draft-ietf-mpls-tp-requirements-08.txt   draft-ietf-mpls-tp-requirements-09.txt 
MPLS Working Group B. Niven-Jenkins, Ed. MPLS Working Group B. Niven-Jenkins, Ed.
Internet-Draft BT Internet-Draft BT
Intended status: Standards Track D. Brungard, Ed. Intended status: Standards Track D. Brungard, Ed.
Expires: November 19, 2009 AT&T Expires: December 24, 2009 AT&T
M. Betts, Ed. M. Betts, Ed.
Nortel Networks Nortel Networks
N. Sprecher N. Sprecher
Nokia Siemens Networks Nokia Siemens Networks
S. Ueno S. Ueno
NTT NTT
May 18, 2009 June 22, 2009
MPLS-TP Requirements MPLS-TP Requirements
draft-ietf-mpls-tp-requirements-08 draft-ietf-mpls-tp-requirements-09
Status of this Memo Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in 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.
This Internet-Draft will expire on November 19, 2009. This Internet-Draft will expire on December 24, 2009.
Copyright Notice Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the Copyright (c) 2009 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 in effect on the date of Provisions Relating to IETF Documents in effect on the date of
publication of this document (http://trustee.ietf.org/license-info). publication of this document (http://trustee.ietf.org/license-info).
Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
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2.3. Data plane requirements . . . . . . . . . . . . . . . . . 17 2.3. Data plane requirements . . . . . . . . . . . . . . . . . 17
2.4. Control plane requirements . . . . . . . . . . . . . . . . 18 2.4. Control plane requirements . . . . . . . . . . . . . . . . 18
2.5. Network Management requirements . . . . . . . . . . . . . 20 2.5. Network Management requirements . . . . . . . . . . . . . 20
2.6. Operation, Administration and Maintenance (OAM) 2.6. Operation, Administration and Maintenance (OAM)
requirements . . . . . . . . . . . . . . . . . . . . . . . 20 requirements . . . . . . . . . . . . . . . . . . . . . . . 20
2.7. Network performance monitoring requirements . . . . . . . 20 2.7. Network performance monitoring requirements . . . . . . . 20
2.8. Recovery requirements . . . . . . . . . . . . . . . . . . 20 2.8. Recovery requirements . . . . . . . . . . . . . . . . . . 20
2.8.1. Data plane behavior requirements . . . . . . . . . . . 21 2.8.1. Data plane behavior requirements . . . . . . . . . . . 21
2.8.1.1. Protection . . . . . . . . . . . . . . . . . . . . 21 2.8.1.1. Protection . . . . . . . . . . . . . . . . . . . . 21
2.8.1.2. Sharing of protection resources . . . . . . . . . 22 2.8.1.2. Sharing of protection resources . . . . . . . . . 22
2.8.1.3. Reversion . . . . . . . . . . . . . . . . . . . . 22
2.8.2. Restoration . . . . . . . . . . . . . . . . . . . . . 22 2.8.2. Restoration . . . . . . . . . . . . . . . . . . . . . 22
2.8.3. Triggers for protection, restoration, and reversion . 23 2.8.3. Triggers for protection, restoration, and reversion . 23
2.8.4. Management plane operation of protection and 2.8.4. Management plane operation of protection and
restoration . . . . . . . . . . . . . . . . . . . . . 23 restoration . . . . . . . . . . . . . . . . . . . . . 23
2.8.5. Control plane and in-band OAM operation of recovery . 24 2.8.5. Control plane and in-band OAM operation of recovery . 24
2.8.6. Topology-specific recovery mechanisms . . . . . . . . 25 2.8.6. Topology-specific recovery mechanisms . . . . . . . . 25
2.8.6.1. Ring protection . . . . . . . . . . . . . . . . . 25 2.8.6.1. Ring protection . . . . . . . . . . . . . . . . . 25
2.9. QoS requirements . . . . . . . . . . . . . . . . . . . . . 28 2.9. QoS requirements . . . . . . . . . . . . . . . . . . . . . 28
2.10. Security requirements . . . . . . . . . . . . . . . . . . 28 2.10. Security requirements . . . . . . . . . . . . . . . . . . 28
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28
4. Security Considerations . . . . . . . . . . . . . . . . . . . 29 4. Security Considerations . . . . . . . . . . . . . . . . . . . 28
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 29 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 29
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
6.1. Normative References . . . . . . . . . . . . . . . . . . . 29 6.1. Normative References . . . . . . . . . . . . . . . . . . . 29
6.2. Informative References . . . . . . . . . . . . . . . . . . 30 6.2. Informative References . . . . . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31
1. Introduction 1. Introduction
Bandwidth demand continues to grow worldwide, stimulated by the Bandwidth demand continues to grow worldwide, stimulated by the
accelerating growth and penetration of new packet based services and accelerating growth and penetration of new packet based services and
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architectures as defined by IETF and packet transport networks as architectures as defined by IETF and packet transport networks as
defined by ITU-T. The requirements of MPLS-TP are provided below. defined by ITU-T. The requirements of MPLS-TP are provided below.
The relevant functions of MPLS and PWE3 are included in MPLS-TP, The relevant functions of MPLS and PWE3 are included in MPLS-TP,
except where explicitly excluded. except where explicitly excluded.
Although both static and dynamic configuration of MPLS-TP transport Although both static and dynamic configuration of MPLS-TP transport
paths (including Operations, Administration and Maintenance (OAM) and paths (including Operations, Administration and Maintenance (OAM) and
protection capabilities) is required by this document, it MUST be protection capabilities) is required by this document, it MUST be
possible for operators to be able to completely operate (including possible for operators to be able to completely operate (including
OAM and protection capabilities) an MPLS-TP network in the absence of OAM and protection capabilities) an MPLS-TP network in the absence of
any control plane protocols for dynamic configuration. any control plane.
