draft-ietf-ccamp-wson-impairments-08.txt   draft-ietf-ccamp-wson-impairments-09.txt 
Network Working Group Y. Lee Network Working Group Y. Lee
Huawei Huawei
G. Bernstein G. Bernstein
Grotto Networking Grotto Networking
D. Li D. Li
Huawei Huawei
G. Martinelli G. Martinelli
Cisco Cisco
Internet Draft Internet Draft
Intended status: Informational November 23, 2011 Intended status: Informational January 4, 2012
Expires: May 2012 Expires: July 2012
A Framework for the Control of Wavelength Switched Optical Networks A Framework for the Control of Wavelength Switched Optical Networks
(WSON) with Impairments (WSON) with Impairments
draft-ietf-ccamp-wson-impairments-08.txt draft-ietf-ccamp-wson-impairments-09.txt
Abstract Abstract
As an optical signal progresses along its path, it may be altered by As an optical signal progresses along its path, it may be altered by
the various physical processes in the optical fibers and devices it the various physical processes in the optical fibers and devices it
encounters. When such alterations result in signal degradation, encounters. When such alterations result in signal degradation,
these processes are usually referred to as "impairments". These these processes are usually referred to as "impairments". These
physical characteristics may be important constraints to consider physical characteristics may be important constraints to consider
when using a GMPLS control plane to support path setup and when using a GMPLS control plane to support path setup and
maintenance in wavelength switched optical networks. maintenance in wavelength switched optical networks.
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months and may be updated, replaced, or obsoleted by other documents months and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet-Drafts as at any time. It is inappropriate to use Internet-Drafts as
reference material or to cite them other than as "work in progress." reference material or to cite them other than as "work in progress."
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This Internet-Draft will expire on May 23, 2009. This Internet-Draft will expire on July 4, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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Section 4.e of the Trust Legal Provisions and are provided without Section 4.e of the Trust Legal Provisions and are provided without
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Table of Contents Table of Contents
1. Introduction...................................................3 1. Introduction...................................................3
2. Terminology....................................................4 2. Terminology....................................................4
3. Applicability..................................................6 3. Applicability..................................................6
4. Impairment Aware Optical Path Computation......................7 4. Impairment Aware Optical Path Computation......................7
4.1. Optical Network Requirements and Constraints..............8 4.1. Optical Network Requirements and Constraints..............8
4.1.1. Impairment Aware Computation Scenarios...............8 4.1.1. Impairment Aware Computation Scenarios...............8
4.1.2. Impairment Computation and Information Sharing 4.1.2. Impairment Computation and Information Sharing
Constraints.................................................9 Constraints.................................................9
In all the above cases it would be the responsibility of the
authority in control of the "black links" to import the shared
impairment information from the other NEs via the control
plane or other means as necessary..........................11
4.1.3. Impairment Estimation Process.......................11 4.1.3. Impairment Estimation Process.......................11
4.2. IA-RWA Computation and Control Plane Architectures.......12 4.2. IA-RWA Computation and Control Plane Architectures.......12
4.2.1. Combined Routing, WA, and IV........................14 4.2.1. Combined Routing, WA, and IV........................14
4.2.2. Separate Routing, WA, or IV.........................14 4.2.2. Separate Routing, WA, or IV.........................14
4.2.3. Distributed WA and/or IV............................15 4.2.3. Distributed WA and/or IV............................15
4.3. Mapping Network Requirements to Architectures............16 4.3. Mapping Network Requirements to Architectures............16
5. Protocol Implications.........................................18 5. Protocol Implications.........................................18
5.1. Information Model for Impairments........................19 5.1. Information Model for Impairments........................19
5.2. Routing..................................................20 5.2. Routing..................................................19
5.3. Signaling................................................20 5.3. Signaling................................................20
5.4. PCE......................................................21 5.4. PCE......................................................20
5.4.1. Combined IV & RWA...................................21 5.4.1. Combined IV & RWA...................................20
5.4.2. IV-Candidates + RWA.................................21 5.4.2. IV-Candidates + RWA.................................21
5.4.3. Approximate IA-RWA + Separate Detailed IV...........24 5.4.3. Approximate IA-RWA + Separate Detailed IV...........23
6. Security Considerations.......................................25 6. Manageability and Operations..................................25
7. IANA Considerations...........................................26 7. Security Considerations.......................................25
8. References....................................................26 8. IANA Considerations...........................................26
8.1. Normative References.....................................26 9. References....................................................26
8.2. Informative References...................................26 9.1. Normative References.....................................26
9. Acknowledgments...............................................27 9.2. Informative References...................................26
10. Acknowledgments..............................................27
1. Introduction 1. Introduction
Wavelength Switched Optical Networks (WSONs) are constructed from Wavelength Switched Optical Networks (WSONs) are constructed from
subsystems that may include Wavelength Division Multiplexed (WDM) subsystems that may include Wavelength Division Multiplexed (WDM)
links, tunable transmitters and receivers, Reconfigurable Optical links, tunable transmitters and receivers, Reconfigurable Optical
Add/Drop Multiplexers (ROADM), wavelength converters, and electro- Add/Drop Multiplexers (ROADM), wavelength converters, and electro-
optical network elements. A WSON is a wavelength division optical network elements. A WSON is a wavelength division
multiplexed (WDM)-based optical network in which switching is multiplexed (WDM)-based optical network in which switching is
performed selectively based on the center wavelength of an optical performed selectively based on the center wavelength of an optical
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PCE-like entity would not need to perform a full RWA computation, PCE-like entity would not need to perform a full RWA computation,
i.e., it would not need to take into account current wavelength i.e., it would not need to take into account current wavelength
availability on links. Such an approach may require PCEP availability on links. Such an approach may require PCEP
extensions for both the request and response information. extensions for both the request and response information.
