| RFC : | rfc6373 |
| Title: | |
| Date: | September 2011 |
| Status: | INFORMATIONAL |
Internet Engineering Task Force (IETF) L. Andersson, Ed.
Request for Comments: 6373 Ericsson
Category: Informational L. Berger, Ed.
ISSN: 2070-1721 LabN
L. Fang, Ed.
Cisco
N. Bitar, Ed.
Verizon
E. Gray, Ed.
Ericsson
September 2011
MPLS Transport Profile (MPLS-TP) Control Plane Framework
Abstract
The MPLS Transport Profile (MPLS-TP) supports static provisioning of
transport paths via a Network Management System (NMS) and dynamic
provisioning of transport paths via a control plane. This document
provides the framework for MPLS-TP dynamic provisioning and covers
control-plane addressing, routing, path computation, signaling,
traffic engineering, and path recovery. MPLS-TP uses GMPLS as the
control plane for MPLS-TP Label Switched Paths (LSPs). MPLS-TP also
uses the pseudowire (PW) control plane for pseudowires. Management-
plane functions are out of scope of this document.
This document is a product of a joint Internet Engineering Task Force
(IETF) / International Telecommunication Union Telecommunication
Standardization Sector (ITU-T) effort to include an MPLS Transport
Profile within the IETF MPLS and Pseudowire Emulation Edge-to-Edge
(PWE3) architectures to support the capabilities and functionalities
of a packet transport network as defined by the ITU-T.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Andersson, et al. Informational [Page 1]
RFC 6373 MPLS-TP Control Plane Framework September 2011
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6373.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................3
1.1. Scope ......................................................4
1.2. Basic Approach .............................................4
1.3. Reference Model ............................................6
2. Control-Plane Requirements ......................................9
2.1. Primary Requirements .......................................9
2.2. Requirements Derived from the MPLS-TP Framework ...........18
2.3. Requirements Derived from the OAM Framework ...............20
2.4. Security Requirements .....................................25
2.5. Identifier Requirements ...................................25
3. Relationship of PWs and TE LSPs ................................26
4. TE LSPs ........................................................27
4.1. GMPLS Functions and MPLS-TP LSPs ..........................27
4.1.1. In-Band and Out-of-Band Control ....................27
4.1.2. Addressing .........................................29
4.1.3. Routing ............................................29
4.1.4. TE LSPs and Constraint-Based Path Computation ......29
4.1.5. Signaling ..........................................30
4.1.6. Unnumbered Links ...................................30
4.1.7. Link Bundling ......................................30
4.1.8. Hierarchical LSPs ..................................31
4.1.9. LSP Recovery .......................................31
4.1.10. Control-Plane Reference Points (E-NNI,
I-NNI, UNI) .......................................32
4.2. OAM, MEP (Hierarchy), MIP Configuration and Control .......32
4.2.1. Management-Plane Support ...........................33
4.3. GMPLS and MPLS-TP Requirements Table ......................34
Andersson, et al. Informational [Page 2]
RFC 6373 MPLS-TP Control Plane Framework September 2011
4.4. Anticipated MPLS-TP-Related Extensions and Definitions ....37
4.4.1. MPLS-TE to MPLS-TP LSP Control-Plane Interworking ..37
4.4.2. Associated Bidirectional LSPs ......................38
4.4.3. Asymmetric Bandwidth LSPs ..........................38
4.4.4. Recovery for P2MP LSPs .............................38
4.4.5. Test Traffic Control and Other OAM Functions .......38
4.4.6. Diffserv Object Usage in GMPLS .....................39
4.4.7. Support for MPLS-TP LSP Identifiers ................39
4.4.8. Support for MPLS-TP Maintenance Identifiers ........39
5. Pseudowires ....................................................39
5.1. LDP Functions and Pseudowires .............................39
5.1.1. Management-Plane Support ...........................40
5.2. PW Control (LDP) and MPLS-TP Requirements Table ...........40
5.3. Anticipated MPLS-TP-Related Extensions ....................44
5.3.1. Extensions to Support Out-of-Band PW Control .......44
5.3.2. Support for Explicit Control of PW-to-LSP Binding ..45
5.3.3. Support for Dynamic Transfer of PW
Control/Ownership ..................................45
5.3.4. Interoperable Support for PW/LSP Resource
Allocation .........................................46
5.3.5. Support for PW Protection and PW OAM
Configuration ......................................46
5.3.6. Client Layer and Cross-Provider Interfaces
to PW Control ......................................47
5.4. ASON Architecture Considerations ..........................47
6. Security Considerations ........................................47
7. Acknowledgments ................................................48
8. References .....................................................48
8.1. Normative References ......................................48
8.2. Informative References ....................................51
9. Contributing Authors ...........................................56
1. Introduction
The Multiprotocol Label Switching Transport Profile (MPLS-TP) is
defined as a joint effort between the International Telecommunication
Union (ITU) and the IETF. The requirements for MPLS-TP are defined
in the requirements document, see [RFC5654]. These requirements
state that "A solution MUST be defined to support dynamic
provisioning of MPLS-TP transport paths via a control plane". This
document provides the framework for such dynamic provisioning. This
document is a product of a joint Internet Engineering Task Force
(IETF) / International Telecommunication Union Telecommunication
Standardization Sector (ITU-T) effort to include an MPLS Transport
Profile within the IETF MPLS and Pseudowire Emulation Edge-to-Edge
(PWE3) architectures to support the capabilities and functions of a
packet transport network as defined by the ITU-T.
Andersson, et al. Informational [Page 3]
RFC 6373 MPLS-TP Control Plane Framework September 2011
1.1. Scope
This document covers the control-plane functions involved in
establishing MPLS-TP Label Switched Paths (LSPs) and pseudowires
(PWs). The control-plane requirements for MPLS-TP are defined in the
MPLS-TP requirements document [RFC5654]. These requirements define
the role of the control plane in MPLS-TP. In particular, Section 2.4
of [RFC5654] and portions of the remainder of Section 2 of [RFC5654]
provide specific control-plane requirements.
The LSPs provided by MPLS-TP are used as a server layer for IP, MPLS,
and PWs, as well as other tunneled MPLS-TP LSPs. The PWs are used to
carry client signals other than IP or MPLS. The relationship between
PWs and MPLS-TP LSPs is exactly the same as between PWs and MPLS LSPs
in an MPLS Packet Switched Network (PSN). The PW encapsulation over
MPLS-TP LSPs used in MPLS-TP networks is also the same as for PWs
over MPLS in an MPLS network. MPLS-TP also defines protection and
restoration (or, collectively, recovery) functions; see [RFC5654] and
[RFC4427]. The MPLS-TP control plane provides methods to establish,
remove, and control MPLS-TP LSPs and PWs. This includes control of
Operations, Administration, and Maintenance (OAM), data-plane, and
recovery functions.
A general framework for MPLS-TP has been defined in [RFC5921], and a
survivability framework for MPLS-TP has been defined in [RFC6372].
These documents scope the approaches and protocols that are the
foundation of MPLS-TP. Notably, Section 3.5 of [RFC5921] scopes the
IETF protocols that serve as the foundation of the MPLS-TP control
plane. The PW control plane is based on the existing PW control
plane (see [RFC4447]) and the PWE3 architecture (see [RFC3985]). The
LSP control plane is based on GMPLS (see [RFC3945]), which is built
on MPLS Traffic Engineering (TE) and its numerous extensions.
[RFC6372] focuses on the recovery functions that must be supported
within MPLS-TP. It does not specify which control-plane mechanisms
are to be used.
The remainder of this document discusses the impact of the MPLS-TP
requirements on the GMPLS signaling and routing protocols that are
used to control MPLS-TP LSPs, and on the control of PWs as specified
in [RFC4447], [RFC6073], and [MS-PW-DYNAMIC].
1.2. Basic Approach
The basic approach taken in defining the MPLS-TP control-plane
framework includes the following:
1) MPLS technology as defined by the IETF is the foundation for
the MPLS Transport Profile.
Andersson, et al. Informational [Page 4]
RFC 6373 MPLS-TP Control Plane Framework September 2011
2) The data plane for MPLS-TP is a standard MPLS data plane
[RFC3031] as profiled in [RFC5960].
3) MPLS PWs are used by MPLS-TP including the use of targeted
Label Distribution Protocol (LDP) as the foundation for PW
signaling [RFC4447]. This also includes the use of Open
Shortest Path First with Traffic Engineering (OSPF-TE),
Intermediate System to Intermediate System (IS-IS) with Traffic
Engineering (ISIS-TE), or Multiprotocol Border Gateway Protocol
(MP-BGP) as they apply for Multi-Segment Pseudowire (MS-PW)
routing. However, the PW can be encapsulated over an MPLS-TP
LSP (established using methods and procedures for MPLS-TP LSP
establishment) in addition to the presently defined methods of
carrying PWs over LSP-based PSNs. That is, the MPLS-TP domain
is a PSN from a PWE3 architecture perspective [RFC3985].
4) The MPLS-TP LSP control plane builds on the GMPLS control plane
as defined by the IETF for transport LSPs. The protocols
within scope are Resource Reservation Protocol with Traffic
Engineering (RSVP-TE) [RFC3473], OSPF-TE [RFC4203] [RFC5392],
and ISIS-TE [RFC5307] [RFC5316]. Automatically Switched
Optical Network (ASON) signaling and routing requirements in
the context of GMPLS can be found in [RFC4139] and [RFC4258].
5) Existing IETF MPLS and GMPLS RFCs and evolving Working Group
Internet-Drafts should be reused wherever possible.
6) If needed, extensions for the MPLS-TP control plane should
first be based on the existing and evolving IETF work, and
secondly be based on work by other standard bodies only when
IETF decides that the work is out of the IETF's scope. New
extensions may be defined otherwise.
7) Extensions to the control plane may be required in order to
fully automate functions related to MPLS-TP LSPs and PWs.
8) Control-plane software upgrades to existing equipment are
acceptable and expected.
9) It is permissible for functions present in the GMPLS and PW
control planes to not be used in MPLS-TP networks.
10) One possible use of the control plane is to configure, enable,
and generally control OAM functionality. This will require
extensions to existing control-plane specifications that will
be usable in MPLS-TP as well as MPLS networks.
Andersson, et al. Informational [Page 5]
RFC 6373 MPLS-TP Control Plane Framework September 2011
11) The foundation for MPLS-TP control-plane requirements is
primarily found in Section 2.4 of [RFC5654] and relevant
portions of the remainder of Section 2 of [RFC5654].
1.3. Reference Model
The control-plane reference model is based on the general MPLS-TP
reference model as defined in the MPLS-TP framework [RFC5921] and
further refined in [RFC6215] on the MPLS-TP User-to-Network and
Network-to-Network Interfaces (UNI and NNI, respectively). Per the
MPLS-TP framework [RFC5921], the MPLS-TP control plane is based on
GMPLS with RSVP-TE for LSP signaling and targeted LDP for PW
signaling. In both cases, OSPF-TE or ISIS-TE with GMPLS extensions
is used for dynamic routing within an MPLS-TP domain.
Note that in this context, "targeted LDP" (or T-LDP) means LDP as
defined in RFC 5036, using Targeted Hello messages. See Section
2.4.2 ("Extended Discovery Mechanism") of [RFC5036]. Use of the
extended discovery mechanism is specified in Section 5 ("LDP") of
[RFC4447].
From a service perspective, MPLS-TP client services may be supported
via both PWs and LSPs. PW client interfaces, or adaptations, are
defined on an interface-technology basis, e.g., Ethernet over PW
[RFC4448]. In the context of MPLS-TP LSP, the client interface is
provided at the network layer and may be controlled via a GMPLS-based
UNI, see [RFC4208], or statically provisioned. As discussed in
[RFC5921] and [RFC6215], MPLS-TP also presumes an NNI reference
point.
The MPLS-TP end-to-end control-plane reference model is shown in
Figure 1. The figure shows the control-plane protocols used by MPLS-
TP, as well as the UNI and NNI reference points, in the case of a
Single-Segment PW supported by an end-to-end LSP without any
hierarchical LSPs. (The MS-PW case is not shown.) Each service
provider node's participation in routing and signaling (both GMPLS
RSVP-TE and PW LDP) is represented. Note that only the service end
points participate in PW LDP signaling, while all service provider
nodes participate in GMPLS TE LSP routing and signaling.
Andersson, et al. Informational [Page 6]
RFC 6373 MPLS-TP Control Plane Framework September 2011
|< ---- client signal (e.g., IP / MPLS / L2) -------- >|
|< --------- SP1 ---------- >|< ------- SP2 ----- >|
|< ---------- MPLS-TP End-to-End PW --------- >|
|< -------- MPLS-TP End-to-End LSP ------ >|
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
|CE1|-|-|PE1|--|P1 |--|P2 |--|PE2|-|-|PEa|--|Pa |--|PEb|-|-|CE2|
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
UNI NNI UNI
GMPLS
TE-RTG, |<-----|------|------|-------|------|----->|
& RSVP-TE
PW LDP |< ---------------------------------------- >|
Figure 1. End-to-End MPLS-TP Control-Plane Reference Model
Legend:
CE: Customer Edge
Client signal: defined in MPLS-TP Requirements
L2: Any layer 2 signal that may be carried
over a PW, e.g., Ethernet
NNI: Network-to-Network Interface
P: Provider
PE: Provider Edge
SP: Service Provider
TE-RTG: GMPLS OSPF-TE or ISIS-TE
UNI: User-to-Network Interface
Note: The MS-PW case is not shown.
Figure 2 adds three hierarchical LSP segments, labeled as "H-LSPs".
These segments are present to support scaling, OAM, and Maintenance
Entity Group End Points (MEPs), see [RFC6371], within each provider
domain and across the inter-provider NNI. (H-LSPs are used to
implement Sub-Path Maintenance Elements (SPMEs) as defined in
[RFC5921].) The MEPs are used to collect performance information,
support diagnostic and fault management functions, and support OAM
triggered survivability schemes as discussed in [RFC6372]. Each
H-LSP may be protected or restored using any of the schemes discussed
in [RFC6372]. End-to-end monitoring is supported via MEPs at the
end-to-end LSP and PW end points. Note that segment MEPs may be co-
located with MIPs of the next higher-layer (e.g., end-to-end) LSPs.
(The MS-PW case is not shown.)
Andersson, et al. Informational [Page 7]
RFC 6373 MPLS-TP Control Plane Framework September 2011
|< ------- client signal (e.g., IP / MPLS / L2) ----- >|
|< -------- SP1 ----------- >|< ------- SP2 ----- >|
|< ----------- MPLS-TP End-to-End PW -------- >|
|< ------- MPLS-TP End-to-End LSP ------- >|
|< -- H-LSP1 ---- >|<-H-LSP2->|<- H-LSP3 ->|
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
|CE1|-|-|PE1|--|P1 |--|P2 |--|PE2|-|-|PEa|--|Pa |--|PEb|-|-|CE2|
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
UNI NNI UNI
..... .....
End2end |MEP|--------------------------------------|MEP|
PW OAM ''''' '''''
..... ..... ..... .....
