MPLS Working Group                                                       M. Vigoureux
Internet Draft Bocci, Ed.
Internet-Draft                                         M. Bocci Vigoureux, Ed.
Updates: 3032, 4385 4385, 5085                                 Alcatel-Lucent
(if approved)                                                 G. Swallow
Intended status: Standard Standards Track
Expires: May 2009                                          G. Swallow                                 D. Ward
Expires: July 10, 2009                                             Cisco Systems, Inc.
                                                             R. Aggarwal
                                                        Juniper Networks

                                                     November 27, 2008
                                                         January 6, 2009

                    MPLS Generic Associated Channel
                      draft-ietf-mpls-tp-gach-gal-00
                     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 this G-ACH, the Generic ACH (G-ACH), this document also assigns of
   one of the reserved MPLS label values to the 'Generic Alert Associated
   channel header Label (GAL)', to be used as a label based exception
   mechanism.

Conventions used in this document

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 [1].

Table of Contents

   1. Introduction................................................3  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Contributing Authors....................................4 Authors . . . . . . . . . . . . . . . . . . .  5
     1.2. Objectives.............................................4  Objectives . . . . . . . . . . . . . . . . . . . . . . . .  5
     1.3. Scope..................................................4  Scope  . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     1.4. Terminology............................................5  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Generic Associated Channel...................................5 Channel Header  . . . . . . . . . . . . . .  6
     2.1.  Allocation of Channel Types.............................6
   3. Generalised Exception Mechanism..............................6
      3.1. Types  . . . . . . . . . . . . . . .  7
   3.  Generalised Exception Mechanism  . . . . . . . . . . . . . . .  7
     3.1.  Relationship with Existing MPLS OAM Alert Mechanisms.....6 Mechanisms . . .  8
     3.2.  GAL Applicability and Usage.............................7 Usage  . . . . . . . . . . . . . . .  8
       3.2.1.  GAL Processing.....................................7
            3.2.1.1. MPLS Section..................................7
            3.2.1.2. Label Switched Paths..........................8
            3.2.1.3. Tandem Connection Monitoring Entity...........9 Processing . . . . . . . . . . . . . . . . . . . .  8
     3.3.  Relationship with wth RFC 3429.............................10 3429  . . . . . . . . . . . . . . . . 11
   4. Compatibility..............................................10  Compatability  . . . . . . . . . . . . . . . . . . . . . . . . 11
   5.  Congestion Considerations...................................10 Considerations  . . . . . . . . . . . . . . . . . . 12
   6.  Security Considerations.....................................11 Consderations . . . . . . . . . . . . . . . . . . . . 12
   7.  IANA Considerations........................................11 Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   8. Acknowledgments............................................12  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
   9. References.................................................12  References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     9.1.  Normative References...................................12 References . . . . . . . . . . . . . . . . . . . 13
     9.2.  Informative References.................................13
   Authors' Addresses............................................14
   Contributing References . . . . . . . . . . . . . . . . . . 14
   Authors' Addresses................................14
   Intellectual Property Statement................................15
   Disclaimer of Validity........................................15 Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14

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 fault
   detection (e.g. between
   any two LSRs or T-PEs/S-PEs along the path of
   an a LSP or PW or an MPLS section [17]), [15]) fault
   detection, diagnostics, maintenance and other functions for a Pseudowire PW and an
   a LSP.  Some of these functions can be supported using tools such as
   VCCV [8], [2], BFD [9], [3], or LSP-Ping
   [6]. [4].  However, a requirement has been
   indicated to extend these
   toolsets, augment the set of maintenance functions, in particular
   where MPLS networks are used for packet transport services and
   network operations [16]. These  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 [11] [5] is used with
   additional code points to support additional MPLS OAM 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 Alert 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 [6] [4] and BFD for MPLS LSPs [9] [3] 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
   [17])
   [15]) particularly when IP based demultiplexing cannot be used.  This
   document proposes an OPTIONAL mechanism that is RECOMMENDED for
   identifying and demultiplexing MPLS OAM packets and other maintenance
   messages when IP based mechanisms such as [6] those in [4] and [9] [3] are
   not available.