3. The authority in control of the "black links" provides a PCE that 3. The authority in control of the "black links" provides a PCE that
performs full IA-RWA services. The difficulty is this requires performs full IA-RWA services. The difficulty is this requires
the one authority to also become the sole source of all RWA the one authority to also become the sole source of all RWA
optimization algorithms. optimization algorithms.
In all the above cases it would be the responsibility of the 4.1.3. In all the above cases it would be the responsibility of the
authority in control of the "black links" to import the shared authority in control of the "black links" to import the shared
impairment information from the other NEs via the control plane or impairment information from the other NEs via the control plane or
other means as necessary. other means as necessary. Impairment Estimation Process
4.1.3. Impairment Estimation Process
The Impairment Estimation Process can be modeled through the The Impairment Estimation Process can be modeled through the
following functional blocks. These blocks are independent of any following functional blocks. These blocks are independent of any
Control Plane architecture, that is, they can be implemented by the Control Plane architecture, that is, they can be implemented by the
same or by different control plane functions as detailed in same or by different control plane functions as detailed in
following sections. following sections.
+-----------------+ +-----------------+
+------------+ +-----------+ | +------------+ | +------------+ +-----------+ | +------------+ |
| | | | | | | | | | | | | | | |
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| |candidates| |----->| +-------+ +--+ | | |Detailed| | | |candidates| |----->| +-------+ +--+ | | |Detailed| |
| +----------+ | | Combined Processes | | +--------+ | | +----------+ | | Combined Processes | | +--------+ |
+--------------+ +----------------------+ | | +--------------+ +----------------------+ | |
(b) +------------+ (b) +------------+
Figure 3 Process flows for the two main detailed impairment Figure 3 Process flows for the two main detailed impairment
validation architectural options. validation architectural options.
The advantages, requirements, and suitability of these detailed The advantages, requirements, and suitability of these detailed
validation options are as follows: validation options are as follows:
o Combined approximate IV & RWA + Detailed-IV o Combined Approximate IV & RWA + Detailed-IV
This alternative combines RWA and approximate IV within a single This alternative combines RWA and approximate IV within a single
computation entity enabling the highest potential optimality and computation entity enabling the highest potential optimality and
efficiency in IA-RWA while keeping a separate entity performing efficiency in IA-RWA while keeping a separate entity performing
detailed impairment validation. In the case of "black links" the detailed impairment validation. In the case of "black links" the
authority controlling the "black links" would need to provide all authority controlling the "black links" would need to provide all
functionality. functionality.
o Candidates-IV + RWA + Detailed-IV o Candidates-IV + RWA + Detailed-IV
This alternative allows separation of approximate impairment This alternative allows separation of approximate impairment
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In term of approximated scenario (see Section 4.1.1.), the model In term of approximated scenario (see Section 4.1.1.), the model
defined by [G.680] will apply and the routing protocol will need to defined by [G.680] will apply and the routing protocol will need to
gather information required for such computation. gather information required for such computation.
In the case of distributed-IV, no new demands would be placed on the In the case of distributed-IV, no new demands would be placed on the
routing protocol. routing protocol.
5.3. Signaling 5.3. Signaling
The largest impacts on signaling occur in the cases where The largest impacts on signaling occur in the cases where
distributed impairment validation is performed. In this case, it ie distributed impairment validation is performed. In this case, it is
necessary to accumulate impairment information as previously necessary to accumulate impairment information as previously
discussed. In addition, since the characteristics of the signal discussed. In addition, since the characteristics of the signal
itself, such as modulation type, can play a major role in the itself, such as modulation type, can play a major role in the
tolerance of impairments, this type of information will need to be tolerance of impairments, this type of information will need to be
implicitly or explicitly signaled so that an impairment validation implicitly or explicitly signaled so that an impairment validation
decision can be made at the destination node. decision can be made at the destination node.