End2end |MEP|----------------|MIP|---|MIP|---------|MEP|
LSP OAM ''''' ''''' ''''' '''''
..... ..... ..... ......... ......... ..... .....
Segment |MEP|-|MIP|-|MIP|-|MEP|MEP|-|MEP|MEP|-|MIP|-|MEP|
LSP OAM ''''' ''''' ''''' ''''''''' ''''''''' ''''' '''''
H-LSP GMPLS
TE-RTG |<-----|------|----->||<---->||<-----|----->|
&RSVP-TE (within an MPLS-TP network)
E2E GMPLS
TE-RTG |< ------------------|--------|------------>|
&RSVP-TE
PW LDP |< ---------------------------------------- >|
Figure 2. MPLS-TP Control-Plane Reference Model with OAM
Legend:
CE: Customer Edge
Client signal: defined in MPLS-TP Requirements
E2E: End-to-End
L2: Any layer 2 signal that may be carried
over a PW, e.g., Ethernet
H-LSP: Hierarchical LSP
MEP: Maintenance Entity Group End Point
MIP: Maintenance Entity Group Intermediate Point
NNI: Network-to-Network Interface
P: Provider
PE: Provider Edge
SP: Service Provider
TE-RTG: GMPLS OSPF-TE or ISIS-TE
Note: The MS-PW case is not shown.
Andersson, et al. Informational [Page 8]
RFC 6373 MPLS-TP Control Plane Framework September 2011
While not shown in the figures above, the MPLS-TP control plane must
support the addressing separation and independence between the data,
control, and management planes. Address separation between the
planes is already included in GMPLS. Such separation is also already
included in LDP as LDP session end point addresses are never
automatically associated with forwarding.
2. Control-Plane Requirements
The requirements for the MPLS-TP control plane are derived from the
MPLS-TP requirements and framework documents, specifically [RFC5654],
[RFC5921], [RFC5860], [RFC6371], and [RFC6372]. The requirements are
summarized in this section, but do not replace those documents. If
there are differences between this section and those documents, those
documents shall be considered authoritative.
2.1. Primary Requirements
These requirements are based on Section 2 of [RFC5654]:
1. Any new functionality that is defined to fulfill the
requirements for MPLS-TP must be agreed within the IETF through
the IETF consensus process as per [RFC4929] and Section 1,
paragraph 15 of [RFC5654].
2. The MPLS-TP control-plane design should as far as reasonably
possible reuse existing MPLS standards ([RFC5654], requirement
2).
3. The MPLS-TP control plane must be able to interoperate with
existing IETF MPLS and PWE3 control planes where appropriate
([RFC5654], requirement 3).
4. The MPLS-TP control plane must be sufficiently well-defined to
ensure that the interworking between equipment supplied by
multiple vendors will be possible both within a single domain
and between domains ([RFC5654], requirement 4).
5. The MPLS-TP control plane must support a connection-oriented
packet switching model with traffic engineering capabilities
that allow deterministic control of the use of network
resources ([RFC5654], requirement 5).
6. The MPLS-TP control plane must support traffic-engineered
point-to-point (P2P) and point-to-multipoint (P2MP) transport
paths ([RFC5654], requirement 6).
Andersson, et al. Informational [Page 9]
RFC 6373 MPLS-TP Control Plane Framework September 2011
7. The MPLS-TP control plane must support unidirectional,
associated bidirectional and co-routed bidirectional point-to-
point transport paths ([RFC5654], requirement 7).
8. The MPLS-TP control plane must support unidirectional point-to-
multipoint transport paths ([RFC5654], requirement 8).
9. The MPLS-TP control plane must enable all nodes (i.e., ingress,
egress, and intermediate) to be aware about the pairing
relationship of the forward and the backward directions
belonging to the same co-routed bidirectional transport path
([RFC5654], requirement 10).
10. The MPLS-TP control plane must enable edge nodes (i.e., ingress
and egress) to be aware of the pairing relationship of the
forward and the backward directions belonging to the same
associated bidirectional transport path ([RFC5654], requirement
11).
11. The MPLS-TP control plane should enable common transit nodes to
be aware of the pairing relationship of the forward and the
backward directions belonging to the same associated
bidirectional transport path ([RFC5654], requirement 12).
12. The MPLS-TP control plane must support bidirectional transport
paths with symmetric bandwidth requirements, i.e., the amount
of reserved bandwidth is the same in the forward and backward
directions ([RFC5654], requirement 13).
13. The MPLS-TP control plane must support bidirectional transport
paths with asymmetric bandwidth requirements, i.e., the amount
of reserved bandwidth differs in the forward and backward
directions ([RFC5654], requirement 14).
14. The MPLS-TP control plane must support the logical separation
of the control plane from the management and data planes
([RFC5654], requirement 15). Note that this implies that the
addresses used in the control plane are independent from the
addresses used in the management and data planes.
15. The MPLS-TP control plane must support the physical separation
of the control plane from the management and data plane, and no
assumptions should be made about the state of the data-plane
channels from information about the control- or management-
plane channels when they are running out-of-band ([RFC5654],
requirement 16).
Andersson, et al. Informational [Page 10]
RFC 6373 MPLS-TP Control Plane Framework September 2011
16. A control plane must be defined to support dynamic provisioning
and restoration of MPLS-TP transport paths, but its use is a
network operator's choice ([RFC5654], requirement 18).
17. The presence of a control plane must not be required for static
provisioning of MPLS-TP transport paths ([RFC5654], requirement
19).
18. The MPLS-TP control plane must permit the coexistence of
statically and dynamically provisioned/managed MPLS-TP
transport paths within the same layer network or domain
([RFC5654], requirement 20).
19. The MPLS-TP control plane should be operable in a way that is
similar to the way the control plane operates in other
transport-layer technologies ([RFC5654], requirement 21).
20. The MPLS-TP control plane must avoid or minimize traffic impact
(e.g., packet delay, reordering, and loss) during network
reconfiguration ([RFC5654], requirement 24).
21. The MPLS-TP control plane must work across multiple homogeneous
domains ([RFC5654], requirement 25), i.e., all domains use the
same MPLS-TP control plane.
22. The MPLS-TP control plane should work across multiple non-
homogeneous domains ([RFC5654], requirement 26), i.e., some
domains use the same control plane and other domains use static
provisioning at the domain boundary.
23. The MPLS-TP control plane must not dictate any particular
physical or logical topology ([RFC5654], requirement 27).
24. The MPLS-TP control plane must include support of ring
topologies that may be deployed with arbitrary interconnection
and support of rings of at least 16 nodes ([RFC5654],
requirements 27.A, 27.B, and 27.C).
25. The MPLS-TP control plane must scale gracefully to support a
large number of transport paths, nodes, and links. That is, it
must be able to scale at least as well as control planes in
existing transport technologies with growing and increasingly
complex network topologies as well as with increasing bandwidth
demands, number of customers, and number of services
([RFC5654], requirements 53 and 28).
26. The MPLS-TP control plane should not provision transport paths
that contain forwarding loops ([RFC5654], requirement 29).
Andersson, et al. Informational [Page 11]
RFC 6373 MPLS-TP Control Plane Framework September 2011
27. The MPLS-TP control plane must support multiple client layers
(e.g., MPLS-TP, IP, MPLS, Ethernet, ATM, Frame Relay, etc.)
([RFC5654], requirement 30).
28. The MPLS-TP control plane must provide a generic and extensible
solution to support the transport of MPLS-TP transport paths
over one or more server-layer networks (such as MPLS-TP,
Ethernet, Synchronous Optical Network / Synchronous Digital
Hierarchy (SONET/SDH), Optical Transport Network (OTN), etc.).
Requirements for bandwidth management within a server-layer
network are outside the scope of this document ([RFC5654],
requirement 31).
29. In an environment where an MPLS-TP layer network is supporting
a client-layer network, and the MPLS-TP layer network is
supported by a server-layer network, then the control-plane
operation of the MPLS-TP layer network must be possible without
any dependencies on the server or client-layer network
([RFC5654], requirement 32).
30. The MPLS-TP control plane must allow for the transport of a
client MPLS or MPLS-TP layer network over a server MPLS or
MPLS-TP layer network ([RFC5654], requirement 33).
31. The MPLS-TP control plane must allow the autonomous operation
of the layers of a multi-layer network that includes an MPLS-TP
layer ([RFC5654], requirement 34).
32. The MPLS-TP control plane must allow the hiding of MPLS-TP
layer network addressing and other information (e.g., topology)
from client-layer networks. However, it should be possible, at
the option of the operator, to leak a limited amount of
summarized information, such as Shared Risk Link Groups (SRLGs)
or reachability, between layers ([RFC5654], requirement 35).
33. The MPLS-TP control plane must allow for the identification of
a transport path on each link within and at the destination
(egress) of the transport network ([RFC5654], requirements 38
and 39).
34. The MPLS-TP control plane must allow for the use of P2MP server
(sub-)layer capabilities as well as P2P server (sub-)layer
capabilities when supporting P2MP MPLS-TP transport paths
([RFC5654], requirement 40).
35. The MPLS-TP control plane must be extensible in order to
accommodate new types of client-layer networks and services
([RFC5654], requirement 41).
Andersson, et al. Informational [Page 12]
RFC 6373 MPLS-TP Control Plane Framework September 2011
36. The MPLS-TP control plane should support the reserved bandwidth
associated with a transport path to be increased without
impacting the existing traffic on that transport path, provided
enough resources are available ([RFC5654], requirement 42)).
37. The MPLS-TP control plane should support the reserved bandwidth
of a transport path being decreased without impacting the
existing traffic on that transport path, provided that the
level of existing traffic is smaller than the reserved
bandwidth following the decrease ([RFC5654], requirement 43).
38. The control plane for MPLS-TP must fit within the ASON
(control-plane) architecture. The ITU-T has defined an
architecture for ASONs in G.8080 [ITU.G8080.2006] and G.8080
Amendment 1 [ITU.G8080.2008]. An interpretation of the ASON
signaling and routing requirements in the context of GMPLS can
be found in [RFC4139], [RFC4258], and Section 2.4, paragraphs 2
and 3 of [RFC5654].
39. The MPLS-TP control plane must support control-plane topology
and data-plane topology independence ([RFC5654], requirement
47).
40. A failure of the MPLS-TP control plane must not interfere with
the delivery of service or recovery of established transport
paths ([RFC5654], requirement 47).
41. The MPLS-TP control plane must be able to operate independent
of any particular client- or server-layer control plane
([RFC5654], requirement 48).
42. The MPLS-TP control plane should support, but not require, an
integrated control plane encompassing MPLS-TP together with its
server- and client-layer networks when these layer networks
belong to the same administrative domain ([RFC5654],
requirement 49).
43. The MPLS-TP control plane must support configuration of
protection functions and any associated maintenance (OAM)
functions ([RFC5654], requirements 50 and 7).
44. The MPLS-TP control plane must support the configuration and
modification of OAM maintenance points as well as the
activation/deactivation of OAM when the transport path or
transport service is established or modified ([RFC5654],
requirement 51).
Andersson, et al. Informational [Page 13]
RFC 6373 MPLS-TP Control Plane Framework September 2011
45. The MPLS-TP control plane must be capable of restarting and
relearning its previous state without impacting forwarding
([RFC5654], requirement 54).
46. The MPLS-TP control plane must provide a mechanism for dynamic
ownership transfer of the control of MPLS-TP transport paths
from the management plane to the control plane and vice versa.
The number of reconfigurations required in the data plane must
be minimized; preferably no data-plane reconfiguration will be
required ([RFC5654], requirement 55). Note, such transfers
cover all transport path control functions including control of
recovery and OAM.
47. The MPLS-TP control plane must support protection and
restoration mechanisms, i.e., recovery ([RFC5654], requirement
52).
Note that the MPLS-TP survivability framework document
[RFC6372] provides additional useful information related to
recovery.
48. The MPLS-TP control-plane mechanisms should be identical (or as
similar as possible) to those already used in existing
transport networks to simplify implementation and operations.
However, this must not override any other requirement
([RFC5654], requirement 56 A).
49. The MPLS-TP control-plane mechanisms used for P2P and P2MP
recovery should be identical to simplify implementation and
operation. However, this must not override any other
requirement ([RFC5654], requirement 56 B).
50. The MPLS-TP control plane must support recovery mechanisms that
are applicable at various levels throughout the network
including support for link, transport path, segment,
concatenated segment, and end-to-end recovery ([RFC5654],
requirement 57).
51. The MPLS-TP control plane must support recovery paths that meet
the Service Level Agreement (SLA) protection objectives of the
service ([RFC5654], requirement 58). These include:
a. Guarantee 50-ms recovery times from the moment of fault
detection in networks with spans less than 1200 km.
b. Protection of 100% of the traffic on the protected path.
c. Recovery must meet SLA requirements over multiple domains.
Andersson, et al. Informational [Page 14]
RFC 6373 MPLS-TP Control Plane Framework September 2011
52. The MPLS-TP control plane should support per-transport-path
recovery objectives ([RFC5654], requirement 59).
53. The MPLS-TP control plane must support recovery mechanisms that
are applicable to any topology ([RFC5654], requirement 60).
54. The MPLS-TP control plane must operate in synergy with
(including coordination of timing/timer settings) the recovery
mechanisms present in any client or server transport networks
(for example, Ethernet, SDH, OTN, Wavelength Division
Multiplexing (WDM)) to avoid race conditions between the layers
([RFC5654], requirement 61).
55. The MPLS-TP control plane must support recovery and reversion
mechanisms that prevent frequent operation of recovery in the
event of an intermittent defect ([RFC5654], requirement 62).
56. The MPLS-TP control plane must support revertive and non-
revertive protection behavior ([RFC5654], requirement 64).
57. The MPLS-TP control plane must support 1+1 bidirectional
protection for P2P transport paths ([RFC5654], requirement 65
A).
58. The MPLS-TP control plane must support 1+1 unidirectional
protection for P2P transport paths ([RFC5654], requirement 65
B).
59. The MPLS-TP control plane must support 1+1 unidirectional
protection for P2MP transport paths ([RFC5654], requirement 65
C).
60. The MPLS-TP control plane must support the ability to share
protection resources amongst a number of transport paths
([RFC5654], requirement 66).
61. The MPLS-TP control plane must support 1:n bidirectional
protection for P2P transport paths. Bidirectional 1:n
protection should be the default for 1:n protection ([RFC5654],
requirement 67 A).
62. The MPLS-TP control plane must support 1:n unidirectional
protection for P2MP transport paths ([RFC5654], requirement 67
B).
63. The MPLS-TP control plane may support 1:n unidirectional
protection for P2P transport paths ([RFC5654], requirement 65
C).
Andersson, et al. Informational [Page 15]
RFC 6373 MPLS-TP Control Plane Framework September 2011
64. The MPLS-TP control plane may support the control of extra-
traffic type traffic ([RFC5654], note after requirement 67).
65. The MPLS-TP control plane should support 1:n (including 1:1)
shared mesh recovery ([RFC5654], requirement 68).
