draft-ietf-mpls-tp-framework-05.txt   draft-ietf-mpls-tp-framework-06.txt 
MPLS Working Group M. Bocci, Ed. MPLS Working Group M. Bocci, Ed.
Internet-Draft Alcatel-Lucent Internet-Draft Alcatel-Lucent
Intended status: Standards Track S. Bryant, Ed. Intended status: Standards Track S. Bryant, Ed.
Expires: March 29, 2010 D. Frost Expires: April 19, 2010 D. Frost
Cisco Systems Cisco Systems
L. Levrau L. Levrau
Alcatel-Lucent Alcatel-Lucent
September 25, 2009 October 16, 2009
A Framework for MPLS in Transport Networks A Framework for MPLS in Transport Networks
draft-ietf-mpls-tp-framework-05 draft-ietf-mpls-tp-framework-06
Status of This Memo Status of This Memo
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This Internet-Draft will expire on March 29, 2010. This Internet-Draft will expire on April 19, 2010.
Copyright Notice Copyright Notice
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Abstract Abstract
This document specifies an architectural framework for the This document specifies an architectural framework for the
application of Multi Protocol Label Switching (MPLS) in transport application of Multi Protocol Label Switching (MPLS) in transport
networks, by enabling the construction of packet switched equivalents networks, by enabling the construction of packet switched equivalents
to traditional circuit switched carrier networks. It describes a to traditional circuit switched carrier networks. It describes a
common set of protocol functions--the MPLS Transport Profile (MPLS- common set of protocol functions - the MPLS Transport Profile
TP)--that supports the operational models and capabilities typical of (MPLS-TP) - that supports the operational models and capabilities
such networks, including signaled or explicitly provisioned bi- typical of such networks for point-to-point paths, including signaled
directional connection-oriented paths, protection and restoration or explicitly provisioned bi-directional connection-oriented paths,
mechanisms, comprehensive Operations, Administration and Maintenance protection and restoration mechanisms, comprehensive Operations,
(OAM) functions, and network operation in the absence of a dynamic Administration and Maintenance (OAM) functions, and network operation
control plane or IP forwarding support. Some of these functions in the absence of a dynamic control plane or IP forwarding support.
exist in existing MPLS specifications, while others require Some of these functions exist in existing MPLS specifications, while
extensions to existing specifications to meet the requirements of the others require extensions to existing specifications to meet the
MPLS-TP. requirements of the MPLS-TP.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119 [RFC2119]. document are to be interpreted as described in RFC2119 [RFC2119].
Although this document is not a protocol specification, these key Although this document is not a protocol specification, these key
words are to be interpreted as instructions to the protocol designers words are to be interpreted as instructions to the protocol designers
producing solutions that satisfy the architectural concepts set out producing solutions that satisfy the architectural concepts set out
in this document. in this document.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Motivation and Background . . . . . . . . . . . . . . . . 4 1.1. Motivation and Background . . . . . . . . . . . . . . . . 4
1.2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6
1.3.1. MPLS Transport Profile. . . . . . . . . . . . . . . . 6 1.3.1. MPLS Transport Profile. . . . . . . . . . . . . . . . 6
1.3.2. MPLS-TP Section . . . . . . . . . . . . . . . . . . . 6 1.3.2. MPLS-TP Section . . . . . . . . . . . . . . . . . . . 6
1.3.3. MPLS-TP Label Switched Path . . . . . . . . . . . . . 6 1.3.3. MPLS-TP Label Switched Path . . . . . . . . . . . . . 6
1.3.4. MPLS-TP Label Switching Router (LSR) and Label 1.3.4. MPLS-TP Label Switching Router (LSR) and Label
Edge Router (LER) . . . . . . . . . . . . . . . . . . 6 Edge Router (LER) . . . . . . . . . . . . . . . . . . 7
1.3.5. MPLS-TP Customer Edge (CE) . . . . . . . . . . . . . . 7 1.3.5. MPLS-TP Customer Edge (CE) . . . . . . . . . . . . . . 8
1.3.6. Additional Definitions and Terminology . . . . . . . . 7 1.3.6. Additional Definitions and Terminology . . . . . . . . 8
1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 7 1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 8
2. Introduction to Requirements . . . . . . . . . . . . . . . . . 8 2. Introduction to Requirements . . . . . . . . . . . . . . . . . 10
3. Transport Profile Overview . . . . . . . . . . . . . . . . . . 8 3. Transport Profile Overview . . . . . . . . . . . . . . . . . . 11
3.1. Packet Transport Services . . . . . . . . . . . . . . . . 8 3.1. Packet Transport Services . . . . . . . . . . . . . . . . 11
3.2. Architecture . . . . . . . . . . . . . . . . . . . . . . . 10 3.2. Scope of MPLS Transport Profile . . . . . . . . . . . . . 12
3.2.1. MPLS-TP Adaptation Functions . . . . . . . . . . . . . 10 3.3. Architecture . . . . . . . . . . . . . . . . . . . . . . . 12
3.2.2. MPLS-TP Forwarding Functions . . . . . . . . . . . . . 11 3.3.1. MPLS-TP Adaptation . . . . . . . . . . . . . . . . . . 13
3.3. MPLS-TP LSP Clients . . . . . . . . . . . . . . . . . . . 12 3.3.2. MPLS-TP Forwarding Functions . . . . . . . . . . . . . 13
3.3.1. Pseudowires . . . . . . . . . . . . . . . . . . . . . 12 3.4. MPLS-TP Client Adaptation . . . . . . . . . . . . . . . . 15
3.3.2. Network Layer Clients . . . . . . . . . . . . . . . . 15 3.4.1. Adaptation using Pseudowires . . . . . . . . . . . . . 15
3.4. Identifiers . . . . . . . . . . . . . . . . . . . . . . . 20 3.4.2. Network Layer Clients . . . . . . . . . . . . . . . . 18
3.5. Operations, Administration and Maintenance (OAM) . . . . . 21 3.5. Identifiers . . . . . . . . . . . . . . . . . . . . . . . 21
3.6. Generic Associated Channel (G-ACh) . . . . . . . . . . . . 25 3.6. Operations, Administration and Maintenance (OAM) . . . . . 22
3.7. Control Plane . . . . . . . . . . . . . . . . . . . . . . 28 3.6.1. OAM Architecture . . . . . . . . . . . . . . . . . . . 22
3.7.1. PW Control Plane . . . . . . . . . . . . . . . . . . . 30 3.6.2. OAM Functions . . . . . . . . . . . . . . . . . . . . 25
3.7.2. LSP Control Plane . . . . . . . . . . . . . . . . . . 30 3.7. Generic Associated Channel (G-ACh) . . . . . . . . . . . . 26
3.8. Static Operation of LSPs and PWs . . . . . . . . . . . . . 31 3.8. Control Plane . . . . . . . . . . . . . . . . . . . . . . 29
3.9. Survivability . . . . . . . . . . . . . . . . . . . . . . 31 3.8.1. PW Control Plane . . . . . . . . . . . . . . . . . . . 31
3.10. Network Management . . . . . . . . . . . . . . . . . . . . 32 3.8.2. LSP Control Plane . . . . . . . . . . . . . . . . . . 31
4. Security Considerations . . . . . . . . . . . . . . . . . . . 33 3.9. Static Operation of LSPs and PWs . . . . . . . . . . . . . 32
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 34 3.10. Survivability . . . . . . . . . . . . . . . . . . . . . . 32
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 34 3.11. Network Management . . . . . . . . . . . . . . . . . . . . 33
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 34 4. Security Considerations . . . . . . . . . . . . . . . . . . . 34
7.1. Normative References . . . . . . . . . . . . . . . . . . . 34 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 35
7.2. Informative References . . . . . . . . . . . . . . . . . . 37 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 35
7. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 36
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 36
8.1. Normative References . . . . . . . . . . . . . . . . . . . 36
8.2. Informative References . . . . . . . . . . . . . . . . . . 38
1. Introduction 1. Introduction
1.1. Motivation and Background 1.1. Motivation and Background
This document describes a framework for a Multiprotocol Label This document describes a framework for a Multiprotocol Label
Switching Transport Profile (MPLS-TP). It presents the architectural Switching Transport Profile (MPLS-TP). It presents the architectural
framework for MPLS-TP, defining those elements of MPLS applicable to framework for MPLS-TP, defining those elements of MPLS applicable to
supporting the requirements in [RFC5654] and what new protocol supporting the requirements in [RFC5654] and what new protocol
elements are required. elements are required.
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o Strictly connection-oriented connectivity, which may be long-lived o Strictly connection-oriented connectivity, which may be long-lived
and may be provisioned manually or by network management. and may be provisioned manually or by network management.
o A high level of protection and availability. o A high level of protection and availability.
o Quality of service. o Quality of service.
o Extended OAM capabilities. o Extended OAM capabilities.
Carriers wish to evolve such transport networks to support packet Carriers wish to evolve such transport networks to support packet
based services and networks, and to take advantage of the flexibility based services, and to take advantage of the flexibility and cost
and cost benefits of packet switching technology. While MPLS is a benefits of packet switching technology. While MPLS is a maturing
maturing packet technology that is already playing an important role packet technology that is already playing an important role in
in transport networks and services, not all of MPLS's capabilities transport networks and services, not all of MPLS's capabilities and
and mechanisms are needed and/or consistent with transport network mechanisms are needed and/or consistent with transport network
operations. There are also transport technology characteristics that operations. There are also transport technology characteristics that
are not currently reflected in MPLS. are not currently reflected in MPLS.
The types of packet transport services delivered by transport The types of packet transport services delivered by transport
networks are very similar to Layer 2 Virtual Private Networks defined networks are very similar to Layer 2 Virtual Private Networks defined
by the IETF. by the IETF.
There are thus two objectives for MPLS-TP: There are thus two objectives for MPLS-TP:
1. To enable MPLS to be deployed in a transport network and operated 1. To enable MPLS to be deployed in a transport network and operated
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applications and networks. This profile specifies the specific MPLS applications and networks. This profile specifies the specific MPLS
characteristics and extensions required to meet transport characteristics and extensions required to meet transport
requirements. requirements.
1.2. Scope 1.2. Scope
This document describes an architectural framework for the This document describes an architectural framework for the
application of MPLS to transport networks. It specifies the common application of MPLS to transport networks. It specifies the common
set of protocol functions that meet the requirements in [RFC5654], set of protocol functions that meet the requirements in [RFC5654],
and that together constitute the MPLS Transport Profile (MPLS-TP). and that together constitute the MPLS Transport Profile (MPLS-TP).
The architecture for point-to-point MPLS-TP paths is described. The
architecture for point-to-multipoint paths is outside the scope of
this document.
1.3. Terminology 1.3. Terminology
Term Definition Term Definition
---------------- ------------------------------------------ ---------------- ------------------------------------------
LSP Label Switched Path LSP Label Switched Path
MPLS-TP MPLS Transport profile MPLS-TP MPLS Transport profile
SDH Synchronous Digital Hierarchy SDH Synchronous Digital Hierarchy
ATM Asynchronous Transfer Mode ATM Asynchronous Transfer Mode
OTN Optical Transport Network OTN Optical Transport Network
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FM Fault Management FM Fault Management
CM Configuration Management CM Configuration Management
PM Performance Management PM Performance Management
LSR Label Switch Router. LSR Label Switch Router.