1.1. Terminology 1.1. Terminology
Note: Mapping between the terms in this section and ITU-T terminology Note: Mapping between the terms in this section and ITU-T terminology
is described in [I-D.helvoort-mpls-tp-rosetta-stone]. is described in [I-D.helvoort-mpls-tp-rosetta-stone].
The recovery requirements in this document use the recovery The recovery requirements in this document use the recovery
terminology defined in RFC 4427 [RFC4427], this is applied to both terminology defined in RFC 4427 [RFC4427], this is applied to both
control plane and management plane based operations of MPLS-TP control plane and management plane based operations of MPLS-TP
transport paths. transport paths.
1.1.1. Abbreviations 1.1.1. Abbreviations
ASON: Automatically Switched Optical Network ASON: Automatically Switched Optical Network
ASTN: Automatic Switched Transport Network
ATM: Asynchronous Transfer Mode ATM: Asynchronous Transfer Mode
CAPEX: Capital Expenditure CAPEX: Capital Expenditure
CE: Customer Edge CE: Customer Edge
FR: Frame Relay FR: Frame Relay
GMPLS: Generalised Multi-Protocol Label Switching
GMPLS: Generalised Multi-Protocol Label Switching
IGP: Interior Gateway Protocol IGP: Interior Gateway Protocol
IPTV: IP Television IPTV: IP Television
L2: Layer 2 L2: Layer 2
L3: Layer 3 L3: Layer 3
LSP: Label Switched Path LSP: Label Switched Path
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P2P: Point to Point P2P: Point to Point
PDU: Protocol Data Unit PDU: Protocol Data Unit
PSC: Protection State Coordination PSC: Protection State Coordination
PW: Pseudo Wire PW: Pseudo Wire
QoS: Quality of Service QoS: Quality of Service
RAN: Radio Access Network
SDH: Synchronous Digital Hierarchy SDH: Synchronous Digital Hierarchy
SLA: Service Level Agreement SLA: Service Level Agreement
SLS: Service Level Specification SLS: Service Level Specification
S-PE: Switching Provider Edge S-PE: Switching Provider Edge
SONET: Synchronous Optical Network SONET: Synchronous Optical Network
SRLG: Shared Risk Link Group SRLG: Shared Risk Link Group
TCO: Total Cost of Ownership TCO: Total Cost of Ownership
T-PE: Terminating Provider Edge T-PE: Terminating Provider Edge
VoIP: Voice over IP VoIP: Voice over IP
VPN: Virtual Private Network VPN: Virtual Private Network
WDM: Wavelength Division Multiplexing WDM: Wavelength Division Multiplexing
1.1.2. Definitions 1.1.2. Definitions
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6 MPLS-TP MUST be a connection-oriented packet switching technology 6 MPLS-TP MUST be a connection-oriented packet switching technology
with traffic engineering capabilities that allow deterministic with traffic engineering capabilities that allow deterministic
control of the use of network resources. control of the use of network resources.
7 MPLS-TP MUST support traffic engineered point to point (P2P) and 7 MPLS-TP MUST support traffic engineered point to point (P2P) and
point to multipoint (P2MP) transport paths. point to multipoint (P2MP) transport paths.
8 MPLS-TP MUST support unidirectional, co-routed bidirectional and 8 MPLS-TP MUST support unidirectional, co-routed bidirectional and
associated bidirectional point-to-point transport paths. associated bidirectional point-to-point transport paths.
9 The end points of a co-routed bidirectional transport path MUST 9 MPLS-TP MUST support unidirectional point-to-multipoint transport
paths.
10 The end points of a co-routed bidirectional transport path MUST
be aware of the pairing relationship of the forward and reverse be aware of the pairing relationship of the forward and reverse
paths used to support the bidirectional service. paths used to support the bidirectional service.
10 All nodes on the path of a co-routed bidirectional transport path 11 All nodes on the path of a co-routed bidirectional transport path
in the same (sub-)layer as the path MUST be aware of the pairing in the same (sub-)layer as the path MUST be aware of the pairing
relationship of the forward and the backward directions of the relationship of the forward and the backward directions of the
transport path. transport path.
11 The end points of an associated bidirectional transport path MUST 12 The end points of an associated bidirectional transport path MUST
be aware of the pairing relationship of the forward and reverse be aware of the pairing relationship of the forward and reverse
paths used to support the bidirectional service. paths used to support the bidirectional service.
12 Nodes on the path of an associated bidirectional transport path 13 Nodes on the path of an associated bidirectional transport path
where both the forward and backward directions transit the same where both the forward and backward directions transit the same
node in the same (sub-)layer as the path SHOULD be aware of the node in the same (sub-)layer as the path SHOULD be aware of the
pairing relationship of the forward and the backward directions pairing relationship of the forward and the backward directions
of the transport path. of the transport path.
13 MPLS-TP MUST support bidirectional transport paths with symmetric 14 MPLS-TP MUST support bidirectional transport paths with symmetric
bandwidth requirements, i.e. the amount of reserved bandwidth is bandwidth requirements, i.e. the amount of reserved bandwidth is
the same between the forward and backward directions. the same between the forward and backward directions.
14 MPLS-TP MUST support bidirectional transport paths with 15 MPLS-TP MUST support bidirectional transport paths with
asymmetric bandwidth requirements, i.e. the amount of reserved asymmetric bandwidth requirements, i.e. the amount of reserved
bandwidth differs between the forward and backward directions. bandwidth differs between the forward and backward directions.
15 MPLS-TP MUST support the logical separation of the control and 16 MPLS-TP MUST support the logical separation of the control and
management planes from the data plane. management planes from the data plane.
16 MPLS-TP MUST support the physical separation of the control and 17 MPLS-TP MUST support the physical separation of the control and
management planes from the data plane. management planes from the data plane.