66. The MPLS-TP control plane must support sharing of protection
resources such that protection paths that are known not to be
required concurrently can share the same resources ([RFC5654],
requirement 69).
67. The MPLS-TP control plane must support the sharing of resources
between a restoration transport path and the transport path
being replaced ([RFC5654], requirement 70).
68. The MPLS-TP control plane must support restoration priority so
that an implementation can determine the order in which
transport paths should be restored ([RFC5654], requirement 71).
69. The MPLS-TP control plane must support preemption priority in
order to allow restoration to displace other transport paths in
the event of resource constraints ([RFC5654], requirements 72
and 86).
70. The MPLS-TP control plane must support revertive and non-
revertive restoration behavior ([RFC5654], requirement 73).
71. The MPLS-TP control plane must support recovery being triggered
by physical (lower) layer fault indications ([RFC5654],
requirement 74).
72. The MPLS-TP control plane must support recovery being triggered
by OAM ([RFC5654], requirement 75).
73. The MPLS-TP control plane must support management-plane
recovery triggers (e.g., forced switch, etc.) ([RFC5654],
requirement 76).
74. The MPLS-TP control plane must support the differentiation of
administrative recovery actions from recovery actions initiated
by other triggers ([RFC5654], requirement 77).
75. The MPLS-TP control plane should support control-plane
restoration triggers (e.g., forced switch, etc.) ([RFC5654],
requirement 78).
Andersson, et al. Informational [Page 16]
RFC 6373 MPLS-TP Control Plane Framework September 2011
76. The MPLS-TP control plane must support priority logic to
negotiate and accommodate coexisting requests (i.e., multiple
requests) for protection switching (e.g., administrative
requests and requests due to link/node failures) ([RFC5654],
requirement 79).
77. The MPLS-TP control plane must support the association of
protection paths and working paths (sometimes known as
protection groups) ([RFC5654], requirement 80).
78. The MPLS-TP control plane must support pre-calculation of
recovery paths ([RFC5654], requirement 81).
79. The MPLS-TP control plane must support pre-provisioning of
recovery paths ([RFC5654], requirement 82).
80. The MPLS-TP control plane must support the external commands
defined in [RFC4427]. External controls overruled by higher
priority requests (e.g., administrative requests and requests
due to link/node failures) or unable to be signaled to the
remote end (e.g., because of a protection state coordination
fail) must be ignored/dropped ([RFC5654], requirement 83).
81. The MPLS-TP control plane must permit the testing and
validation of the integrity of the protection/recovery
transport path ([RFC5654], requirement 84 A).
82. The MPLS-TP control plane must permit the testing and
validation of protection/restoration mechanisms without
triggering the actual protection/restoration ([RFC5654],
requirement 84 B).
83. The MPLS-TP control plane must permit the testing and
validation of protection/restoration mechanisms while the
working path is in service ([RFC5654], requirement 84 C).
84. The MPLS-TP control plane must permit the testing and
validation of protection/restoration mechanisms while the
working path is out of service ([RFC5654], requirement 84 D).
85. The MPLS-TP control plane must support the establishment and
maintenance of all recovery entities and functions ([RFC5654],
requirement 89 A).
86. The MPLS-TP control plane must support signaling of recovery
administrative control ([RFC5654], requirement 89 B).
Andersson, et al. Informational [Page 17]
RFC 6373 MPLS-TP Control Plane Framework September 2011
87. The MPLS-TP control plane must support protection state
coordination. Since control-plane network topology is
independent from the data-plane network topology, the
protection state coordination supported by the MPLS-TP control
plane may run on resources different than the data-plane
resources handled within the recovery mechanism (e.g., backup)
([RFC5654], requirement 89 C).
88. When present, the MPLS-TP control plane must support recovery
mechanisms that are optimized for specific network topologies.
These mechanisms must be interoperable with the mechanisms
defined for arbitrary topology (mesh) networks to enable
protection of end-to-end transport paths ([RFC5654],
requirement 91).
89. When present, the MPLS-TP control plane must support the
control of ring-topology-specific recovery mechanisms
([RFC5654], Section 2.5.6.1).
90. The MPLS-TP control plane must include support for
differentiated services and different traffic types with
traffic class separation associated with different traffic
([RFC5654], requirement 110).
91. The MPLS-TP control plane must support the provisioning of
services that provide guaranteed Service Level Specifications
(SLSs), with support for hard ([RFC3209] style) and relative
([RFC3270] style) end-to-end bandwidth guarantees ([RFC5654],
requirement 111).
92. The MPLS-TP control plane must support the provisioning of
services that are sensitive to jitter and delay ([RFC5654],
requirement 112).
2.2. Requirements Derived from the MPLS-TP Framework
The following additional requirements are based on [RFC5921],
[TP-P2MP-FWK], and [RFC5960]:
93. Per-packet Equal Cost Multi-Path (ECMP) load balancing is
currently outside the scope of MPLS-TP ([RFC5960], Section
3.1.1, paragraph 6).
94. Penultimate Hop Popping (PHP) must be disabled on MPLS-TP LSPs
by default ([RFC5960], Section 3.1.1, paragraph 7).
Andersson, et al. Informational [Page 18]
RFC 6373 MPLS-TP Control Plane Framework September 2011
95. The MPLS-TP control plane must support both E-LSP (Explicitly
TC-encoded-PSC LSP) and L-LSP (Label-Only-Inferred-PSC LSP)
MPLS Diffserv modes as specified in [RFC3270], [RFC5462], and
Section 3.3.2, paragraph 12 of [RFC5960].
96. Both Single-Segment PWs (see [RFC3985]) and Multi-Segment PWs
(see [RFC5659]) shall be supported by the MPLS-TP control
plane. MPLS-TP shall use the definition of Multi-Segment PWs
as defined by the IETF ([RFC5921], Section 3.4.4).
97. The MPLS-TP control plane must support the control of PWs and
their associated labels ([RFC5921], Section 3.4.4).
98. The MPLS-TP control plane must support network-layer clients,
i.e., clients whose traffic is transported over an MPLS-TP
network without the use of PWs ([RFC5921], Section 3.4.5).
a. The MPLS-TP control plane must support the use of network-
layer protocol-specific LSPs and labels ([RFC5921], Section
3.4.5).
b. The MPLS-TP control plane must support the use of a client-
service-specific LSPs and labels ([RFC5921], Section 3.4.5).
99. The MPLS-TP control plane for LSPs must be based on the GMPLS
control plane. More specifically, GMPLS RSVP-TE [RFC3473] and
related extensions are used for LSP signaling, and GMPLS OSPF-
TE [RFC5392] and ISIS-TE [RFC5316] are used for routing
([RFC5921], Section 3.9).
100. The MPLS-TP control plane for PWs must be based on the MPLS
control plane for PWs, and more specifically, targeted LDP (T-
LDP) [RFC4447] is used for PW signaling ([RFC5921], Section
3.9, paragraph 5).
101. The MPLS-TP control plane must ensure its own survivability and
be able to recover gracefully from failures and degradations.
These include graceful restart and hot redundant configurations
([RFC5921], Section 3.9, paragraph 16).
102. The MPLS-TP control plane must support linear, ring, and meshed
protection schemes ([RFC5921], Section 3.12, paragraph 3).
103. The MPLS-TP control plane must support the control of SPMEs
(hierarchical LSPs) for new or existing end-to-end LSPs
([RFC5921], Section 3.12, paragraph 7).
Andersson, et al. Informational [Page 19]
RFC 6373 MPLS-TP Control Plane Framework September 2011
2.3. Requirements Derived from the OAM Framework
The following additional requirements are based on [RFC5860] and
[RFC6371]:
104. The MPLS-TP control plane must support the capability to
enable/disable OAM functions as part of service establishment
([RFC5860], Section 2.1.6, paragraph 1. Note that OAM
functions are applicable regardless of the label stack depth
(i.e., level of LSP hierarchy or PW) ([RFC5860], Section 2.1.1,
paragraph 3).
105. The MPLS-TP control plane must support the capability to
enable/disable OAM functions after service establishment. In
such cases, the customer must not perceive service degradation
as a result of OAM enabling/disabling ([RFC5860], Section
2.1.6, paragraphs 1 and 2).
106. The MPLS-TP control plane must support dynamic control of any
of the existing IP/MPLS and PW OAM protocols, e.g., LSP-Ping
[RFC4379], MPLS-BFD [RFC5884], VCCV [RFC5085], and VCCV-BFD
[RFC5885] ([RFC5860], Section 2.1.4, paragraph 2).
107. The MPLS-TP control plane must allow for the ability to support
experimental OAM functions. These functions must be disabled
by default ([RFC5860], Section 2.2, paragraph 2).
108. The MPLS-TP control plane must support the choice of which (if
any) OAM function(s) to use and to which PW, LSP or Section it
applies ([RFC5860], Section 2.2, paragraph 3).
109. The MPLS-TP control plane must allow (e.g., enable/disable)
mechanisms that support the localization of faults and the
notification of appropriate nodes ([RFC5860], Section 2.2.1,
paragraph 1).
110. The MPLS-TP control plane may support mechanisms that permit
the service provider to be informed of a fault or defect
affecting the service(s) it provides, even if the fault or
defect is located outside of his domain ([RFC5860], Section
2.2.1, paragraph 2).
111. Information exchange between various nodes involved in the
MPLS-TP control plane should be reliable such that, for
example, defects or faults are properly detected or that state
changes are effectively known by the appropriate nodes
([RFC5860], Section 2.2.1, paragraph 3).
Andersson, et al. Informational [Page 20]
RFC 6373 MPLS-TP Control Plane Framework September 2011
112. The MPLS-TP control plane must provide functionality to control
an end point's ability to monitor the liveness of a PW, LSP, or
Section ([RFC5860], Section 2.2.2, paragraph 1).
113. The MPLS-TP control plane must provide functionality to control
an end point's ability to determine whether or not it is
connected to specific end point(s) by means of the expected PW,
LSP, or Section ([RFC5860], Section 2.2.3, paragraph 1).
a. The MPLS-TP control plane must provide mechanisms to control
an end point's ability to perform this function proactively
([RFC5860], Section 2.2.3, paragraph 2).
b. The MPLS-TP control plane must provide mechanisms to control
an end point's ability to perform this function on-demand
([RFC5860], Section 2.2.3, paragraph 3).
114. The MPLS-TP control plane must provide functionality to control
diagnostic testing on a PW, LSP or Section ([RFC5860], Section
2.2.5, paragraph 1).
a. The MPLS-TP control plane must provide mechanisms to control
the performance of this function on-demand ([RFC5860],
Section 2.2.5, paragraph 2).
115. The MPLS-TP control plane must provide functionality to enable
an end point to discover the Intermediate Point(s) (if any) and
end point(s) along a PW, LSP, or Section, and more generally to
trace (record) the route of a PW, LSP, or Section ([RFC5860],
Section 2.2.4, paragraph 1).
a. The MPLS-TP control plane must provide mechanisms to control
the performance of this function on-demand ([RFC5860],
Section 2.2.4, paragraph 2).
116. The MPLS-TP control plane must provide functionality to enable
an end point of a PW, LSP, or Section to instruct its
associated end point(s) to lock the PW, LSP, or Section
([RFC5860], Section 2.2.6, paragraph 1).
a. The MPLS-TP control plane must provide mechanisms to control
the performance of this function on-demand ([RFC5860],
Section 2.2.6, paragraph 2).
Andersson, et al. Informational [Page 21]
RFC 6373 MPLS-TP Control Plane Framework September 2011
117. The MPLS-TP control plane must provide functionality to enable
an Intermediate Point of a PW or LSP to report, to an end point
of that same PW or LSP, a lock condition indirectly affecting
that PW or LSP ([RFC5860], Section 2.2.7, paragraph 1).
a. The MPLS-TP control plane must provide mechanisms to control
the performance of this function proactively ([RFC5860],
Section 2.2.7, paragraph 2).
118. The MPLS-TP control plane must provide functionality to enable
an Intermediate Point of a PW or LSP to report, to an end point
of that same PW or LSP, a fault or defect condition affecting
that PW or LSP ([RFC5860], Section 2.2.8, paragraph 1).
a. The MPLS-TP control plane must provide mechanisms to control
the performance of this function proactively ([RFC5860],
Section 2.2.8, paragraph 2).
119. The MPLS-TP control plane must provide functionality to enable
an end point to report, to its associated end point, a fault or
defect condition that it detects on a PW, LSP, or Section for
which they are the end points ([RFC5860], Section 2.2.9,
paragraph 1).
a. The MPLS-TP control plane must provide mechanisms to control
the performance of this function proactively ([RFC5860],
Section 2.2.9, paragraph 2).
120. The MPLS-TP control plane must provide functionality to enable
the propagation, across an MPLS-TP network, of information
pertaining to a client defect or fault condition detected at an
end point of a PW or LSP, if the client-layer mechanisms do not
provide an alarm notification/propagation mechanism ([RFC5860],
Section 2.2.10, paragraph 1).
a. The MPLS-TP control plane must provide mechanisms to control
the performance of this function proactively ([RFC5860],
Section 2.2.10, paragraph 2).
121. The MPLS-TP control plane must provide functionality to enable
the control of quantification of packet loss ratio over a PW,
LSP, or Section ([RFC5860], Section 2.2.11, paragraph 1).
a. The MPLS-TP control plane must provide mechanisms to control
the performance of this function proactively and on-demand
([RFC5860], Section 2.2.11, paragraph 4).
Andersson, et al. Informational [Page 22]
RFC 6373 MPLS-TP Control Plane Framework September 2011
122. The MPLS-TP control plane must provide functionality to control
the quantification and reporting of the one-way, and if
appropriate, the two-way, delay of a PW, LSP, or Section
([RFC5860], Section 2.2.12, paragraph 1).
a. The MPLS-TP control plane must provide mechanisms to control
the performance of this function proactively and on-demand
([RFC5860], Section 2.2.12, paragraph 6).
123. The MPLS-TP control plane must support the configuration of OAM
functional components that include Maintenance Entities (MEs)
and Maintenance Entity Groups (MEGs) as instantiated in MEPs,
MIPs, and SPMEs ([RFC6371], Section 3.6).
124. For dynamically established transport paths, the control plane
must support the configuration of OAM operations ([RFC6371],
Section 5).
a. The MPLS-TP control plane must provide mechanisms to
configure proactive monitoring for a MEG at, or after,
transport path creation time.
b. The MPLS-TP control plane must provide mechanisms to
configure the operational characteristics of in-band
measurement transactions (e.g., Connectivity Verification
(CV), Loss Measurement (LM), etc.) at MEPs (associated with
a transport path).
c. The MPLS-TP control plane may provide mechanisms to
configure server-layer event reporting by intermediate
nodes.
d. The MPLS-TP control plane may provide mechanisms to
configure the reporting of measurements resulting from
proactive monitoring.
125. The MPLS-TP control plane must support the control of the loss
of continuity (LOC) traffic block consequent action ([RFC6371],
Section 5.1.2, paragraph 4).