MPLS-TP PE MPLS-TP Provider Edge MPLS-TP PE MPLS-TP Provider Edge
MPLS-TP P Router An MPLS-TP Provider (P) router MPLS-TP P Router An MPLS-TP Provider (P) router
PW Pseudowire PW Pseudowire
1.3.1. MPLS Transport Profile. 1.3.1. MPLS Transport Profile.
The MPLS Transport Profile (MPLS-TP) is the set of MPLS functions The MPLS Transport Profile (MPLS-TP) is the subset of MPLS functions
that meet the requirements in [RFC5654]. Note that MPLS is defined that meet the requirements in [RFC5654]. Note that MPLS is defined
to include any present and future MPLS capability specified by the to include any present and future MPLS capability specified by the
IETF, include those capabilities specifically added to support the IETF, including those capabilities specifically added to support the
transport network requirement [RFC5654]. transport network requirement [RFC5654].
1.3.2. MPLS-TP Section 1.3.2. MPLS-TP Section
An MPLS-TP Section is defined in Secion 1.1.2 of [RFC5654]. An MPLS-TP Section is defined in Section 1.1.2 of [RFC5654].
1.3.3. MPLS-TP Label Switched Path 1.3.3. MPLS-TP Label Switched Path
An MPLS-TP Label Switched Path (MPLS-TP LSP) is an LSP that uses a An MPLS-TP Label Switched Path (MPLS-TP LSP) is an LSP that uses a
subset of the capabilities of an MPLS LSP in order to meet the subset of the capabilities of an MPLS LSP in order to meet the
requirements of an MPLS transport network as set out in [RFC5654]. requirements of an MPLS transport network as set out in [RFC5654].
The characteristics of an MPLS-TP LSP are primarily that it: The characteristics of an MPLS-TP LSP are primarily that it:
1. Uses a subset of the MPLS OAM tools defined as described in 1. Uses a subset of the MPLS OAM tools defined as described in
[I-D.ietf-mpls-tp-oam-framework]. [I-D.ietf-mpls-tp-oam-framework].
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3. Is traffic engineered. 3. Is traffic engineered.
4. Is established and maintained using GMPLS protocols when a 4. Is established and maintained using GMPLS protocols when a
control plane is used. control plane is used.
5. LSPs can only be point to point or point to multipoint, i.e. the 5. LSPs can only be point to point or point to multipoint, i.e. the
merging of LSPs is not permitted. merging of LSPs is not permitted.
Note that an MPLS LSP is defined to include any present and future Note that an MPLS LSP is defined to include any present and future
MPLS capability include those specifically added to support the MPLS capability include those specifically added to support the
transport network requrements. transport network requirements.
1.3.4. MPLS-TP Label Switching Router (LSR) and Label Edge Router (LER) 1.3.4. MPLS-TP Label Switching Router (LSR) and Label Edge Router (LER)
An MPLS-TP Label Switching Router (MPLS-TP LSR) is either an MPLS-TP An MPLS-TP Label Switching Router (MPLS-TP LSR) is either an MPLS-TP
Provider Edge (MPLS-TP PE) or an MPLS-TP Provider (MPLS-TP P Router) Provider Edge (MPLS-TP PE) or an MPLS-TP Provider (MPLS-TP P Router)
router as defined below. The terms MPLS-TP PE and MPLS-TP P router router for a given LSP, as defined below. The terms MPLS-TP PE and
describe functions and specific node may undertake both roles. Note MPLS-TP P router describe functions and specific node may undertake
that the use of the term "router" in this context is historic and both roles.
neither requires nor precludes the ability to perform IP forwarding.
Note that the use of the term "router" in this context is historic
and neither requires nor precludes the ability to perform IP
forwarding.
1.3.4.1. MPLS-TP Provider Edge Router (PE) 1.3.4.1. MPLS-TP Provider Edge Router (PE)
An MPLS-TP Provider Edge Router is an MPLS-TP LSR that adapts client An MPLS-TP Provider Edge Router is an MPLS-TP LSR that adapts client
traffic and encapsulates it to be carried over an MPLS-TP LSP. traffic and encapsulates it to be carried over an MPLS-TP LSP.
Encapsulation may be as simple as pushing a label, or it may require Encapsulation may be as simple as pushing a label, or it may require
the use of a pseudowire. An MPLS-TP PE exists at the interface the use of a pseudowire. An MPLS-TP PE exists at the interface
between a pair of layer networks. between a pair of layer networks. For an MS-PW, an MPLS-TP PE may be
either an S-PE or a T-PE.
A layer network is defined in [I-D.ietf-mpls-tp-rosetta-stone]. A layer network is defined in [G.805].
1.3.4.2. MPLS-TP Provider Router (P) 1.3.4.2. MPLS-TP Provider Router (P)
An MPLS-TP Provider router is an MPLS-TP LSR that does not provide An MPLS-TP Provider router is an MPLS-TP LSR that does not provide
MPLS-TP PE functionality. An MPLS-TP P router switches LSPs which MPLS-TP PE functionality. An MPLS-TP P router switches LSPs which
carry client traffic, but do not adapt the client traffic and carry client traffic, but do not adapt the client traffic and
encapsulate it to be carried over an MPLS-TP LSP. encapsulate it to be carried over an MPLS-TP LSP.
1.3.5. MPLS-TP Customer Edge (CE) 1.3.5. MPLS-TP Customer Edge (CE)
An MPLS-TP Customer Edge is the client function sourcing or sinking An MPLS-TP Customer Edge is the client function sourcing or sinking
client traffic to or from the MPLS-TP network. CEs on either side of client traffic to or from the MPLS-TP network. CEs on either side of
the MPLS-TP network are peers and view the MPLS-TP network as a the MPLS-TP network are peers and view the MPLS-TP network as a
single point to point or point to multi-point link. These clients single point to point or point to multi-point link. These clients
have no knowledge of the presence of the interveining MPLS-TP have no knowledge of the presence of the interveining MPLS-TP
network. network.
1.3.6. Additional Definitions and Terminology 1.3.6. Additional Definitions and Terminology
Detailed definitions and additional terminology may be found in . Detailed definitions and additional terminology may be found in
[RFC5654]. [RFC5654].
1.4. Applicability 1.4. Applicability
MPLS-TP can be used to construct a packet transport networks and is MPLS-TP can be used to construct a packet transport networks and is
therefore applicable in any packet transport network application. It therefore applicable in any packet transport network application. It
is also as an alternative architecture for subsets of a packet is also as an alternative architecture for subsets of a packet
network where the transport network model is deemed attractive. network where the transport network model is deemed attractive. The
following are examples of MPLS-TP applicability models:
These two modes can be considered vertical and horizontal 1. MPLS-TP provided by a network that only supports MPLS-TP, acting
applicability models. In the first case an MPLS-TP network is viewed as a server for other layer 1, layer 2 and layer 3 networks
as below an IP packet network i.e. provides the data link layer (Figure 1).
service for an IP network; in the second case, MPLS-TP acts as an
aggregation for client traffic into an IP-based MPLS network, or a 2. MPLS-TP provided by a network that also supports non-MPLS-TP
transit for client traffic between IP-based MPLS networks. These functions, acting as a server for other layer 1, layer 2 and
models are not mutually exclusive. layer 3 networks (Figure 2).
3. MPLS-TP as a server layer for client layer traffic of IP or MPLS
networks which do not use functions of the MPLS transport profile
(Figure 3).
These models are not mutually exclusive.
MPLS-TP LSP, provided by a network that only supports MPLS-TP, acting as a server
for other layer 1, layer 2 and layer 3 networks.
|<-- L1/2/3 -->|<-- MPLS-TP-->|<-- L1/2/3 -->|
Only
MPLS-TP
+---+ LSP +---+
+---+ Client | |----------| | Client +---+
|CE1|==Traffic=|PE2|==========|PE3|=Traffic==|CE1|
+---+ | |----------| | +---+
+---+ +---+
Example a) [Ethernet] [Ethernet] [Ethernet]
layering [ PW ]
[-TP LSP ]
b) [ IP ] [ IP ] [ IP ]
[ LSP ]
[-TP LSP ]
Figure 1: MPLS-TP Server Layer Example
MPLS-TP LSP, provided by a network that also supports non-MPLS-TP functions,
acting as a server for other layer 1, layer 2 and layer 3 networks.
|<-- L1/2/3 -->|<-- MPLS -->|<-- L1/2/3 -->|
MPLS-TP
+---+ LSP +---+
+---+ Client | |----------| | Client +---+
|CE1|==Traffic=|PE2|==========|PE3|=Traffic==|CE1|
+---+ | |----------| | +---+
+---+ +---+
Example a) [Ethernet] [Ethernet] [Ethernet]
layering [ PW ]
[-TP LSP ]
b) [ IP ] [ IP ] [ IP ]
[ LSP ]
[-TP LSP ]
Figure 2: MPLS-TP in MPLS Network Example
MPLS-TP as a server layer for client layer traffic of IP or MPLS networks which
do not use functions of the MPLS transport profile.
|<-- MPLS ---->|<-- MPLS-TP-->|<--- MPLS --->|
Only
+---+ +---+ Non-TP +---+ MPLS-TP +---+ Non-TP +---+ +---+
|CE1|---|PE1|====LSP===|PE2|====LSP===|PE3|====LSP===|PE4|-----|CE2|
+---+ +---+ +---+ +---+ +---+ +---+
(a) [ Eth ] [ Eth ] [ Eth ] [ Eth ] [ Eth ]
[ MS-PW ] [ MS-PW ] [ MS-PW ]
[ LSP ] [-TP LSP ] [ LSP ]
(a) [ IP ] [ IP ] [ IP ] [ IP ] [ IP ]
[ LSP ] [-TP LSP ] [ LSP ]
Figure 3: MPLS-TP Transporting Client Service Traffic
2. Introduction to Requirements 2. Introduction to Requirements
The requirements for MPLS-TP are specified in [RFC5654], The requirements for MPLS-TP are specified in [RFC5654],
[I-D.ietf-mpls-tp-oam-requirements], and [I-D.ietf-mpls-tp-nm-req]. [I-D.ietf-mpls-tp-oam-requirements], and [I-D.ietf-mpls-tp-nm-req].
This section provides a brief reminder to guide the reader. It is This section provides a brief reminder to guide the reader and is
not intended as a substitute for these documents. therefore not normative. It is not intended as a substitute for
these documents.
MPLS-TP MUST NOT modify the MPLS forwarding architecture and MUST be MPLS-TP must not modify the MPLS forwarding architecture and must be
based on existing pseudowire and LSP constructs. Any new mechanisms based on existing pseudowire and LSP constructs.
and capabilities added to support transport networks and packet
transport services must be able to inter-operate with existing MPLS
and pseudowire control and forwarding planes.
Point to point LSPs MAY be unidirectional or bi-directional, and it Point to point LSPs may be unidirectional or bi-directional, and it
MUST be possible to construct congruent Bi-directional LSPs. Point must be possible to construct congruent Bi-directional LSPs.
to multipoint LSPs are unidirectional.
MPLS-TP LSPs do not merge with other LSPs at an MPLS-TP LSR and it MPLS-TP LSPs do not merge with other LSPs at an MPLS-TP LSR and it
MUST be possible to detect if a merged LSP has been created. must be possible to detect if a merged LSP has been created.
It MUST be possible to forward packets solely based on switching the It must be possible to forward packets solely based on switching the
MPLS or PW label. It MUST also be possible to establish and maintain MPLS or PW label. It must also be possible to establish and maintain
LSPs and/or pseudowires both in the absence or presence of a dynamic LSPs and/or pseudowires both in the absence or presence of a dynamic
control plane. When static provisioning is used, there MUST be no control plane. When static provisioning is used, there must be no
dependency on dynamic routing or signaling. dependency on dynamic routing or signaling.
OAM, protection and forwarding of data packets MUST be able to OAM, protection and forwarding of data packets must be able to
operate without IP forwarding support. operate without IP forwarding support.