17 MPLS-TP MUST support static provisioning of transport paths via 18 MPLS-TP MUST support static provisioning of transport paths via
the management plane. the management plane.
18 Mechanisms in an MPLS-TP layer network that satisfy functional 19 A solution MUST be defined to support dynamic provisioning and
restoration of MPLS-TP transport paths via a control plane.
20 Static provisioning MUST NOT depend on the presence of any
element of a control plane.
21 MPLS-TP MUST support the co-existence of statically and
dynamically provisioned/managed MPLS-TP transport paths within
the same layer network or domain.
22 Mechanisms in an MPLS-TP layer network that satisfy functional
requirements that are common to general transport layer networks requirements that are common to general transport layer networks
(i.e., independent of technology) SHOULD be operable in a way (i.e., independent of technology) SHOULD be operable in a way
that is similar to the way the equivalent mechanisms are operated that is similar to the way the equivalent mechanisms are operated
in other transport layer technologies. in other transport layer technologies.
19 Static provisioning MUST NOT depend on the presence of any 23 MPLS-TP MUST support the capability for network operation
element of a control plane.
20 MPLS-TP MUST support the capability for network operation
(including OAM and recovery) via the management plane (without (including OAM and recovery) via the management plane (without
the use of any control plane protocols). the use of any control plane protocols).
21 A solution MUST be defined to support dynamic provisioning and 24 The MPLS-TP data plane MUST be capable of
restoration of MPLS-TP transport paths via a control plane.
22 MPLS-TP MUST support the co-existence of statically and
dynamically provisioned/managed MPLS-TP transport paths within
the same layer network or domain.
23 The MPLS-TP data plane MUST be capable of
A. forwarding data independent of the control or management A. forwarding data independent of the control or management
plane used to configure and operate the MPLS-TP layer plane used to configure and operate the MPLS-TP layer
network. network.
B. taking recovery actions independent of the control or B. taking recovery actions independent of the control or
management plane used to configure the MPLS-TP layer network. management plane used to configure the MPLS-TP layer network.
C. operating normally (i.e. forwarding, OAM and protection MUST C. operating normally (i.e. forwarding, OAM and protection MUST
continue to operate) if the management plane or control plane continue to operate) if the management plane or control plane
that configured the transport paths fails. that configured the transport paths fails.
24 MPLS-TP MUST support mechanisms to avoid or minimize traffic 25 MPLS-TP MUST support mechanisms to avoid or minimize traffic
impact (e.g. packet delay, reordering and loss) during network impact (e.g. packet delay, reordering and loss) during network
reconfiguration. reconfiguration.
25 MPLS-TP MUST support transport paths through multiple homogeneous 26 MPLS-TP MUST support transport paths through multiple homogeneous
domains. domains.
26 MPLS-TP SHOULD support transport paths through multiple non- 27 MPLS-TP SHOULD support transport paths through multiple non-
homogeneous domains. homogeneous domains.
27 MPLS-TP MUST NOT dictate the deployment of any particular network 28 MPLS-TP MUST NOT dictate the deployment of any particular network
topology either physical or logical, however: topology either physical or logical, however:
A. It MUST be possible to deploy MPLS-TP in rings. A. It MUST be possible to deploy MPLS-TP in rings.
B. It MUST be possible to deploy MPLS-TP in arbitrarily B. It MUST be possible to deploy MPLS-TP in arbitrarily
interconnected rings with one or two points of interconnected rings with one or two points of
interconnection. interconnection.
C. MPLS-TP MUST support rings of at least 16 nodes in order to C. MPLS-TP MUST support rings of at least 16 nodes in order to
support the upgrade of existing TDM rings to MPLS-TP. support the upgrade of existing TDM rings to MPLS-TP.
MPLS-TP SHOULD support rings with more than 16 nodes. MPLS-TP SHOULD support rings with more than 16 nodes.
28 MPLS-TP MUST be able to scale at least as well as existing 29 MPLS-TP MUST be able to scale at least as well as existing
transport technologies with growing and increasingly complex transport technologies with growing and increasingly complex
network topologies as well as with increasing bandwidth demands, network topologies as well as with increasing bandwidth demands,
number of customers, and number of services. number of customers, and number of services.
29 MPLS-TP SHOULD support mechanisms to safeguard against the 30 MPLS-TP SHOULD support mechanisms to safeguard against the
provisioning of transport paths which contain forwarding loops. provisioning of transport paths which contain forwarding loops.
2.2. Layering requirements 2.2. Layering requirements
30 A generic and extensible solution MUST be provided to support the 31 A generic and extensible solution MUST be provided to support the
transport of one or more client layer networks (e.g. MPLS-TP, transport of one or more client layer networks (e.g. MPLS-TP,
IP, MPLS, Ethernet, ATM, FR, etc.) over an MPLS-TP layer network. IP, MPLS, Ethernet, ATM, FR, etc.) over an MPLS-TP layer network.
31 A generic and extensible solution MUST be provided to support the 32 A generic and extensible solution MUST be provided to support the
transport of MPLS-TP transport paths over one or more server transport of MPLS-TP transport paths over one or more server
layer networks (such as MPLS-TP, Ethernet, SONET/SDH, OTN, etc.). layer networks (such as MPLS-TP, Ethernet, SONET/SDH, OTN, etc.).
Requirements for bandwidth management within a server layer Requirements for bandwidth management within a server layer
network are outside the scope of this document. network are outside the scope of this document.
32 In an environment where an MPLS-TP layer network is supporting a 33 In an environment where an MPLS-TP layer network is supporting a
client layer network, and the MPLS-TP layer network is supported client layer network, and the MPLS-TP layer network is supported
by a server layer network then operation of the MPLS-TP layer by a server layer network then operation of the MPLS-TP layer
network MUST be possible without any dependencies on the server network MUST be possible without any dependencies on the server
or client layer network. or client layer network.