126. For dynamically established transport paths that have a
proactive Continuity Check and Connectivity Verification (CC-V)
function enabled, the control plane must support the signaling
of the following MEP configuration information ([RFC6371],
Section 5.1.3):
a. The MPLS-TP control plane must provide mechanisms to
configure the MEG identifier to which the MEP belongs.
Andersson, et al. Informational [Page 23]
RFC 6373 MPLS-TP Control Plane Framework September 2011
b. The MPLS-TP control plane must provide mechanisms to
configure a MEP's own identity inside a MEG.
c. The MPLS-TP control plane must provide mechanisms to
configure the list of the other MEPs in the MEG.
d. The MPLS-TP control plane must provide mechanisms to
configure the CC-V transmission rate / reception period
(covering all application types).
127. The MPLS-TP control plane must provide mechanisms to configure
the generation of Alarm Indication Signal (AIS) packets for
each MEG ([RFC6371], Section 5.3, paragraph 9).
128. The MPLS-TP control plane must provide mechanisms to configure
the generation of Lock Report (LKR) packets for each MEG
([RFC6371], Section 5.4, paragraph 9).
129. The MPLS-TP control plane must provide mechanisms to configure
the use of proactive Packet Loss Measurement (LM), and the
transmission rate and Per-Hop Behavior (PHB) class associated
with the LM OAM packets originating from a MEP ([RFC6371],
Section 5.5.1, paragraph 1).
130. The MPLS-TP control plane must provide mechanisms to configure
the use of proactive Packet Delay Measurement (DM), and the
transmission rate and PHB class associated with the DM OAM
packets originating from a MEP ([RFC6371], Section 5.6.1,
paragraph 1).
131. The MPLS-TP control plane must provide mechanisms to configure
the use of Client Failure Indication (CFI), and the
transmission rate and PHB class associated with the CFI OAM
packets originating from a MEP ([RFC6371], Section 5.7.1,
paragraph 1).
132. The MPLS-TP control plane should provide mechanisms to control
the use of on-demand CV packets ([RFC6371], Section 6.1).
a. The MPLS-TP control plane should provide mechanisms to
configure the number of packets to be transmitted/received
in each burst of on-demand CV packets and their packet size
([RFC6371], Section 6.1.1, paragraph 1).
b. When an on-demand CV packet is used to check connectivity
toward a target MIP, the MPLS-TP control plane should
provide mechanisms to configure the number of hops to reach
the target MIP ([RFC6371], Section 6.1.1, paragraph 2).
Andersson, et al. Informational [Page 24]
RFC 6373 MPLS-TP Control Plane Framework September 2011
c. The MPLS-TP control plane should provide mechanisms to
configure the PHB of on-demand CV packets ([RFC6371],
Section 6.1.1, paragraph 3).
133. The MPLS-TP control plane should provide mechanisms to control
the use of on-demand LM, including configuration of the
beginning and duration of the LM procedures, the transmission
rate, and PHB associated with the LM OAM packets originating
from a MEP ([RFC6371], Section 6.2.1).
134. The MPLS-TP control plane should provide mechanisms to control
the use of throughput estimation ([RFC6371], Section 6.3.1).
135. The MPLS-TP control plane should provide mechanisms to control
the use of on-demand DM, including configuration of the
beginning and duration of the DM procedures, the transmission
rate, and PHB associated with the DM OAM packets originating
from a MEP ([RFC6371], Section 6.5.1).
2.4. Security Requirements
There are no specific MPLS-TP control-plane security requirements.
The existing framework for MPLS and GMPLS security is documented in
[RFC5920], and that document applies equally to MPLS-TP.
2.5. Identifier Requirements
The following are requirements based on [RFC6370]:
136. The MPLS-TP control plane must support MPLS-TP point-to-point
tunnel identifiers of the forms defined in Section 5.1 of
[RFC6370].
137. The MPLS-TP control plane must support MPLS-TP LSP identifiers
of the forms defined in Section 5.2 of [RFC6370], and the
mappings to GMPLS as defined in Section 5.3 of [RFC6370].
138. The MPLS-TP control plane must support pseudowire path
identifiers of the form defined in Section 6 of [RFC6370].
139. The MPLS-TP control plane must support MEG_IDs for LSPs and PWs
as defined in Section 7.1.1 of [RFC6370].
140. The MPLS-TP control plane must support IP-compatible MEG_IDs
for LSPs and PWs as defined in Section 7.1.2 of [RFC6370].
141. The MPLS-TP control plane must support MEP_IDs for LSPs and PWs
of the forms defined in Section 7.2.1 of [RFC6370].
Andersson, et al. Informational [Page 25]
RFC 6373 MPLS-TP Control Plane Framework September 2011
142. The MPLS-TP control plane must support IP-based MEP_IDs for
MPLS-TP LSP of the forms defined in Section 7.2.2.1 of
[RFC6370].
143. The MPLS-TP control plane must support IP-based MEP_IDs for
Pseudowires of the form defined in Section 7.2.2.2 of
[RFC6370].
3. Relationship of PWs and TE LSPs
The data-plane relationship between PWs and LSPs is inherited from
standard MPLS and is reviewed in the MPLS-TP framework [RFC5921].
Likewise, the control-plane relationship between PWs and LSPs is
inherited from standard MPLS. This relationship is reviewed in this
document. The relationship between the PW and LSP control planes in
MPLS-TP is the same as the relationship found in the PWE3 Maintenance
Reference Model as presented in the PWE3 architecture; see Figure 6
of [RFC3985]. The PWE3 architecture [RFC3985] states: "The PWE3
protocol-layering model is intended to minimize the differences
between PWs operating over different PSN types". Additionally, PW
control (maintenance) takes place separately from LSP signaling.
[RFC4447] and [MS-PW-DYNAMIC] provide such extensions for the use of
LDP as the control plane for PWs. This control can provide PW
control without providing LSP control.
In the context of MPLS-TP, LSP tunnel signaling is provided via GMPLS
RSVP-TE. While RSVP-TE could be extended to support PW control much
as LDP was extended in [RFC4447], such extensions are out of scope of
this document. This means that the control of PWs and LSPs will
operate largely independently. The main coordination between LSP and
PW control will occur within the nodes that terminate PWs or PW
segments. See Section 5.3.2 for an additional discussion on such
coordination.
It is worth noting that the control planes for PWs and LSPs may be
used independently, and that one may be employed without the other.
This translates into four possible scenarios: (1) no control plane is
employed; (2) a control plane is used for both LSPs and PWs; (3) a
control plane is used for LSPs, but not PWs; (4) a control plane is
used for PWs, but not LSPs.
The PW and LSP control planes, collectively, must satisfy the MPLS-TP
control-plane requirements reviewed in this document. When client
services are provided directly via LSPs, all requirements must be
satisfied by the LSP control plane. When client services are
provided via PWs, the PW and LSP control planes can operate in
combination, and some functions may be satisfied via the PW control
plane while others are provided to PWs by the LSP control plane. For
Andersson, et al. Informational [Page 26]
RFC 6373 MPLS-TP Control Plane Framework September 2011
example, to support the recovery functions described in [RFC6372],
this document focuses on the control of the recovery functions at the
LSP layer. PW-based recovery is under development at this time and
may be used once defined.
4. TE LSPs
MPLS-TP uses Generalized MPLS (GMPLS) signaling and routing, see
[RFC3945], as the control plane for LSPs. The GMPLS control plane is
based on the MPLS control plane. GMPLS includes support for MPLS
labeled data and transport data planes. GMPLS includes most of the
transport-centric features required to support MPLS-TP LSPs. This
section will first review the features of GMPLS relevant to MPLS-TP
LSPs, then identify how specific requirements can be met using
existing GMPLS functions, and will conclude with extensions that are
anticipated to support the remaining MPLS-TP control-plane
requirements.
4.1. GMPLS Functions and MPLS-TP LSPs
This section reviews how existing GMPLS functions can be applied to
MPLS-TP.
4.1.1. In-Band and Out-of-Band Control
GMPLS supports both in-band and out-of-band control. The terms "in-
band" and "out-of-band", in the context of this document, refer to
the relationship of the control plane relative to the management and
data planes. The terms may be used to refer to the control plane
independent of the management plane, or to both of them in concert.
The remainder of this section describes the relationship of the
control plane to the management and data planes.
There are multiple uses of both terms "in-band" and "out-of-band".
The terms may relate to a channel, a path, or a network. Each of
these can be used independently or in combination. Briefly, some
typical usage of the terms is as follows:
o In-band
This term is used to refer to cases where control-plane traffic is
sent in the same communication channel used to transport
associated user data or management traffic. IP, MPLS, and
Ethernet networks are all examples where control traffic is
typically sent in-band with the data traffic. An example of this
case in the context of MPLS-TP is where control-plane traffic is
sent via the MPLS Generic Associated Channel (G-ACh), see
[RFC5586], using the same LSP as controlled user traffic.
Andersson, et al. Informational [Page 27]
RFC 6373 MPLS-TP Control Plane Framework September 2011
o Out-of-band, in-fiber (same physical connection)
This term is used to refer to cases where control-plane traffic is
sent using a different communication channel from the associated
data or management traffic, and the control communication channel
resides in the same fiber as either the management or data
traffic. An example of this case in the context of MPLS-TP is
where control-plane traffic is sent via the G-ACh using a
dedicated LSP on the same link (interface) that carries controlled
user traffic.
o Out-of-band, aligned topology
This term is used to refer to the cases where control-plane
traffic is sent using a different communication channel from the
associated data or management traffic, and the control traffic
follows the same node-to-node path as either the data or
management traffic.
Such topologies are usually supported using a parallel fiber or
other configurations where multiple data channels are available
and one is (dynamically) selected as the control channel. An
example of this case in the context of MPLS-TP is where control-
plane traffic is sent along the same nodal path, but not
necessarily the same links (interfaces), as the corresponding
controlled user traffic.
o Out-of-band, independent topology
This term is used to refer to the cases where control-plane
traffic is sent using a different communication channel from the
associated data or management traffic, and the control traffic may
follow a path that is completely independent of the data traffic.
Such configurations are a superset of the other cases and do not
preclude the use of in-fiber or aligned topology links, but
alignment is not required. An example of this case in the context
of MPLS-TP is where control-plane traffic is sent between
controlling nodes using any available path and links, completely
without regard for the path(s) taken by corresponding management
or user traffic.
In the context of MPLS-TP requirements, requirement 14 (see Section 2
above) can be met using out-of-band in-fiber or aligned topology
types of control. Requirement 15 can only be met by using out-of-
band, independent topology. G-ACh is likely to be used extensively
in MPLS-TP networks to support the MPLS-TP control (and management)
planes.
Andersson, et al. Informational [Page 28]
RFC 6373 MPLS-TP Control Plane Framework September 2011
4.1.2. Addressing
MPLS-TP reuses and supports the addressing mechanisms supported by
MPLS. The MPLS-TP identifiers document (see [RFC6370]) provides
additional context on how IP addresses are used within MPLS-TP.
MPLS, and consequently MPLS-TP, uses the IPv4 and IPv6 address
families to identify MPLS-TP nodes by default for network management
and signaling purposes. The address spaces and neighbor adjacencies
in the control, management, and data planes used in an MPLS-TP
network may be completely separated or combined at the discretion of
an MPLS-TP operator and based on the equipment capabilities of a
vendor. The separation of the control and management planes from the
data plane allows each plane to be independently addressable. Each
plane may use addresses that are not mutually reachable, e.g., it is
likely that the data plane will not be able to reach an address from
the management or control planes and vice versa. Each plane may also
use a different address family. It is even possible to reuse
addresses in each plane, but this is not recommended as it may lead
to operational confusion. As previously mentioned, the G-ACh
mechanism defined in [RFC5586] is expected to be used extensively in
MPLS-TP networks to support the MPLS-TP control (and management)
planes.
4.1.3. Routing
Routing support for MPLS-TP LSPs is based on GMPLS routing. GMPLS
routing builds on TE routing and has been extended to support
multiple switching technologies per [RFC3945] and [RFC4202] as well
as multiple levels of packet switching within a single network. IS-
IS extensions for GMPLS are defined in [RFC5307] and [RFC5316], which
build on the TE extensions to IS-IS defined in [RFC5305]. OSPF
extensions for GMPLS are defined in [RFC4203] and [RFC5392], which
build on the TE extensions to OSPF defined in [RFC3630]. The listed
RFCs should be viewed as a starting point rather than a comprehensive
list as there are other IS-IS and OSPF extensions, as defined in IETF
RFCs, that can be used within an MPLS-TP network.
4.1.4. TE LSPs and Constraint-Based Path Computation
Both MPLS and GMPLS allow for traffic engineering and constraint-
based path computation. MPLS path computation provides paths for
MPLS-TE unidirectional P2P and P2MP LSPs. GMPLS path computation
adds bidirectional LSPs, explicit recovery path computation, as well
as support for the other functions discussed in this section.
Both MPLS and GMPLS path computation allow for the restriction of
path selection based on the use of Explicit Route Objects (EROs) and
other LSP attributes; see [RFC3209] and [RFC3473]. In all cases, no
Andersson, et al. Informational [Page 29]
RFC 6373 MPLS-TP Control Plane Framework September 2011
specific algorithm is standardized by the IETF. This is anticipated
to continue to be the case for MPLS-TP LSPs.
4.1.4.1. Relation to PCE
Path Computation Element (PCE)-based approaches, see [RFC4655], may
be used for path computation of a GMPLS LSP, and consequently an
MPLS-TP LSP, across domains and in a single domain. In cases where
PCE is used, the PCE Communication Protocol (PCEP), see [RFC5440],
will be used to communicate PCE-related requests and responses.
MPLS-TP-specific extensions to PCEP are currently out of scope of the
MPLS-TP project and this document.
4.1.5. Signaling
GMPLS signaling is defined in [RFC3471] and [RFC3473] and is based on
RSVP-TE [RFC3209]. Constraint-based Routed LDP (CR-LDP) GMPLS (see
[RFC3472]) is no longer under active development within the IETF,
i.e., it is deprecated (see [RFC3468]) and must not be used for MPLS
nor MPLS-TP consequently. In general, all RSVP-TE extensions that
apply to MPLS may also be used for GMPLS and consequently MPLS-TP.
Most notably, this includes support for P2MP signaling as defined in
[RFC4875].
GMPLS signaling includes a number of MPLS-TP required functions --
notably, support for out-of-band control, bidirectional LSPs, and
independent control- and data-plane fault management. There are also
numerous other GMPLS and MPLS extensions that can be used to provide
specific functions in MPLS-TP networks. Specific references are
provided below.
4.1.6. Unnumbered Links
Support for unnumbered links (i.e., links that do not have IP
addresses) is permitted in MPLS-TP and its usage is at the discretion
of the network operator. Support for unnumbered links is included
for routing using OSPF [RFC4203] and IS-IS [RFC5307], and for
signaling in [RFC3477].