It MUST be possible to monitor LSPs and pseudowires through the use It must be possible to monitor LSPs and pseudowires through the use
of OAM in the absence of control plane or routing functions. In this of OAM in the absence of control plane or routing functions. In this
case information gained from the OAM functions is used to initiate case information gained from the OAM functions is used to initiate
path recovery actions at either the PW or LSP layers. path recovery actions at either the PW or LSP layers.
3. Transport Profile Overview 3. Transport Profile Overview
3.1. Packet Transport Services 3.1. Packet Transport Services
One objective of MPLS-TP is to enable MPLS networks to provide packet One objective of MPLS-TP is to enable MPLS networks to provide packet
transport services with a similar degree of predictability to that transport services with a similar degree of predictability to that
found in existing transport networks. Such packet transport services found in existing transport networks. Such packet transport services
inherit a number of characteristics, defined in [RFC5654]. inherit a number of characteristics, defined in [RFC5654]:
o In an environment where an MPLS-TP layer network is supporting a o 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 or network MUST be possible without any dependencies on the server or
client layer network. client layer network.
o The service provided by the MPLS-TP network to the client is o The service provided by the MPLS-TP network to the client is
guaranteed not to fall below the agreed level regardless of other guaranteed not to fall below the agreed level regardless of other
client activity. client activity.
skipping to change at page 9, line 28 skipping to change at page 11, line 45
o The complete set of packets generated by a client MPLS(-TP) layer o The complete set of packets generated by a client MPLS(-TP) layer
network using the packet transport service, which may contain network using the packet transport service, which may contain
packets that are not MPLS packets (e.g. IP or CNLS packets used packets that are not MPLS packets (e.g. IP or CNLS packets used
by the control/management plane of the client MPLS(-TP) layer by the control/management plane of the client MPLS(-TP) layer
network), are transported by the MPLS-TP server layer network. network), are transported by the MPLS-TP server layer network.
o The packet transport service enables the MPLS-TP layer network o The packet transport service enables the MPLS-TP layer network
addressing and other information (e.g. topology) to be hidden from addressing and other information (e.g. topology) to be hidden from
any client layer networks using that service, and vice-versa. any client layer networks using that service, and vice-versa.
Figure 1 illustrates the range of services that MPLS-TP is intended Therefore, a packet transport service doe not support a
to address. MPLS-TP is intended to support a range of layer 1, layer connectionless packet switched forwarding mode. However, this does
2 and layer 3 services, and is not limited to layer 3 services only. not preclude it carrying client traffic associated with a
Networks implementing MPLS-TP may choose to only support a subset of connectionless service.
these services.
MPLS-TP Solution exists 3.2. Scope of MPLS Transport Profile
over this spectrum
|<-------------------------->|
cl-ps Multi-Service co-cs & co-ps Figure 4 illustrates the scope of MPLS-TP. MPLS-TP solutions are
(cl-ps & co-ps) (Label is primarily intended for packet transport applications. MPLS-TP is a
| | service context) strict sub-set of MPLS, and comprises those functions that meet the
| | | requirements of [RFC5654]. This includes MPLS functions that were
|<--------------------------|--------------------------->| defined prior to [RFC5654] but that meet the requirements of
| | | [RFC5654], together with additional functions defined to meet those
L3 Only L1, L2, L3 Services L1, L2 Services requirements. Some MPLS functions defined before [RFC5654] e.g.
Pt-Pt, Pt-MP, MP-MP Pt-Pt and Pt-MP Equal Cost Multi-Path, LDP signaling used in such a way that it
creates multi-point to point LSPs, and IP forwarding in the data
plane are explicitly excluded from MPLS-TP by that requirements
specification.
Figure 1: Packet Transport Service Characteristics Note that this does not preclude the future definition of MPLS
functions that do not meet the requirements of [RFC5654] and thus
fall outside the scope of MPLS-TP as defined by this document.
The diagram above shows the spectrum of services that can be {Additional Transport Functions}
supported by MPLS. MPLS-TP solutions are primarily intended for |<============== MPLS-TP ==================>|
packet transport applications. These can be deployed using a profile { ECMP, mp2p LDP, IP fwd }
of MPLS that is strictly connection oriented and does not rely on IP |<====== Pre-RFC5654 MPLS ===========>|
forwarding or routing (shown on the right hand side of the figure), |<============================== MPLS ==============================>|
or in conjunction with an MPLS network that does use IP forwarding
and that supports a broader range of IP services. This is the multi-
service solution in the centre of the figure.
3.2. Architecture Figure 4: Scope of MPLS-TP
3.3. Architecture
MPLS-TP comprises the following MPLS-TP comprises the following
o Sections, point to point and point to multipoint LSPs and PWs that o Sections, LSPs and PWs that provide a packet transport service for
provide a packet transport service for a client network. a client network.
o Proactive and on demand Operations Administration and Maintenance o Proactive and on demand Operations Administration and Maintenance
(OAM) functions to monitor and diagnose the MPLS-TP network. e.g. (OAM) functions to monitor and diagnose the MPLS-TP network. e.g.
connectivity check, connectivity verification, and performance connectivity check, connectivity verification, and performance
monitoring. monitoring.
o Optional control planes for LSPs and PWs, as well as static o Optional control planes for LSPs and PWs, as well as static
configuration. configuration.
o Path protection mechanisms to ensure that the packet transport o Path protection mechanisms to ensure that the packet transport
service survives anticipated failures and degradations of the service survives anticipated failures and degradations of the
MPLS-TP network. MPLS-TP network.
o Network management functions. o Network management functions.
The MPLS-TP architecture for LSPs and PWs includes the the following The MPLS-TP architecture for LSPs and PWs includes the the following
two sets of functions: two sets of functions:
o MPLS-TP adaptation functions o MPLS-TP adaptation
o MPLS-TP forwarding functions o MPLS-TP forwarding
The adaptation functions interface the client service to MPLS-TP. The adaptation functions interface the client service to MPLS-TP.
This includes the case where the client service is an MPLS-TP LSP. This includes the case where the client service is an MPLS-TP LSP.
For example, in the case of a PW, the adaptation function is the
payload encapsulation fillustrated in shown in Figure 4a of [RFC3985]
and Figure 7 of [I-D.ietf-pwe3-ms-pw-arch].
The forwarding functions comprise the mechanisms required for The forwarding functions comprise the mechanisms required for
forwarding the encapsulated client over an MPLS-TP server layer forwarding the encapsulated client over an MPLS-TP server layer
network E.g. PW label and LSP label. network E.g. PW label and LSP label.
3.2.1. MPLS-TP Adaptation Functions 3.3.1. MPLS-TP Adaptation
The MPLS-TP adaptation functions interface the client service to The MPLS-TP adaptation interfaces the client service to MPLS-TP. For
MPLS-TP. For pseudowires, these adaptation functions are the payload pseudowires, these adaptation functions are the payload encapsulation
encapsulation shown in Figure 4a of [RFC3985] and Figure 7 of shown in Figure 7 of [RFC3985] and Figure 7 of
[I-D.ietf-pwe3-ms-pw-arch]. For network layer client services, the [I-D.ietf-pwe3-ms-pw-arch]. For network layer client services, the
adaptation function uses the MPLS encapsulation format as defined in adaptation function uses the MPLS encapsulation format as defined in
RFC 3032[RFC3032]. RFC 3032[RFC3032].
The purpose of this encapsulation is to abstract the client service The purpose of this encapsulation is to abstract the client service
data plane from the MPLS-TP data plane, thus contributing to the data plane from the MPLS-TP data plane, thus contributing to the
independent operation of the MPLS-TP network. independent operation of the MPLS-TP network.
MPLS-TP is itself a client of an underlying server layer. MPLS-TP is MPLS-TP is itself a client of an underlying server layer. MPLS-TP is
thus also bounded by a set of adaptation functions to this server thus also bounded by a set of adaptation functions to this server
layer network, which may itself be MPLS-TP. These adaptation layer network, which may itself be MPLS-TP. These adaptation
functions provide encapsulation of the MPLS-TP frames and for the functions provide encapsulation of the MPLS-TP frames and for the
transparent transport of those frames over the server layer network. transparent transport of those frames over the server layer network.
The MPLS-TP client inherits its QoS from the MPLS-TP network, which The MPLS-TP client inherits its QoS from the MPLS-TP network, which
in turn inherits its QoS from the server layer. The server layer in turn inherits its QoS from the server layer. The server layer
must therefore provide the necessary Quality of Service (QoS) to must therefore provide the necessary Quality of Service (QoS) to
ensure that the MPLS-TP client QoS commitments are satisfied. ensure that the MPLS-TP client QoS commitments are satisfied.
3.2.2. MPLS-TP Forwarding Functions 3.3.2. MPLS-TP Forwarding Functions
The forwarding functions comprise the mechanisms required for The forwarding functions comprise the mechanisms required for
forwarding the encapsulated client over an MPLS-TP server layer forwarding the encapsulated client over an MPLS-TP server layer
network E.g. PW label and LSP label. network E.g. PW label and LSP label.
MPLS-TP LSPs use the MPLS label switching operations defined in MPLS-TP LSPs use the MPLS label switching operations and TTL
[RFC3031] for point-to-point LSPs and [RFC5332] for point to processing procedures defined in [RFC3031] and [RFC3032]. These
multipoint LSPs. These operations are highly optimized for operations are highly optimized for performance and are not modified
performance and are not modified by the MPLS-TP profile. by the MPLS-TP profile.
In addition, MPLS-TP PWs use the PW and MS-PW forwarding operations In addition, MPLS-TP PWs use the PW and MS-PW forwarding operations
defined in[RFC3985] and [I-D.ietf-pwe3-ms-pw-arch]. The PW label is defined in[RFC3985] and [I-D.ietf-pwe3-ms-pw-arch]. The PW label is
processed by a PW forwarder and is always at the bottom of the label processed by a PW forwarder and is always at the bottom of the label
stack for a given MPLS-TP layer network. stack for a given MPLS-TP layer network.
Per-platform label space is used for PWs. Either per-platform or Per-platform label space is used for PWs. Either per-platform, per-
per-interface label space may be used for LSPs. interface or other context-specific label space may be used for LSPs.
During forwarding a label is pushed to associate a forwarding MPLS-TP forwarding is based on the label that identifies the
equivalence class (FEC) with the LSP or PW. This specifies the transport path (LSP or PW). The label value specifies the processing
processing operation to be performed by the next hop at that level of operation to be performed by the next hop at that level of
encapsulation. A swap of this label is an atomic operation in which encapsulation. A swap of this label is an atomic operation in which
the contents of the packet after the swapped label are opaque to the the contents of the packet after the swapped label are opaque to the
forwarder. The only event that interrupts a swap operation is TTL forwarder. The only event that interrupts a swap operation is TTL
expiry, in which case the packet may be inspected and either expiry. This is a fundamental architectural construct of MPLS to be
discarded or subjected to further processing within the LSR. TTL taken into account when design protocol extensions that requires
expiry causes an exception which forces a packet to be further packets (e.g. OAM packets) to be sent to an intermediate LSR.
inspected and processed. While this occurs, the forwarding of
succeeding packets continues without interruption. Therefore, the Further processing to determine the context of a packet occurs when a
only way to cause a P (intermediate) LSR to inspect a packet (for swap operation is interrupted in this manner, or a pop operation
example for OAM purposes) is to set the TTL to expire at that LSR. exposes a specific reserved label at the top of the stack. Otherwise
the packet is forwarded according to the procedures in [RFC3032].
Point to point MPLS-TP LSPs can be either unidirectional or Point to point MPLS-TP LSPs can be either unidirectional or
bidirectional. Point-to-multipoint MPLS-TP LSPs are unidirectional. bidirectional.
Point-to-multipont PWs are currently being defined in the IETF and
may be incorporated in MPLS-TP if required.