A. The server layer MUST guarantee that the traffic loading A. The server layer MUST guarantee that the traffic loading
imposed by other clients does not cause the transport service imposed by other clients does not cause the transport service
provided to the MPLS-TP layer to fall bellow the agreed provided to the MPLS-TP layer to fall below the agreed level.
level. Mechanisms to achieve this are outside the scope of
these requirements. Mechanisms to achieve this are outside the scope of these
requirements.
B. It MUST be possible to isolate the control and management B. It MUST be possible to isolate the control and management
planes of the MPLS-TP layer network from the control and planes of the MPLS-TP layer network from the control and
management planes of the client and server layer networks. management planes of the client and server layer networks.
33 A solution MUST be provided to support the transport of a client 34 A solution MUST be provided to support the transport of a client
MPLS or MPLS-TP layer network over a server MPLS or MPLS-TP layer MPLS or MPLS-TP layer network over a server MPLS or MPLS-TP layer
network. network.
A. The level of co-ordination required between the client and A. The level of co-ordination required between the client and
server MPLS(-TP) layer networks MUST be minimized (preferably server MPLS(-TP) layer networks MUST be minimized (preferably
no co-ordination will be required). no co-ordination will be required).
B. The MPLS(-TP) server layer network MUST be capable of B. The MPLS(-TP) server layer network MUST be capable of
transporting the complete set of packets generated by the transporting the complete set of packets generated by the
client MPLS(-TP) layer network, which may contain packets client MPLS(-TP) layer network, which may contain packets
that are not MPLS packets (e.g. IP or CNLS packets used by that are not MPLS packets (e.g. IP or CNLS packets used by
the control/management plane of the client MPLS(-TP) layer the control/management plane of the client MPLS(-TP) layer
network). network).
34 It MUST be possible to operate the layers of a multi-layer 35 It MUST be possible to operate the layers of a multi-layer
network that includes an MPLS-TP layer autonomously. network that includes an MPLS-TP layer autonomously.
The above are not only technology requirements, but also operational The above are not only technology requirements, but also operational
requirements. Different administrative groups may be responsible for requirements. Different administrative groups may be responsible for
the same layer network or different layer networks. the same layer network or different layer networks.
35 It MUST be possible to hide MPLS-TP layer network addressing and 36 It MUST be possible to hide MPLS-TP layer network addressing and
other information (e.g. topology) from client layer networks. other information (e.g. topology) from client layer networks.
However, it SHOULD be possible, at the option of the operator, to However, it SHOULD be possible, at the option of the operator, to
leak a limited amount of summarized information (such as SRLGs or leak a limited amount of summarized information (such as SRLGs or
reachability) between layers. reachability) between layers.
2.3. Data plane requirements 2.3. Data plane requirements
36 It MUST be possible for the end points of an MPLS-TP transport 37 It MUST be possible to operate and configure the MPLS-TP data
plane without any IP forwarding capability in the MPLS-TP data
plane. i.e. the data plane only operates on the MPLS label.
38 It MUST be possible for the end points of an MPLS-TP transport
path that is carrying an aggregate of client transport paths to path that is carrying an aggregate of client transport paths to
be able to decompose the aggregate transport path into its be able to decompose the aggregate transport path into its
component client transport paths. component client transport paths.
37 A transport path on a link MUST be uniquely identifiable by a 39 A transport path on a link MUST be uniquely identifiable by a
single label on that link. single label on that link.
38 A transport path's source MUST be identifiable at its destination 40 A transport path's source MUST be identifiable at its destination
within its layer network. within its layer network.
39 MPLS-TP MUST be capable of using P2MP server (sub-)layer 41 MPLS-TP MUST be capable of using P2MP server (sub-)layer
capabilities as well as P2P server (sub-)layer capabilities when capabilities as well as P2P server (sub-)layer capabilities when
supporting P2MP MPLS-TP transport paths. supporting P2MP MPLS-TP transport paths.
40 MPLS-TP MUST support unidirectional point-to-multipoint transport 42 MPLS-TP MUST be extensible in order to accommodate new types of
paths.
41 MPLS-TP MUST be extensible in order to accommodate new types of
client layer networks and services. client layer networks and services.
42 MPLS-TP SHOULD support mechanisms to enable the reserved 43 MPLS-TP SHOULD support mechanisms to enable the reserved
bandwidth associated with a transport path to be increased bandwidth associated with a transport path to be increased
without impacting the existing traffic on that transport path without impacting the existing traffic on that transport path
provided enough resources are available. provided enough resources are available.
43 MPLS-TP SHOULD support mechanisms to enable the reserved 44 MPLS-TP SHOULD support mechanisms to enable the reserved
bandwidth of a transport path to be decreased without impacting bandwidth of a transport path to be decreased without impacting
the existing traffic on that transport path, provided that the the existing traffic on that transport path, provided that the
level of existing traffic is smaller than the reserved bandwidth level of existing traffic is smaller than the reserved bandwidth
following the decrease. following the decrease.
44 MPLS-TP MUST support mechanisms which ensure the integrity of the 45 MPLS-TP MUST support mechanisms which ensure the integrity of the
transported customer's service traffic as required by its transported customer's service traffic as required by its
associated SLA. Loss of integrity may be defined as packet associated SLA. Loss of integrity may be defined as packet
corruption, re-ordering or loss during normal network conditions. corruption, re-ordering or loss during normal network conditions.
45 MPLS-TP MUST support mechanisms to detect when loss of integrity 46 MPLS-TP MUST support mechanisms to detect when loss of integrity
of the transported customer's service traffic has occurred. of the transported customer's service traffic has occurred.
