administrative and policy constraints. The perhaps along with administrative and policy constraints. The
objective of path computation could be to minimize the total objective of path computation could be to minimize the total
capacity required for routing lightpaths [15]. capacity required for routing lightpaths [15].
Route computation with constraints may be accomplished using a Route computation with constraints may be accomplished using a
number of algorithms [16]. When 1+1 protection is used, a back-up number of algorithms [16]. When 1+1 protection is used, a back-up
skipping to change at line 1410 skipping to change at line 1431
link refers to, and the relationship between links belonging to link refers to, and the relationship between links belonging to
different SRLGs in the bundle. For example, considering Figure 3, different SRLGs in the bundle. For example, considering Figure 3,
if links 1,2,3 and 4 are bundled together in an LSA, the bundled LSA if links 1,2,3 and 4 are bundled together in an LSA, the bundled LSA
must indicate that there are three SRLGs which are part of the must indicate that there are three SRLGs which are part of the
bundle (i.e., 1, 2 and 3), and that links in SRLGs 2 and 3 are also bundle (i.e., 1, 2 and 3), and that links in SRLGs 2 and 3 are also
part of SRLG 1. part of SRLG 1.
To encode the SRLG relationships in a link bundle LSA, only links To encode the SRLG relationships in a link bundle LSA, only links
which belong to exactly the same set of SRLGs must be bundled which belong to exactly the same set of SRLGs must be bundled
together. With reference to Figure 3, for example, two bundles can together. With reference to Figure 3, for example, two bundles can
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be advertised for links between OXC1 and OXC2, with the following be advertised for links between OXC1 and OXC2, with the following
information: information:
Bundle No. SRLGs Link Type Number Other Info Bundle No. SRLGs Link Type Number Other Info
---------- ----- --------- ------ ---------- ---------- ----- --------- ------ ----------
1 1,2 OC-48 3 --- 1 1,2 OC-48 3 ---
2 1,3 OC-192 1 --- 2 1,3 OC-192 1 ---
Assuming that the above information is available for each bundle at Assuming that the above information is available for each bundle at
every node, there are several approaches possible for path every node, there are several approaches possible for path
computation. For instance, computation. For instance,
1. The primary path can be computed first, and the (exclusive 1. The primary path can be computed first, and the (exclusive
or shared) back-up is computed next based on the SRLGs chosen or shared) back-up is computed next based on the SRLGs chosen
for the primary path. In this regard, for the primary path. In this regard,
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o The primary path computation procedure can output a series of o The primary path computation procedure can output a series of
bundles the path is routed over. Since a bundle is uniquely bundles the path is routed over. Since a bundle is uniquely
identified with a set of SRLGs, the alternate path can be identified with a set of SRLGs, the alternate path can be
computed right away based on this knowledge. In this case, if computed right away based on this knowledge. In this case, if
the primary path set up does not succeed for lack of resources the primary path set up does not succeed for lack of resources
in a chosen bundle, the primary and backup paths must be in a chosen bundle, the primary and backup paths must be
recomputed. recomputed.
o It might be desirable to compute primary paths without choosing o It might be desirable to compute primary paths without choosing
skipping to change at line 1449 skipping to change at line 1471
path computation procedure would output a series of nodes the path computation procedure would output a series of nodes the
path traverses. Each OXC in the path would have the freedom to path traverses. Each OXC in the path would have the freedom to
choose the particular bundle to route that segment of the choose the particular bundle to route that segment of the
primary path. This procedure would increase the chances of primary path. This procedure would increase the chances of
successfully setting up the primary path when link state successfully setting up the primary path when link state
information is not up to date everywhere. But the specific information is not up to date everywhere. But the specific
bundle chosen, and hence the SRLGs in the primary path, must be bundle chosen, and hence the SRLGs in the primary path, must be
captured during primary path set-up, for example, using the captured during primary path set-up, for example, using the
RSVP-TE Route Record Object [17]. This SRLG information is RSVP-TE Route Record Object [17]. This SRLG information is
then used for computing the back-up path. The back-up path may then used for computing the back-up path. The back-up path may
also be established specifying only which SRLGs to AVOID in a also be established specifying only which SRLGs to avoid in a
given segment, rather than which bundles to use. This would given segment, rather than which bundles to use. This would
maximize the chances of establishing the back-up path. maximize the chances of establishing the back-up path.
2. The primary path and the back-up path are comptuted together in 2. The primary path and the back-up path are computed together in
one step, for example, using Suurbaale's algorithm [18]. In this one step, for example, using Suurbaale's algorithm [18]. In this
case, the paths must be computed using specific bundle case, the paths must be computed using specific bundle
information. information.
To summarize, it is essential to capture sufficient information in To summarize, it is essential to capture sufficient information in
link bundle LSAs to accommodate different path computation link bundle LSAs to accommodate different path computation
procedures and to maximize the chances of successful path procedures and to maximize the chances of successful path
establishment. Depending on the path computation procedure used, establishment. Depending on the path computation procedure used,
the type of support needed during path establishment (e.g., the the type of support needed during path establishment (e.g., the
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recording of link group or SRLG information during path recording of link group or SRLG information during path
establishment) may differ. establishment) may differ.
When shared protection is used, the route computation algorithm must When shared protection is used, the route computation algorithm must
take into account the possibility of sharing links among multiple take into account the possibility of sharing links among multiple
back-up paths. Under shared protection, the back-up paths back-up paths. Under shared protection, the back-up paths
corresponding to SRLG-disjoint primary paths can be assigned the corresponding to SRLG-disjoint primary paths can be assigned the
same links. The assumption here is that since the primary paths are same links. The assumption here is that since the primary paths are
not routed over links that have the same SRLG, a given failure will not routed over links that have the same SRLG, a given failure will
affect only one of them. Furthermore, it is assumed that multiple affect only one of them. Furthermore, it is assumed that multiple
failure events affecting links belonging to more than one SRLG will failure events affecting links belonging to more than one SRLG will
not occur concurrently. Unlike the case of 1+1 protection, the not occur concurrently. Unlike the case of 1+1 protection, the
back-up paths are not established apriori. Rather, a failure event back-up paths are not established apriori. Rather, a failure event
triggers the establishment of a single back-up path corresponding to triggers the establishment of a single back-up path corresponding to
the affected primary path. the affected primary path.