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

   Note that, in this document, OAM maintenace functions and packets should
   be understood in the broad sense, that is, as a set of FCAPS
   mechanisms that also include OAM, Automatic Protection Switching (APS),
   Signalling
   Control Communication Channel (SCC) and Management Control Communication
   Channel (MCC). (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 [17] [15] and [18]. [17].

1.1.  Contributing Authors

   The editors gratefully acknowledge the following additional
   contributors: contibution of Stewart Bryant,
   Italo Busi, Marc Lasserre, Lieven
   Levrau, and Lou Berger. Lieven Levrau.

1.2.  Objectives

   This document proposes a mechanism to provide for the extended OAM
   maintenance needs of emerging applications for MPLS.  It creates a
   generic OAM control channel identification mechanism that may be applied
   to all MPLS LSPs, while maintaining compatibility with the PW
   associated channel header (ACH)
   [11]. .  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, or 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 Alert 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 [8] [2] 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 router alert label 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 routers 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| 1|Version|A|  Reserved   |         Channel Type          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 1 : 1: Generic Associated Channel Header

   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 and
   Reserved fields are field
   is set to 0, as specified in RFC 4385 [11]. [5].  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 Control
   Channel and connectivity verification Connectivity Verification (i.e.  OAM functions) types Types
   between PEs. These  It is anticipated that similar mechanisms need to will be extended when a Generalised
   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 used for e.g. MPLS LSP OAM. This will most
   likely require extensions to label distribution protocols and not used.  For G-ACH packets where IP is
   outside not used
   as the multiplexer, the scope of this document.

2.1. Allocation of Channel Types Type SHOULD indicate the specific
   maintenance protocol carried in the associated channel.

   Values for the Channel Type field, field currently used for VCCV, VCCV are
   specified in RFC 4446 [12]. [6].  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 for further
   details.

3.  Generalised Exception Mechanism

   The above mechanism enables the multiplexing of various OAM maintenace
   packets onto a PW, LSP or section Section and provides information on the
   type of OAM 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. However, in
   the  A special case of an MPLS LSP or section, there the control word (the G-ACH) is a need
   used to notify an LSR
   of the presence of an identify packets belonging to a PW associated channel packet i.e. channel.

   Generalizing the ACH mechanism to MPLS LSPs and
   sections require MPLS Sections also
   requires a mechanism method to differentiate specific packets (e.g.
   OAM) from others, such as normal user-plane ones. identify that a packet contains a G-ACH followed
   by a non-service payload.  This document
   proposes specifies that a label be
   used and calls this special label the 'Generic Alert Associated channel
   header Label (GAL)'.  One of the reserved label values defined in RFC
   3032 [3] [7] 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:

   o  Differentiate specific packets (e.g. OAM) those containing OAM
      messages) from others, such as normal user-plane ones,

   o  Indicate that the Generic Associated Channel Header (G-ACH)
      appears immediately after the bottom of the label stack.

   The 'Generic Alert 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 [6] [4] and BFD for MPLS LSPs [9] [3] 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 Alert Associated channel header Label (GAL)' MUST only be used
   with Label Switched Paths (LSPs), with their associated Tandem
   Connection Monitoring Entities (see [18] [17] for definitions of TCMEs)
   and with MPLS Sections.
   An MPLS Section is a network segment between two LSRs that are
   immediately adjacent at the MPLS layer.

   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 G-ACH MUST be used for PWs when OAM functions that cannot be
   demultiplexed using the IP mechanisms described in section 1. The
   PWE3 control word MUST be present in the encapsulation of user
   packets when the G-ACH is used to demultiplex OAM on a PW.

   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 OAM packets of a given layer. 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 [10]. [8].

   The Time-To-Live (TTL) field of the label stack entry that contains
   the GAL follows the definition and processing rules specified in [4]. [9].

3.2.1.1.  MPLS Section

   The following figure (Figure 2) depicts two MPLS LSRs immediately
   adjacent at the MPLS layer.

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

       Figure 2 : MPLS-TP OAM 2: Maintenance over a an MPLS Section Associated Channel

   With regards to the MPLS Section, both LERs contain are Maintenance End
   Points (see [18] [17] for definitions of MEPs).