It MUST be possible to configure an MPLS-TP LSP such that the forward It MUST be possible to configure an MPLS-TP LSP such that the forward
and backward directions of a bidirectional MPLS-TP LSP are co-routed and backward directions of a bidirectional MPLS-TP LSP are co-routed
i.e. they follow the same path. The pairing relationship between the i.e. they follow the same path. The pairing relationship between the
forward and the backward directions must be known at each LSR or LER forward and the backward directions must be known at each LSR or LER
on a bidirectional LSP. on a bidirectional LSP.
Per-packet equal cost multi-path (ECMP) load balancing is not In normal conditions, all the packets sent over a PW or an LSP follow
applicable to MPLS-TP LSPs. the same path through the network and those that belong to a common
ordered aggregate are delivered in order. For example per-packet
equal cost multi-path (ECMP) load balancing is not applicable to
MPLS-TP LSPs.
Penultimate hop popping (PHP) is disabled on MPLS-TP LSPs by default. Penultimate hop popping (PHP) is disabled on MPLS-TP LSPs by default.
Both E-LSP and L-LSP are supported in MPLS-TP, as defined in Both E-LSP and L-LSP are supported in MPLS-TP, as defined in
[RFC3270]. [RFC3270].
The Traffic Class field (formerly the MPLS EXP field) follows the The Traffic Class field (formerly the MPLS EXP field) follows the
definition and processing rules of [RFC5462] and [RFC3270]. Only the definition and processing rules of [RFC5462] and [RFC3270].
pipe and short-pipe models are supported in MPLS-TP.
3.3. MPLS-TP LSP Clients Only the pipe and short-pipe models are supported in MPLS-TP.
This document specifies the architecture for two types of client: 3.4. MPLS-TP Client Adaptation
This document specifies the architecture for two types of client
adaptation:
o A PW o A PW
o A network layer transport service o An MPLS Label
When the client is a PW, the MPLS-TP transport domain consists of the When the client is a PW, the MPLS-TP client adaptation functions
PW encapsulation mechanisms, including the PW control word. When the include the PW encapsulation mechanisms, including the PW control
client is operating at the network layer the mechanism described in word. When the client is operating at the network layer the
Section 3.3.2 is used. mechanism described in Section 3.4.2 is used.
3.3.1. Pseudowires 3.4.1. Adaptation using Pseudowires
The architecture for a transport profile of MPLS (MPLS-TP) that uses The architecture for a transport profile of MPLS (MPLS-TP) that uses
PWs is based on the MPLS [RFC3031] and pseudowire [RFC3985] PWs is based on the MPLS [RFC3031] and pseudowire [RFC3985]
architectures. If multi-segment pseudowires are used to provide a architectures. If multi-segment pseudowires are used to provide a
packet transport service, motivated by, for example, the requirements packet transport service, motivated by, for example, the requirements
specified in [RFC5254] then the MS-PW architecture specified in [RFC5254] then the MS-PW architecture
[I-D.ietf-pwe3-ms-pw-arch] also applies. [I-D.ietf-pwe3-ms-pw-arch] also applies.
Figure 2 shows the architecture for an MPLS-TP network using single- Figure 5 shows the architecture for an MPLS-TP network using single-
segment PWs. segment PWs.
|<-------------- Emulated Service ---------------->| |<-------------- Emulated Service ---------------->|
| | | |
| |<------- Pseudowire ------->| | | |<------- Pseudowire ------->| |
| | encapsulated | | | | encapsulated | |
| | Pkt Xport Service | | | | Pkt Xport Service | |
| | | | | | | |
| | |<-- PSN Tunnel -->| | | | | |<-- PSN Tunnel -->| | |
| V V V V | | V V V V |
skipping to change at page 13, line 31 skipping to change at page 16, line 28
+-----+ ^ | | |======:=X=:=======| | | ^ +-----+ +-----+ ^ | | |======:=X=:=======| | | ^ +-----+
^ | +----+ +---+ +----+ | | ^ ^ | +----+ +---+ +----+ | | ^
| | Provider Edge 1 ^ Provider Edge 2 | | | | Provider Edge 1 ^ Provider Edge 2 | |
| | | | | | | | | |
Customer | P Router | Customer Customer | P Router | Customer
Edge 1 | | Edge 2 Edge 1 | | Edge 2
| | | |
| | | |
Native service Native service Native service Native service
Figure 2: MPLS-TP Architecture (Single Segment PW) Figure 5: MPLS-TP Architecture (Single Segment PW)
Figure 3 shows the architecture for an MPLS-TP network when multi- Figure 6 shows the architecture for an MPLS-TP network when multi-
segment pseudowires are used. Note that as in the SS-PW case, segment pseudowires are used. Note that as in the SS-PW case,
P-routers may also exist. P-routers may also exist.
|<------------Pseudowire-------------->| |<-------------------Pseudowire-------------------->|
| encapsulated | | encapsulated |
| Pkt Xport Service | | Pkt Xport Service |
| | | |
| PSN PSN | | PSN |
AC | |<--tun1->| |<--tun2--->| | AC AC | |<------- PSN tun1------>| |<--tun2-->| | AC
| V V V V V V | | V V V V V V |
| +----+ +-----+ +----+ | | +----+ +-----+ +----+ +----+ |
+----+ | |TPE1|===========|SPE1 |==========|TPE2| | +----+ +---+ | |TPE1|===============\ /=====|SPE1|==========|TPE2| | +---+
| |------|..... PW.Seg't1....X....PW.Seg't3.....|-------| | | |---|......PW.Seg't1... | \ / | ......X...PW.Seg't3.....|---| |
| CE1| | | | | | | | | |CE2 | |CE1| | | | | X | | | | | | |CE2|
| |------|..... PW.Seg't2....X....PW.Seg't4.....|-------| | | |---|......PW.Seg't2... | / \ | ......X...PW.Seg't4.....|---| |
+----+ | | |===========| |==========| | | +----+ +---+ | | |===============/ \=====| |==========| | | +---+
^ +----+ ^ +-----+ ^ +----+ ^ ^ +----+ ^ +-----+ +----+ ^ +----+ ^
| | | | | | ^ | |
| TE LSP TE LSP | | TE LSP | TE LSP |
| | | P-router |
| | | |
|<---------------- Emulated Service ----------------->| |<-------------------- Emulated Service ------------------->|
Figure 3: MPLS-TP Architecture (Multi-Segment PW) Figure 6: MPLS-TP Architecture (Multi-Segment PW)
The corresponding domain of the MPLS-TP protocol stack including PWs The corresponding domain of the MPLS-TP protocol stack including PWs
is shown in Figure 4. In transport network nomenclature, the is shown in Figure 7.
pseudowire maps to the MPLS-TP channel, while the LSP maps to the
MPLS-TP path.
+---------------------------+ +-------------------+
| Client service | | Client Layer |
/===========================\ /===================\ /===================\
H PW Encapsulation H \ <---- PW Control word H PW Encap H H PW OAM H
H---------------------------H \ <---- Normalised client H-------------------H H-------------------H /===================\
H PW OAM H MPLS-TP channel H PW Demux (S=1) H H PW Demux (S=1) H H LSP OAM H
H---------------------------H / H-------------------H H-------------------H H-------------------H
H PW Demux (S=1) H / H LSP Demux(s) H H LSP Demux(s) H H LSP Demux(s) H
H---------------------------H \ \===================/ \===================/ \===================/
H LSP OAM H \ | Server Layer | | Server Layer | | Server Layer |
H---------------------------H / MPLS-TP Path(s) +-------------------+ +-------------------+ +-------------------+
H LSP Demultiplexer(s) H /
\===========================/
| Server |
+---------------------------+
Figure 4: Domain of MPLS-TP Layer Network using Pseudowires User Traffic PW OAM LSP OAM
Note: Transport Service Layer = PW Demux
Transport Path Layer = LSP Demux
Figure 7: MPLS-TP Layer Network using Pseudowires
When providing a Virtual Private Wire Service (VPWS), Virtual Private When providing a Virtual Private Wire Service (VPWS), Virtual Private
Local Area Network Service (VPLS), Virtual Private Multicast Service Local Area Network Service (VPLS), Virtual Private Multicast Service
(VPMS) or Internet Protocol Local Area Network Service (IPLS), (VPMS) or Internet Protocol Local Area Network Service (IPLS),
pseudowires MUST be used to carry a client service. pseudowires MUST be used to carry the client service. These PWs can
be configured either statically or via the control plane defined in
[RFC4447].
Note that in MPLS-TP environments where IP is used for control or OAM Note that in MPLS-TP environments where IP is used for control or OAM
purposes, IP MAY be carried over the LSP demultiplexers as per purposes, IP MAY be carried over the LSP demultiplexers as per
RFC3031 [RFC3031], or directly over the server. RFC3031 [RFC3031], or directly over the server.
3.3.2. Network Layer Clients 3.4.2. Network Layer Clients
MPLS-TP LSPs can be used to deliver a transport service for network MPLS-TP LSPs can be used to transport network layer clients. Any
layer clients. Such a network layer transport service (NLTS) can be network layer protocol can be transported between service interfaces.
used to transport any network layer protocol between service Examples of network layer protocols include IP, MPLS and MPLS-TP.
interfaces. Examples of network layer protocols include IP, MPLS and
MPLS-TP.
|<--------------- Client Service ----------------->| With network layer transport, the MPLS-TP domain provides a
bidirectional point-to-point connection between two customer edge
(CE) nodes. Note that a CE may be an an IP, MPLS or MPLS-TP node.
As shown in Figure 8, there is an attachment circuit between the CE
node on the left and its corresponding provider edge (PE) node that
provides the service interface, a bidirectional LSP across the
MPLS-TP service network to the corresponding PE node on the right,
and an attachment circuit between that PE node and the corresponding
CE node for this service.
|<------------- Client Network Layer-------------->|
| | | |
| |<---- Pkt Xport Service --->| | |<---- Pkt Xport Service --->|
| | | | | | | |
| | |<-- PSN Tunnel -->| | | | | |<-- PSN Tunnel -->| | |
| V V V V | | V V V V |
V AC +----+ +---+ +----+ AC V V AC +----+ +---+ +----+ AC V
+-----+ | | PE1|======:=X=:=======| PE2| | +-----+ +-----+ | | PE1|======:=X=:=======| PE2| | +-----+
| |----------|...........:LSP:............|----------| | | |----------|...........:LSP:............|----------| |
| CE1 | | | | | : | | | | CE2 | | CE1 | | | | | : | | | | CE2 |
| |----------|...........: IP:............|----------| | | |----------|...........: IP:............|----------| |
+-----+ ^ | | |======:=X=:=======| | | ^ +-----+ +-----+ ^ | | |======:=X=:=======| | | ^ +-----+
^ | +----+ +---+ +----+ | | ^ ^ | +----+ +---+ +----+ | | ^
| | Provider Edge 1 ^ Provider Edge 2 | | | | Provider Edge 1 ^ Provider Edge 2 | |
| | | | | | | | | |
Customer | P Router | Customer Customer | P Router | Customer
Edge 1 | | Edge 2 Edge 1 | | Edge 2
| | | |
| | | |
Native service Native service Native service Native service
Figure 5: MPLS-TP Architecture for Network Layer Clients Figure 8: MPLS-TP Architecture for Network Layer Clients
+---------------------------+
| Client service |
/===========================\ <---- Normalised client
H Service LSP OAM H \
H---------------------------H } MPLS-TP channel
H Svc LSP Demux (S=1) H /
H---------------------------H \
H LSP OAM H \
H---------------------------H / MPLS-TP Path(s)
H LSP Demultiplexer(s) H /
\===========================/
| Server |
+---------------------------+
Figure 6: Domain of MPLS-TP Layer Network for IP and LSP Clients At the ingress service interface the PE transforms the ingress packet
to the format that will be carried over the transport network, and
similarly the corresponding service interface at the egress PE
transforms the packet to the format needed by the attached CE. The
attachment circuits may be heterogeneous (e.g., any combination of
SDH, PPP, Frame Relay etc) and network layer protocol payloads arrive
at the service interface encapsulated in the Layer1/Layer2 encoding
defined for that access link type. It should be noted that the set
of network layer protocols includes MPLS and hence MPLS encoded
packets with an MPLS label stack (the client MPLS stack), may appear
at the service interface.