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The distributed implementation of route computation for shared back- The distributed implementation of route computation for shared back-
up paths require knowledge about the routing of all primary and up paths require knowledge about the routing of all primary and
back-up paths at every node. This raises scalability concerns. For back-up paths at every node. This raises scalability concerns. For
this reason, it may be practical to consider the centralization of this reason, it may be practical to consider the centralization of
the route computation algorithm in a route server that has complete the route computation algorithm in a route server that has complete
knowledge of the link state and path routes. Heuristics for fully knowledge of the link state and path routes. Heuristics for fully
distributed route computation without complete knowledge of path distributed route computation without complete knowledge of path
routes are to be determined. Path computation for restoration is routes are to be determined. Path computation for restoration is
further described in [13]. further described in [13].
7.6 Signaling Issues 6.6 Signaling Issues
Signaling within an optical network for lightpath provisioning Signaling within an optical network for lightpath provisioning
is a relatively simple operation if a standard procedure is is a relatively simple operation if a standard procedure is
implemented within all sub-networks. Otherwise, proprietary implemented within all sub-networks. Otherwise, proprietary
signaling may be implemented within sub-networks, but converted back signaling may be implemented within sub-networks, but converted back
to standard signaling across the INNI. This is similar to signaling to standard signaling across the INNI. This is similar to signaling
across the ENNI, as described in Section 8.7. In the former case, across the ENNI, as described in Section 6.7. In the former case,
signaling messages could carry a strict explicit route in signaling signaling messages could carry a strict explicit route in signaling
messages, while in the latter case the route should be loose, at the messages, while in the latter case the route should be loose, at the
level of sub-networks. Once a route is determined for a lightpath, level of sub-networks. Once a route is determined for a lightpath,
each OXC in the path must establish appropriate cross-connects in a each OXC in the path must establish appropriate cross-connects in a
coordinated fashion. This coordination is akin to selecting incoming coordinated fashion. This coordination is akin to selecting incoming
and outgoing labels in a label-switched environment. Thus, protocols and outgoing labels in a label-switched environment. Thus, protocols
like RSVP-TE [11] and CR-LDP [10] can be used across the INNI for like RSVP-TE [11] and CR-LDP [10] can be used across the INNI for
this. A few new concerns, however, must be addressed. this. A few new concerns, however, must be addressed.
7.6.1 Bi-Directional Lightpath Establishment 6.6.1 Bi-Directional Lightpath Establishment
Lightpaths are typically bi-directional. That is, the output port Lightpaths are typically bi-directional. That is, the output port
selected at an OXC for the forward direction is also the input port selected at an OXC for the forward direction is also the input port
for the reverse direction of the path. Since signaling for optical for the reverse direction of the path. Since signaling for optical
paths may be autonomously initiated by different nodes, it is paths may be autonomously initiated by different nodes, it is
possible that two path set-up attempts are in progress at the same possible that two path set-up attempts are in progress at the same
time. Specifically, while setting up an optical path, an OXC A may time. Specifically, while setting up an optical path, an OXC A may
select output port i which is connected to input port j of the select output port i which is connected to input port j of the
"next" OXC B. Concurrently, OXC B may select output port j for "next" OXC B. Concurrently, OXC B may select output port j for
draft-ietf-ipo-framework-03.txt
setting up a different optical path, where the "next" OXC is A. This setting up a different optical path, where the "next" OXC is A. This
results in a "collision". Similarly, when WDM functionality is built results in a "collision". Similarly, when WDM functionality is built
into OXCs, a collision occurs when adjacent OXCs choose directly into OXCs, a collision occurs when adjacent OXCs choose directly
connected output ports and the same wavelength for two different connected output ports and the same wavelength for two different
optical paths. There are two ways to deal with such collisions. optical paths. There are two ways to deal with such collisions.
First, collisions may be detected and the involved paths may be torn First, collisions may be detected and the involved paths may be torn
down and re-established. Or, collisions may be avoided altogether. down and re-established. Or, collisions may be avoided altogether.
7.6.2 Failure Recovery 6.6.2 Failure Recovery
The impact of transient partial failures must be minimized in an The impact of transient partial failures must be minimized in an
optical network. Specifically, optical paths that are not directly optical network. Specifically, optical paths that are not directly
affected by a failure must not be torn down due to the failure. For affected by a failure must not be torn down due to the failure. For
example, the control processor in an OXC may fail, affecting example, the control processor in an OXC may fail, affecting
signaling and other internodal control communication. Similarly, signaling and other internodal control communication. Similarly,
draft-ietf-ipo-framework-02.txt
the control channel between OXCs may be affected temporarily by a the control channel between OXCs may be affected temporarily by a
failure. These failure may not affect already established optical failure. These failure may not affect already established optical
paths passing through the OXC fabric. The detection of such failures paths passing through the OXC fabric. The detection of such failures
by adjacent nodes, for example, through a keepalive mechanism by adjacent nodes, for example, through a keepalive mechanism
between signaling peers, must not result in these optical paths between signaling peers, must not result in these optical paths
being torn down. being torn down.
It is likely that when the above failures occur, a backup processor It is likely that when the above failures occur, a backup processor
or a backup control channel will be activated. The signaling or a backup control channel will be activated. The signaling
protocol must be designed such that it is resilient to transient protocol must be designed such that it is resilient to transient
failures. During failure recovery, it is desirable to recover local failures. During failure recovery, it is desirable to recover local
state at the concerned OXC with least disruption to existing optical state at the concerned OXC with least disruption to existing optical
paths. paths.
7.6.3 Restoration 6.6.3 Restoration
Signaling for restoration has two distict phases. There is a Signaling for restoration has two distict phases. There is a
reservation phase in which capacity for the protection path is reservation phase in which capacity for the protection path is
established. Then, there is an activation phase in which the established. Then, there is an activation phase in which the
back-up path is actually put in service. The former phase typically back-up path is actually put in service. The former phase typically
is not subject to strict time constraints, while the latter is. is not subject to strict time constraints, while the latter is.
Signaling to establish a "1+1" back-up path is relatively straight- Signaling to establish a "1+1" back-up path is relatively straight-
forward. This signaling is very similar to signaling used for forward. This signaling is very similar to signaling used for
establishing the primary path. Signaling to establish a shared back- establishing the primary path. Signaling to establish a shared back-
up path is a little bit different. Here, each OXC must understand up path is a little bit different. Here, each OXC must understand
which back-up paths can share resources. The signaling message must which back-up paths can share resources. The signaling message must
itself indicate shared reservation. The sharing rule is as described itself indicate shared reservation. The sharing rule is as described
in Section 8.4: back-up paths corresponding to physically diverse in Section 6.4: back-up paths corresponding to physically diverse
primary paths may share the same network resources. It is primary paths may share the same network resources. It is
therefore necessary for the signaling message to carry adequate therefore necessary for the signaling message to carry adequate
information that allows an OXC to verify that back-up paths that information that allows an OXC to verify that back-up paths that
share a certain resources are allowed to do so. share a certain resources are allowed to do so.