It remains for further study if it may be beneficial to include It remains for further study if it may be beneficial to include
additional information to a connection request such as desired additional information to a connection request such as desired
egress signal quality (defined in some appropriate sense) in non- egress signal quality (defined in some appropriate sense) in non-
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Coordinating-PCE, and the IV-Candidates-PCE. Coordinating-PCE, and the IV-Candidates-PCE.
In step (a), the PCC requests a path meeting specified quality In step (a), the PCC requests a path meeting specified quality
constraints between two nodes (A and Z) for a given signal constraints between two nodes (A and Z) for a given signal
represented either by a specific type or a general class with represented either by a specific type or a general class with
associated parameters. In step (b), the RWA-Coordinating-PCE associated parameters. In step (b), the RWA-Coordinating-PCE
requests up to K candidate paths between nodes A and Z and requests up to K candidate paths between nodes A and Z and
associated acceptable wavelengths. The term "K candidate paths" is associated acceptable wavelengths. The term "K candidate paths" is
associated with K-shortest path algorithm. It refers to an algorithm associated with K-shortest path algorithm. It refers to an algorithm
that finds multiple K short paths connecting the source and the that finds multiple K short paths connecting the source and the
destination in a graph (allowing repeated vertices and edges in the destination in a graph allowing repeated vertices and edges in the
paths) [Eppstein]. paths. See details in [Eppstein].
In step (c), The IV-Candidates PCE returns this list to the RWA- In step (c), The IV-Candidates PCE returns this list to the RWA-
Coordinating PCE which then uses this set of paths and wavelengths Coordinating PCE which then uses this set of paths and wavelengths
as input (e.g., a constraint) to its RWA computation. In step (d) as input (e.g., a constraint) to its RWA computation. In step (d)
the RWA-Coordinating PCE returns the overall IA-RWA computation the RWA-Coordinating PCE returns the overall IA-RWA computation
results to the PCC. results to the PCC.
5.4.3. Approximate IA-RWA + Separate Detailed IV 5.4.3. Approximate IA-RWA + Separate Detailed IV
Previously, Figure 3 showed two cases where a separate detailed Previously, Figure 3 showed two cases where a separate detailed
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| | _____.....-----''''' | | | _____.....-----''''' |
| |<----''''' | | |<----''''' |
| (f) __.| | | (f) __.| |
| __.--'' | | __.--'' |
|<-'' | |<-'' |
| | | |
Figure 6 Sequence diagram for the interactions between PCC, RWA- Figure 6 Sequence diagram for the interactions between PCC, RWA-
Coordinating-PCE, IV-Candidates-PCE, and IV-Detailed-PCE. Coordinating-PCE, IV-Candidates-PCE, and IV-Detailed-PCE.
6. Security Considerations 6. Manageability and Operations
The issues concerning manageability and operations are beyond the
scope of this document. The details of manageability and operational
issues will have to be deferred to future protocol implementation.
On a high-level, the GMPLS-routing based architecture discussed in
Section 5.2. may have to deal with how to resolve potential scaling
issues associated with disseminating a large amount of impairment
characteristics of the network elements and links.
From a scaling point of view, the GMPLS-signaling based architecture
discussed in Section 5.3. would be more scalable than other
alternatives as this architecture would avoid the dissemination of a
large amount of data to the networks. This benefit may come,
however, at the expense of potentially inefficient use of network
resources.
The PCE-based architectures discussed in Section 5.4. would have to
consider operational complexity when implementing options that
require the use of multiple PCE servers. The most serious case is
the option discussed in Section 5.4.3., namely, "Approximate IA-RWA
+ Separate Detailed IV". The combined IV & RWA option (which was
discussed on Section 5.4.1.), on the other hand, is simpler than
other alternatives to operate as one PCE server handles all
functionality; however, this option may suffer from a heavy
computation and processing burden compared to other alternatives.
Interoperability may be a hurdle to overcome when trying to agree on
some impairment parameters especially those which are associated
with the black links. This work has been in progress in ITU-T and
needs some more time to mature.
7. Security Considerations
This document discusses a number of control plane architectures that This document discusses a number of control plane architectures that
incorporate knowledge of impairments in optical networks. If such incorporate knowledge of impairments in optical networks. If such
architecture is put into use within a network, it will by its nature architecture is put into use within a network, it will by its nature
contain details of the physical characteristics of an optical contain details of the physical characteristics of an optical
network. Such information would need to be protected from network. Such information would need to be protected from
intentional or unintentional disclosure similar to other network intentional or unintentional disclosure similar to other network
information used within intra-domain protocols. information used within intra-domain protocols.