46 MPLS-TP MUST support an unambiguous and reliable means of 47 MPLS-TP MUST support an unambiguous and reliable means of
distinguishing users' (client) packets from MPLS-TP control distinguishing users' (client) packets from MPLS-TP control
packets (e.g. control plane, management plane, OAM and protection packets (e.g. control plane, management plane, OAM and protection
switching packets). switching packets).
2.4. Control plane requirements 2.4. Control plane requirements
This section defines the requirements that apply to an MPLS-TP This section defines the requirements that apply to an MPLS-TP
control plane. Note that it MUST be possible to operate an MPLS-TP control plane. Note that it MUST be possible to operate an MPLS-TP
network without using a control plane. network without using a control plane.
The ITU-T has defined an architecture for Automatically Switched The ITU-T has defined an architecture for Automatically Switched
Optical Networks (ASON) in G.8080 [ITU.G8080.2006] and G.8080 Amd1 Optical Networks (ASON) in G.8080 [ITU.G8080.2006] and G.8080 Amd1
[ITU.G8080.2008]. The control plane for MPLS-TP MUST fit within the [ITU.G8080.2008]. The control plane for MPLS-TP MUST fit within the
ASON architecture. ASON architecture.
An interpretation of the ASON/ASTN signaling and routing requirements An interpretation of the ASON signaling and routing requirements in
in the context of GMPLS can be found in [RFC4139] and [RFC4258]. the context of GMPLS can be found in [RFC4139] and [RFC4258].
Additionally: Additionally:
47 It MUST be possible to operate and configure the MPLS-TP data
plane without any IP forwarding capability in the MPLS-TP data
plane. i.e. the data plane only operates on the MPLS label.
48 The MPLS-TP control plane MUST support control plane topology and 48 The MPLS-TP control plane MUST support control plane topology and
data plane topology independence. As a consequence a failure of data plane topology independence. As a consequence a failure of
the control plane does not imply that there has also been a the control plane does not imply that there has also been a
failure of the data plane. failure of the data plane.
49 The MPLS-TP control plane MUST be able to be operated independent 49 The MPLS-TP control plane MUST be able to be operated independent
of any particular client or server layer control plane. of any particular client or server layer control plane.
50 MPLS-TP SHOULD define a solution to support an integrated control 50 MPLS-TP SHOULD define a solution to support an integrated control
plane encompassing MPLS-TP together with its server and client plane encompassing MPLS-TP together with its server and client
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59 MPLS-TP recovery paths MUST meet the SLA protection objectives of 59 MPLS-TP recovery paths MUST meet the SLA protection objectives of
the service. the service.
A. MPLS-TP MUST provide mechanisms to guarantee 50ms recovery A. MPLS-TP MUST provide mechanisms to guarantee 50ms recovery
times from the moment of fault detection in networks with times from the moment of fault detection in networks with
spans less than 1200 km. spans less than 1200 km.
B. For protection it MUST be possible to require protection of B. For protection it MUST be possible to require protection of
100% of the traffic on the protected path. 100% of the traffic on the protected path.
C. Recovery objectives SHOULD be configurable per transport C. Recovery MUST meet SLA requirements over multiple domains.
path.
D. Recovery MUST meet SLA requirements over multiple domains. 60 Recovery objectives SHOULD be configurable per transport path.
60 The recovery mechanisms SHOULD be applicable to any topology. 61 The recovery mechanisms SHOULD be applicable to any topology.
61 The recovery mechanisms MUST support the means to operate in 62 The recovery mechanisms MUST support the means to operate in
synergy with (including coordination of timing) the recovery synergy with (including coordination of timing) the recovery
mechanisms present in any client or server transport networks mechanisms present in any client or server transport networks
(for example, Ethernet, SDH, OTN, WDM) to avoid race conditions (for example, Ethernet, SDH, OTN, WDM) to avoid race conditions
between the layers. between the layers.
62 MPLS-TP recovery and reversion mechanisms MUST prevent frequent 63 MPLS-TP recovery and reversion mechanisms MUST prevent frequent
operation of recovery in the event of an intermittent defect. operation of recovery in the event of an intermittent defect.
2.8.1. Data plane behavior requirements 2.8.1. Data plane behavior requirements
General protection and survivability requirements are expressed in General protection and survivability requirements are expressed in
terms of the behavior in the data plane. terms of the behavior in the data plane.
2.8.1.1. Protection 2.8.1.1. Protection
Note: Only nodes that are aware of the pairing relationship between Note: Only nodes that are aware of the pairing relationship between
the forward and backward directions of an associated bidirectional the forward and backward directions of an associated bidirectional
transport path can be used as end points to protect all or part of transport path can be used as end points to protect all or part of
that transport path. that transport path.
63 It MUST be possible to provide protection for the MPLS-TP data 64 It MUST be possible to provide protection for the MPLS-TP data
plane without any IP forwarding capability in the MPLS-TP data plane without any IP forwarding capability in the MPLS-TP data
plane. i.e. the data plane only operates on the MPLS label. plane. i.e. the data plane only operates on the MPLS label.
64 MPLS-TP MUST support 1+1 protection. 65 MPLS-TP protection mechanisms MUST support revertive and non-
revertive behavior.
66 MPLS-TP MUST support 1+1 protection.
A. Bidirectional 1+1 protection for P2P connectivity MUST be A. Bidirectional 1+1 protection for P2P connectivity MUST be
supported. supported.
B. Unidirectional 1+1 protection for P2P connectivity MUST be B. Unidirectional 1+1 protection for P2P connectivity MUST be
supported. supported.
C. Unidirectional 1+1 protection for P2MP connectivity MUST be C. Unidirectional 1+1 protection for P2MP connectivity MUST be
supported. supported.
65 MPLS-TP MUST support the ability to share protection resources 67 MPLS-TP MUST support the ability to share protection resources
amongst a number of transport paths. amongst a number of transport paths.