Under both 1+1 and shared protection, the activation phase has two Under both 1+1 and shared protection, the activation phase has two
parts: propagation of failure information to the source OXC from the parts: propagation of failure information to the source OXC from the
point of failure, and activation of the back-up path. The signaling point of failure, and activation of the back-up path. The signaling
draft-ietf-ipo-framework-03.txt
for these two phases must be very fast in order to realize response for these two phases must be very fast in order to realize response
times in the order of tens of milliseconds. When optical links are times in the order of tens of milliseconds. When optical links are
SONET-based, in-band signals may be used, resulting in quick SONET-based, in-band signals may be used, resulting in quick
response. With out-of-band control, it is necessary to consider response. With out-of-band control, it is necessary to consider
fast signaling over the control channel using very short IP packets fast signaling over the control channel using very short IP packets
and prioritized processing. While it is possible to use RSVP or CR- and prioritized processing. While it is possible to use RSVP or CR-
LDP for activating protection paths, these protocols do not provide LDP for activating protection paths, these protocols do not provide
any means to give priority to restoration signaling as opposed to any means to give priority to restoration signaling as opposed to
signaling for provisioning. For instance, it is possible for a signaling for provisioning. For instance, it is possible for a
restoration-related RSVP message to be queued behind a number of restoration-related RSVP message to be queued behind a number of
provisioning messages thereby delaying restoration. It is therefore provisioning messages thereby delaying restoration. It is therefore
necessary to develop a definition of QoS for restoration signaling necessary to develop a definition of QoS for restoration signaling
and incorporate mechanisms in existing signaling protocols to and incorporate mechanisms in existing signaling protocols to
achieve this. Or, a new signaling protocol may be developed achieve this. Or, a new signaling protocol may be developed
exclusively for activating protection paths during restoration. exclusively for activating protection paths during restoration.
draft-ietf-ipo-framework-02.txt 6.7 Optical Internetworking
7.7 Optical Internetworking
Within an optical internetwork, it must be possible to dynamically Within an optical internetwork, it must be possible to dynamically
provision and restore lightpaths across optical networks. Therefore: provision and restore lightpaths across optical networks. Therefore:
o A standard scheme for uniquely identifying lightpath end-points in o A standard scheme for uniquely identifying lightpath end-points in
different networks is required. different networks is required.
o A protocol is required for determining reachability of end-points o A protocol is required for determining reachability of end-points
across networks. across networks.
skipping to change at line 1616 skipping to change at line 1638
o Support for policies that affect the flow of control information o Support for policies that affect the flow of control information
across networks will be required. across networks will be required.
The IP-centric control architecture for optical networks can be The IP-centric control architecture for optical networks can be
extended to satisfy the functional requirements of optical extended to satisfy the functional requirements of optical
internetworking. Routing and signaling interaction between optical internetworking. Routing and signaling interaction between optical
networks can be standardized across the ENNI (Figure 1). The networks can be standardized across the ENNI (Figure 1). The
functionality provided across ENNI is as follows. functionality provided across ENNI is as follows.
7.7.1 Neighbor Discovery 6.7.1 Neighbor Discovery
Neighbor discovery procedure, as described in Section 8.2, can be Neighbor discovery procedure, as described in Section 6.2, can be
used for this. Indeed, a single protocol should be standardized for used for this. Indeed, a single protocol should be standardized for
neighbor discovery within and across networks. neighbor discovery within and across networks.
7.7.2 Addressing and Routing Model 6.7.2 Addressing and Routing Model
The addressing mechanisms described in Section 6.1 can be used to
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The addressing mechanisms described in Section 8.1 can be used to
identify OXCs, ports, channels and sub-channels in each network. identify OXCs, ports, channels and sub-channels in each network.
It is essential that the OXC IP addresses are unique within the It is essential that the OXC IP addresses are unique within the
internetwork. internetwork.
Provisioning an end-to-end lightpath across multiple networks Provisioning an end-to-end lightpath across multiple networks
involves the establishment of path segments in each network involves the establishment of path segments in each network
sequentially. Thus, a path segment is established from the source sequentially. Thus, a path segment is established from the source
OXC to a border OXC in the source network. From this border OXC, OXC to a border OXC in the source network. From this border OXC,
signaling across NNI is used to establish a path segment to a border signaling across NNI is used to establish a path segment to a border
OXC in the next network. Provisioning then continues in the next OXC in the next network. Provisioning then continues in the next
network and so on until the destination OXC is reached. The usage of network and so on until the destination OXC is reached. The usage of
protocols like BGP for this purpose need to be explored. protocols like BGP for this purpose need to be explored.
draft-ietf-ipo-framework-02.txt 6.7.3 Restoration
7.7.3 Restoration
Local restoration across the ENNI is similar to that across INNI Local restoration across the ENNI is similar to that across INNI
described in Section 8.6.3. End-to-end restoration across networks described in Section 6.6.3. End-to-end restoration across networks
is likely to be either of the 1+1 type, or segmented within each is likely to be either of the 1+1 type, or segmented within each
network, as described in Section 8.4. network, as described in Section 6.4.
8. Other Issues 7. Other Issues
8.1 WDM and TDM in the Same Network 7.1 WDM and TDM in the Same Network
A practical assumption would be that if SONET (or some other TDM A practical assumption would be that if SONET (or some other TDM
mechanism that is capable partitioning the bandwidth of a mechanism that is capable partitioning the bandwidth of a
wavelength) is used, then TDM is leveraged as an additional method wavelength) is used, then TDM is leveraged as an additional method
to differentiate between "flows." In such cases, wavelengths and to differentiate between "flows." In such cases, wavelengths and
time intervals (sub-channels) within a wavelength become analogous time intervals (sub-channels) within a wavelength become analogous
to labels (as noted in [1]) which can be used to make switching to labels (as noted in [1]) which can be used to make switching
decisions. This would be somewhat akin to using VPI (e.g., decisions. This would be somewhat akin to using VPI (e.g.,
wavelength) and VCI (e.g., TDM sub-channel) in ATM networks. More wavelength) and VCI (e.g., TDM sub-channel) in ATM networks. More
generally, this will be akin to label stacking and to LSP nesting generally, this will be akin to label stacking and to LSP nesting
within the context of Multi-Protocol Lambda Switching [1]. GMPLS within the context of Multi-Protocol Lambda Switching [1]. GMPLS
signaling [4] supports this type of multiplexing. signaling [4] supports this type of multiplexing.