This document does not require changes to the security models within This document does not require changes to the security models within
GMPLS and associated protocols. That is, the OSPF-TE, RSVP-TE, and GMPLS and associated protocols. That is, the OSPF-TE, RSVP-TE, and
PCEP security models could be operated unchanged. However, PCEP security models could be operated unchanged. However,
satisfying the requirements for impairment information dissemination satisfying the requirements for impairment information dissemination
using the existing protocols may significantly affect the loading of using the existing protocols may significantly affect the loading of
those protocols. those protocols.
This may make the operation of the network more vulnerable to active This may make the operation of the network more vulnerable to active
attacks such as injections, impersonation, and MITMs. Therefore, attacks such as injections, impersonation, and MITMs. Therefore,
additional care maybe required to ensure that the protocols are additional care may be required to ensure that the protocols are
secure in the impairment-aware WSON environment. secure in the impairment-aware WSON environment.
Furthermore, the additional information distributed in order to Furthermore, the additional information distributed in order to
address impairment information represents a disclosure of network address impairment information represents a disclosure of network
capabilities that an operator may wish to keep private. capabilities that an operator may wish to keep private.
Consideration should be given to securing this information. For a Consideration should be given to securing this information. For a
general discussion on MPLS- and GMPLS-related security issues, see general discussion on MPLS- and GMPLS-related security issues, see
the MPLS/GMPLS security framework [RFC5920] and, in particular, text the MPLS/GMPLS security framework [RFC5920] and, in particular, text
detailing security issues when Control Plane is physically separated detailing security issues when Control Plane is physically separated
from Data Plane. from Data Plane.
7. IANA Considerations 8. IANA Considerations
This draft does not currently require any consideration from IANA. This draft does not currently require any consideration from IANA.
8. References 9. References
8.1. Normative References 9.1. Normative References
[G.680] ITU-T Recommendation G.680, Physical transfer functions of [G.680] ITU-T Recommendation G.680, Physical transfer functions of
optical network elements, July 2007. optical network elements, July 2007.
[RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label [RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture", RFC 3945, October 2004. Switching (GMPLS) Architecture", RFC 3945, October 2004.
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path [RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655, Computation Element (PCE)-Based Architecture", RFC 4655,
August 2006. August 2006.
8.2. Informative References 9.2. Informative References
[G.Sup39] ITU-T Series G Supplement 39, Optical system design and [G.Sup39] ITU-T Series G Supplement 39, Optical system design and
engineering considerations, February 2006. engineering considerations, February 2006.
[G.698.1] ITU-T Recommendation G.698.1, Multichannel DWDM [G.698.1] ITU-T Recommendation G.698.1, Multichannel DWDM
applications with Single-Channel optical interface, applications with Single-Channel optical interface,
December 2006. December 2006.
[G.698.2] ITU-T Recommendation G.698.2, Amplified multichannel DWDM [G.698.2] ITU-T Recommendation G.698.2, Amplified multichannel DWDM
applications with Single-Channel optical interface, July applications with Single-Channel optical interface, July
2007. 2007.
[RFC4054] Strand, J., Ed., and A. Chiu, Ed., "Impairments and Other [RFC4054] Strand, J., Ed., and A. Chiu, Ed., "Impairments and Other
Constraints on Optical Layer Routing", RFC 4054, May 2005. Constraints on Optical Layer Routing", RFC 4054, May 2005.
[RFC6163] Y. Lee, G. Bernstein, W. Imajuku, "Framework for GMPLS and [RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
PCE Control of Wavelength Switched Optical Networks", RFC Networks", RFC 5920, July 2010.
6163, April 2011. [Eppstein]D. Eppstein, "Finding the k
shortest paths," 35th IEEE Symp. Foundations of Comp.
Sci., Santa Fe, pp. 154-165, 1994.
9. Acknowledgments [RFC6163] Lee, Y., Ed., G. Bernstein, Ed., and W. Imajuku,
"Framework for GMPLS and PCE Control of Wavelength
Switched Optical Networks", RFC 6163, April 2011.
[Eppstein] Eppstein, D., "Finding the k shortest paths", 35th IEEE
Symp. Foundations of Comp. Sci., Santa Fe, pp. 154-165,
1994.
10. Acknowledgments
This document was prepared using 2-Word-v2.0.template.dot. This document was prepared using 2-Word-v2.0.template.dot.
Copyright (c) 2011 IETF Trust and the persons identified as authors Copyright (c) 2012 IETF Trust and the persons identified as authors
of the code. All rights reserved. of the code. All rights reserved.
Redistribution and use in source and binary forms, with or without Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions modification, are permitted provided that the following conditions
are met: are met:
o Redistributions of source code must retain the above copyright o Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer. notice, this list of conditions and the following disclaimer.
o Redistributions in binary form must reproduce the above copyright o Redistributions in binary form must reproduce the above copyright
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