66 MPLS-TP MUST support 1:n protection (including 1:1 protection). 68 MPLS-TP MUST support 1:n protection (including 1:1 protection).
A. Bidirectional 1:n protection for P2P connectivity MUST be A. Bidirectional 1:n protection for P2P connectivity MUST be
supported, and SHOULD be the default behavior for 1:n supported, and SHOULD be the default behavior for 1:n
protection. protection.
B. Unidirectional 1:n protection for P2MP connectivity MUST be B. Unidirectional 1:n protection for P2MP connectivity MUST be
supported. supported.
C. Unidirectional 1:n protection for P2P connectivity is not C. Unidirectional 1:n protection for P2P connectivity is not
required and MAY be omitted from the MPLS-TP specifications. required and MAY be omitted from the MPLS-TP specifications.
D. The action of protection switching MUST NOT cause user data D. The action of protection switching MUST NOT cause the user
to loop. Backtracking is allowed. data to enter an uncontrolled loop. The protection switching
system MAY cause traffic to pass over a given link more than
once, but it must do so in a controlled way such that
uncontrolled loops do not form.
Note: Support for extra traffic (as defined in [RFC4427]) is not Note: Support for extra traffic (as defined in [RFC4427]) is not
required in MPLS-TP and MAY be omitted from the MPLS-TP required in MPLS-TP and MAY be omitted from the MPLS-TP
specifications. specifications.
2.8.1.2. Sharing of protection resources 2.8.1.2. Sharing of protection resources
67 MPLS-TP SHOULD support 1:n (including 1:1) shared mesh recovery. 69 MPLS-TP SHOULD support 1:n (including 1:1) shared mesh recovery.
68 MPLS-TP MUST support sharing of protection resources such that 70 MPLS-TP MUST support sharing of protection resources such that
protection paths that are known not to be required concurrently protection paths that are known not to be required concurrently
can share the same resources. can share the same resources.
2.8.1.3. Reversion
69 MPLS-TP protection mechanisms MUST support revertive and non-
revertive behavior.
70 MPLS-TP restoration mechanisms MUST support revertive and non-
revertive behavior.
2.8.2. Restoration 2.8.2. Restoration
71 The restoration transport path MUST be able to share resources 71 The restoration transport path MUST be able to share resources
with the transport path being replaced (sometimes known as soft with the transport path being replaced (sometimes known as soft
rerouting). rerouting).
72 Restoration priority MUST be supported so that an implementation 72 Restoration priority MUST be supported so that an implementation
can determine the order in which transport paths should be can determine the order in which transport paths should be
restored (to minimize service restoration time as well as to gain restored (to minimize service restoration time as well as to gain
access to available spare capacity on the best paths). access to available spare capacity on the best paths).
73 Preemption priority MUST be supported to allow restoration to 73 Preemption priority MUST be supported to allow restoration to
displace other transport paths in the event of resource displace other transport paths in the event of resource
constraint. constraint.
74 MPLS-TP restoration mechanisms MUST support revertive and non-
revertive behavior.
2.8.3. Triggers for protection, restoration, and reversion 2.8.3. Triggers for protection, restoration, and reversion
Recovery actions may be triggered from different places as follows: Recovery actions may be triggered from different places as follows:
74 MPLS-TP MUST support physical layer fault indication triggers. 75 MPLS-TP MUST support physical layer fault indication triggers.
75 MPLS-TP MUST support OAM-based triggers. 76 MPLS-TP MUST support OAM-based triggers.
76 MPLS-TP MUST support management plane triggers (e.g., forced 77 MPLS-TP MUST support management plane triggers (e.g., forced
switch, etc.). switch, etc.).
77 There MUST be a mechanism to allow administrative recovery 78 There MUST be a mechanism to allow administrative recovery
actions to be distinguished from recovery actions initiated by actions to be distinguished from recovery actions initiated by
other triggers. other triggers.
78 Where a control plane is present, MPLS-TP SHOULD support control 79 Where a control plane is present, MPLS-TP SHOULD support control
plane restoration triggers. plane restoration triggers.
79 MPLS-TP protection mechanisms MUST support priority logic to 80 MPLS-TP protection mechanisms MUST support priority logic to
negotiate and accommodate coexisting requests (i.e., multiple negotiate and accommodate coexisting requests (i.e., multiple
requests) for protection switching (e.g., administrative requests requests) for protection switching (e.g., administrative requests
and requests due to link/node failures). and requests due to link/node failures).
2.8.4. Management plane operation of protection and restoration 2.8.4. Management plane operation of protection and restoration
All functions described here are for control by the operator. All functions described here are for control by the operator.
80 It MUST be possible to configure protection paths and protection- 81 It MUST be possible to configure protection paths and protection-
to-working path relationships (sometimes known as protection to-working path relationships (sometimes known as protection
groups). groups).
81 There MUST be support for pre-calculation of recovery paths. 82 There MUST be support for pre-calculation of recovery paths.
82 There MUST be support for pre-provisioning of recovery paths. 83 There MUST be support for pre-provisioning of recovery paths.
83 The external controls as defined in [RFC4427] MUST be supported. 84 The external controls as defined in [RFC4427] MUST be supported.
A. External controls overruled by higher priority requests A. External controls overruled by higher priority requests
(e.g., administrative requests and requests due to link/node (e.g., administrative requests and requests due to link/node
failures) or unable to be signaled to the remote end (e.g. failures) or unable to be signaled to the remote end (e.g.
because of a protection state coordination fail) MUST be because of a protection state coordination fail) MUST be
dropped. dropped.
84 It MUST be possible to test and validate any protection/ 85 It MUST be possible to test and validate any protection/
restoration mechanisms and protocols: restoration mechanisms and protocols:
A. Including the integrity of the protection/recovery transport A. Including the integrity of the protection/recovery transport
path. path.