With network layer transport, the MPLS-TP domain provides a +-------------------+
bidirectional point-to-point connection between two customer edge | Client Layer |
(CE) nodes. Note that a CE may be an an IP, MPLS or MPLS-TP node. /===================\ /===================\
Point-to- multipoint service is for further study. As shown in H Encap Label (S=1) H H SvcLSP OAM H
Figure 7, there is an attachment circuit between the CE node on the H-------------------H H-------------------H /===================\
left and its corresponding provider edge (PE) node that provides the H SvcLSP Demux H H SvcLSP Demux (S=1)H H LSP OAM H
service interface, a bidirectional LSP across the MPLS-TP service H-------------------H H-------------------H H-------------------H
network to the corresponding PE node on the right, and an attachment H LSP Demux(s) H H LSP Demux(s) H H LSP Demux(s) H
circuit between that PE node and the corresponding CE node for this \===================/ \===================/ \===================/
service. | Server Layer | | Server Layer | | Server Layer |
+-------------------+ +-------------------+ +-------------------+
: +--------------------+ : User Traffic Service LSP OAM LSP OAM
: | +------------+ | :
: | | Management | | :
+------+ : | | system(s) | | : +------+
| C | : | +------------+ | : | CE | +------+
|device| : | | : |device|--| C |
+------+ : | +------+ : | of | |device|
| : | | x=:=|SVC A| +------+
| : | | | : +------+
+------+ : | | PE | :
+------+ | CE | : | |device| :
| C | |device| : +------+ +------+ | | :
|device|--| of |=:=x |--| |--| | :
+------+ |SVC A| : | | | | +------+ :
+------+ : | PE | | P | | :
+------+ : |device| |device| | :
+------+ | CE | : | | | | +------+ :
| C |--|device|=:=x |--| |--| | :
|device| | of | : +------+ +------+ | | :
+------+ |SVC B| : | | PE | :
+------+ : | |device| :
| : | | | : +------+
| : | | x=:=| CE | +------+
+------+ : | +------+ : |device| | C |
| C | : | | : | of |--|device|
|device| : | | : |SVC B| +------+
+------+ : | | : +------+
: | | :
Customer | | Customer
interface | MPLS-TP | interface
+--------------------+
|<---- Provider ---->|
| network |
Key: ==== attachment circuit Note: Transport Service Layer = SvcLSP Demux
x service interface Transport Path Layer = LSP Demux
---- link
Figure 7: Network Layer Transport Service Components Note that the functions of the Encap label and the Service Label may represented
by a single label
At the service interface the PE transforms the ingress packet to the Figure 9: Domain of MPLS-TP Layer Network for IP and LSP Clients
format that will be carried over the transport network, and similarly
the corresponding service interface at the egress PE transforms the
packet to the format needed by the attached CE. The attachment
circuits may be heterogeneous (e.g., any combination of SDH, PPP,
Frame Relay etc) and network layer protocol payloads arrive at the
service interface encapsulated in the Layer1/Layer2 encoding defined
for that access link type. It should be noted that the set of
network layer protocols includes MPLS and hence MPLS encoded packets
with an MPLS label stack (the client MPLS stack), may appear at the
service interface.
Within the MPLS-TP transport network, the network layer protocols are Within the MPLS-TP transport network, the network layer protocols are
carried over the MPLS-TP LSP using a separate MPLS label stack (the carried over the MPLS-TP LSP using a separate MPLS label stack (the
server stack). The server stack is entirely under the control of the server stack). The server stack is entirely under the control of the
nodes within the MPLS-TP transport network and it is not visible nodes within the MPLS-TP transport network and it is not visible
outside that network. In accordance with [RFC3032], the bottom outside that network. In accordance with [RFC3032], the bottom
label, with the 'bottom of stack' bit set to '1', defines the network label, with the 'bottom of stack' bit set to '1', defines the network
layer protocol being transported. Figure 8 shows how an a client layer protocol being transported. Figure 9 shows how an a client
network protocol stack (which may be an MPLS label stack and payload) network protocol stack (which may be an MPLS label stack and payload)
is carried over as a network layer transport service over an MPLS-TP is carried over as a network layer transport service over an MPLS-TP
transport network. transport network.
+------------------------------------+
| MPLS-TP LSP label(s) (S=0) | n*4 octets
. . (four octets per label)
+------------------------------------+
| Service label (s=1) | 4 octets
+------------------------------------+
| Client Network |
| Layer Protocol |
| Stack. |
+------------------------------------+
Note that the Client Network Layer Protocol
Stack may include an MPLS label stack
with the S bit set (S=1).
Figure 8: Network Layer Transport Service Protocol Stack
A label per network layer protocol payload type that is to be A label per network layer protocol payload type that is to be
transported is REQUIRED. Such labels are referred to as "Service transported is REQUIRED. Such labels are referred to as "Service
Labels", one of which is shown in Figure 8. The mapping between Labels", one of which is shown in Figure 9. The mapping between
protocol payload type and Service Label is either configured or protocol payload type and Service Label is either configured or
signaled. signaled.
Service labels are typically carried over an MPLS-TP edge-to-edge Service labels are typically carried over an MPLS-TP edge-to-edge
LSP, which is also shown in Figure 8. The use of an edge-to-edge LSP LSP, which is also shown in Figure 9. The use of an edge-to-edge LSP
is RECOMMENDED when more than one protocol payload type is to be is RECOMMENDED when more than one protocol payload type is to be
transported. For example, if only MPLS is carried then a single transported. For example, if only MPLS is carried then a single
Service Label would be used to provided both payload type indication Service Label would be used to provided both payload type indication
and the MPLS-TP edge-to-edge LSP. Alternatively, if both IP and MPLS and the MPLS-TP edge-to-edge LSP. Alternatively, if both IP and MPLS
is to be carried then two Service Labels would be mapped on to a is to be carried then two Service Labels would be mapped on to a
common MPLS-TP edge-to-edge LSP. common MPLS-TP edge-to-edge LSP.
As noted above, any layer 2 and layer 1 protocols used to carry the As noted above, any layer 2 and layer 1 protocols used to carry the
network layer protocol over the attachment circuit is terminated at network layer protocol over the attachment circuit is terminated at
the service interface and is not transported across the MPLS-TP the service interface and is not transported across the MPLS-TP
network. This enables the use of different L2/L1 technologies at two network. This enables the use of different layer 2 / layer 1
service interfaces. technologies at two service interfaces.
At each service interface, Layer 2 addressing must be used to ensure At each service interface, Layer 2 addressing must be used to ensure
the proper delivery of a network layer packet to the adjacent node. the proper delivery of a network layer packet to the adjacent node.
This is typically only an issue for LAN media technologies (e.g., This is typically only an issue for LAN media technologies (e.g.,
Ethernet) which have Media Access Control (MAC) addresses. In cases Ethernet) which have Media Access Control (MAC) addresses. In cases
where a MAC address is needed, the sending node MUST set the where a MAC address is needed, the sending node MUST set the
destination MAC address to an address that ensures delivery to the destination MAC address to an address that ensures delivery to the
adjacent node. That is the CE sets the destination MAC address to an adjacent node. That is the CE sets the destination MAC address to an
address that ensures delivery to the PE, and the PE sets the address that ensures delivery to the PE, and the PE sets the
destination MAC address to an address that ensures delivery to the destination MAC address to an address that ensures delivery to the
CE. The specific address used is technology type specific and is not CE. The specific address used is technology type specific and is not
covered in this document. (Examples for the Ethernet case include a covered in this document. In some technologies the MAC address will
need to be configured (Examples for the Ethernet case include a
configured unicast MAC address for the adjacent node, or even using configured unicast MAC address for the adjacent node, or even using
the broadcast MAC address when the CE-PE service interface is the broadcast MAC address when the CE-PE service interface is
dedicated. The configured address is then used as the MAC dedicated. The configured address is then used as the MAC
destination address for all packets sent over the service interface.) destination address for all packets sent over the service interface.)
A PE MAY be configured to participate in the client network's link
layer in order to simplify CE configuration, for example to execute
neighbor discover protocols such as Address Resolution Protocol
(ARP), [RFC0826], inverse ARP[RFC2390], IPv6 neighbor discovery
[RFC2461] or IPv6 inverse neighbor discovery[RFC3122]. Mechanisms to
achieve such participation are outside the scope of this document.
See [I-D.ietf-l2vpn-arp-mediation] for an example mechanism.
Note that when the two CEs operating over the network layer transport Note that when the two CEs operating over the network layer transport
service are running a routing protocol such as ISIS or OSPF some care service are running a routing protocol such as ISIS or OSPF some care
should be taken to configure the routing protocols to use point- to- should be taken to configure the routing protocols to use point- to-
point adjacencies. The specifics of such configuration is outside point adjacencies. The specifics of such configuration is outside
the scope of this document. the scope of this document.
[Editors Note we need to confer with ISIS and OSPF WG to verify that [Editors Note we need to confer with ISIS and OSPF WG to verify that
the cautionary note above is necessary and sufficient.] the cautionary note above is necessary and sufficient.]
The CE to CE service types and corresponding labels may be configured The CE to CE service types and corresponding labels may be configured
skipping to change at page 20, line 23 skipping to change at page 21, line 29
o It could be carried over the attachment circuit in IP. o It could be carried over the attachment circuit in IP.
In the MPLS and ACH cases above, this label value is used to carry In the MPLS and ACH cases above, this label value is used to carry
LSP signaling without any further encapsulation. This signaling LSP signaling without any further encapsulation. This signaling
channel is always point-to-point and MUST use local CE and PE channel is always point-to-point and MUST use local CE and PE
addressing. addressing.
The method(s) to be used will be described in a future version of the The method(s) to be used will be described in a future version of the
document. document.
3.4. Identifiers 3.5. Identifiers
Identifiers to be used in within MPLS-TP where compatibility with Identifiers to be used in within MPLS-TP where compatibility with
existing MPLS control plane conventions are necessary are described existing MPLS control plane conventions are necessary are described
in [draft-swallow-mpls-tp-identifiers-00]. The MPLS-TP requirements in [draft-swallow-mpls-tp-identifiers-00]. The MPLS-TP requirements
[RFC5654] require that the elements and objects in an MPLS-TP [RFC5654] require that the elements and objects in an MPLS-TP
environment are able to be configured and managed without a control environment are able to be configured and managed without a control
plane. In such an environment many conventions for defining plane. In such an environment many conventions for defining
identifiers are possible. However it is also anticipated that identifiers are possible. However it is also anticipated that
operational environments where MPLS-TP objects, LSPs and PWs will be operational environments where MPLS-TP objects, LSPs and PWs will be
signaled via existing protocols such as the Label Distribution signaled via existing protocols such as the Label Distribution
skipping to change at page 21, line 10 skipping to change at page 22, line 17
[RFC4379]and BFD for MPLS LSPs [I-D.ietf-bfd-mpls] have defined alert [RFC4379]and BFD for MPLS LSPs [I-D.ietf-bfd-mpls] have defined alert
mechanisms that enable an MPLS LSR to identify and process MPLS OAM mechanisms that enable an MPLS LSR to identify and process MPLS OAM
packets when the OAM packets are encapsulated in an IP header. These packets when the OAM packets are encapsulated in an IP header. These
alert mechanisms are based on TTL expiration and/or use an IP alert mechanisms are based on TTL expiration and/or use an IP
destination address in the range 127/8. These mechanisms are the destination address in the range 127/8. These mechanisms are the
default mechanisms for MPLS networks in general for identifying MPLS default mechanisms for MPLS networks in general for identifying MPLS
OAM packets when the OAM packets are encapsulated in an IP header. OAM packets when the OAM packets are encapsulated in an IP header.
