MPLS Generic Associated Channel
draft-ietf-mpls-tp-gach-gal-01

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Abstract

This document generalises the applicability of the pseudowire Associated Channel Header (ACH), enabling the realization of a control channel associated to MPLS Label Switched Paths (LSP), MPLS pseudowires (PW) and MPLS Sections. In order to identify the presence of the Generic ACH (G-ACH), this document also assigns of one of the reserved MPLS label values to the 'Generic Associated channel header Label (GAL)', to be used as a label based exception mechanism.

Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.) [1].

Table of Contents

1.  Introduction
    1.1.  Contributing Authors
    1.2.  Objectives
    1.3.  Scope
    1.4.  Terminology
2.  Generic Associated Channel Header
    2.1.  Allocation of Channel Types
3.  Generalised Exception Mechanism
    3.1.  Relationship with Existing MPLS OAM Alert Mechanisms
    3.2.  GAL Applicability and Usage
        3.2.1.  GAL Processing
    3.3.  Relationship wth RFC 3429
4.  Compatability
5.  Congestion Considerations
6.  Security Consderations
7.  IANA Considerations
8.  Acknowledgements
9.  References
    9.1.  Normative References
    9.2.  Informative References
§  Authors' Addresses

1.  Introduction

There is a need for Operations, Administration and Maintenance (OAM) mechanisms that can be used for edge-to-edge (i.e. between originating and terminating LSRs or T-PEs) and segment (e.g. between any two LSRs or T-PEs/S-PEs along the path of a LSP or PW [15] (Bocci, M., Bryant, S., Frost, D., Levrau, L., and L. Berger, “A Framework for MPLS in Transport Networks,” April 2010.)) fault detection, diagnostics, maintenance and other functions for a PW and a LSP. Some of these functions can be supported using tools such as VCCV [2] (Nadeau, T. and C. Pignataro, “Pseudowire Virtual Circuit Connectivity Verification (VCCV): A Control Channel for Pseudowires,” December 2007.), BFD [3] (Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, “BFD For MPLS LSPs,” June 2008.), or LSP-Ping [4] (Kompella, K. and G. Swallow, “Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures,” February 2006.). However, a requirement has been indicated to augment the set of maintenance functions, in particular where MPLS networks are used for packet transport services and network operations [16] (Vigoureux, M. and D. Ward, “Requirements for OAM in MPLS Transport Networks,” March 2010.). Examples include performance monitoring, automatic protection switching, and support for management and signaling communication channels. These tools must be applicable to, and function in essentially the same manner (from an operational point of view) on both MPLS PWs and MPLS LSPs. They must also operate in-band on the PW or LSP such that they do not depend on PSN routing, user data traffic or ultimately on PSN or other dynamic control plane functions.

Virtual Circuit Connectivity Verification (VCCV) can use an associated channel to provide a control channel between a PW's ingress and egress points and over which OAM and other control messages can be exchanged. In this document, we propose a generic associated channel header (G-ACH) to enable the same control channel mechanism be used for MPLS Sections, LSPs and PWs. The associated channel header (ACH) specified in RFC 4385 [5] (Bryant, S., Swallow, G., Martini, L., and D. McPherson, “Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over an MPLS PSN,” February 2006.) is used with additional code points to support additional MPLS maintenance functions.

Generalizing the ACH mechanism to MPLS LSPs and MPLS Sections also requires a method to identify that a packet contains a G-ACH followed by a non-service payload. This document therefore also defines a label based exception mechanism (the Generic Associated channel header Label, or GAL) that serves to inform an LSR that a packet that it receives on an LSP or section belongs to an associated channel.

RFC 4379 [4] (Kompella, K. and G. Swallow, “Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures,” February 2006.) and BFD for MPLS LSPs [3] (Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, “BFD For MPLS LSPs,” June 2008.) have defined alert mechanisms that enable a MPLS LSR to identify and process MPLS OAM packets when the OAM packets are encapsulated in an IP header. These alert mechanisms are based on TTL expiration and/or use an IP destination address in the range 127/8. These mechanisms are the default mechanisms for identifying MPLS OAM packets when the OAM packets are encapsulated in an IP header. However it may not always be possible to use these mechanisms in some MPLS applications, (e.g. MPLS-TP [15] (Bocci, M., Bryant, S., Frost, D., Levrau, L., and L. Berger, “A Framework for MPLS in Transport Networks,” April 2010.)) particularly when IP based demultiplexing cannot be used. This document proposes an OPTIONAL mechanism that is RECOMMENDED for identifying and demultiplexing MPLS OAM and other maintenance messages when IP based mechanisms such as those in [4] (Kompella, K. and G. Swallow, “Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures,” February 2006.) and [3] (Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, “BFD For MPLS LSPs,” June 2008.) are not available.