B. Without triggering the actual protection/restoration. B. Without triggering the actual protection/restoration.
C. While the working path is in service. C. While the working path is in service.
D. While the working path is out of service. D. While the working path is out of service.
85 Restoration resources MAY be pre-planned and selected a priori, 86 Restoration resources MAY be pre-planned and selected a priori,
or computed after failure occurrence. or computed after failure occurrence.
86 When preemption is supported for restoration purposes, it MUST be 87 When preemption is supported for restoration purposes, it MUST be
possible for the operator to configure it. possible for the operator to configure it.
87 The management plane MUST provide indications of protection 88 The management plane MUST provide indications of protection
events and triggers. events and triggers.
88 The management plane MUST allow the current protection status of 89 The management plane MUST allow the current protection status of
all transport paths to be determined. all transport paths to be determined.
2.8.5. Control plane and in-band OAM operation of recovery 2.8.5. Control plane and in-band OAM operation of recovery
89 The MPLS-TP control plane (which is not mandatory in an MPLS-TP 90 The MPLS-TP control plane (which is not mandatory in an MPLS-TP
implementation) MUST be capable of supporting: implementation) MUST be capable of supporting:
A. establishment and maintenance of all recovery entities and A. establishment and maintenance of all recovery entities and
functions functions
B. signaling of administrative control B. signaling of administrative control
C. protection state coordination (PSC). Since control plane C. protection state coordination (PSC). Since control plane
network topology is independent from the data plane network network topology is independent from the data plane network
topology, the PSC supported by the MPLS-TP control plane MAY topology, the PSC supported by the MPLS-TP control plane MAY
run on resources different than the data plane resources run on resources different than the data plane resources
handled within the recovery mechanism (e.g. backup). handled within the recovery mechanism (e.g. backup).
90 In-band OAM MUST be capable of supporting: 91 In-band OAM MUST be capable of supporting:
A. signaling of administrative control A. signaling of administrative control
B. protection state coordination (PSC). Since in-band OAM tools B. protection state coordination (PSC). Since in-band OAM tools
share the data plane with the carried transport service, in share the data plane with the carried transport service, in
order to optimize the usage of network resources, the PSC order to optimize the usage of network resources, the PSC
supported by in-band OAM MUST run on protection resources. supported by in-band OAM MUST run on protection resources.
2.8.6. Topology-specific recovery mechanisms 2.8.6. Topology-specific recovery mechanisms
91 MPLS-TP MAY support recovery mechanisms that are optimized for 92 MPLS-TP MAY support recovery mechanisms that are optimized for
specific network topologies. These mechanisms MUST be specific network topologies. These mechanisms MUST be
interoperable with the mechanisms defined for arbitrary topology interoperable with the mechanisms defined for arbitrary topology
(mesh) networks to enable protection of end-to-end transport (mesh) networks to enable protection of end-to-end transport
paths. paths.
2.8.6.1. Ring protection 2.8.6.1. Ring protection
Several service providers have expressed a high level of interest in Several service providers have expressed a high level of interest in
operating MPLS-TP in ring topologies and require a high level of operating MPLS-TP in ring topologies and require a high level of
survivability function in these topologies. The requirements listed survivability function in these topologies. The requirements listed
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mechanisms. mechanisms.
d. Minimize the amount of control and management plane transactions d. Minimize the amount of control and management plane transactions
during a maintenance operation (e.g., ring upgrade) - less than during a maintenance operation (e.g., ring upgrade) - less than
are required by other recovery mechanisms. are required by other recovery mechanisms.
e. When a control plane is supported, minimize the impact on e. When a control plane is supported, minimize the impact on
signaling and routing information exchange during protection - signaling and routing information exchange during protection -
less than are required by other recovery mechanisms. less than are required by other recovery mechanisms.
It may be observed that the requirements in this section are fully It may be observed that the requirements in Section 2.8.6.1 are fully
compatible with the generic requirements expressed above, and that no compatible with the generic requirements expressed in Section 2.8
requirements that are specific to ring topologies have been through Section 2.8.6 inclusive, and that no requirements that are
identified. specific to ring topologies have been identified.
92 MPLS-TP MUST include recovery mechanisms that operate in any 93 MPLS-TP MUST include recovery mechanisms that operate in any
single ring supported in MPLS-TP, and continue to operate within single ring supported in MPLS-TP, and continue to operate within
the single rings even when the rings are interconnected. the single rings even when the rings are interconnected.
93 When a network is constructed from interconnected rings, MPLS-TP 94 When a network is constructed from interconnected rings, MPLS-TP
MUST support recovery mechanisms that protect user data that MUST support recovery mechanisms that protect user data that
traverses more than one ring. This includes the possibility of traverses more than one ring. This includes the possibility of
failure of the ring-interconnect nodes and links. failure of the ring-interconnect nodes and links.
94 MPLS-TP recovery in a ring MUST protect unidirectional and 95 MPLS-TP recovery in a ring MUST protect unidirectional and
bidirectional P2P transport paths. bidirectional P2P transport paths.
95 MPLS-TP recovery in a ring MUST protect unidirectional P2MP 96 MPLS-TP recovery in a ring MUST protect unidirectional P2MP
transport paths. transport paths.
96 MPLS-TP 1+1 and 1:1 protection in a ring MUST support switching 97 MPLS-TP 1+1 and 1:1 protection in a ring MUST support switching
time within 50 ms from the moment of fault detection in a time within 50 ms from the moment of fault detection in a
network with a 16 nodes ring with less than 1200 km of fiber. network with a 16 nodes ring with less than 1200 km of fiber.
97 The protection switching time in a ring MUST be independent of 98 The protection switching time in a ring MUST be independent of
the number of LSPs crossing the ring. the number of LSPs crossing the ring.