MPLS-TP is unable to rely on the availability of IP and thus uses the MPLS-TP is unable to rely on the availability of IP and thus uses the
GACH/GAL to demultiplex OAM packets. GACH/GAL to demultiplex OAM packets.
3.5. Operations, Administration and Maintenance (OAM) 3.6. Operations, Administration and Maintenance (OAM)
MPLS-TP supports a comprehensive set of OAM capabilities for packet MPLS-TP supports a comprehensive set of OAM capabilities for packet
transport applications, with equivalent capabilities to those transport applications, with equivalent capabilities to those
provided in SONET/SDH. provided in SONET/SDH.
MPLS-TP defines mechanisms to differentiate specific packets (e.g. MPLS-TP defines mechanisms to differentiate specific packets (e.g.
OAM, APS, MCC or SCC) from those carrying user data packets on the OAM, APS, MCC or SCC) from those carrying user data packets on the
same LSP. These mechanisms are described in [RFC5586]. same LSP. These mechanisms are described in [RFC5586].
MPLS-TP requires [I-D.ietf-mpls-tp-oam-requirements] that a set of MPLS-TP requires [I-D.ietf-mpls-tp-oam-requirements] that a set of
OAM capabilities is available to perform fault management (e.g. fault OAM capabilities is available to perform fault management (e.g. fault
detection and localization) and performance monitoring (e.g. packet detection and localization) and performance monitoring (e.g. packet
delay and loss measurement) of the LSP, PW or section. The framework delay and loss measurement) of the LSP, PW or section. The framework
for OAM in MPLS-TP is specified in [I-D.ietf-mpls-tp-oam-framework]. for OAM in MPLS-TP is specified in [I-D.ietf-mpls-tp-oam-framework].
MPLS-TP OAM packets share the same fate as their corresponding data
packets, and are identified through the Generic Associated Channel
mechanism [RFC5586]. This uses a combination of an Associated
Channel Header (ACH) and a Generic Alert Label (GAL) to create a
control channel associated to an LSP, Section or PW.
3.6.1. OAM Architecture
OAM and monitoring in MPLS-TP is based on the concept of maintenance OAM and monitoring in MPLS-TP is based on the concept of maintenance
entities, as described in [I-D.ietf-mpls-tp-oam-framework]. A entities, as described in [I-D.ietf-mpls-tp-oam-framework]. A
Maintenance Entity can be viewed as the association of two (or more) Maintenance Entity can be viewed as the association of two (or more)
Maintenance End Points (MEPs) (see example in Figure 9 ). The MEPs Maintenance End Points (MEPs) (see example in Figure 10 ). The MEPs
that form an ME should be configured and managed to limit the OAM that form an ME should be configured and managed to limit the OAM
responsibilities of an OAM flow within a network or sub- network, or responsibilities of an OAM flow within a network or sub- network, or
a transport path or segment, in the specific layer network that is a transport path or segment, in the specific layer network that is
being monitored and managed. being monitored and managed.
Each OAM flow is associated with a single ME. Each MEP within an ME Each OAM flow is associated with a single ME. Each MEP within an ME
resides at the boundaries of that ME. An ME may also include a set resides at the boundaries of that ME. An ME may also include a set
of zero or more Maintenance Intermediate Points (MIPs), which reside of zero or more Maintenance Intermediate Points (MIPs), which reside
within the Maintenance Entity. Maintenance end points (MEPs) are within the Maintenance Entity. Maintenance end points (MEPs) are
capable of sourcing and sinking OAM flows, while maintenance capable of sourcing and sinking OAM flows, while maintenance
skipping to change at page 22, line 28 skipping to change at page 23, line 32
(Carrier 1) LSP OAM (Carrier 2) (Carrier 1) LSP OAM (Carrier 2)
(inter-carrier) (inter-carrier)
..... ..... ..... .......... .......... ..... ..... ..... ..... ..... .......... .......... ..... .....
|MEP|---|MIP|---|MIP|--|MEP||MEP|---|MEP||MEP|--|MIP|----|MEP| |MEP|---|MIP|---|MIP|--|MEP||MEP|---|MEP||MEP|--|MIP|----|MEP|
''''' ''''' ''''' '''''''''' '''''''''' ''''' ''''' ''''' ''''' ''''' '''''''''' '''''''''' ''''' '''''
<------------ ME ----------><--- ME ----><------- ME --------> <------------ ME ----------><--- ME ----><------- ME -------->
Note: MEPs for End-to-end LSP OAM exist outside of the scope Note: MEPs for End-to-end LSP OAM exist outside of the scope
of this figure. of this figure.
Figure 9: Example of MPLS-TP OAM Figure 10: Example of MPLS-TP OAM
Figure 10 illustrates how the concept of Maintenance Entities can be Figure 11 illustrates how the concept of Maintenance Entities can be
mapped to sections, LSPs and PWs in an MPLS-TP network that uses MS- mapped to sections, LSPs and PWs in an MPLS-TP network that uses MS-
PWs. PWs.
Native |<-------------------- PW15 --------------------->| Native Native |<-------------------- PW15 --------------------->| Native
Layer | | Layer Layer | | Layer
Service | |<-PSN13->| |<-PSN3X->| |<-PSNXZ->| | Service Service | |<-PSN13->| |<-PSN3X->| |<-PSNXZ->| | Service
(AC1) V V LSP V V LSP V V LSP V V (AC2) (AC1) V V LSP V V LSP V V LSP V V (AC2)
+----+ +-+ +----+ +----+ +-+ +----+ +----+ +-+ +----+ +----+ +-+ +----+
+---+ |TPE1| | | |SPE3| |SPEX| | | |TPEZ| +---+ +---+ |TPE1| | | |SPE3| |SPEX| | | |TPEZ| +---+
| | | |=========| |=========| |=========| | | | | | | |=========| |=========| |=========| | | |
skipping to change at page 23, line 36 skipping to change at page 24, line 36
TPE1: Terminating Provider Edge 1 SPE2: Switching Provider Edge 3 TPE1: Terminating Provider Edge 1 SPE2: Switching Provider Edge 3
TPEX: Terminating Provider Edge X SPEZ: Switching Provider Edge Z TPEX: Terminating Provider Edge X SPEZ: Switching Provider Edge Z
.---. ME . MEP ==== LSP .... PW .---. ME . MEP ==== LSP .... PW
SME: Section Maintenance Entity SME: Section Maintenance Entity
LME: LSP Maintenance Entity LME: LSP Maintenance Entity
PME: PW Maintenance Entity PME: PW Maintenance Entity
Figure 10: MPLS-TP OAM archtecture Figure 11: MPLS-TP OAM archtecture
The following MPLS-TP MEs are specified in The following MPLS-TP MEs are specified in
[I-D.ietf-mpls-tp-oam-framework]: [I-D.ietf-mpls-tp-oam-framework]:
o A Section Maintenance Entity (SME), allowing monitoring and o A Section Maintenance Entity (SME), allowing monitoring and
management of MPLS-TP Sections (between MPLS LSRs). management of MPLS-TP Sections (between MPLS LSRs).
o A LSP Maintenance Entity (LME), allowing monitoring and management o A LSP Maintenance Entity (LME), allowing monitoring and management
of an end-to-end LSP (between LERs). of an end-to-end LSP (between LERs).
skipping to change at page 24, line 26 skipping to change at page 25, line 26
Individual MIPs along the path of an LSP or PW are addressed by Individual MIPs along the path of an LSP or PW are addressed by
setting the appropriate TTL in the label for the OAM packet, as per setting the appropriate TTL in the label for the OAM packet, as per
[I-D.ietf-pwe3-segmented-pw]. Note that this works when the location [I-D.ietf-pwe3-segmented-pw]. Note that this works when the location
of MIPs along the LSP or PW path is known by the MEP. There may be of MIPs along the LSP or PW path is known by the MEP. There may be
cases where this is not the case in general MPLS networks e.g. cases where this is not the case in general MPLS networks e.g.
following restoration using a facility bypass LSP. In these cases, following restoration using a facility bypass LSP. In these cases,
tools to trace the path of the LSP may be used to determine the tools to trace the path of the LSP may be used to determine the
appropriate setting for the TTL to reach a specific MIP. appropriate setting for the TTL to reach a specific MIP.
MPLS-TP OAM packets share the same fate as their corresponding data Within an LSR or PE, MEPs and MIPs can only be placed where MPLS
packets, and are identified through the Generic Associated Channel layer processing is performed on a packet. The architecture mandates
mechanism [RFC5586]. This uses a combination of an Associated that this must occur at least once.
Channel Header (ACH) and a Generic Alert Label (GAL) to create a
control channel associated to an LSP, Section or PW. There is only one MIP on an LSP or PW in each node. That MIP is for
all applicable OAM functions on its associated LSP or PW. This
document does not specify the default position of the MIP within the
node. Therefore, this document does not specify where the exception
mechanism resides (i.e. at the ingress interface, the egress
interface, or some other location within the node). An optional
protocol may be developed that sets the position of a MIP along the
path of an LSP or PW within the node (and thus determines the
exception processing location).
MEPs may only act as a sink of OAM packets when the label associated
with the LSP or PW for that ME is popped. MIPs can only be placed
where an exception to the normal forwarding operation occurs. A MEP
may act as a source of OAM packets whereever a label is pushed or
swapped. For example, on a MS-PW, a MEP may source OAM within an
S-PE or a T-PE, but a MIP may only be associated with a S-PE and a
sink MEP can only be associated with a T-PE.
3.6.2. OAM Functions
The MPLS-TP OAM architecture support a wide range of OAM functions, The MPLS-TP OAM architecture support a wide range of OAM functions,
including the following including the following
o Continuity Check o Continuity Check
o Connectivity Verification o Connectivity Verification
o Performance monitoring (e.g. loss and delay) o Performance monitoring (e.g. loss and delay)
o Alarm suppression o Alarm suppression
o Remote Integrity o Remote Integrity
skipping to change at page 25, line 11 skipping to change at page 26, line 29
the case of MPLS-TP deployment with IP functionality, all existing the case of MPLS-TP deployment with IP functionality, all existing
IP-MPLS OAM functions, e.g. LSP-Ping, BFD and VCCV, may be used. IP-MPLS OAM functions, e.g. LSP-Ping, BFD and VCCV, may be used.
This does not preclude the use of other OAM tools in an IP This does not preclude the use of other OAM tools in an IP
addressable network. addressable network.
One use of OAM mechanisms is to detect link failures, node failures One use of OAM mechanisms is to detect link failures, node failures
and performance outside the required specification which then may be and performance outside the required specification which then may be
used to trigger recovery actions, according to the requirements of used to trigger recovery actions, according to the requirements of
the service. the service.