The G-ACH and GAL mechanisms are defined to work together.

Note that, in this document, maintenace functions and packets should be understood in the broad sense, that is, as a set of FCAPS mechanisms that include OAM, Automatic Protection Switching (APS), Signalling Communication Channel (SCC) and Management Communication Channel (MCC) messages.

Note that the GAL and G-ACH are applicable to MPLS in general. Their applicability to specific applications is outside the scope of this document. For example, the applicability of the GAL and G-ACH to MPLS-TP is described in [15] (Bocci, M., Bryant, S., Frost, D., Levrau, L., and L. Berger, “A Framework for MPLS in Transport Networks,” April 2010.) and [17] (Busi, I. and B. Niven-Jenkins, “MPLS-TP OAM Framework and Overview,” March 2009.).

1.1.  Contributing Authors

The editors gratefully acknowledge the contibution of Stewart Bryant, Italo Busi, Marc Lasserre, and Lieven Levrau.

1.2.  Objectives

This document proposes a mechanism to provide for the extended maintenance needs of emerging applications for MPLS. It creates a generic control channel identification mechanism that may be applied to all MPLS LSPs, while maintaining compatibility with the PW associated channel header (ACH) . It also normalizes the use of the ACH for PWs in a transport context.

1.3.  Scope

This document defines the encapsulation header for LSP, MPLS Section and PW associated channel messages.

It does not define how associated channel capabilities are signaled or negotiated between LSRs or PEs, the operation of various OAM functions, nor how the messages transmitted on the associated channel.

This document does not deprecate existing MPLS and PW OAM mechanisms.

1.4.  Terminology

G-ACH: Generic Associated Channel Header

GAL: Generic Associated Channel Header Label

MPLS Section: A network segment between two LSRs that are immediately adjacent at the MPLS layer

Maintenance Packet: Any packet containing a message belonging to a maintenace protocol that is carried on a PW, LSP or MPLS Section associated channel. Examples of such maintenance protocols include OAM functions, signaling communications or management communications.

2.  Generic Associated Channel Header

VCCV [2] (Nadeau, T. and C. Pignataro, “Pseudowire Virtual Circuit Connectivity Verification (VCCV): A Control Channel for Pseudowires,” December 2007.) defines three MPLS Control Channel (CC) Types that may be used to multiplex OAM messages onto a PW: CC Type 1 uses an associated channel header and is referred to as "In-band VCCV"; CC Type 2 uses the MPLS Router Alert Label to indicate VCCV packets and is referred to as "Out of Band VCCV"; CC Type 3 uses the TTL to force the packet to be processed by the targeted router control plane and is referred to as "MPLS PW Label with TTL == 1".

The use of the CC Type 1, currently limited to MPLS PWs, is here extended to apply to MPLS LSPs as well as to MPLS Sections. This associated channel header is called the Generic Associated Channel Header (G- ACH). The PWE3 control word MUST be present in the encapsulation of user packets when the G-ACH is used to demultiplex the associated channel packet on a PW.

The CC Type 1 channel header is depicted in figure below:

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version|A|  Reserved   |         Channel Type          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

In the above figure, the first nibble is set to 0001b to indicate a channel associated with a PW, a LSP or a Section. The Version field is set to 0, as specified in RFC 4385 [5] (Bryant, S., Swallow, G., Martini, L., and D. McPherson, “Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over an MPLS PSN,” February 2006.). This draft allocates Bit 8 of the ACH to the ACH TLV bit. This bit is set to 1 to indicate that an object defined in the ACH TLV registry immediately follows the G-ACH, otherwise it is set to 0. Bits 8 to 14 of the G-ACH are reserved and MUST be set to 0..

Note that VCCV also includes mechanisms for negotiating the Control Channel and Connectivity Verification (i.e. OAM functions) Types between PEs. It is anticipated that similar mechanisms will be applied to existing MPLS LSPs. Such application will require further specification. However, such specification is beyond the scope of this document.