4.1.7. Link Bundling
Link bundling provides a local construct that can be used to improve
scaling of TE routing when multiple data links are shared between
node pairs. Link bundling for MPLS and GMPLS networks is defined in
[RFC4201]. Link bundling may be used in MPLS-TP networks, and its
use is at the discretion of the network operator.
Andersson, et al. Informational [Page 30]
RFC 6373 MPLS-TP Control Plane Framework September 2011
4.1.8. Hierarchical LSPs
This section reuses text from [RFC6107].
[RFC3031] describes how MPLS labels may be stacked so that LSPs may
be nested with one LSP running through another. This concept of
hierarchical LSPs (H-LSPs) is formalized in [RFC4206] with a set of
protocol mechanisms for the establishment of a hierarchical LSP that
can carry one or more other LSPs.
[RFC4206] goes on to explain that a hierarchical LSP may carry other
LSPs only according to their switching types. This is a function of
the way labels are carried. In a packet switch capable network, the
hierarchical LSP can carry other packet switch capable LSPs using the
MPLS label stack.
Signaling mechanisms defined in [RFC4206] allow a hierarchical LSP to
be treated as a single hop in the path of another LSP. This
mechanism is also sometimes known as "non-adjacent signaling", see
[RFC4208].
A Forwarding Adjacency (FA) is defined in [RFC4206] as a data link
created from an LSP and advertised in the same instance of the
control plane that advertises the TE links from which the LSP is
constructed. The LSP itself is called an FA-LSP. FA-LSPs are
analogous to MPLS-TP Sections as discussed in [RFC5960].
Thus, a hierarchical LSP may form an FA such that it is advertised as
a TE link in the same instance of the routing protocol as was used to
advertise the TE links that the LSP traverses.
As observed in [RFC4206], the nodes at the ends of an FA would not
usually have a routing adjacency.
LSP hierarchy is expected to play an important role in MPLS-TP
networks, particularly in the context of scaling and recovery as well
as supporting SPMEs.
4.1.9. LSP Recovery
GMPLS defines RSVP-TE extensions in support for end-to-end GMPLS LSPs
recovery in [RFC4872] and segment recovery in [RFC4873]. GMPLS
segment recovery provides a superset of the function in end-to-end
recovery. End-to-end recovery can be viewed as a special case of
segment recovery where there is a single recovery domain whose
borders coincide with the ingress and egress of the LSP, although
specific procedures are defined.
Andersson, et al. Informational [Page 31]
RFC 6373 MPLS-TP Control Plane Framework September 2011
The five defined types of recovery defined in GMPLS are:
- 1+1 bidirectional protection for P2P LSPs
- 1+1 unidirectional protection for P2MP LSPs
- 1:n (including 1:1) protection with or without extra traffic
- Rerouting without extra traffic (sometimes known as soft
rerouting), including shared mesh restoration
- Full LSP rerouting
Recovery for MPLS-TP LSPs, as discussed in [RFC6372], is signaled
using the mechanism defined in [RFC4872] and [RFC4873]. Note that
when MEPs are required for the OAM CC function and the MEPs exist at
LSP transit nodes, each MEP is instantiated at a hierarchical LSP end
point, and protection is provided end-to-end for the hierarchical
LSP. (Protection can be signaled using either [RFC4872] or [RFC4873]
defined procedures.) The use of Notify messages to trigger
protection switching and recovery is not required in MPLS-TP, as this
function is expected to be supported via OAM. However, its use is
not precluded.
4.1.10. Control-Plane Reference Points (E-NNI, I-NNI, UNI)
The majority of RFCs about the GMPLS control plane define the control
plane from the context of an internal Network-to-Network Interface
(I-NNI). In the MPLS-TP context, some operators may choose to deploy
signaled interfaces across User-to-Network Interfaces (UNIs) and
across inter-provider, external Network-to-Network Interfaces
(E-NNIs). Such support is embodied in [RFC4208] for UNIs and in
[RFC5787] for routing areas in support of E-NNIs. This work may
require extensions in order to meet the specific needs of an MPLS-TP
UNI and E-NNI.
4.2. OAM, MEP (Hierarchy), MIP Configuration and Control
MPLS-TP is defined to support a comprehensive set of MPLS-TP OAM
functions. The MPLS-TP control plane will not itself provide OAM
functions, but it will be used to instantiate and otherwise control
MPLS-TP OAM functions.
Specific OAM requirements for MPLS-TP are documented in [RFC5860].
This document also states that it is required that the control plane
be able to configure and control OAM entities. This requirement is
not yet addressed by the existing RFCs, but such work is now under
way, e.g., [CCAMP-OAM-FWK] and [CCAMP-OAM-EXT].
Many OAM functions occur on a per-LSP basis, are typically in-band,
and are initiated immediately after LSP establishment. Hence, it is
desirable that such functions be established and activated via the
Andersson, et al. Informational [Page 32]
RFC 6373 MPLS-TP Control Plane Framework September 2011
same control-plane signaling used to set up the LSP, as this
effectively synchronizes OAM with the LSP lifetime and avoids the
extra overhead and potential errors associated with separate OAM
configuration mechanisms.
4.2.1. Management-Plane Support
There is no MPLS-TP requirement for a standardized management
interface to the MPLS-TP control plane. That said, MPLS and GMPLS
support a number of standardized management functions. These include
the MPLS-TE/GMPLS TE Database Management Information Base [TE-MIB];
the MPLS-TE MIB [RFC3812]; the MPLS LSR MIB [RFC3813]; the GMPLS TE
MIB [RFC4802]; and the GMPLS LSR MIB [RFC4803]. These MIB modules
may be used in MPLS-TP networks. A general overview of MPLS-TP
related MIB modules can be found in [TP-MIB]. Network management
requirements for MPLS-based transport networks are provided in
[RFC5951].
4.2.1.1. Recovery Triggers
The GMPLS control plane allows for management-plane recovery triggers
and directly supports control-plane recovery triggers. Support for
control-plane recovery triggers is defined in [RFC4872], which refers
to the triggers as "Recovery Commands". These commands can be used
with both end-to-end and segment recovery, but are always controlled
on an end-to-end basis. The recovery triggers/commands defined in
[RFC4872] are:
a. Lockout of recovery LSP
b. Lockout of normal traffic
c. Forced switch for normal traffic
d. Requested switch for normal traffic
e. Requested switch for recovery LSP
Note that control-plane triggers are typically invoked in response to
a management-plane request at the ingress.
4.2.1.2. Management-Plane / Control-Plane Ownership Transfer
In networks where both the control plane and management plane are
provided, LSP provisioning can be done either by the control plane or
management plane. As mentioned in the requirements section above, it
must be possible to transfer, or handover, a management-plane-created
LSP to the control-plane domain and vice versa. [RFC5493] defines
Andersson, et al. Informational [Page 33]
RFC 6373 MPLS-TP Control Plane Framework September 2011
the specific requirements for an LSP ownership handover procedure.
It must be possible for the control plane to provide the management
plane, in a reliable manner, with the status or result of an
operation performed by the management plane. This notification may
be either synchronous or asynchronous with respect to the operation.
Moreover, it must be possible for the management plane to monitor the
status of the control plane, for example, the status of a TE link,
its available resources, etc. This monitoring may be based on
queries initiated by the management plane or on notifications
generated by the control plane. A mechanism must be made available
by the control plane to the management plane to log operation of a
control-plane LSP; that is, it must be possible from the NMS to have
a clear view of the life (traffic hit, action performed, signaling,
etc.) of a given LSP. The LSP handover procedure for MPLS-TP LSPs is
supported via [RFC5852].
4.3. GMPLS and MPLS-TP Requirements Table
The following table shows how the MPLS-TP control-plane requirements
can be met using the existing GMPLS control plane (which builds on
the MPLS control plane). Areas where additional specifications are
required are also identified. The table lists references based on
the control-plane requirements as identified and numbered above in
Section 2.
+=======+===========================================================+
| Req # | References |
+-------+-----------------------------------------------------------+
| 1 | Generic requirement met by using Standards Track RFCs |
| 2 | [RFC3945], [RFC4202], [RFC3473], [RFC4203], [RFC5307] |
| 3 | [RFC5145] + Formal Definition (See Section 4.4.1) |
| 4 | Generic requirement met by using Standards Track RFCs |
| 5 | [RFC3945], [RFC4202], [RFC3473], [RFC4203], [RFC5307] |
| 6 | [RFC3471], [RFC3473], [RFC4875] |
| 7 | [RFC3471], [RFC3473] + |
| | Associated bidirectional LSPs (See Section 4.4.2) |
| 8 | [RFC4875] |
| 9 | [RFC3473] |
| 10 | Associated bidirectional LSPs (See Section 4.4.2) |
| 11 | Associated bidirectional LSPs (See Section 4.4.2) |
| 12 | [RFC3473] |
| 13 | [RFC5467] (Currently Experimental; See Section 4.4.3) |
| 14 | [RFC3945], [RFC3473], [RFC4202], [RFC4203], [RFC5307] |
| 15 | [RFC3945], [RFC3473], [RFC4202], [RFC4203], [RFC5307] |
| 16 | [RFC3945], [RFC4202], [RFC3473], [RFC4203], [RFC5307] |
| 17 | [RFC3945], [RFC4202] + proper vendor implementation |
| 18 | [RFC3945], [RFC4202] + proper vendor implementation |
| 19 | [RFC3945], [RFC4202] |
Andersson, et al. Informational [Page 34]
RFC 6373 MPLS-TP Control Plane Framework September 2011
| 20 | [RFC3473] |
| 21 | [RFC3945], [RFC4202], [RFC3473], [RFC4203], [RFC5307], |
| | [RFC5151] |
| 22 | [RFC3945], [RFC4202], [RFC3473], [RFC4203], [RFC5307], |
| | [RFC5151] |
| 23 | [RFC3945], [RFC4202], [RFC3473], [RFC4203], [RFC5307] |
| 24 | [RFC3945], [RFC4202], [RFC3473], [RFC4203], [RFC5307] |
| 25 | [RFC3945], [RFC4202], [RFC3473], [RFC4203], [RFC5307], |
| | [RFC6107] |
| 26 | [RFC3473], [RFC4875] |
| 27 | [RFC3473], [RFC4875] |
| 28 | [RFC3945], [RFC3471], [RFC4202] |
| 29 | [RFC3945], [RFC4202], [RFC3473], [RFC4203], [RFC5307] |
| 30 | [RFC3945], [RFC3471], [RFC4202] |
| 31 | [RFC3945], [RFC3471], [RFC4202] |
| 32 | [RFC4208], [RFC4974], [RFC5787], [RFC6001] |
| 33 | [RFC3473], [RFC4875] |
| 34 | [RFC4875] |
| 35 | [RFC3945], [RFC4202], [RFC3473], [RFC4203], [RFC5307] |
| 36 | [RFC3473], [RFC3209] (Make-before-break) |
| 37 | [RFC3473], [RFC3209] (Make-before-break) |
| 38 | [RFC4139], [RFC4258], [RFC5787] |
| 39 | [RFC3945], [RFC4202], [RFC3473], [RFC4203], [RFC5307] |
| 40 | [RFC3473], [RFC5063] |
| 41 | [RFC3945], [RFC3471], [RFC4202], [RFC4208] |
| 42 | [RFC3945], [RFC3471], [RFC4202] |
| 43 | [RFC4872], [RFC4873], [CCAMP-OAM-FWK], [CCAMP-OAM-EXT] |
| 44 | [RFC6107], [CCAMP-OAM-FWK], [CCAMP-OAM-EXT] |
| 45 | [RFC3473], [RFC4203], [RFC5307], [RFC5063] |
| 46 | [RFC5493] |
| 47 | [RFC4872], [RFC4873] |
| 48 | [RFC3945], [RFC3471], [RFC4202] |
| 49 | [RFC4872], [RFC4873] + Recovery for P2MP (see Sec. 4.4.4) |
| 50 | [RFC4872], [RFC4873] |
| 51 | [RFC4872], [RFC4873] + proper vendor implementation |
| 52 | [RFC4872], [RFC4873], [GMPLS-PS] |
| 53 | [RFC4872], [RFC4873] |
| 54 | [RFC3473], [RFC4872], [RFC4873], [GMPLS-PS] |
| | Timers are a local implementation matter |
| 55 | [RFC4872], [RFC4873], [GMPLS-PS] + |
| | implementation of timers |
| 56 | [RFC4872], [RFC4873], [GMPLS-PS] |
| 57 | [RFC4872], [RFC4873] |
| 58 | [RFC4872], [RFC4873] |
| 59 | [RFC4872], [RFC4873] |
| 60 | [RFC4872], [RFC4873], [RFC6107] |
| 61 | [RFC4872], [RFC4873] |
| 62 | [RFC4872], [RFC4873] + Recovery for P2MP (see Sec. 4.4.4) |
Andersson, et al. Informational [Page 35]
RFC 6373 MPLS-TP Control Plane Framework September 2011
| 63 | [RFC4872], [RFC4873] |
| 64 | [RFC4872], [RFC4873] |
| 65 | [RFC4872], [RFC4873] |
| 66 | [RFC4872], [RFC4873], [RFC6107] |
| 67 | [RFC4872], [RFC4873] |
| 68 | [RFC3473], [RFC4872], [RFC4873] |
| 69 | [RFC3473] |
| 70 | [RFC3473], [RFC4872], [GMPLS-PS] |
| 71 | [RFC3473], [RFC4872] |
| 72 | [RFC4872], [RFC4873], [CCAMP-OAM-FWK], [CCAMP-OAM-EXT] |
| 73 | [RFC4426], [RFC4872], [RFC4873] |
| 74 | [RFC4426], [RFC4872], [RFC4873] |
| 75 | [RFC4426], [RFC4872], [RFC4873] |
| 76 | [RFC4426], [RFC4872], [RFC4873] |
| 77 | [RFC4426], [RFC4872], [RFC4873] |
| 78 | [RFC4426], [RFC4872], [RFC4873] + vendor implementation |
| 79 | [RFC4426], [RFC4872], [RFC4873] |
| 80 | [RFC4426], [RFC4872], [RFC4873] |
| 81 | [RFC4872], [RFC4873] + Testing control (See Sec. 4.4.5) |
| 82 | [RFC4872], [RFC4873] + Testing control (See Sec. 4.4.5) |
| 83 | [RFC4872], [RFC4873] + Testing control (See Sec. 4.4.5) |
| 84 | [RFC4872], [RFC4873] + Testing control (See Sec. 4.4.5) |
| 85 | [RFC4872], [RFC4873], [CCAMP-OAM-FWK], [CCAMP-OAM-EXT] |
| 86 | [RFC4872], [RFC4873] |
| 87 | [RFC4872], [RFC4873] |
| 88 | [RFC4872], [RFC4873], [TP-RING] |
| 89 | [RFC4872], [RFC4873], [TP-RING] |
| 90 | [RFC3270], [RFC3473], [RFC4124] + GMPLS Usage (See 4.4.6) |
| 91 | [RFC3945], [RFC4202], [RFC3473], [RFC4203], [RFC5307] |
| 92 | [RFC3945], [RFC3473], [RFC2210], [RFC2211], [RFC2212] |
| 93 | Generic requirement on data plane (correct implementation)|
| 94 | [RFC3473], [NO-PHP] |
| 95 | [RFC3270], [RFC3473], [RFC4124] + GMPLS Usage (See 4.4.6) |
| 96 | PW only requirement; see PW Requirements Table (5.2) |
| 97 | PW only requirement; see PW Requirements Table (5.2) |
| 98 | [RFC3945], [RFC3473], [RFC6107] |
| 99 | [RFC3945], [RFC4202], [RFC3473], [RFC4203], [RFC5307] + |
| | [RFC5392] and [RFC5316] |
| 100 | PW only requirement; see PW Requirements Table (5.2) |
| 101 | [RFC3473], [RFC4203], [RFC5307], [RFC5063] |
| 102 | [RFC4872], [RFC4873], [TP-RING] |
| 103 | [RFC3945], [RFC3473], [RFC6107] |
| 104 | [CCAMP-OAM-FWK], [CCAMP-OAM-EXT] |
| 105 | [RFC3473], [CCAMP-OAM-FWK], [CCAMP-OAM-EXT] |
| 106 | [CCAMP-OAM-FWK], [CCAMP-OAM-EXT] |
| 107 | [CCAMP-OAM-FWK], [CCAMP-OAM-EXT] + (See Sec. 4.4.5) |
| 108 | [CCAMP-OAM-FWK], [CCAMP-OAM-EXT] |
| 109 | [RFC3473], [RFC4872], [RFC4873] |
Andersson, et al. Informational [Page 36]
RFC 6373 MPLS-TP Control Plane Framework September 2011
| 110 | [RFC3473], [RFC4872], [RFC4873] |
| 111 | [RFC3473], [RFC4783] |
| 112 | [CCAMP-OAM-FWK], [CCAMP-OAM-EXT] |
| 113 | [CCAMP-OAM-FWK], [CCAMP-OAM-EXT] + (See Sec. 4.4.5) |
| 114 | [CCAMP-OAM-FWK], [CCAMP-OAM-EXT] + (See Sec. 4.4.5) |
| 115 | [RFC3473] |
| 116 | [RFC4426], [RFC4872], [RFC4873] |
| 117 | [RFC3473], [RFC4872], [RFC4873] |
| 118 | [RFC3473], [RFC4783] |
| 119 | [RFC3473] |
| 120 | [RFC3473], [RFC4783] |
| 121 | [CCAMP-OAM-FWK], [CCAMP-OAM-EXT] + (See Sec. 4.4.5) |
| 122 | [CCAMP-OAM-FWK], [CCAMP-OAM-EXT] + (See Sec. 4.4.5) |
| 123 | [CCAMP-OAM-FWK], [CCAMP-OAM-EXT], [RFC6107] |
| 124 - | |
| 135 | [CCAMP-OAM-FWK], [CCAMP-OAM-EXT] + (See Sec. 4.4.5) |
| 136a | [RFC3473] |
| 136b | [RFC3473] + (See Sec. 4.4.7) |
| 137a | [RFC3473] |
| 137b | [RFC3473] + (See Sec. 4.4.7) |
| 138 | PW only requirement; see PW Requirements Table (5.2) |
| 139 - | |
| 143 | [CCAMP-OAM-FWK], [CCAMP-OAM-EXT] + (See Sec. 4.4.8) |
+=======+===========================================================+
Table 1: GMPLS and MPLS-TP Requirements Table
4.4. Anticipated MPLS-TP-Related Extensions and Definitions
This section identifies the extensions and other documents that have
been identified as likely to be needed to support the full set of
MPLS-TP control-plane requirements.