3.6. Generic Associated Channel (G-ACh) 3.7. Generic Associated Channel (G-ACh)
For correct operation of the OAM it is important that the OAM packets For correct operation of the OAM it is important that the OAM packets
fate share with the data packets. In addition in MPSL-TP it is fate share with the data packets. In addition in MPSL-TP it is
necessary to discriminate between user data payloads and other types necessary to discriminate between user data payloads and other types
of payload. For example the packet may contain a Signaling of payload. For example the packet may contain a Signaling
Communication Channel (SCC), or a channel used for Automatic Communication Channel (SCC), or a channel used for Automatic
Protection Switching (APS) data. Such packets are carried on a Protection Switching (APS) data. Such packets are carried on a
control channel associated to the LSP, Section or PW. This is control channel associated to the LSP, Section or PW. This is
achieved by carrying such packets on a generic control channel achieved by carrying such packets on a generic control channel
associated to the LSP, PW or section. associated to the LSP, PW or section.
skipping to change at page 26, line 36 skipping to change at page 28, line 6
a PW type. a PW type.
Since the G-ACh traffic is indistinguishable from the user data Since the G-ACh traffic is indistinguishable from the user data
traffic at the server layer, bandwidth and QoS commitments apply to traffic at the server layer, bandwidth and QoS commitments apply to
the gross traffic on the LSP, PW or section. Protocols using the the gross traffic on the LSP, PW or section. Protocols using the
G-ACh must therefore take into consideration the impact they have on G-ACh must therefore take into consideration the impact they have on
the user data that they are sharing resources with. In addition, the user data that they are sharing resources with. In addition,
protocols using the G-ACh MUST conform to the security and congestion protocols using the G-ACh MUST conform to the security and congestion
considerations described in [RFC5586]. . considerations described in [RFC5586]. .
Figure 11 shows the reference model depicting how the control channel Figure 12 shows the reference model depicting how the control channel
is associated with the pseudowire protocol stack. This is based on is associated with the pseudowire protocol stack. This is based on
the reference model for VCCV shown in Figure 2 of [RFC5085]. the reference model for VCCV shown in Figure 2 of [RFC5085].
+-------------+ +-------------+ +-------------+ +-------------+
| Payload | < Service / FCAPS > | Payload | | Payload | < Service / FCAPS > | Payload |
+-------------+ +-------------+ +-------------+ +-------------+
| Demux / | < CW / ACH for PWs > | Demux / | | Demux / | < CW / ACH for PWs > | Demux / |
|Discriminator| |Discriminator| |Discriminator| |Discriminator|
+-------------+ +-------------+ +-------------+ +-------------+
| PW | < PW > | PW | | PW | < PW > | PW |
skipping to change at page 27, line 27 skipping to change at page 28, line 32
| | | |
| ____ ___ ____ | | ____ ___ ____ |
| _/ \___/ \ _/ \__ | | _/ \___/ \ _/ \__ |
| / \__/ \_ | | / \__/ \_ |
| / \ | | / \ |
+--------| MPLS/MPLS-TP Network |---+ +--------| MPLS/MPLS-TP Network |---+
\ / \ /
\ ___ ___ __ _/ \ ___ ___ __ _/
\_/ \____/ \___/ \____/ \_/ \____/ \___/ \____/
Figure 11: PWE3 Protocol Stack Reference Model including the G-ACh Figure 12: PWE3 Protocol Stack Reference Model including the G-ACh
PW associated channel messages are encapsulated using the PWE3 PW associated channel messages are encapsulated using the PWE3
encapsulation, so that they are handled and processed in the same encapsulation, so that they are handled and processed in the same
manner (or in some cases, an analogous manner) as the PW PDUs for manner (or in some cases, an analogous manner) as the PW PDUs for
which they provide a control channel. which they provide a control channel.
Figure 12 shows the reference model depicting how the control channel Figure 13 shows the reference model depicting how the control channel
is associated with the LSP protocol stack. is associated with the LSP protocol stack.
+-------------+ +-------------+ +-------------+ +-------------+
| Payload | < Service > | Payload | | Payload | < Service > | Payload |
+-------------+ +-------------+ +-------------+ +-------------+
|Discriminator| < ACH on LSP > |Discriminator| |Discriminator| < ACH on LSP > |Discriminator|
+-------------+ +-------------+ +-------------+ +-------------+
|Demultiplexer| < GAL on LSP > |Demultiplexer| |Demultiplexer| < GAL on LSP > |Demultiplexer|
+-------------+ +-------------+ +-------------+ +-------------+
| PSN | < LSP > | PSN | | PSN | < LSP > | PSN |
skipping to change at page 28, line 26 skipping to change at page 29, line 26
| | | |
| ____ ___ ____ | | ____ ___ ____ |
| _/ \___/ \ _/ \__ | | _/ \___/ \ _/ \__ |
| / \__/ \_ | | / \__/ \_ |
| / \ | | / \ |
+--------| MPLS/MPLS-TP Network |---+ +--------| MPLS/MPLS-TP Network |---+
\ / \ /
\ ___ ___ __ _/ \ ___ ___ __ _/
\_/ \____/ \___/ \____/ \_/ \____/ \___/ \____/
Figure 12: MPLS Protocol Stack Reference Model including the LSP Figure 13: MPLS Protocol Stack Reference Model including the LSP
Associated Control Channel Associated Control Channel
3.7. Control Plane 3.8. Control Plane
MPLS-TP should be capable of being operated with centralized Network MPLS-TP should be capable of being operated with centralized Network
Management Systems (NMS). The NMS may be supported by a distributed Management Systems (NMS). The NMS may be supported by a distributed
control plane, but MPLS-TP can operated in the absence of such a control plane, but MPLS-TP can operated in the absence of such a
control plane. A distributed control plane may be used to enable control plane. A distributed control plane may be used to enable
dynamic service provisioning in multi-vendor and multi-domain dynamic service provisioning in multi-vendor and multi-domain
environments using standardized protocols that guarantee environments using standardized protocols that guarantee
interoperability. Where the requirements specified in [RFC5654] can interoperability. Where the requirements specified in [RFC5654] can
be met, the MPLS transport profile uses existing control plane be met, the MPLS transport profile uses existing control plane
protocols for LSPs and PWs. protocols for LSPs and PWs.
Figure 13 illustrates the relationship between the MPLS-TP control Figure 14 illustrates the relationship between the MPLS-TP control
plane, the forwarding plane, the management plane, and OAM for point- plane, the forwarding plane, the management plane, and OAM for point-
to-point MPLS-TP LSPs or PWs. to-point MPLS-TP LSPs or PWs.
+------------------------------------------------------------------+ +------------------------------------------------------------------+
| | | |
| Network Management System and/or | | Network Management System and/or |
| | | |
| Control Plane for Point to Point Connections | | Control Plane for Point to Point Connections |
| | | |
+------------------------------------------------------------------+ +------------------------------------------------------------------+
skipping to change at page 29, line 32 skipping to change at page 30, line 32
''''''''''''''''''''''' ''''''''''''''' ''''''''''''''''''''''' ''''''''''''''''''''''' ''''''''''''''' '''''''''''''''''''''''
Note: Note:
1) NMS may be centralised or distributed. Control plane is 1) NMS may be centralised or distributed. Control plane is
distributed distributed
2) 'Edge' functions refers to those functions present at 2) 'Edge' functions refers to those functions present at
the edge of a PSN domain, e.g. NSP or classification. the edge of a PSN domain, e.g. NSP or classification.
3) The control plane may be transported over the server 3) The control plane may be transported over the server
layer, and LSP or a G-ACh. layer, and LSP or a G-ACh.
Figure 13: MPLS-TP Control Plane Architecture Context Figure 14: MPLS-TP Control Plane Architecture Context
The MPLS-TP control plane is based on a combination of the LDP-based The MPLS-TP control plane is based on a combination of the LDP-based
control plane for pseudowires [RFC4447] and the RSVP-TE based control control plane for pseudowires [RFC4447] and the RSVP-TE based control
plane for MPLS-TP LSPs [RFC3471]. Some of the RSVP-TE functions that plane for MPLS-TP LSPs [RFC3471]. Some of the RSVP-TE functions that
are required for LSP signaling for MPLS-TP are based on GMPLS. are required for LSP signaling for MPLS-TP are based on GMPLS.
The distributed MPLS-TP control plane provides the following The distributed MPLS-TP control plane provides the following
functions: functions:
o Signaling o Signaling
skipping to change at page 30, line 9 skipping to change at page 31, line 9
In a multi-domain environment, the MPLS-TP control plane supports In a multi-domain environment, the MPLS-TP control plane supports
different types of interfaces at domain boundaries or within the different types of interfaces at domain boundaries or within the
domains. These include the User-Network Interface (UNI), Internal domains. These include the User-Network Interface (UNI), Internal
Network Node Interface (I-NNI), and External Network Node Interface Network Node Interface (I-NNI), and External Network Node Interface
(E-NNI). Note that different policies may be defined that control (E-NNI). Note that different policies may be defined that control
the information exchanged across these interface types. the information exchanged across these interface types.
The MPLS-TP control plane is capable of activating MPLS-TP OAM The MPLS-TP control plane is capable of activating MPLS-TP OAM
functions as described in the OAM section of this document functions as described in the OAM section of this document
Section 3.5 e.g. for fault detection and localization in the event of Section 3.6 e.g. for fault detection and localization in the event of
a failure in order to efficiently restore failed transport paths. a failure in order to efficiently restore failed transport paths.
The MPLS-TP control plane supports all MPLS-TP data plane The MPLS-TP control plane supports all MPLS-TP data plane
connectivity patterns that are needed for establishing transport connectivity patterns that are needed for establishing transport
paths including protected paths as described in the survivability paths including protected paths as described in the survivability
section Section 3.9 of this document. Examples of the MPLS-TP data section Section 3.10 of this document. Examples of the MPLS-TP data
plane connectivity patterns are LSPs utilizing the fast reroute plane connectivity patterns are LSPs utilizing the fast reroute
backup methods as defined in [RFC4090] and ingress-to-egress 1+1 or backup methods as defined in [RFC4090] and ingress-to-egress 1+1 or
1:1 protected LSPs. 1:1 protected LSPs.
The MPLS-TP control plane provides functions to ensure its own The MPLS-TP control plane provides functions to ensure its own
survivability and to enable it to recover gracefully from failures survivability and to enable it to recover gracefully from failures
and degradations. These include graceful restart and hot redundant and degradations. These include graceful restart and hot redundant
configurations. Depending on how the control plane is transported, configurations. Depending on how the control plane is transported,
varying degrees of decoupling between the control plane and data varying degrees of decoupling between the control plane and data
plane may be achieved. plane may be achieved.
3.7.1. PW Control Plane 3.8.1. PW Control Plane
An MPLS-TP network provides many of its transport services using An MPLS-TP network provides many of its transport services using
single-segment or multi-segment pseudowires, in compliance with the single-segment or multi-segment pseudowires, in compliance with the
PWE3 architecture ([RFC3985] and [I-D.ietf-pwe3-ms-pw-arch] ). The PWE3 architecture ([RFC3985] and [I-D.ietf-pwe3-ms-pw-arch] ). The
setup and maintenance of single-segment or multi- segment pseudowires setup and maintenance of single-segment or multi- segment pseudowires
uses the Label Distribution Protocol (LDP) as per [RFC4447] and uses the Label Distribution Protocol (LDP) as per [RFC4447] and
extensions for MS-PWs [I-D.ietf-pwe3-segmented-pw] and extensions for MS-PWs [I-D.ietf-pwe3-segmented-pw] and
[I-D.ietf-pwe3-dynamic-ms-pw]. [I-D.ietf-pwe3-dynamic-ms-pw].