2.1.  Allocation of Channel Types

The Channel Type field indicates the type of message carried on the associated channel e.g. IPv4 or IPv6 if IP demultiplexing is used for messages on the G-ACH, or OAM or other FCAPS function if IP demultiplexing is not used. For G-ACH packets where IP is not used as the multiplexer, the Channel Type SHOULD indicate the specific maintenance protocol carried in the associated channel.

Values for the Channel Type field currently used for VCCV are specified in RFC 4446 [6] (Martini, L., “IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3),” April 2006.). The functionality of any additional channel types will be defined in another document. Each associated channel protocol solution document must specify the value to use for any additional channel types.

Note that these values are allocated from the PW Associated Channel Type registry, but this document modifies the existing policy to accomodate a level of experimentation. See Section 7 (IANA Considerations) for further details.

3.  Generalised Exception Mechanism

The above mechanism enables the multiplexing of various maintenace packets onto a PW, LSP or Section and provides information on the type of function being performed. In the case of a PW, the use of a control word is negotiated or configured at the time of the PW establishment. A special case of the control word (the G-ACH) is used to identify packets belonging to a PW associated channel.

Generalizing the ACH mechanism to MPLS LSPs and MPLS Sections also requires a method to identify that a packet contains a G-ACH followed by a non-service payload. This document specifies that a label be used and calls this special label the 'Generic Associated channel header Label (GAL)'. One of the reserved label values defined in RFC 3032 [7] (Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., Farinacci, D., Li, T., and A. Conta, “MPLS Label Stack Encoding,” January 2001.) is assigned for this purpose. The value of the label is to be allocated by IANA; this document suggests the value 13.

The GAL provides a generalised exception mechanism to:

• Differentiate specific packets (e.g. those containing OAM messages) from others, such as normal user-plane ones,
• Indicate that the Generic Associated Channel Header (G-ACH) appears immediately after the bottom of the label stack.

The 'Generic Associated channel header Label (GAL)' MUST only be used where both of these purposes are applicable.

3.1.  Relationship with Existing MPLS OAM Alert Mechanisms

RFC 4379 [4] (Kompella, K. and G. Swallow, “Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures,” February 2006.) and BFD for MPLS LSPs [3] (Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, “BFD For MPLS LSPs,” June 2008.) have defined alert mechanisms that enable a MPLS LSR to identify and process MPLS OAM packets when the OAM packets are encapsulated in an IP header. These alert mechanisms are based on TTL expiration and/or use an IP destination address in the range 127/8.

These alert mechanisms SHOULD preferably be used in non MPLS-TP environments. The mechanism defined in this document MAY also be used.

3.2.  GAL Applicability and Usage

The 'Generic Associated channel header Label (GAL)' MUST only be used with Label Switched Paths (LSPs), with their associated Tandem Connection Monitoring Entities (see [17] (Busi, I. and B. Niven-Jenkins, “MPLS-TP OAM Framework and Overview,” March 2009.) for definitions of TCMEs) and with MPLS Sections.

The GAL applies to both P2P and P2MP LSPs, unless otherwise stated.

In MPLS-TP, the GAL MUST always be at the bottom of the label stack (i.e. S bit set to 1). However, in other MPLS environments, this document places no restrictions on where the GAL may appear within the label stack.

The GAL MUST NOT appear in the label stack when transporting normal user-plane packets. Furthermore, the GAL MUST only appear once in the label stack for packets on the generic associated channel.

3.2.1.  GAL Processing

The Traffic Class (TC) field (formerly known as the EXP field) of the label stack entry containing the GAL follows the definition and processing rules specified and referenced in [8] (Andersson, L. and R. Asati, “Multi-Protocol Label Switching (MPLS) label stack entry: "EXP" field renamed to "Traffic Class" field,” December 2008.).

The Time-To-Live (TTL) field of the label stack entry that contains the GAL follows the definition and processing rules specified in [9] (Agarwal, P. and B. Akyol, “Time To Live (TTL) Processing in Multi-Protocol Label Switching (MPLS) Networks,” January 2003.).

3.2.1.1.  MPLS Section

The following figure (Figure 2 (Maintenance over an MPLS Section Associated Channel)) depicts two MPLS LSRs immediately adjacent at the MPLS layer.

                    +---+             +---+
                    | A |-------------| Z |
                    +---+             +---+

With regards to the MPLS Section, both LERs are Maintenance End Points (see [17] (Busi, I. and B. Niven-Jenkins, “MPLS-TP OAM Framework and Overview,” March 2009.) for definitions of MEPs).