   The following figure (Figure 3) depicts the format of a labelled OAM
   packet on an associated channel when used for MPLS Section OAM.
   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                          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               .
       .                       MPLS-TP OAM packet                      Maintenance Message                      .
       .                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Figure 3 : Labelled MPLS-TP OAM packet 3: Maintenance Packet Format for MPLS Section OAM

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

   o  The TTL field of the GAL SHOULD be set to 1.

   o  The S bit of the GAL MUST be set to 1. 1 in MPLS-TP.

   The OAM 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) depicts four LSRs.  A LSP is
   established from A to D and switched in B and C.

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

           Figure 4 : MPLS-TP OAM 4: Maintenance over a an LSP Associated Channel

   LERs A and D contain are Maintenance End Points (MEPs) with respect to this
   LSP.  Furthermore, LSRs B and C could also contain be Maintenance
   Intermediate Points (MIPs) with respect to this LSP (see [18] [17] for
   definitions of MEPs and MIPs).

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

            Figure 5 : Labelled MPLS-TP OAM packet 5: Maintenance Packet Format for MPLS-TP LSP OAM

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

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

   o  The TTL field of the GAL SHOULD be set to 1.

   o  The S bit of the GAL SHOULD be set to 1, 1 in MPLS-TP.

   The MPLS-TP OAM packet, 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 with wth RFC 3429

   RFC 3429 [15] [18] describes the assignment of one of the reserved label
   values, defined in RFC 3032 [3], [7], 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] 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:

   o  Unlike the mechanisms described and referenced in RFC 3429, MPLS-
      TP 3429 [18],
      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 [7]. [10].

   o  The set of OAM maintenance functions potentially operated in the
      context of the generic associated channel is wider than the set of
      OAM functions referenced in RFC 3429. 3429 [18].

   o  It has been reported that there are existing implementations and
      running deployments using the 'OAM Alert Label' as described in
      RFC 3429. 3429 [18].  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. Compatibility  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 [8] [2] apply.
   Further generic associated channel-specific congestion considerations
   will be detailed in a future revision of this document.

6.  Security Considerations Consderations

   The security considerations detailed in RFC 5085 [1], [2], the MPLS
   architecture [2], [11], the PWE3 architecture [5] [12] and the MPLS-TP
   framework
   [17]apply. [15] apply.

7.  IANA Considerations

   This document requests that IANA allocates a Label value, to the
   'Generalised-ACH
   '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 [12]. [6].  The PW Associated
   Channel Type registry is currently allocated based on the IETF
   consensus process, described in [13]. in[13].  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]) 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 [14]. 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].  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. Acknowledgments

   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

   [1]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
   [2]  Rosen, E., Viswanathan, A., Callon, R., "Multiprotocol Label
         Switching Architecture", RFC 3031, January 2001

   [3]  Rosen, E., et al., "MPLS Label Stack Encoding", RFC 3032,
         January 2001

   [4]  Agarwal, P., Akyol, B., "Time To Live (TTL) Processing in
         Multi-Protocol Label Switching (MPLS) Networks", RFC 3443,
         January 2003

   [5]  Bryant, S., Pate, P., "Pseudo Wire Emulation Edge-to-Edge
   [6]  Kompella, K., Swallow, G., "Detecting Multi-Protocol Label
         Switched (MPLS) Data Plane Failures", RFC 4379, February 2006

   [7]  Swallow, G., Bryant, S., Andersson, L., "Avoiding Equal Cost
         Multipath Treatment 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 Networks", Transport Profile.

9.  References

9.1.  Normative References

   [1]   Bradner, S., "Key words for use in RFCs to Indicate Requirement
         Levels", BCP 128, 14, RFC 4928, June
         2007

   [8] 2119, March 1997.

   [2]   Nadeau, T., T. and C. Pignataro, S., "Pseudowire Virtual Circuit
         Connectivity Verification (VCCV): A Control Channel for
         Pseudowires", RFC 5085, December 2007

   [9] 2007.

   [3]   Aggarwal, R., Kompella, K., Swallow, G., Nadeau, T., and G. Swallow, "BFD
         For
   [10] Andersson, L., ""EXP field" renamed to "CoS Field"", draft-
   [11] MPLS LSPs", draft-ietf-bfd-mpls-07 (work in progress),
         June 2008.

   [4]   Kompella, K. and G. Swallow, "Detecting Multi-Protocol Label
         Switched (MPLS) Data Plane Failures", RFC 4379, February 2006.