8.2 Wavelength Conversion 7.2 Wavelength Conversion
Some form of wavelength conversion may exist at some switching Some form of wavelength conversion may exist at some switching
elements. This however may not be the case in some pure optical elements. This however may not be the case in some pure optical
switching elements. A switching element is essentially anything switching elements. A switching element is essentially anything
more sophisticated than a simple repeater, that is capable of more sophisticated than a simple repeater, that is capable of
switching and converting a wavelength Lambda(k) from an input port switching and converting a wavelength Lambda(k) from an input port
to a wavelength Lambda(l) on an output port. In this display, it to a wavelength Lambda(l) on an output port. In this display, it
is not necessarily the case that Lambda(k) = Lambda(l), nor is it is not necessarily the case that Lambda(k) = Lambda(l), nor is it
necessarily the case that the data carried on Lambda(k) is switched necessarily the case that the data carried on Lambda(k) is switched
through the device without being examined or modified. through the device without being examined or modified.
It is not necessary to have a wavelength converter at every It is not necessary to have a wavelength converter at every
switching element. A number of studies have attempted to address switching element. A number of studies have attempted to address
the issue of the value of wavelength conversion in an optical the issue of the value of wavelength conversion in an optical
network. Such studies typically use the blocking probability (the network. Such studies typically use the blocking probability (the
probability that a lightpath cannot be established because the probability that a lightpath cannot be established because the
draft-ietf-ipo-framework-03.txt
requisite wavelengths are not available) as a metric to adjudicate requisite wavelengths are not available) as a metric to adjudicate
the effectiveness of wavelength conversion. The IP over optical the effectiveness of wavelength conversion. The IP over optical
architecture must take into account hybrid networks with some OXCs architecture must take into account hybrid networks with some OXCs
capable of wavelength conversion and others incapable of this. The capable of wavelength conversion and others incapable of this. The
GMPLS "label set" mechanism [4] supports the selection of the same GMPLS "label set" mechanism [4] supports the selection of the same
label (i.e., wavelength) across an NNI. label (i.e., wavelength) across an NNI.
8.3 Service Provider Peering Points 7.3 Service Provider Peering Points
There are proposed inter-network interconnect models which allow There are proposed inter-network interconnect models which allow
certain types of peering relationships to occur at the optical certain types of peering relationships to occur at the optical
layer. This is consistent with the need to support optical layer layer. This is consistent with the need to support optical layer
draft-ietf-ipo-framework-02.txt
services independent of higher layers payloads. In the context of IP services independent of higher layers payloads. In the context of IP
over optical networks, peering relationships between different trust over optical networks, peering relationships between different trust
domains will eventually have to occur at the IP layer, on IP routing domains will eventually have to occur at the IP layer, on IP routing
elements, even though non-IP paths may exist between the peering elements, even though non-IP paths may exist between the peering
routers. routers.
8.4 Rate of Lightpath Set-Up 7.4 Rate of Lightpath Set-Up
Dynamic establishment of optical channel trails and lightpaths is Dynamic establishment of optical channel trails and lightpaths is
quite desirable in IP over optical networks, especially when such quite desirable in IP over optical networks, especially when such
instantiations are driven by a stable traffic engineering control instantiations are driven by a stable traffic engineering control
system, or in response to authenticated and authorized requests from system, or in response to authenticated and authorized requests from
clients. clients.
However, there are many proposals suggesting the use of dynamic, However, there are many proposals suggesting the use of dynamic,
data-driven shortcut-lightpath setups in IP over optical networks. data-driven shortcut-lightpath setups in IP over optical networks.
The arguments put forth in such proposals are quite reminiscent of The arguments put forth in such proposals are quite reminiscent of
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routed data traffic, routed data traffic,
o Establishment and re-arrangement of arbitrary virtual topologies o Establishment and re-arrangement of arbitrary virtual topologies
over rings and other physical layer topologies. over rings and other physical layer topologies.
o Use of stable traffic engineering control systems to engineer o Use of stable traffic engineering control systems to engineer
lightpath connections to enhance network performance, either for lightpath connections to enhance network performance, either for
explicit demand based QoS reasons or for load balancing). explicit demand based QoS reasons or for load balancing).
Other issues surrounding dynamic connection setup within the core Other issues surrounding dynamic connection setup within the core
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center around resource usage at the edge of the optical domain. center around resource usage at the edge of the optical domain.
One potential issue pertains to the number of flows that can be One potential issue pertains to the number of flows that can be
processed by an ingress or egress network element either because of processed by an ingress or egress network element either because of
aggregate bandwidth limitations or because of a limitation on the aggregate bandwidth limitations or because of a limitation on the
number of flows (e.g., lightpaths) that can be processed number of flows (e.g., lightpaths) that can be processed
concurrently. concurrently.
Another possible short term reason for dynamic shortcut lightpath Another possible short term reason for dynamic shortcut lightpath
setup would be to quickly pre-provisioned paths based on some setup would be to quickly pre-provision paths based on some criteria
criteria (TOD, CEO wants a high BW reliable connection, etc.). In (e.g., a corporate executive wants a high bandwidth reliable
this scenario, a set of paths is pre-provisioned, but not actually connection, etc.). In this scenario, a set of paths can be pre-
instantiated until the customer initiates an authenticated and provisioned, but not actually instantiated until the customer
draft-ietf-ipo-framework-02.txt initiates an authenticated and authorized setup requests, which is
consistent with existing agreements between the provider and the
authorized setup requests, which is consistent with existing customer. In a sense, the
agreements between the provider and the customer. In a sense, the
provider may have already agreed to supply this service, but will provider may have already agreed to supply this service, but will
only instantiate it by setting up a lightpath when the customer only instantiate it by setting up a lightpath when the customer
submits an explicit request. submits an explicit request.
8.5 Distributed vs. Centralized Provisioning 7.5 Distributed vs. Centralized Provisioning
This document has mainly dealt with a distributed model for This document has mainly dealt with a distributed model for
lightpath provisioning, in which all nodes maintain a synchronized lightpath provisioning, in which all nodes maintain a synchronized
topology database, and advertise topology state information to topology database, and advertise topology state information to
maintain and refresh the database. A constraint-based routing entity maintain and refresh the database. A constraint-based routing entity
in each node then uses the information in the topology database and in each node then uses the information in the topology database and
other relevant details to compute appropriate paths through the other relevant details to compute appropriate paths through the
optical domain. Once a path is computed, a signaling protocol (e.g., optical domain. Once a path is computed, a signaling protocol (e.g.,
[11]) is used to instantiate the lightpath. [11]) is used to instantiate the lightpath.