3.7.2. LSP Control Plane 3.8.2. LSP Control Plane
MPLS-TP provider edge nodes aggregate multiple pseudowires and carry MPLS-TP provider edge nodes aggregate multiple pseudowires and carry
them across the MPLS-TP network through MPLS-TP tunnels (MPLS-TP them across the MPLS-TP network through MPLS-TP tunnels (MPLS-TP
LSPs). Applicable functions from the Generalized MPLS (GMPLS) LSPs). Applicable functions from the Generalized MPLS (GMPLS)
protocol suite supporting packet-switched capable (PSC) technologies protocol suite supporting packet-switched capable (PSC) technologies
are used as the control plane for MPLS-TP transport paths (LSPs). are used as the control plane for MPLS-TP transport paths (LSPs).
The LSP control plane includes: The LSP control plane includes:
o RSVP-TE for signalling o RSVP-TE for signalling
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RSVP explicit route object (ERO) is utilized for the setup of the RSVP explicit route object (ERO) is utilized for the setup of the
transport path exactly following the given route. GMPLS based transport path exactly following the given route. GMPLS based
MPLS-TP LSPs must be able to inter-operate with RSVP-TE based MPLS-TE MPLS-TP LSPs must be able to inter-operate with RSVP-TE based MPLS-TE
LSPs, as per [RFC5146] LSPs, as per [RFC5146]
OSPF-TE routing in support of GMPLS as defined in [RFC4203] is used OSPF-TE routing in support of GMPLS as defined in [RFC4203] is used
for carrying link state information in a MPLS-TP network. ISIS-TE for carrying link state information in a MPLS-TP network. ISIS-TE
routing in support of GMPLS as defined in [RFC5307] is used for routing in support of GMPLS as defined in [RFC5307] is used for
carrying link state information in a MPLS-TP network. carrying link state information in a MPLS-TP network.
3.8. Static Operation of LSPs and PWs 3.9. Static Operation of LSPs and PWs
A PW or LSP may be statically configured without the support of a A PW or LSP may be statically configured without the support of a
dynamic control plane. This may be either by direct configuration of dynamic control plane. This may be either by direct configuration of
the PEs/LSRs, or via a network management system. The collateral the PEs/LSRs, or via a network management system. The collateral
damage that loops can cause during the time taken to detect the damage that loops can cause during the time taken to detect the
failure may be severe. When static configuration mechanisms are failure may be severe. When static configuration mechanisms are
used, care must be taken to ensure that loops to not form. used, care must be taken to ensure that loops to not form.
3.9. Survivability 3.10. Survivability
Survivability requirements for MPLS-TP are specified in Survivability requirements for MPLS-TP are specified in
[I-D.ietf-mpls-tp-survive-fwk]. [I-D.ietf-mpls-tp-survive-fwk].
A wide variety of resiliency schemes have been developed to meet the A wide variety of resiliency schemes have been developed to meet the
various network and service survivability objectives. For example, various network and service survivability objectives. For example,
as part of the MPLS/PW paradigms, MPLS provides methods for local as part of the MPLS/PW paradigms, MPLS provides methods for local
repair using back-up LSP tunnels ([RFC4090]), while pseudowire repair using back-up LSP tunnels ([RFC4090]), while pseudowire
redundancy [I-D.ietf-pwe3-redundancy] supports scenarios where the redundancy [I-D.ietf-pwe3-redundancy] supports scenarios where the
protection for the PW can not be fully provided by the PSN layer protection for the PW can not be fully provided by the PSN layer
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o MPLS-TP recovery mechanisms support the coordination of protection o MPLS-TP recovery mechanisms support the coordination of protection
switching at multiple levels to prevent race conditions occurring switching at multiple levels to prevent race conditions occurring
between a client and its server layer. between a client and its server layer.
o MPLS-TP recovery mechanisms can be data plane, control plane or o MPLS-TP recovery mechanisms can be data plane, control plane or
management plane based. management plane based.
o MPLS-TP supports revertive and non-revertive behavior. o MPLS-TP supports revertive and non-revertive behavior.
3.10. Network Management 3.11. Network Management
The network management architecture and requirements for MPLS-TP are The network management architecture and requirements for MPLS-TP are
specified in [I-D.ietf-mpls-tp-nm-req]. It derives from the generic specified in [I-D.ietf-mpls-tp-nm-req]. It derives from the generic
specifications described in ITU-T G.7710/Y.1701 [G.7710] for specifications described in ITU-T G.7710/Y.1701 [G.7710] for
transport technologies. It also incorporates the OAM requirements transport technologies. It also incorporates the OAM requirements
for MPLS Networks [RFC4377] and MPLS-TP Networks for MPLS Networks [RFC4377] and MPLS-TP Networks
[I-D.ietf-mpls-tp-oam-requirements] and expands on those requirements [I-D.ietf-mpls-tp-oam-requirements] and expands on those requirements
to cover the modifications necessary for fault, configuration, to cover the modifications necessary for fault, configuration,
performance, and security in a transport network. performance, and security in a transport network.
skipping to change at page 33, line 10 skipping to change at page 34, line 10
information. For the management interface from a management system information. For the management interface from a management system
to a MPLS-TP NE, there is no restriction on which management protocol to a MPLS-TP NE, there is no restriction on which management protocol
should be used. It is used to provision and manage an end-to-end should be used. It is used to provision and manage an end-to-end
connection across a network where some segments are create/managed, connection across a network where some segments are create/managed,
for examples by Netconf or SNMP and other segments by XML or CORBA for examples by Netconf or SNMP and other segments by XML or CORBA
interfaces. Maintenance operations are run on a connection (LSP or interfaces. Maintenance operations are run on a connection (LSP or
PW) in a manner that is independent of the provisioning mechanism. PW) in a manner that is independent of the provisioning mechanism.
An MPLS-TP NE is not required to offer more than one standard An MPLS-TP NE is not required to offer more than one standard
management interface. In MPLS-TP, the EMF must be capable of management interface. In MPLS-TP, the EMF must be capable of
statically provisioning LSPs for an LSR or LER, and PWs for a PE, as statically provisioning LSPs for an LSR or LER, and PWs for a PE, as
per Section 3.8. per Section 3.9.
Fault Management (FM) functions within the EMF of an MPLS-TP NE Fault Management (FM) functions within the EMF of an MPLS-TP NE
enable the supervision, detection, validation, isolation, correction, enable the supervision, detection, validation, isolation, correction,
and alarm handling of abnormal conditions in the MPLS-TP network and and alarm handling of abnormal conditions in the MPLS-TP network and
its environment. FM must provide for the supervision of transmission its environment. FM must provide for the supervision of transmission
(such as continuity, connectivity, etc.), software processing, (such as continuity, connectivity, etc.), software processing,
hardware, and environment. Alarm handling includes alarm severity hardware, and environment. Alarm handling includes alarm severity
assignment, alarm suppression/aggregation/correlation, alarm assignment, alarm suppression/aggregation/correlation, alarm
reporting control, and alarm reporting. reporting control, and alarm reporting.
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4. Security Considerations 4. Security Considerations
The introduction of MPLS-TP into transport networks means that the The introduction of MPLS-TP into transport networks means that the
security considerations applicable to both MPLS and PWE3 apply to security considerations applicable to both MPLS and PWE3 apply to
those transport networks. Furthermore, when general MPLS networks those transport networks. Furthermore, when general MPLS networks
that utilise functionality outside of the strict MPLS-TP profile are that utilise functionality outside of the strict MPLS-TP profile are
used to support packet transport services, the security used to support packet transport services, the security
considerations of that additional functionality also apply. considerations of that additional functionality also apply.
The security considerations of [RFC3985] and For pseudowires, the security considerations of [RFC3985] and
[I-D.ietf-pwe3-ms-pw-arch] apply. [I-D.ietf-pwe3-ms-pw-arch] apply.
Packets that arrive on an interface with a given label value should
not be forwarded unless that label value was previously assigned to
an LSP or PW to a peer LSR or PE that it reachable via that
interface.
Each MPLS-TP solution must specify the additional security Each MPLS-TP solution must specify the additional security
considerations that apply. considerations that apply.
5. IANA Considerations 5. IANA Considerations
IANA considerations resulting from specific elements of MPLS-TP IANA considerations resulting from specific elements of MPLS-TP
functionality will be detailed in the documents specifying that functionality will be detailed in the documents specifying that
functionality. functionality.
This document introduces no additional IANA considerations in itself. This document introduces no additional IANA considerations in itself.
skipping to change at page 34, line 45 skipping to change at page 36, line 5
o John E Drake o John E Drake
o Hing-Kam Lam o Hing-Kam Lam
o Marc Lasserre o Marc Lasserre
o Vincenzo Sestito o Vincenzo Sestito
o Martin Vigoureux o Martin Vigoureux
7. References 7. Open Issues
7.1. Normative References This section contains a list of issues that must be resolved before
last call.
o Add addition detail on survivability architectures.
o Consider whether there is too much detail in the OAM, network
management, identifiers and control plane sections. Should this
framework document reduce the discussion on these topics in order
to minimise the dependency on other components not yet ready for
publication.
o There is some text missing from the network layer clients section.
Text is invited covering the use of out of band signaling on the
AC.
o Need text to address how the LSR next hop MAC address is
determined for Ethernet link layers when no IP (i.e. ARP) is
available. If statically configured, what is the default?
o Are there any other invariants of a typical LSR/PE architecture
that need to be clarified in the context of MPLS-TP.
8. References
8.1. Normative References
[G.7710] "ITU-T Recommendation G.7710/ [G.7710] "ITU-T Recommendation G.7710/
Y.1701 (07/07), "Common Y.1701 (07/07), "Common
equipment management function equipment management function
requirements"", 2005. requirements"", 2005.
[G.805] "ITU-T Recommendation G.805
(11/95), "Generic Functional
Architecture of Transport
Networks"", November 1995.
[RFC2119] Bradner, S., "Key words for use [RFC2119] Bradner, S., "Key words for use
in RFCs to Indicate Requirement in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, Levels", BCP 14, RFC 2119,
March 1997. March 1997.
[RFC3031] Rosen, E., Viswanathan, A., and [RFC3031] Rosen, E., Viswanathan, A., and
R. Callon, "Multiprotocol Label R. Callon, "Multiprotocol Label
Switching Architecture", Switching Architecture",
RFC 3031, January 2001. RFC 3031, January 2001.
skipping to change at page 37, line 11 skipping to change at page 38, line 48
[RFC5462] Andersson, L. and R. Asati, [RFC5462] Andersson, L. and R. Asati,
"Multiprotocol Label Switching "Multiprotocol Label Switching
(MPLS) Label Stack Entry: "EXP" (MPLS) Label Stack Entry: "EXP"
Field Renamed to "Traffic Class" Field Renamed to "Traffic Class"
Field", RFC 5462, February 2009. Field", RFC 5462, February 2009.
[RFC5586] Bocci, M., Vigoureux, M., and S. [RFC5586] Bocci, M., Vigoureux, M., and S.
Bryant, "MPLS Generic Associated Bryant, "MPLS Generic Associated
Channel", RFC 5586, June 2009. Channel", RFC 5586, June 2009.
7.2. Informative References 8.2. Informative References
[I-D.ietf-bfd-mpls] Aggarwal, R., Kompella, K., [I-D.ietf-bfd-mpls] Aggarwal, R., Kompella, K.,
Nadeau, T., and G. Swallow, "BFD Nadeau, T., and G. Swallow, "BFD
For MPLS LSPs", For MPLS LSPs",
draft-ietf-bfd-mpls-07 (work in draft-ietf-bfd-mpls-07 (work in
progress), June 2008. progress), June 2008.
[I-D.ietf-l2vpn-arp-mediation] Rosen, E., Shah, H., Heron, G., [I-D.ietf-l2vpn-arp-mediation] Rosen, E., Shah, H., Heron, G.,
and V. Kompella, "ARP Mediation and V. Kompella, "ARP Mediation
for IP Interworking of Layer 2 for IP Interworking of Layer 2
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