4.4.1. MPLS-TE to MPLS-TP LSP Control-Plane Interworking
While no interworking function is expected in the data plane to
support the interconnection of MPLS-TE and MPLS-TP networking, this
is not the case for the control plane. MPLS-TE networks typically
use LSP signaling based on [RFC3209], while MPLS-TP LSPs will be
signaled using GMPLS RSVP-TE, i.e., [RFC3473]. [RFC5145] identifies
a set of solutions that are aimed to aid in the interworking of MPLS-
TE and GMPLS control planes. [RFC5145] work will serve as the
foundation for a formal definition of MPLS to MPLS-TP control-plane
interworking.
Andersson, et al. Informational [Page 37]
RFC 6373 MPLS-TP Control Plane Framework September 2011
4.4.2. Associated Bidirectional LSPs
GMPLS signaling, [RFC3473], supports unidirectional and co-routed,
bidirectional point-to-point LSPs. MPLS-TP also requires support for
associated bidirectional point-to-point LSPs. Such support will
require an extension or a formal definition of how the LSP end points
supporting an associated bidirectional service will coordinate the
two LSPs used to provide such a service. Per requirement 11, transit
nodes that support an associated bidirectional service should be
aware of the association of the LSPs used to support the service when
both LSPs are supported on that transit node. There are several
existing protocol mechanisms on which to base such support,
including, but not limited to:
o GMPLS calls [RFC4974].
o The ASSOCIATION object [RFC4872].
o The LSP_TUNNEL_INTERFACE_ID object [RFC6107].
4.4.3. Asymmetric Bandwidth LSPs
[RFC5467] defines support for bidirectional LSPs that have different
(asymmetric) bandwidth requirements for each direction. That RFC can
be used to meet the related MPLS-TP technical requirement, but it is
currently an Experimental RFC. To fully satisfy the MPLS-TP
requirement, RFC 5467 will need to become a Standards Track RFC.
4.4.4. Recovery for P2MP LSPs
The definitions of P2MP, [RFC4875], and GMPLS recovery, [RFC4872] and
[RFC4873], do not explicitly cover their interactions. MPLS-TP
requires a formal definition of recovery techniques for P2MP LSPs.
Such a formal definition will be based on existing RFCs and may not
require any new protocol mechanisms but, nonetheless, must be
documented.
4.4.5. Test Traffic Control and Other OAM Functions
[CCAMP-OAM-FWK] and [CCAMP-OAM-EXT] are examples of OAM-related
control extensions to GMPLS. These extensions cover a portion of,
but not all, OAM-related control functions that have been identified
in the context of MPLS-TP. As discussed above, the MPLS-TP control
plane must support the selection of which OAM function(s) (if any) to
use (including support to select experimental OAM functions) and what
OAM functionality to run, including Continuity Check (CC),
Andersson, et al. Informational [Page 38]
RFC 6373 MPLS-TP Control Plane Framework September 2011
Connectivity Verification (CV), packet loss, delay quantification,
and diagnostic testing of a service. Such support may be included in
the listed documents or in other documents.
4.4.6. Diffserv Object Usage in GMPLS
[RFC3270] and [RFC4124] define support for Diffserv-enabled MPLS
LSPs. While [RFC4124] references GMPLS signaling, there is no
explicit discussion on the use of the Diffserv-related objects in
GMPLS signaling. A (possibly Informational) document on how GMPLS
supports Diffserv LSPs is likely to prove useful in the context of
MPLS-TP.
4.4.7. Support for MPLS-TP LSP Identifiers
MPLS-TP uses two forms of LSP identifiers, see [RFC6370]. One form
is based on existing GMPLS fields. The other form is based on either
the globally unique Attachment Interface Identifier (AII) defined in
[RFC5003] or the ITU Carrier Code (ICC) defined in ITU-T
Recommendation M.1400. Neither form is currently supported in GMPLS,
and such extensions will need to be documented.
4.4.8. Support for MPLS-TP Maintenance Identifiers
MPLS-TP defines several forms of maintenance-entity-related
identifiers. Both node-unique and global forms are defined.
Extensions will be required to GMPLS to support these identifiers.
These extensions may be added to existing works in progress, such as
[CCAMP-OAM-FWK] and [CCAMP-OAM-EXT], or may be defined in independent
documents.
5. Pseudowires
5.1. LDP Functions and Pseudowires
MPLS PWs are defined in [RFC3985] and [RFC5659], and provide for
emulated services over an MPLS Packet Switched Network (PSN).
Several types of PWs have been defined: (1) Ethernet PWs providing
for Ethernet port or Ethernet VLAN transport over MPLS [RFC4448], (2)
High-Level Data Link Control (HDLC) / PPP PW providing for HDLC/PPP
leased line transport over MPLS [RFC4618], (3) ATM PWs [RFC4816], (4)
Frame Relay PWs [RFC4619], and (5) circuit Emulation PWs [RFC4553].
Today's transport networks based on Plesiochronous Digital Hierarchy
(PDH), WDM, or SONET/SDH provide transport for PDH or SONET (e.g.,
ATM over SONET or Packet PPP over SONET) client signals with no
payload awareness. Implementing PW capability allows for the use of
an existing technology to substitute the Time-Division Multiplexing
Andersson, et al. Informational [Page 39]
RFC 6373 MPLS-TP Control Plane Framework September 2011
(TDM) transport with packet-based transport, using well-defined PW
encapsulation methods for carrying various packet services over MPLS,
and providing for potentially better bandwidth utilization.
There are two general classes of PWs: (1) Single-Segment Pseudowires
(SS-PWs) [RFC3985] and (2) Multi-segment Pseudowires (MS-PWs)
[RFC5659]. An MPLS-TP network domain may transparently transport a
PW whose end points are within a client network. Alternatively, an
MPLS-TP edge node may be the Terminating PE (T-PE) for a PW,
performing adaptation from the native attachment circuit technology
(e.g., Ethernet 802.1Q) to an MPLS PW that is then transported in an
LSP over an MPLS-TP network. In this way, the PW is analogous to a
transport channel in a TDM network, and the LSP is equivalent to a
container of multiple non-concatenated channels, albeit they are
packet containers. An MPLS-TP network may also contain Switching PEs
(S-PEs) for a Multi-Segment PW whereby the T-PEs may be at the edge
of an MPLS-TP network or in a client network. In the latter case, a
T-PE in a client network performs the adaptation of the native
service to MPLS and the MPLS-TP network performs pseudowire
switching.
The SS-PW signaling control plane is based on targeted LDP (T-LDP)
with specific procedures defined in [RFC4447]. The MS-PW signaling
control plane is also based on T-LDP as allowed for in [RFC5659],
[RFC6073], and [MS-PW-DYNAMIC]. An MPLS-TP network shall use the
same PW signaling protocols and procedures for placing SS-PWs and
MS-PWs. This will leverage existing technology as well as facilitate
interoperability with client networks with native attachment circuits
or PW segments that are switched across an MPLS-TP network.
5.1.1. Management-Plane Support
There is no MPLS-TP requirement for a standardized management
interface to the MPLS-TP control plane. A general overview of MPLS-
TP-related MIB modules can be found in [TP-MIB]. Network management
requirements for MPLS-based transport networks are provided in
[RFC5951].
5.2. PW Control (LDP) and MPLS-TP Requirements Table
The following table shows how the MPLS-TP control-plane requirements
can be met using the existing LDP control plane for pseudowires
(targeted LDP). Areas where additional specifications are required
are also identified. The table lists references based on the
control-plane requirements as identified and numbered above in
Section 2.
Andersson, et al. Informational [Page 40]
RFC 6373 MPLS-TP Control Plane Framework September 2011
In the table below, several of the requirements shown are addressed
-- in part or in full -- by the use of MPLS-TP LSPs to carry
pseudowires. This is reflected by including "TP-LSPs" as a reference
for those requirements. Section 5.3.2 provides additional context
for the binding of PWs to TP-LSPs.
Andersson, et al. Informational [Page 41]
RFC 6373 MPLS-TP Control Plane Framework September 2011
+=======+===========================================================+
| Req # | References |
+-------+-----------------------------------------------------------+
| 1 | Generic requirement met by using Standards Track RFCs |
| 2 | [RFC3985], [RFC4447], Together with TP-LSPs (Sec. 4.3) |
| 3 | [RFC3985], [RFC4447] |
| 4 | Generic requirement met by using Standards Track RFCs |
| 5 | [RFC3985], [RFC4447], Together with TP-LSPs |
| 6 | [RFC3985], [RFC4447], [PW-P2MPR], [PW-P2MPE] + TP-LSPs |
| 7 | [RFC3985], [RFC4447], + TP-LSPs |
| 8 | [PW-P2MPR], [PW-P2MPE] |
| 9 | [RFC3985], end-node only involvement for PW |
| 10 | [RFC3985], proper vendor implementation |
| 11 | [RFC3985], end-node only involvement for PW |
| 12-13 | [RFC3985], [RFC4447], See Section 5.3.4 |
| 14 | [RFC3985], [RFC4447] |
| 15 | [RFC4447], [RFC3478], proper vendor implementation |
| 16 | [RFC3985], [RFC4447] |
| 17-18 | [RFC3985], proper vendor implementation |
| 19-26 | [RFC3985], [RFC4447], [RFC5659], implementation |
| 27 | [RFC4448], [RFC4816], [RFC4618], [RFC4619], [RFC4553] |
| | [RFC4842], [RFC5287] |
| 28 | [RFC3985] |
| 29-31 | [RFC3985], [RFC4447] |
| 32 | [RFC3985], [RFC4447], [RFC5659], See Section 5.3.6 |
| 33 | [RFC4385], [RFC4447], [RFC5586] |
| 34 | [PW-P2MPR], [PW-P2MPE] |
| 35 | [RFC4863] |
| 36-37 | [RFC3985], [RFC4447], See Section 5.3.4 |
| 38 | Provided by TP-LSPs |
| 39 | [RFC3985], [RFC4447], + TP-LSPs |
| 40 | [RFC3478] |
| 41-42 | [RFC3985], [RFC4447] |
| 43-44 | [RFC3985], [RFC4447], + TP-LSPs - See Section 5.3.5 |
| 45 | [RFC3985], [RFC4447], [RFC5659] + TP-LSPs |
| 46 | [RFC3985], [RFC4447], + TP-LSPs - See Section 5.3.3 |
| 47 | [PW-RED], [PW-REDB] |
| 48-49 | [RFC3985], [RFC4447], + TP-LSPs, implementation |
| 50-52 | Provided by TP-LSPs, and Section 5.3.5 |
| 53-55 | [RFC3985], [RFC4447], See Section 5.3.5 |
| 56 | [PW-RED], [PW-REDB] |
| | revertive/non-revertive behavior is a local matter for PW |
| 57-58 | [PW-RED], [PW-REDB] |
| 59-81 | [RFC3985], [RFC4447], [PW-RED], [PW-REDB], Section 5.3.5 |
| 82-83 | [RFC5085], [RFC5586], [RFC5885] |
| 84-89 | [RFC3985], [RFC4447], [PW-RED], [PW-REDB], Section 5.3.5 |
| 90-95 | [RFC3985], [RFC4447], + TP-LSPs, implementation |
| 96 | [RFC4447], [MS-PW-DYNAMIC] |
Andersson, et al. Informational [Page 42]
RFC 6373 MPLS-TP Control Plane Framework September 2011
| 97 | [RFC4447] |
| 98 - | |
| 99 | Not Applicable to PW |
| 100 | [RFC4447] |
| 101 | [RFC3478] |
| 102 | [RFC3985], + TP-LSPs |
| 103 | Not Applicable to PW |
| 104 | [PW-OAM] |
| 105 | [PW-OAM] |
| 106 - | |
| 108 | [RFC5085], [RFC5586], [RFC5885] |
| 109 | [RFC5085], [RFC5586], [RFC5885] |
| | fault reporting and protection triggering is a local |
| | matter for PW |
| 110 | [RFC5085], [RFC5586], [RFC5885] |
| | fault reporting and protection triggering is a local |
| | matter for PW |
| 111 | [RFC4447] |
| 112 | [RFC4447], [RFC5085], [RFC5586], [RFC5885] |
| 113 | [RFC5085], [RFC5586], [RFC5885] |
| 114 | [RFC5085], [RFC5586], [RFC5885] |
| 115 | path traversed by PW is determined by LSP path; see |
| | GMPLS and MPLS-TP Requirements Table, Section 4.3 |
| 116 | [PW-RED], [PW-REDB], administrative control of redundant |
| | PW is a local matter at the PW head-end |
| 117 | [PW-RED], [PW-REDB], [RFC5085], [RFC5586], [RFC5885] |
| 118 | [RFC3985], [RFC4447], [PW-RED], [PW-REDB], Section 5.3.5 |
| 119 | [RFC4447] |
| 120 - | |
| 125 | [RFC5085], [RFC5586], [RFC5885] |
| 126 - | |
| 130 | [PW-OAM] |
| 131 | Section 5.3.5 |
| 132 | [PW-OAM] |
| 133 | [PW-OAM] |
| 134 | Section 5.3.5 |
| 135 | [PW-OAM] |
| 136 | Not Applicable to PW |
| 137 | Not Applicable to PW |
| 138 | [RFC4447], [RFC5003], [MS-PW-DYNAMIC] |
| 139 - | |
| 143 | [PW-OAM] |
+=======+===========================================================+
Table 2: PW Control (LDP) and MPLS-TP Requirements Table
Andersson, et al. Informational [Page 43]
RFC 6373 MPLS-TP Control Plane Framework September 2011
5.3. Anticipated MPLS-TP-Related Extensions
Existing control protocol and procedures will be reused as much as
possible to support MPLS-TP. However, when using PWs in MPLS-TP, a
set of new requirements is defined that may require extensions of the
existing control mechanisms. This section clarifies the areas where
extensions are needed based on the requirements that are related to
the PW control plane and documented in [RFC5654].