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information to the client or to some other entity to allow the information to the client or to some other entity to allow the
lightpath to be instantiated. lightpath to be instantiated.
Centralization aids in implementing complex capacity optimization Centralization aids in implementing complex capacity optimization
schemes, and may be the near-term provisioning solution in optical schemes, and may be the near-term provisioning solution in optical
networks with interconnected multi-vendor optical sub-networks. In networks with interconnected multi-vendor optical sub-networks. In
the long term, however, the distributed solution with centralization the long term, however, the distributed solution with centralization
of some control procedures (e.g., traffic engineering) is likely to of some control procedures (e.g., traffic engineering) is likely to
be the approach followed. be the approach followed.
8.6 Optical Networks with Additional Configurable Components draft-ietf-ipo-framework-03.txt
7.6 Optical Networks with Additional Configurable Components
Thus far, this memo has focused mainly on IP over optical networks Thus far, this memo has focused mainly on IP over optical networks
where the cross-connect is the basic dynamically re-configurable where the cross-connect is the basic dynamically re-configurable
device in the optical network. Recently, as a consequence of device in the optical network. Recently, as a consequence of
technology evolution, various types of re-configurable optical technology evolution, various types of re-configurable optical
components are now available, including tunable lasers, tunable components are now available, including tunable lasers, tunable
filters, etc. Under certain circumstances, it may be necessary to filters, etc. Under certain circumstances, it may be necessary to
parameterize the characteristics of these components and advertise parameterize the characteristics of these components and advertise
them within the control plane. This aspect is left for further them within the control plane. This aspect is left for further
study. study.
draft-ietf-ipo-framework-02.txt 7.7 Optical Networks with Limited Wavelength Conversion Capability
8.7 Optical Networks with Limited Wavelength Conversion Capability
At the time of the writing of this document, the majority of optical At the time of the writing of this document, the majority of optical
networks being deployed are "opaque". In this context the term networks being deployed are "opaque". In this context the term
opaque means that each link is optically isolated by transponders opaque means that each link is optically isolated by transponders
doing optical-electrical-optical conversions. Such conversions have doing optical-electrical-optical conversions. Such conversions have
the added benefit of permitting 3R regeneration. The 3Rs refer to the added benefit of permitting 3R regeneration. The 3Rs refer to
re-power, signal retiming and reshaping. Unfortunately, this re-power, signal retiming and reshaping. Unfortunately, this
regeneration requires that the underlying optical equipment be aware regeneration requires that the underlying optical equipment be aware
of both the bit rate and frame format of the carried signal. These of both the bit rate and frame format of the carried signal. These
transponders are quite expensive and their lack of transparency transponders are quite expensive and their lack of transparency
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are strong motivators to introduce "domains of transparency" wherein are strong motivators to introduce "domains of transparency" wherein
all-optical networking equipment would transport data unfettered by all-optical networking equipment would transport data unfettered by
these drawbacks. these drawbacks.
Thus, the issue of IP over optical networking in all optical sub- Thus, the issue of IP over optical networking in all optical sub-
networks, and sub-networks with limited wavelength conversion networks, and sub-networks with limited wavelength conversion
capability merits special attention. In such networks, transmission capability merits special attention. In such networks, transmission
impairments resulting from the peculiar characteristics of optical impairments resulting from the peculiar characteristics of optical
communications complicate the process of path selection. These communications complicate the process of path selection. These
transmission impairments include loss, noise (due primarily to transmission impairments include loss, noise (due primarily to
amplifier spontaneous emission - ASE), dispersion (chromatic and amplifier spontaneous emission -- ASE), dispersion (chromatic
PMD), cross-talk, and non-linear effects. In such networks, the dispersion and polarization mode dispersion), cross-talk, and non-
feasibility of a path between two nodes is no longer simply a linear effects. In such networks, the feasibility of a path between
function of topology and resource availability but will also depend two nodes is no longer simply a function of topology and resource
on the accumulation of impairments along the path. If the impairment availability but will also depend on the accumulation of impairments
accumulation is excessive, the optical signal to noise ratio (OSNR) along the path. If the impairment accumulation is excessive, the
and hence the electrical bit error rate (BER) at the destination optical signal to noise ratio (OSNR) and hence the electrical bit
node may exceed prescribed thresholds, making the resultant optical error rate (BER) at the destination node may exceed prescribed
channel unusable for data communication. The challenge in the thresholds, making the resultant optical channel unusable for data
development of IP-based control plane for optical networks is to communication. The challenge in the development of IP-based control
abstract these peculiar characteristics of the optical layer [19] in plane for optical networks is to abstract these peculiar
a generic fashion, so that they can be used for path computation. characteristics of the optical layer [19] in a generic fashion, so
that they can be used for path computation.
9. Evolution Path for IP over Optical Architecture 8. Evolution Path for IP over Optical Architecture
The architectural models described in Section 7 imply a certain The architectural models described in Section 5 imply a certain
degree of implementation complexity. Specifically, the overlay degree of implementation complexity. Specifically, the overlay
model was described as the least complex for near term deployment model was described as the least complex for near term deployment
draft-ietf-ipo-framework-03.txt
and the peer model the most complex. Nevertheless, each model has and the peer model the most complex. Nevertheless, each model has
certain advantages and this raises the question as to the evolution certain advantages and this raises the question as to the evolution
path for IP over optical network architectures. path for IP over optical network architectures.
The evolution approach recommended in this framework is the The evolution approach recommended in this framework is the
definition of capability sets that start with simpler functionality definition of capability sets that start with simpler functionality
in the beginning and include more complex functionality later. In in the beginning and include more complex functionality later. In
this regard, it is realistic to expect that initial IP over optical this regard, it is realistic to expect that initial IP over optical
deployments will be based on the domain services model (with overlay deployments will be based on the domain services model (with overlay
interconnection), with no routing exchange between the IP and interconnection), with no routing exchange between the IP and
optical domains. Under this model, direct signaling between IP optical domains. Under this model, direct signaling between IP
routers and optical networks is likely to be triggered by offline routers and optical networks is likely to be triggered by offline
traffic engineering decisions. The next step in the evolution of IP- traffic engineering decisions. The next step in the evolution of IP-
draft-ietf-ipo-framework-02.txt
optical interaction is the introduction of reachability information optical interaction is the introduction of reachability information
exchange between the two domains. This would potentially allow exchange between the two domains. This would potentially allow
lightpaths to be established as part of end-to-end LSP set-up. The lightpaths to be established as part of end-to-end LSP set-up. The
final phase is the support for the full peer model with more final phase is the support for the full peer model with more
sophisticated routing interaction between IP and optical domains. sophisticated routing interaction between IP and optical domains.