98 The configuration and operation of recovery mechanisms in a ring 99 The configuration and operation of recovery mechanisms in a ring
MUST scale well with: MUST scale well with:
A. the number of transport paths (must be better than linear A. the number of transport paths (must be better than linear
scaling) scaling)
B. the number of nodes on the ring (must be at least as good as B. the number of nodes on the ring (must be at least as good as
linear scaling) linear scaling)
C. the number of ring interconnects (must be at least as good C. the number of ring interconnects (must be at least as good
as linear scaling) as linear scaling)
99 Recovery techniques used in a ring MUST NOT prevent the ring
100 Recovery techniques used in a ring MUST NOT prevent the ring
from being connected to a general MPLS-TP network in any from being connected to a general MPLS-TP network in any
arbitrary way, and MUST NOT prevent the operation of recovery arbitrary way, and MUST NOT prevent the operation of recovery
techniques in the rest of the network. techniques in the rest of the network.
100 MPLS-TP Recovery mechanisms applicable to a ring MUST be equally
applicable in physical and logical rings.
101 Recovery techniques in a ring SHOULD be identical (or as similar 101 Recovery techniques in a ring SHOULD be identical (or as similar
as possible) to those in general transport networks to simplify as possible) to those in general transport networks to simplify
implementation and operations. However, this MUST NOT override implementation and operations. However, this MUST NOT override
any other requirement. any other requirement.
102 Recovery techniques in logical and physical rings SHOULD be 102 Recovery techniques in logical and physical rings SHOULD be
identical to simplify implementation and operation. However, identical to simplify implementation and operation. However,
this MUST NOT override any other requirement. this MUST NOT override any other requirement.
103 The default recovery scheme in a ring MUST be bidirectional 103 The default recovery scheme in a ring MUST be bidirectional
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107 MPLS-TP recovery mechanisms in a ring: 107 MPLS-TP recovery mechanisms in a ring:
A. MUST include a mechanism to allow an implementation to A. MUST include a mechanism to allow an implementation to
handle (including the coordination of) coexisting requests handle (including the coordination of) coexisting requests
or triggers (i.e., multiple requests - not necessarily or triggers (i.e., multiple requests - not necessarily
arriving simultaneously and located anywhere in the ring) arriving simultaneously and located anywhere in the ring)
for protection switching based on priority. Note that such for protection switching based on priority. Note that such
coordination is the ring equivalent of the definition of coordination is the ring equivalent of the definition of
shared protection groups. shared protection groups.
B. MAY support multiple failures without reconfiguring the B. SHOULD protect against multiple failures
protection actions.
108 MPLS-TP recovery and reversion mechanisms in a ring MUST offer a 108 MPLS-TP recovery and reversion mechanisms in a ring MUST offer a
way to prevent frequent operation of recovery in the event of an way to prevent frequent operation of recovery in the event of an
intermittent defect. intermittent defect.
109 MPLS-TP MUST support the sharing of protection bandwidth in a 109 MPLS-TP MUST support the sharing of protection bandwidth in a
ring by allowing best effort traffic. ring by allowing best effort traffic.
110 MPLS-TP MUST support sharing of ring protection resources such 110 MPLS-TP MUST support sharing of ring protection resources such
that protection paths that are known not to be required that protection paths that are known not to be required
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5. Acknowledgements 5. Acknowledgements
The authors would like to thank all members of the teams (the Joint The authors would like to thank all members of the teams (the Joint
Working Team, the MPLS Interoperability Design Team in the IETF, and Working Team, the MPLS Interoperability Design Team in the IETF, and
the T-MPLS Ad Hoc Group in the ITU-T) involved in the definition and the T-MPLS Ad Hoc Group in the ITU-T) involved in the definition and
specification of MPLS Transport Profile. specification of MPLS Transport Profile.
The authors would also like to thank Loa Andersson, Dieter Beller, The authors would also like to thank Loa Andersson, Dieter Beller,
Lou Berger, Italo Busi, John Drake, Adrian Farrel, Annamaria Lou Berger, Italo Busi, John Drake, Adrian Farrel, Annamaria
Fulignoli, Pietro Grandi, Eric Gray, Neil Harrison, Huub van Fulignoli, Pietro Grandi, Eric Gray, Neil Harrison, Jia He, Huub van
Helvoort, Enrique Hernandez-Valencia, Wataru Imajuku, Kam Lam, Andy Helvoort, Enrique Hernandez-Valencia, Wataru Imajuku, Kam Lam, Andy
Malis, Alan McGuire, Julien Meuric, Greg Mirsky, Tom Nadeau, Hiroshi Malis, Alan McGuire, Julien Meuric, Greg Mirsky, Tom Nadeau, Hiroshi
Ohta, Tom Petch, Andy Reid, Vincenzo Sestito, George Swallow, Lubo Ohta, Tom Petch, Andy Reid, Vincenzo Sestito, George Swallow, Lubo
Tancevski, Tomonori Takeda, Yuji Tochio, Alexander Vainshtein, Eve Tancevski, Tomonori Takeda, Yuji Tochio, Alexander Vainshtein, Eve
Varma and Maarten Vissers for their comments and enhancements to the Varma and Maarten Vissers for their comments and enhancements to the
text. text.
An ad hoc discussion group consisting of Stewart Bryant, Italo Busi, An ad hoc discussion group consisting of Stewart Bryant, Italo Busi,
Andrea Digiglio, Li Fang, Adrian Farrel, Jia He, Huub van Helvoort, Andrea Digiglio, Li Fang, Adrian Farrel, Jia He, Huub van Helvoort,
Feng Huang, Harald Kullman, Han Li, Hao Long and Nurit Sprecher Feng Huang, Harald Kullman, Han Li, Hao Long and Nurit Sprecher
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