   [5]   Bryant, S., et al., 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
   [12] 2006.

   [6]   Martini, L., "IANA Allocations for Pseudowire Edge to Edge
         Emulation (PWE3)", BCP 116, RFC 4446, April 2006.

   [7]   Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., Farinacci,
         D., Li, T., and A. Conta, "MPLS Label Stack Encoding",
         RFC 3032, January 2001.

   [8]   Andersson, L. and R. Asati, "Multi-Protocol Label Switching
         (MPLS) label stack entry: "EXP" field renamed  to "Traffic
         Class" field", draft-ietf-mpls-cosfield-def-08 (work in
         progress), December 2008.

   [9]   Agarwal, P. and B. Akyol, "Time To Live (TTL) Processing in
         Multi-Protocol Label Switching (MPLS) Networks", RFC 3443,
         January 2003.

   [10]  Swallow, G., Bryant, S., and L. Andersson, "Avoiding Equal Cost
         Multipath Treatment in MPLS Networks", BCP 128, RFC 4928,
         June 2007.

   [11]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol Label
         Switching Architecture", RFC 3031, January 2001.

   [12]  Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to-Edge
         (PWE3) Architecture", RFC 3985, March 2005.

   [13]  Narten, T., T. and H. Alvestrand, H., " Guidelines "Guidelines for Writing an IANA
         Considerations Section in RFCs", BCP 26, RFC 2434,
         October 1998 1998.

   [14]  Narten, T., "Assigning Experimental and Testing Numbers
         Considered Useful", RFC 3692, January 2004

9.2. Informative References

   [15] Testing Numbers
         Considered Useful", BCP 82, RFC 3692, January 2004.

9.2.  Informative References

   [15]  Bocci, M., Bryant, S., and L. Levrau, "A Framework for MPLS in
         Transport Networks", draft-ietf-mpls-tp-framework-00 (work in
         progress), November 2008.

   [16]  Vigoureux, M., Ward, D., and M. Betts, "Requirements for OAM in
         MPLS Transport Networks",
         draft-ietf-mpls-tp-oam-requirements-00 (work in progress),
         December 2008.

   [17]  Busi, I. and B. Niven-Jenkins, "MPLS-TP OAM Framework and
         Overview", draft-busi-mpls-tp-oam-framework-00 (work in
         progress), October 2008.

   [18]  Ohta, H., "Assignment of the 'OAM Alert Label' for
         Multiprotocol Label Switching Architecture (MPLS) Operation and
         Maintenance (OAM) Functions", RFC 3429, November 2002

   [16] Vigoureux, M., Betts, M., Ward, D., "Requirements for OAM in
         MPLS Transport Networks", draft-vigoureux-mpls-tp-oam-
   [17] Bryant, S., Bocci, M., Lasserre, M., "A Framework for MPLS in
         Transport Networks", draft-ietf-mpls-tp-framework-00.txt,
         November 2008

   [18] Busi, I., Niven-Jenkins B., "MPLS-TP OAM Framework and
         Overview", draft-busi-mpls-tp-oam-framework-00, October 2008 2002.

Authors' Addresses

   Martin Vigoureux (Editor)
   Alcatel-Lucent

   Email: martin.vigoureux@alcatel-lucent.com

   Matthew Bocci (Editor) (editor)
   Alcatel-Lucent

   Email: matthew.bocci@alcatel-lucent.com

   David Ward (Editor)
   Cisco Systems, Inc.
   Martin Vigoureux (editor)
   Alcatel-Lucent

   Email: dward@cisco.com martin.vigoureux@alcatel-lucent.com

   George Swallow (Editor)
   Cisco Systems, Inc.

   Email: swallow@cisco.com

   David Ward
   Cisco

   Email: dward@cisco.com

   Rahul Aggarwal (Editor)
   Juniper Networks

   Email: rahul@juniper.net

Contributing Authors' Addresses

   Stewart Bryant
   Cisco Systems, Inc.

   Email: stbryant@cisco.com

   Italo Busi
   Alcatel-Lucent

   Email: italo.busi@alcatel-lucent.it
   Marc Lasserre
   Alcatel-Lucent

   Email: mlasserre@alcatel-lucent.com

   Lieven Levrau
   Alcatel-Lucent

   Email: llevrau@alcatel-lucent.com

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