Using a common signaling framework (based on GMPLS) from the Using a common signaling framework (based on GMPLS) from the
beginning facilitates this type of evolution. For the domain beginning facilitates this type of evolution. For the domain
services model, implementation agreement based on GMPLS UNI services model, implementation agreement based on GMPLS UNI
signaling is being developed in the Optical Interworking Forum (OIF) signaling is being developed in the Optical Interworking Forum (OIF)
[5, 6]. This agreement is aimed at near term deployment and this [5, 6]. This agreement is aimed at near term deployment and this
could be the precursor to a future peer model architecture. In this could be the precursor to a future peer model architecture. In this
evolution, the signaling capability and semantics at the IP-optical evolution, the signaling capability and semantics at the IP-optical
boundary would become more sophisticated, but the basic structure of boundary would become more sophisticated, but the basic structure of
signaling would remain. This would allow incremental developments as signaling would remain. This would allow incremental developments as
the interconnection model becomes more sophisticated, rather than the interconnection model becomes more sophisticated, rather than
complete re-development of signaling capabilities. complete re-development of signaling capabilities.
From a routing point of view, the use of Network Management Systems From a routing point of view, the use of Network Management Systems
(NMS) for static connection management is prevelant in legacy (NMS) for static connection management is prevalent in legacy
optical networks. Going forward, it can be expected that connection optical networks. Going forward, it can be expected that connection
routing using the control plane will be gradually introduced and routing using the control plane will be gradually introduced and
integrated into operational infrastructures. The introduction of integrated into operational infrastructures. The introduction of
routing capabilities can be expected to occur in a phased approach. routing capabilities can be expected to occur in a phased approach.
It is likely that in the first phase, service providers will either It is likely that in the first phase, service providers will either
upgrade existing local element management (EMS) software with upgrade existing local element management (EMS) software with
additional control plane capabilities (and perhaps the hardware as additional control plane capabilities (and perhaps the hardware as
well), or updrade the NMS software in order to introduce some degree well), or upgrade the NMS software in order to introduce some degree
of automation within each optical subnetwork. For this reason, it of automation within each optical subnetwork. For this reason, it
may be desirable to partition the network into subnetworks and may be desirable to partition the network into subnetworks and
introduce IGP interoperability within each subnetwork (i.e. at the introduce IGP interoperability within each subnetwork (i.e. at the
I-NNI level), and employ either static or signaled interoperability I-NNI level), and employ either static or signaled interoperability
between subnetworks. Consequently, it can be envisioned that the between subnetworks. Consequently, it can be envisioned that the
first phase in the evolution towards network level control plane first phase in the evolution towards network level control plane
interoperability in IP over Optical networks will be organized interoperability in IP over Optical networks will be organized
around a system of optical subnetworks which are interconnected around a system of optical subnetworks which are interconnected
statically (or dynamically in a signaled configuration). During this statically (or dynamically in a signaled configuration). During this
phase, an overlay interconnection model will be used between the phase, an overlay interconnection model will be used between the
optical network itself and external IP and MPLS routers (as optical network itself and external IP and MPLS routers (as
described in Section 7.2.3). described in Section 5.2.3).
draft-ietf-ipo-framework-03.txt
Progressing with this phased approach to IPO routing Progressing with this phased approach to IPO routing
interoperabibility evolution, the next level of integration will be interoperabibility evolution, the next level of integration will be
achieved when a single carrier provides dynamic optical routing achieved when a single carrier provides dynamic optical routing
interoperability between subnetworks and between domains. In order interoperability between subnetworks and between domains. In order
to become completely independent of the network switching capability to become completely independent of the network switching capability
within subnetworks and across domains, routing information exchange within subnetworks and across domains, routing information exchange
may need to be enabled at the UNI level. This would constitute a may need to be enabled at the UNI level. This would constitute a
significant evolution: even if the routing instances are kept significant evolution: even if the routing instances are kept
separate and independent, it would still be possible to dynamicallhy separate and independent, it would still be possible to dynamicallhy
exchange reachability and other types of routing information. exchange reachability and other types of routing information.
Another more sophisticated step during this phase is to introduce Another more sophisticated step during this phase is to introduce
draft-ietf-ipo-framework-02.txt
dynamic routing at the E-NNI level. This means that any neighboring dynamic routing at the E-NNI level. This means that any neighboring
networks (independent of internal switching capability) would be networks (independent of internal switching capability) would be
capable of exchanging routing information with peers across the E- capable of exchanging routing information with peers across the E-
NNI. NNI.
Another alternative would be for private networks to bypass these Another alternative would be for private networks to bypass these
intermediate steps and directly consider an integrated routing model intermediate steps and directly consider an integrated routing model
from the onset. This direct evolution strategy is realistic, but is from the onset. This direct evolution strategy is realistic, but is
more likely to occur in operational contexts where both the IP (or more likely to occur in operational contexts where both the IP (or
MPLS) and optical networks are built simultaneously, using equipment MPLS) and optical networks are built simultaneously, using equipment
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likely to be the most viable initial option. Alternatively, a very likely to be the most viable initial option. Alternatively, a very
modular or hierarchical peer model may be contemplated. There may be modular or hierarchical peer model may be contemplated. There may be
other challenges (not just of a technical, but also administrative other challenges (not just of a technical, but also administrative
and even political issues) that may be need to be resolved in order and even political issues) that may be need to be resolved in order
to achieve full a peer model at the routing level in a multi- to achieve full a peer model at the routing level in a multi-
technology and multi-vendor environment. Ultimately, the main technology and multi-vendor environment. Ultimately, the main
technical improvement would likely arise from efficiencies derived technical improvement would likely arise from efficiencies derived
from the integration of traffic-engineering capabilities in the from the integration of traffic-engineering capabilities in the
dynamic inter-domain routing environments. dynamic inter-domain routing environments.