Table 2 lists how requirements defined in [RFC5654] are expected to
be addressed.
The baseline requirement for extensions to support transport
applications is that any new mechanisms and capabilities must be able
to interoperate with existing IETF MPLS [RFC3031] and IETF PWE3
[RFC3985] control and data planes where appropriate. Hence,
extensions of the PW control plane must be in-line with the
procedures defined in [RFC4447], [RFC6073], and [MS-PW-DYNAMIC].
5.3.1. Extensions to Support Out-of-Band PW Control
For MPLS-TP, it is required that the data and control planes can be
both logically and physically separated. That is, the PW control
plane must be able to operate out-of-band (OOB). This separation
ensures, among other things, that in the case of control-plane
failures the data plane is not affected and can continue to operate
normally. This was not a design requirement for the current PW
control plane. However, due to the PW concept, i.e., PWs are
connecting logical entities ('forwarders'), and the operation of the
PW control protocol, i.e., only edge PE nodes (T-PE, S-PE) take part
in the signaling exchanges: moving T-LDP out-of-band seems to be,
theoretically, a straightforward exercise.
In fact, as a strictly local matter, ensuring that targeted LDP
(T-LDP) uses out-of-band signaling requires only that the local
implementation is configured in such a way that reachability for a
target LSR address is via the out-of-band channel.
More precisely, if IP addressing is used in the MPLS-TP control
plane, then T-LDP addressing can be maintained, although all
addresses will refer to control-plane entities. Both the PWid
Forwarding Equivalence Class (FEC) and Generalized PWid FEC Elements
can possibly be used in an OOB case as well. (Detailed evaluation is
outside the scope of this document.) The PW label allocation and
exchange mechanisms should be reused without change.
Andersson, et al. Informational [Page 44]
RFC 6373 MPLS-TP Control Plane Framework September 2011
5.3.2. Support for Explicit Control of PW-to-LSP Binding
Binding a PW to an LSP, or PW segments to LSPs, is left to nodes
acting as T-PEs and S-PEs or a control-plane entity that may be the
same one signaling the PW. However, an extension of the PW signaling
protocol is required to allow the LSR at the signal initiation end to
inform the targeted LSR (at the signal termination end) to which LSP
the resulting PW is to be bound, in the event that more than one such
LSP exists and the choice of LSPs is important to the service being
setup (for example, if the service requires co-routed bidirectional
paths). This is also particularly important to support transport
path (symmetric and asymmetric) bandwidth requirements.
For transport services, MPLS-TP requires support for bidirectional
traffic that follows congruent paths. Currently, each direction of a
PW or a PW segment is bound to a unidirectional LSP that extends
between two T-PEs, two S-PEs, or a T-PE and an S-PE. The
unidirectional LSPs in both directions are not required to follow
congruent paths, and therefore both directions of a PW may not follow
congruent paths, i.e., they are associated bidirectional paths. The
only requirement in [RFC5659] is that a PW or a PW segment shares the
same T-PEs in both directions and the same S-PEs in both directions.
MPLS-TP imposes new requirements on the PW control plane, in
requiring that both end points map the PW or PW segment to the same
transport path for the case where this is an objective of the
service. When a bidirectional LSP is selected on one end to
transport the PW, a mechanism is needed that signals to the remote
end which LSP has been selected locally to transport the PW. This
would be accomplished by adding a new TLV to PW signaling.
Note that this coincides with the gap identified for OOB support: a
new mechanism is needed to allow explicit binding of a PW to the
supporting transport LSP.
The case of unidirectional transport paths may also require
additional protocol mechanisms, as today's PWs are always
bidirectional. One potential approach for providing a unidirectional
PW-based transport path is for the PW to associate different
(asymmetric) bandwidths in each direction, with a zero or minimal
bandwidth for the return path. This approach is consistent with
Section 3.8.2 of [RFC5921] but does not address P2MP paths.
5.3.3. Support for Dynamic Transfer of PW Control/Ownership
In order to satisfy requirement 47 (as defined in Section 2), it will
be necessary to specify methods for transfer of PW ownership from the
management to the control plane (and vice versa).
Andersson, et al. Informational [Page 45]
RFC 6373 MPLS-TP Control Plane Framework September 2011
5.3.4. Interoperable Support for PW/LSP Resource Allocation
Transport applications may require resource guarantees. For such
transport LSPs, resource reservation mechanisms are provided via
RSVP-TE and the use of Diffserv. If multiple PWs are multiplexed
into the same transport LSP resources, contention may occur.
However, local policy at PEs should ensure proper resource sharing
among PWs mapped into a resource-guaranteed LSP. In the case of
MS-PWs, signaling carries the PW traffic parameters [MS-PW-DYNAMIC]
to enable admission control of a PW segment over a resource-
guaranteed LSP.
In conjunction with explicit PW-to-LSP binding, existing mechanisms
may be sufficient; however, this needs to be verified in detailed
evaluation.
5.3.5. Support for PW Protection and PW OAM Configuration
Many of the requirements listed in Section 2 are intended to support
connectivity and performance monitoring (grouped together as OAM), as
well as protection conformant with the transport services model.
In general, protection of MPLS-TP transported services is provided by
way of protection of transport LSPs. PW protection requires that
mechanisms be defined to support redundant pseudowires, including a
mechanism already described above for associating such pseudowires
with specific protected ("working" and "protection") LSPs. Also
required are definitions of local protection control functions, to
include test/verification operations, and protection status signals
needed to ensure that PW termination points are in agreement as to
which of a set of redundant pseudowires are in use for which
transport services at any given point in time.
Much of this work is currently being done in documents [PW-RED] and
[PW-REDB] that define, respectively, how to establish redundant
pseudowires and how to indicate which is in use. Additional work may
be required.
Protection switching may be triggered manually by the operator, or as
a result of loss of connectivity (detected using the mechanisms of
[RFC5085] and [RFC5586]), or service degradation (detected using
mechanisms yet to be defined).
Automated protection switching is just one of the functions for which
a transport service requires OAM. OAM is generally referred to as
either "proactive" or "on-demand", where the distinction is whether a
specific OAM tool is being used continuously over time (for the
purpose of detecting a need for protection switching, for example) or
Andersson, et al. Informational [Page 46]
RFC 6373 MPLS-TP Control Plane Framework September 2011
is only used -- either a limited number of times or over a short
period of time -- when explicitly enabled (for diagnostics, for
example).
PW OAM currently consists of connectivity verification defined by
[RFC5085]. Work is currently in progress to extend PW OAM to include
bidirectional forwarding detection (BFD) in [RFC5885], and work has
begun on extending BFD to include performance-related monitor
functions.
5.3.6. Client-Layer and Cross-Provider Interfaces to PW Control
Additional work is likely to be required to define consistent access
by a client-layer network, as well as between provider networks, to
control information available to each type of network, for example,
about the topology of an MS-PW. This information may be required by
the client-layer network in order to provide hints that may help to
avoid establishment of fate-sharing alternate paths. Such work will
need to fit within the ASON architecture; see requirement 38 above.
5.4. ASON Architecture Considerations
MPLS-TP PWs are always transported using LSPs, and these LSPs will
either have been statically provisioned or signaled using GMPLS.
For LSPs signaled using the MPLS-TP LSP control plane (GMPLS),
conformance with the ASON architecture is as described in Section 1.2
("Basic Approach"), bullet 4, of this framework document.
As discussed above in Section 5.3, there are anticipated extensions
in the following areas that may be related to ASON architecture:
- PW-to-LSP binding (Section 5.3.2)
- PW/LSP resource allocation (Section 5.3.4)
- PW protection and OAM configuration (Section 5.3.5)
- Client-layer interfaces for PW control (Section 5.3.6)
This work is expected to be consistent with ASON architecture and may
require additional specification in order to achieve this goal.
6. Security Considerations
This document primarily describes how existing mechanisms can be used
to meet the MPLS-TP control-plane requirements. The documents that
describe each mechanism contain their own security considerations
sections. For a general discussion on MPLS- and GMPLS-related
Andersson, et al. Informational [Page 47]
RFC 6373 MPLS-TP Control Plane Framework September 2011
security issues, see the MPLS/GMPLS security framework [RFC5920]. As
mentioned above in Section 2.4, there are no specific MPLS-TP
control-plane security requirements.
This document also identifies a number of needed control-plane
extensions. It is expected that the documents that define such
extensions will also include any appropriate security considerations.
7. Acknowledgments
The authors would like to acknowledge the contributions of Yannick
Brehon, Diego Caviglia, Nic Neate, Dave Mcdysan, Dan Frost, and Eric
Osborne to this work. We also thank Dan Frost in his help responding
to Last Call comments.
8. References
8.1. Normative References
[RFC2210] Wroclawski, J., "The Use of RSVP with IETF Integrated
Services", RFC 2210, September 1997.
[RFC2211] Wroclawski, J., "Specification of the Controlled-Load
Network Element Service", RFC 2211, September 1997.
[RFC2212] Shenker, S., Partridge, C., and R. Guerin, "Specification
of Guaranteed Quality of Service", RFC 2212, September
1997.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, January 2001.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC3471] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description", RFC
3471, January 2003.
[RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
January 2003.
[RFC3478] Leelanivas, M., Rekhter, Y., and R. Aggarwal, "Graceful
Restart Mechanism for Label Distribution Protocol", RFC
3478, February 2003.
Andersson, et al. Informational [Page 48]
RFC 6373 MPLS-TP Control Plane Framework September 2011
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630, September
2003.
[RFC4124] Le Faucheur, F., Ed., "Protocol Extensions for Support of
Diffserv-aware MPLS Traffic Engineering", RFC 4124, June
2005.
[RFC4202] Kompella, K., Ed., and Y. Rekhter, Ed., "Routing
Extensions in Support of Generalized Multi-Protocol Label
Switching (GMPLS)", RFC 4202, October 2005.
[RFC4203] Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF Extensions
in Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4203, October 2005.
[RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
Hierarchy with Generalized Multi-Protocol Label Switching
(GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005.
[RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson,
"Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
Use over an MPLS PSN", RFC 4385, February 2006.
[RFC4447] Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and
G. Heron, "Pseudowire Setup and Maintenance Using the
Label Distribution Protocol (LDP)", RFC 4447, April 2006.
[RFC4448] Martini, L., Ed., Rosen, E., El-Aawar, N., and G. Heron,
"Encapsulation Methods for Transport of Ethernet over MPLS
Networks", RFC 4448, April 2006.
[RFC4842] Malis, A., Pate, P., Cohen, R., Ed., and D. Zelig,
"Synchronous Optical Network/Synchronous Digital Hierarchy
(SONET/SDH) Circuit Emulation over Packet (CEP)", RFC
4842, April 2007.
[RFC4863] Martini, L. and G. Swallow, "Wildcard Pseudowire Type",
RFC 4863, May 2007.
[RFC4872] Lang, J., Ed., Rekhter, Y., Ed., and D. Papadimitriou,
Ed., "RSVP-TE Extensions in Support of End-to-End
Generalized Multi-Protocol Label Switching (GMPLS)
Recovery", RFC 4872, May 2007.
[RFC4873] Berger, L., Bryskin, I., Papadimitriou, D., and A. Farrel,
"GMPLS Segment Recovery", RFC 4873, May 2007.
Andersson, et al. Informational [Page 49]
RFC 6373 MPLS-TP Control Plane Framework September 2011
[RFC4929] Andersson, L., Ed., and A. Farrel, Ed., "Change Process
for Multiprotocol Label Switching (MPLS) and Generalized
MPLS (GMPLS) Protocols and Procedures", BCP 129, RFC 4929,
June 2007.
[RFC4974] Papadimitriou, D. and A. Farrel, "Generalized MPLS (GMPLS)
RSVP-TE Signaling Extensions in Support of Calls", RFC
4974, August 2007.
[RFC5063] Satyanarayana, A., Ed., and R. Rahman, Ed., "Extensions to
GMPLS Resource Reservation Protocol (RSVP) Graceful
Restart", RFC 5063, October 2007.
[RFC5151] Farrel, A., Ed., Ayyangar, A., and JP. Vasseur, "Inter-
Domain MPLS and GMPLS Traffic Engineering -- Resource
Reservation Protocol-Traffic Engineering (RSVP-TE)
Extensions", RFC 5151, February 2008.
[RFC5287] Vainshtein, A. and Y(J). Stein, "Control Protocol
Extensions for the Setup of Time-Division Multiplexing
(TDM) Pseudowires in MPLS Networks", RFC 5287, August
2008.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, October 2008.
[RFC5307] Kompella, K., Ed., and Y. Rekhter, Ed., "IS-IS Extensions
in Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 5307, October 2008.
[RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in
Support of Inter-Autonomous System (AS) MPLS and GMPLS
Traffic Engineering", RFC 5316, December 2008.
[RFC5392] Chen, M., Zhang, R., and X. Duan, "OSPF Extensions in
Support of Inter-Autonomous System (AS) MPLS and GMPLS
Traffic Engineering", RFC 5392, January 2009.
[RFC5467] Berger, L., Takacs, A., Caviglia, D., Fedyk, D., and J.
Meuric, "GMPLS Asymmetric Bandwidth Bidirectional Label
Switched Paths (LSPs)", RFC 5467, March 2009.
[RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
"MPLS Generic Associated Channel", RFC 5586, June 2009.
[RFC5654] Niven-Jenkins, B., Ed., Brungard, D., Ed., Betts, M., Ed.,
Sprecher, N., and S. Ueno, "Requirements of an MPLS
Transport Profile", RFC 5654, September 2009.
Andersson, et al. Informational [Page 50]
RFC 6373 MPLS-TP Control Plane Framework September 2011
[RFC5860] Vigoureux, M., Ed., Ward, D., Ed., and M. Betts, Ed.,
"Requirements for Operations, Administration, and
Maintenance (OAM) in MPLS Transport Networks", RFC 5860,
May 2010.
[RFC5921] Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau,
L., and L. Berger, "A Framework for MPLS in Transport
Networks", RFC 5921, July 2010.
[RFC5960] Frost, D., Ed., Bryant, S., Ed., and M. Bocci, Ed., "MPLS
Transport Profile Data Plane Architecture", RFC 5960,
August 2010.
[RFC6370] Bocci, M., Swallow, G., and E. Gray, "MPLS Transport
Profile (MPLS-TP) Identifiers", RFC 6370, September 2011.
[RFC6371] Busi, I., Ed., and D. Allan, Ed., "Operations,
Administration, and Maintenance Framework for MPLS-Based
Transport Networks", RFC 6371, September 2011.
[RFC6372] Sprecher, N., Ed., and A. Farrel, Ed., "MPLS Transport
Profile (MPLS-TP) Survivability Framework", RFC 6372,
September 2011.
8.2. Informative References
[CCAMP-OAM-EXT]
Bellagamba, E., Ed., Andersson, L., Ed., Skoldstrom, P.,
Ed., Ward, D., and A. Takacs, "Configuration of Pro-Active
Operations, Administration, and Maintenance (OAM)
Functions for MPLS-based Transport Networks using RSVP-
TE", Work in Progress, July 2011.
[CCAMP-OAM-FWK]
Takacs, A., Fedyk, D., and J. He, "GMPLS RSVP-TE
extensions for OAM Configuration", Work in Progress, July
2011.
[GMPLS-PS] Takacs, A., Fondelli, F., and B. Tremblay, "GMPLS RSVP-TE
Recovery Extension for data plane initiated reversion and
protection timer signalling", Work in Progress, April
2011.
[ITU.G8080.2006]
International Telecommunication Union, "Architecture for
the automatically switched optical network (ASON)", ITU-T
Recommendation G.8080, June 2006.
Andersson, et al. Informational [Page 51]
RFC 6373 MPLS-TP Control Plane Framework September 2011
[ITU.G8080.2008]
International Telecommunication Union, "Architecture for
the automatically switched optical network (ASON)
Amendment 1", ITU-T Recommendation G.8080 Amendment 1,
March 2008.
[MS-PW-DYNAMIC]
Martini, L., Ed., Bocci, M., Ed., and F. Balus, Ed.,
"Dynamic Placement of Multi Segment Pseudowires", Work in
Progress, July 2011.
[NO-PHP] Ali, z., et al, "Non Penultimate Hop Popping Behavior and
out-of-band mapping for RSVP-TE Label Switched Paths",
Work in Progress, August 2011.
[PW-OAM] Zhang, F., Ed., Wu, B., Ed., and E. Bellagamba, Ed., "
Label Distribution Protocol Extensions for Proactive
Operations, Administration and Maintenance Configuration
of Dynamic MPLS Transport Profile PseudoWire", Work in
Progress, August 2011.
[PW-P2MPE] Aggarwal, R. and F. Jounay, "Point-to-Multipoint Pseudo-
Wire Encapsulation", Work in Progress, March 2010.
[PW-P2MPR] Jounay, F., Ed., Kamite, Y., Heron, G., and M. Bocci,
"Requirements and Framework for Point-to-Multipoint
Pseudowire", Work in Progress, July 2011.
[PW-RED] Muley, P., Ed., Aissaoui, M., Ed., and M. Bocci,
"Pseudowire Redundancy", Work in Progress, July 2011.
[PW-REDB] Muley, P., Ed., and M. Aissaoui, Ed., "Preferential
Forwarding Status Bit", Work in Progress, March 2011.
[RFC3270] Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen,
P., Krishnan, R., Cheval, P., and J. Heinanen, "Multi-
Protocol Label Switching (MPLS) Support of Differentiated
Services", RFC 3270, May 2002.
[RFC3468] Andersson, L. and G. Swallow, "The Multiprotocol Label
Switching (MPLS) Working Group decision on MPLS signaling
protocols", RFC 3468, February 2003.
[RFC3472] Ashwood-Smith, P., Ed., and L. Berger, Ed., "Generalized
Multi-Protocol Label Switching (GMPLS) Signaling
Constraint-based Routed Label Distribution Protocol (CR-
LDP) Extensions", RFC 3472, January 2003.
Andersson, et al. Informational [Page 52]
RFC 6373 MPLS-TP Control Plane Framework September 2011
[RFC3477] Kompella, K. and Y. Rekhter, "Signalling Unnumbered Links
in Resource ReSerVation Protocol - Traffic Engineering
(RSVP-TE)", RFC 3477, January 2003.
[RFC3812] Srinivasan, C., Viswanathan, A., and T. Nadeau,
"Multiprotocol Label Switching (MPLS) Traffic Engineering
(TE) Management Information Base (MIB)", RFC 3812, June
2004.
[RFC3813] Srinivasan, C., Viswanathan, A., and T. Nadeau,
"Multiprotocol Label Switching (MPLS) Label Switching
Router (LSR) Management Information Base (MIB)", RFC 3813,
June 2004.
[RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture", RFC 3945, October 2004.
[RFC3985] Bryant, S., Ed., and P. Pate, Ed., "Pseudo Wire Emulation
Edge-to-Edge (PWE3) Architecture", RFC 3985, March 2005.
[RFC4139] Papadimitriou, D., Drake, J., Ash, J., Farrel, A., and L.
Ong, "Requirements for Generalized MPLS (GMPLS) Signaling
Usage and Extensions for Automatically Switched Optical
Network (ASON)", RFC 4139, July 2005.
[RFC4201] Kompella, K., Rekhter, Y., and L. Berger, "Link Bundling
in MPLS Traffic Engineering (TE)", RFC 4201, October 2005.
[RFC4208] Swallow, G., Drake, J., Ishimatsu, H., and Y. Rekhter,
"Generalized Multiprotocol Label Switching (GMPLS) User-
Network Interface (UNI): Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Support for the Overlay
Model", RFC 4208, October 2005.
[RFC4258] Brungard, D., Ed., "Requirements for Generalized Multi-
Protocol Label Switching (GMPLS) Routing for the
Automatically Switched Optical Network (ASON)", RFC 4258,
November 2005.
[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures", RFC 4379,
February 2006.
[RFC4426] Lang, J., Ed., Rajagopalan, B., Ed., and D. Papadimitriou,
Ed., "Generalized Multi-Protocol Label Switching (GMPLS)
Recovery Functional Specification", RFC 4426, March 2006.
Andersson, et al. Informational [Page 53]
RFC 6373 MPLS-TP Control Plane Framework September 2011
[RFC4427] Mannie, E., Ed., and D. Papadimitriou, Ed., "Recovery
(Protection and Restoration) Terminology for Generalized
Multi-Protocol Label Switching (GMPLS)", RFC 4427, March
2006.
[RFC4553] Vainshtein, A., Ed., and YJ. Stein, Ed., "Structure-
Agnostic Time Division Multiplexing (TDM) over Packet
(SAToP)", RFC 4553, June 2006.
[RFC4618] Martini, L., Rosen, E., Heron, G., and A. Malis,
"Encapsulation Methods for Transport of PPP/High-Level
Data Link Control (HDLC) over MPLS Networks", RFC 4618,
September 2006.
[RFC4619] Martini, L., Ed., Kawa, C., Ed., and A. Malis, Ed.,
"Encapsulation Methods for Transport of Frame Relay over
Multiprotocol Label Switching (MPLS) Networks", RFC 4619,
September 2006.
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
August 2006.
[RFC4783] Berger, L., Ed., "GMPLS - Communication of Alarm
Information", RFC 4783, December 2006.
[RFC4802] Nadeau, T., Ed., and A. Farrel, Ed., "Generalized
Multiprotocol Label Switching (GMPLS) Traffic Engineering
Management Information Base", RFC 4802, February 2007.
[RFC4803] Nadeau, T., Ed., and A. Farrel, Ed., "Generalized
Multiprotocol Label Switching (GMPLS) Label Switching
Router (LSR) Management Information Base", RFC 4803,
February 2007.
[RFC4816] Malis, A., Martini, L., Brayley, J., and T. Walsh,
"Pseudowire Emulation Edge-to-Edge (PWE3) Asynchronous
Transfer Mode (ATM) Transparent Cell Transport Service",
RFC 4816, February 2007.
[RFC4875] Aggarwal, R., Ed., Papadimitriou, D., Ed., and S.
Yasukawa, Ed., "Extensions to Resource Reservation
Protocol - Traffic Engineering (RSVP-TE) for Point-to-
Multipoint TE Label Switched Paths (LSPs)", RFC 4875, May
2007.
Andersson, et al. Informational [Page 54]
RFC 6373 MPLS-TP Control Plane Framework September 2011
[RFC5003] Metz, C., Martini, L., Balus, F., and J. Sugimoto,
"Attachment Individual Identifier (AII) Types for
Aggregation", RFC 5003, September 2007.
[RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
"LDP Specification", RFC 5036, October 2007.
[RFC5085] Nadeau, T., Ed., and C. Pignataro, Ed., "Pseudowire
Virtual Circuit Connectivity Verification (VCCV): A
Control Channel for Pseudowires", RFC 5085, December 2007.
[RFC5145] Shiomoto, K., Ed., "Framework for MPLS-TE to GMPLS
Migration", RFC 5145, March 2008.
[RFC5440] Vasseur, JP., Ed., and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
March 2009.
[RFC5493] Caviglia, D., Bramanti, D., Li, D., and D. McDysan,
"Requirements for the Conversion between Permanent
Connections and Switched Connections in a Generalized
Multiprotocol Label Switching (GMPLS) Network", RFC 5493,
April 2009.
[RFC5659] Bocci, M. and S. Bryant, "An Architecture for Multi-
Segment Pseudowire Emulation Edge-to-Edge", RFC 5659,
October 2009.
[RFC5787] Papadimitriou, D., "OSPFv2 Routing Protocols Extensions
for Automatically Switched Optical Network (ASON)
Routing", RFC 5787, March 2010.
[RFC5852] Caviglia, D., Ceccarelli, D., Bramanti, D., Li, D., and S.
Bardalai, "RSVP-TE Signaling Extension for LSP Handover
from the Management Plane to the Control Plane in a GMPLS-
Enabled Transport Network", RFC 5852, April 2010.
[RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
"Bidirectional Forwarding Detection (BFD) for MPLS Label
Switched Paths (LSPs)", RFC 5884, June 2010.
[RFC5885] Nadeau, T., Ed., and C. Pignataro, Ed., "Bidirectional
Forwarding Detection (BFD) for the Pseudowire Virtual
Circuit Connectivity Verification (VCCV)", RFC 5885, June
2010.
[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, July 2010.
Andersson, et al. Informational [Page 55]
RFC 6373 MPLS-TP Control Plane Framework September 2011
[RFC5951] Lam, K., Mansfield, S., and E. Gray, "Network Management
Requirements for MPLS-based Transport Networks", RFC 5951,
September 2010.
[RFC6001] Papadimitriou, D., Vigoureux, M., Shiomoto, K., Brungard,
D., and JL. Le Roux, "Generalized MPLS (GMPLS) Protocol
Extensions for Multi-Layer and Multi-Region Networks
(MLN/MRN)", RFC 6001, October 2010.
[RFC6073] Martini, L., Metz, C., Nadeau, T., Bocci, M., and M.
Aissaoui, "Segmented Pseudowire", RFC 6073, January 2011.
[RFC6107] Shiomoto, K., Ed., and A. Farrel, Ed., "Procedures for
Dynamically Signaled Hierarchical Label Switched Paths",
RFC 6107, February 2011.
[RFC6215] Bocci, M., Levrau, L., and D. Frost, "MPLS Transport
Profile User-to-Network and Network-to-Network
Interfaces", RFC 6215, April 2011.
[TE-MIB] Miyazawa, M., Otani, T., Kumaki, K., and T. Nadeau,
"Traffic Engineering Database Management Information Base
in support of MPLS-TE/GMPLS", Work in Progress, July 2011.
[TP-MIB] King, D., Ed., and M. Venkatesan, Ed., "Multiprotocol
Label Switching Transport Profile (MPLS-TP) MIB-based
Management Overview", Work in Progress, August 2011.
[TP-P2MP-FWK]
Frost, D., Ed., Bocci, M., Ed., and L. Berger, Ed., "A
Framework for Point-to-Multipoint MPLS in Transport
Networks", Work in Progress, July 2011.
[TP-RING] Weingarten, Y., Ed., "MPLS-TP Ring Protection", Work in
Progress, June 2011
9. Contributing Authors
Attila Takacs
Ericsson
1. Laborc u.
Budapest 1037
HUNGARY
EMail: attila.takacs@ericsson.com
Martin Vigoureux
Alcatel-Lucent
EMail: martin.vigoureux@alcatel-lucent.fr
Andersson, et al. Informational [Page 56]
RFC 6373 MPLS-TP Control Plane Framework September 2011
Elisa Bellagamba
Ericsson
Farogatan, 6
164 40, Kista, Stockholm
SWEDEN
EMail: elisa.bellagamba@ericsson.com
Authors' Addresses
Loa Andersson (editor)
Ericsson
Phone: +46 10 717 52 13
EMail: loa.andersson@ericsson.com
Lou Berger (editor)
LabN Consulting, L.L.C.
Phone: +1-301-468-9228
EMail: lberger@labn.net
Luyuan Fang (editor)
Cisco Systems, Inc.
111 Wood Avenue South
Iselin, NJ 08830
USA
EMail: lufang@cisco.com
Nabil Bitar (editor)
Verizon
60 Sylvan Road
Waltham, MA 02451
USA
EMail: nabil.n.bitar@verizon.com
Eric Gray (editor)
Ericsson
900 Chelmsford Street
Lowell, MA 01851
USA
Phone: +1 978 275 7470
EMail: Eric.Gray@Ericsson.com
Andersson, et al. Informational [Page 57]