The following figure (Figure 3 (Maintenance Packet Format for MPLS Section)) depicts the format of a labelled OAM packet on an associated channel when used for MPLS Section maintenance.

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  GAL                  |  TC |S|       TTL     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                          Generic-ACH                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               .
     .                      Maintenance Message                      .
     .                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

To send a MPLS-TP maintenance packet on an associated channel of the MPLS Section, the head-end LSR (A) of the MPLS Section generates a maintenance packet with a G-ACH to which it pushes a GAL.

• The TTL field of the GAL SHOULD be set to 1.
• The S bit of the GAL MUST be set to 1 in MPLS-TP.

The maintenance packet, the G-ACH and the GAL SHOULD NOT be modified towards the tail-end LSR (Z). Upon reception of the labelled packet, the tail-end LSR (Z), after having checked the GAL fields, SHOULD pass the whole packet to the appropriate processing entity.

3.2.1.2.  Label Switched Paths

The following figure (Figure 4 (Maintenance over an LSP Associated Channel)) depicts four LSRs. A LSP is established from A to D and switched in B and C.

        +---+             +---+             +---+             +---+
        | A |-------------| B |-------------| C |-------------| D |
        +---+             +---+             +---+             +---+

LERs A and D are Maintenance End Points (MEPs) with respect to this LSP. Furthermore, LSRs B and C could also be Maintenance Intermediate Points (MIPs) with respect to this LSP (see [17] (Busi, I. and B. Niven-Jenkins, “MPLS-TP OAM Framework and Overview,” March 2009.) for definitions of MEPs and MIPs).

The following figure (Figure 5 (Maintenance Packet Format for MPLS-TP LSP)) depicts the format of a labelled maintenance packet when used for a MPLS-TP LSP.

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |               LSP Label               |  TC |S|       TTL     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  GAL                  |  TC |S|       TTL     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                          Generic-ACH                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               .
     .                      Maintenance Message                      .
     .                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Note that it is possible that the LSP MAY also be tunnelled in another LSP (e.g. if a MPLS Tunnel exists between B and C), and as such other labels MAY be present above it in the label stack.

To send a maintenance packet on the LSP associated channel, the head-end LSR (A) generates a OAM message with a G-ACH on which it first pushes a GAL followed by the LSP label.

• The TTL field of the GAL SHOULD be set to 1.
• The S bit of the GAL SHOULD be set to 1 in MPLS-TP.

The maintenance message, the G-ACH or the GAL SHOULD NOT be modified towards the targeted destination. Upon reception of the labelled packet, the targeted destination, after having checked both the LSP label and GAL fields, SHOULD pass the whole packet to the appropriate processing entity.

3.2.1.3.  Tandem Connection Monitoring Entity

Tandem Connection Monitoring will be specified in a separate document.

3.3.  Relationship wth RFC 3429

RFC 3429 [18] (Ohta, H., “Assignment of the 'OAM Alert Label' for Multiprotocol Label Switching Architecture (MPLS) Operation and Maintenance (OAM) Functions,” November 2002.) describes the assignment of one of the reserved label values, defined in RFC 3032 [7] (Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., Farinacci, D., Li, T., and A. Conta, “MPLS Label Stack Encoding,” January 2001.), to the 'OAM Alert Label' that is used by user-plane MPLS OAM functions for the identification of MPLS OAM packets. The value of 14 is used for that purpose.

Both this document and RFC 3429 [18] (Ohta, H., “Assignment of the 'OAM Alert Label' for Multiprotocol Label Switching Architecture (MPLS) Operation and Maintenance (OAM) Functions,” November 2002.) therefore describe the assignment of reserved label values for similar purposes. The rationale for the assignment of a new reserved label can be summarized as follows:

• Unlike the mechanisms described and referenced in RFC 3429 [18] (Ohta, H., “Assignment of the 'OAM Alert Label' for Multiprotocol Label Switching Architecture (MPLS) Operation and Maintenance (OAM) Functions,” November 2002.), MPLS-TP OAM packet payloads will not reside immediately after the GAL but instead behind the G-ACH, which itself resides immediately after the bottom of the label stack when the GAL is present. This ensures that OAM using the generic associated channel complies with RFC 4928 [10] (Swallow, G., Bryant, S., and L. Andersson, “Avoiding Equal Cost Multipath Treatment in MPLS Networks,” June 2007.).
• The set of maintenance functions potentially operated in the context of the generic associated channel is wider than the set of OAM functions referenced in RFC 3429 [18] (Ohta, H., “Assignment of the 'OAM Alert Label' for Multiprotocol Label Switching Architecture (MPLS) Operation and Maintenance (OAM) Functions,” November 2002.).
• It has been reported that there are existing implementations and running deployments using the 'OAM Alert Label' as described in RFC 3429 [18] (Ohta, H., “Assignment of the 'OAM Alert Label' for Multiprotocol Label Switching Architecture (MPLS) Operation and Maintenance (OAM) Functions,” November 2002.). It is therefore not possible to modify the 'OAM Alert Label' allocation, purpose or usage. Nevertheless, it is RECOMMENDED by this document that no further OAM extensions based on 'OAM Alert Label' (Label 14) usage be specified or developed.

4.  Compatability

An LER, LSR or PE MUST discard received G-ACH packets if it is not G- ACH capable, if it is not capable of processing packets on the indicated G-ACH channel, or if it has not, through means outside the scope of this document, indicated to the sending LSR, LER or PE that it will process G-ACH packets received on the indicated channel. The LER, LSR or PE MAY increment an error counter and MAY also optionally issue a system and/or SNMP notification.

5.  Congestion Considerations

The congestion considerations detailed in RFC 5085 [2] (Nadeau, T. and C. Pignataro, “Pseudowire Virtual Circuit Connectivity Verification (VCCV): A Control Channel for Pseudowires,” December 2007.) apply. Further generic associated channel-specific congestion considerations will be detailed in a future revision of this document.

6.  Security Consderations

The security considerations detailed in RFC 5085 [2] (Nadeau, T. and C. Pignataro, “Pseudowire Virtual Circuit Connectivity Verification (VCCV): A Control Channel for Pseudowires,” December 2007.), the MPLS architecture [11] (Rosen, E., Viswanathan, A., and R. Callon, “Multiprotocol Label Switching Architecture,” January 2001.), the PWE3 architecture [12] (Bryant, S. and P. Pate, “Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture,” March 2005.) and the MPLS-TP framework [15] (Bocci, M., Bryant, S., Frost, D., Levrau, L., and L. Berger, “A Framework for MPLS in Transport Networks,” April 2010.) apply.

7.  IANA Considerations

This document requests that IANA allocates a Label value, to the 'Generic Associated channel header Label (GAL)', from the pool of reserved labels, and suggests this value to be 13.

Channel Types for the Generic Associated Channel are allocated from the IANA PW Associated Channel Type registry [6] (Martini, L., “IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3),” April 2006.). The PW Associated Channel Type registry is currently allocated based on the IETF consensus process, described in[13] (Narten, T. and H. Alvestrand, “Guidelines for Writing an IANA Considerations Section in RFCs,” October 1998.). This allocation process was chosen based on the consensus reached in the PWE3 working group that pseudowire associated channel mechanisms should be reviewed by the IETF and only those that are consistent with the PWE3 architecture and requirements should be allocated a code point.

However, a requirement has emerged (see [16] (Vigoureux, M. and D. Ward, “Requirements for OAM in MPLS Transport Networks,” March 2010.)) to allow for optimizations or extensions to OAM and other control protocols running in an associated channel to be experimented with without resorting to the IETF standards process, by supporting experimental code points. This would prevent code points used for such functions from being used from the range allocated through the IETF standards and thus protects an installed base of equipment from potential inadvertent overloading of code points. In order to support this requirement, this document requests that the code-point allocation scheme for the PW Associated Channel Type be changed as follows:

0 - 32751 : IETF Consensus

32752 - 32767 : Experimental

Code points in the experimental range MUST be used according to the guidelines of RFC 3692 [14] (Narten, T., “Assigning Experimental and Testing Numbers Considered Useful,” January 2004.). Experimental OAM functions MUST be disabled by default. The channel type value used for a given experimental OAM function MUST be configurable, and care MUST be taken to ensure that different OAM functions that are not interoperable are configured to use different channel type values.

8.  Acknowledgements

The authors would like to thank all members of the teams (the Joint Working Team, the MPLS Interoperability Design Team in IETF and the T-MPLS Ad Hoc Group in ITU-T) involved in the definition and specification of MPLS Transport Profile.

9.  References

9.1. Normative References

9.2. Informative References

Authors' Addresses