10. Security Considerations 9. Security Considerations
The architectural framework described in this document requires The architectural framework described in this document requires
different protocol mechanisms for its realization. Specifically, the different protocol mechanisms for its realization. Specifically, the
role of neighbor discovery, routing and signaling protocols were role of neighbor discovery, routing and signaling protocols were
described in previous sections. The general security issues that described in previous sections. The general security issues that
arise with these protocols include: arise with these protocols include:
o The authentication of entities exchanging information o The authentication of entities exchanging information
(signaling, routing or link management) across a control (signaling, routing or link management) across a control
interface; interface;
o Ensuring the integrity of the information exchanged across the o Ensuring the integrity of the information exchanged across the
interface, and interface, and
draft-ietf-ipo-framework-03.txt
o Protection of the control mechanisms from outside interference o Protection of the control mechanisms from outside interference
Because optical connections may carry high volumes of data and Because optical connections may carry high volumes of data and
consume significant network resources, mechanisms are required to consume significant network resources, mechanisms are required to
safeguard an optical network against unauthorized use of network safeguard an optical network against unauthorized use of network
resources. resources.
In addition to the security aspects related to the control plane, In addition to the security aspects related to the control plane,
the data plane must also be protected from external interference. the data plane must also be protected from external interference.
draft-ietf-ipo-framework-02.txt 9.1 General security aspects
10.1 General security aspects
Communication protocols usually require two main security Communication protocols usually require two main security
mechanisms: authentication and confidentiality. Authentication mechanisms: authentication and confidentiality. Authentication
mechanisms ensure data origin verification and message integrity so mechanisms ensure data origin verification and message integrity so
that unauthorized operations can be detectedd and discarded. For that unauthorized operations can be detectedd and discarded. For
example, with reference to Figure 1, message authentication service example, with reference to Figure 1, message authentication service
can prevent a malicious IP client from mounting a denial of service can prevent a malicious IP client from mounting a denial of service
attack against the optical network by inserting an excessive number attack against the optical network by inserting an excessive number
of UNI connection creation requests. Additionally, authentication of UNI connection creation requests. Additionally, authentication
mechanisms can provide mechanisms can provide
1. Replay protection, which detects and rejects attempts to 1. Replay protection, which detects and rejects attempts to
reorder, duplicate, truncate, or otherwise tamper with the reorder, duplicate, truncate, or otherwise tamper with the
proper sequence of messages, and proper sequence of messages, and
2. Non-repudiation, which may be desirable for accounting and 2. Non-repudiation, which may be desirable for accounting and
billing purposes. billing purposes.
Authentication and confidentiality can be achieved using either
symmetric or public-key cryptographic algorithms. Simple message
integrity and confidentiality are normally achieved using symmetric
cryptographic algorithms. These algorithms typically require pair-
wise shared secret keys and do not provide non-repudiation, but are
typically less computationally intensive. Replay protection is
normally achieved by adding sequence numbers to the messages or by
relying on other protocol (e.g., TCP) to guarantee the proper
sequencing of the message stream above the integrity service.
Public-key or asymmetric cryptographic algorithms are typically
used, initially, to provide two-way peer entity authentication and
key agreement, which facilitate use of the integrity and
confidentiality services described above. Asymmetric algorithms also
provide digital signatures used to implement a non-repudiation
service. The use of asymmetric algorithms may be supported by a
public-key infrastructure (PKI) or some other, community-defined,
key assignment scheme. Asymmetric algorithms are typically more
computationally intensive than symmetric algorithms.
Confidentiality of signaling messages is also likely to be Confidentiality of signaling messages is also likely to be
desirable, especially in cases where message attributes include desirable, especially in cases where message attributes include
information private to the communicating parties (client and optical information private to the communicating parties (client and optical
network operator). Examples of such attributes include account network operator). Examples of such attributes include account
numbers, contract identification numbers, etc, exchanged over the numbers, contract identification numbers, etc, exchanged over the
UNI (Figure 1). UNI (Figure 1).
The case of non-co-located equipment presents increased security The case of non-co-located equipment presents increases security
requirements. In this scenario, the signaling (or routing) peers may requirements. In this scenario, the signaling (or routing) peers may
be connected using an external network. Since such a network could be connected using an external network. Since such a network could
be outside the control of the optical (or client) network operator, be outside the control of the optical (or client) network operator,
control communication between peers may be subject to increased control communication between peers may be subject to increased
security threats, such as address spoofing, eavesdropping and security threats, such as address spoofing, eavesdropping and
unauthorized intrusion attempts. To counter these threats , unauthorized intrusion attempts. To counter these threats ,
appropriate security mechanisms have to be employed to protect the appropriate security mechanisms have to be employed to protect the
signaling and control channel(s). signaling and control channel(s).
draft-ietf-ipo-framework-02.txt Requests for optical connections from client networks must be
filtered against policy to guard against security infringements and
excess resource consumption.
10.2 Protocol Mechanisms There may be a need for confidentiality for SRLGs in some
circumstances.
draft-ietf-ipo-framework-03.txt
Optical networks may also be subject to subtle forms of denial of
service attacks. An example of this would be requests for optical
connections with explicit routes that induce a high degree of
blocking for subsequent requests. This aspect might require some
global coordination of resource allocation.
9.2 Protocol Mechanisms
The security-related mechanisms required in IP-centric control The security-related mechanisms required in IP-centric control
protocols would depend on the specific security requirements. Such protocols would depend on the specific security requirements. Such
details are beyond the scope of this document and hence are not details are beyond the scope of this document and hence are not
considered further. considered further.
11. Summary and Conclusions 10. Summary and Conclusions
The objective of this document was to define a framework for IP over The objective of this document was to define a framework for IP over
optical networks, considering the service models, routing and optical networks, considering the service models, routing and
signaling issues. There are a diversity of choices, as described signaling issues. There are a diversity of choices, as described
in this document, for IP-optical interconnection, service models in this document, for IP-optical interconnection, service models
and protocol mechanisms. The approach advocated in this document and protocol mechanisms. The approach advocated in this document
was to allow different service models and proprietary enhancements was to allow different service models and proprietary enhancements
in optical networks, and define complementary signaling and in optical networks, and define complementary signaling and
routing mechanisms that would support these. An evolution scenario, routing mechanisms that would support these. An evolution scenario,
based on a common GMPLS-based signaling framework with increasing based on a common GMPLS-based signaling framework with increasing
interworking functionality was suggested. Under this scenario, the interworking functionality was suggested. Under this scenario, the
IP-optical interaction is first based on the domain services model IP-optical interaction is first based on the domain services model
with overlay interconnection that eventually evolves to support full with overlay interconnection that eventually evolves to support full
peer interaction. peer interaction.
12. References 11. References
Note: All references are informative:
1. D. Awduche and Y. Rekhter, , "Multi-Protocol 1. D. Awduche and Y. Rekhter, , "Multi-Protocol
Lambda Switching: Combining MPLS Traffic Engineering Control With Lambda Switching: Combining MPLS Traffic Engineering Control With
Optical Crossconnects," IEEE Communications Magazine, March 2001. Optical Crossconnects," IEEE Communications Magazine, March 2001.
2. J. P. Lang, et. al., "Link Management Protocol," Internet Draft, 2. J. P. Lang, et. al., "Link Management Protocol," Internet Draft,
Work in progress. Work in progress.
3. K. Kompella and Y. Rekhter, "LSP Hierarchy with MPLS TE," 3. K. Kompella and Y. Rekhter, "LSP Hierarchy with MPLS TE,"
Internet Draft, Work in progress. Internet Draft, Work in progress.
4. P. Ashwood-Smith et. al, "Generalized MPLS - Signaling Functional 4. P. Ashwood-Smith et. al, "Generalized MPLS - Signaling Functional
Description", Internet Draft, Work in Progress. Description", Internet Draft, Work in Progress.
5. B. Rajagopalan, "LMP, LDP and RSVP Extensions for Optical UNI 5. B. Rajagopalan, "LDP and RSVP Extensions for Optical UNI
Signaling," Internet Draft, Work in Progress. Signaling," Internet Draft, Work in Progress.
draft-ietf-ipo-framework-03.txt
6. The Optical Interworking Forum, "UNI 1.0 Signaling 6. The Optical Interworking Forum, "UNI 1.0 Signaling
Specification," December, 2001. Specification," December, 2001.
7. K. Kompella et al, "OSPF Extensions in Support of Generalized 7. K. Kompella et al, "OSPF Extensions in Support of Generalized
MPLS," Internet Draft, Work in Progress. MPLS," Internet Draft, Work in Progress.
8. Y. Rekhter and T. Li, "A Border Gateway Protocol 4 (BGP4)",RFC 8. Y. Rekhter and T. Li, "A Border Gateway Protocol 4 (BGP4)",RFC
1771, March, 1995. 1771, March, 1995.
draft-ietf-ipo-framework-02.txt
9. E. Rosen and Y. Rekhter, "BGP/MPLS VPNs", RFC 2547, March, 1999. 9. E. Rosen and Y. Rekhter, "BGP/MPLS VPNs", RFC 2547, March, 1999.
10. P. Ashwood-Smith, et. al., "Generalized MPLS - CR-LDP Signaling 10. P. Ashwood-Smith, et. al., "Generalized MPLS - CR-LDP Signaling
Functional Description," Internet Draft, Work in Progress. Functional Description," Internet Draft, Work in Progress.
11. P. Ashwood-Smith, et. al., "Generalized MPLS - RSVP-TE 11. P. Ashwood-Smith, et. al., "Generalized MPLS - RSVP-TE
Signaling Functional Description", Internet Draft, Work in Signaling Functional Description", Internet Draft, Work in
Progress. Progress.
12. E. Mannie, et. al., "GMPLS Extensions for SONET/SDH Control," 12. E. Mannie, et. al., "GMPLS Extensions for SONET/SDH Control,"
skipping to change at line 2102 skipping to change at line 2121
Framework for QoS-based Routing in the Internet," RFC 2386, Framework for QoS-based Routing in the Internet," RFC 2386,
August, 1998. August, 1998.
17. D. Awduche, L. Berger, Der-Hwa Gan, T. Li, G. Swallow, V. 17. D. Awduche, L. Berger, Der-Hwa Gan, T. Li, G. Swallow, V.
Srinivasan, "RSVP-TE: Extensions to RSVP for LSP Tunnels," RFC Srinivasan, "RSVP-TE: Extensions to RSVP for LSP Tunnels," RFC
3209. 3209.
18. J. Suurballe, "Disjoint Paths in a Network," Networks, vol. 4, 18. J. Suurballe, "Disjoint Paths in a Network," Networks, vol. 4,
1974. 1974.
19. A. Chie et al., "Impairments And Other Constraints On Optical 19. A. Chiu et al., "Impairments and Other Constraints On Optical
Layer Routing", Internet Draft, Work in Progress. Layer Routing", Internet Draft, Work in Progress.
13. Acknowledgments 12. Acknowledgments
We would like to thank Zouheir Mansourati (Movaz Networks), Ian We would like to thank Zouheir Mansourati (Movaz Networks), Ian
Duncan (Nortel Networks), Dimitri Papadimitriou (Alcatel), and Duncan (Nortel Networks), Dimitri Papadimitriou (Alcatel), and
Dimitrios Pendarakis (Tellium) for their contributions to this Dimitrios Pendarakis (Tellium) for their contributions to this
document. document.
draft-ietf-ipo-framework-02.txt draft-ietf-ipo-framework-03.txt
14. Author's Addresses 13. Contributors
Bala Rajagopalan James V. Luciani Contributors are listed alphabetically.
Debanjan Saha Crescent Networks
Tellium, Inc. 900 Chelmsford St.
2 Crescent Place Lowell, MA 01851
P.O. Box 901 Email: jluciani@CrescentNetworks.com
Oceanport, NJ 07757-0901
Email: {braja, dsaha}@tellium.com
Daniel O. Awduche Bilel Jamoussi Daniel O. Awduche
Movaz Networks Nortel Networks Isocore
7926 Jones Branch Dr. 600 Tech Park 8201 Greensboro Drive, Suite 102,
McLean, VA 22102 Billerica, MA 01821 McLean, VA 22102
Phone: 703-298-5291 Phone: 978-288-4734 Phone: 703-298-5291
Email: awduche@movaz.com Email: jamoussi @nortelnetworks.com Email: awduche@awduche.com
Brad Cain Brad Cain
Cereva Networks Cereva Networks
3 Network Dr. 3 Network Dr.
Marlborough, MA 01752 Marlborough, MA 01752
Email: bcain@cereva.com Email: bcain@cereva.com
Bilel Jamoussi
Nortel Networks
600 Tech Park
Billerica, MA 01821
Phone: 978-288-4734
Email: jamoussi @nortelnetworks.com
James V. Luciani
Independent Consultant
PO Box 1010
Concord, MA 01742
Email: james_luciani@mindspring.com
Bala Rajagopalan
Tellium, Inc.
2 Crescent Place
P.O. Box 901
Oceanport, NJ 07757-0901
Email: braja@tellium.com
Debanjan Saha
Email: debanjan@acm.org
 End of changes. 

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