Working GroupM. Vigoureux Internet DraftBocci, Ed. Internet-Draft M. BocciVigoureux, Ed. Updates: 3032, 43854385, 5085 Alcatel-Lucent (if approved) G. Swallow Intended status: StandardStandards Track Expires: May 2009 G. SwallowD. Ward Expires: July 10, 2009 Cisco Systems, Inc.R. Aggarwal Juniper Networks November 27, 2008January 6, 2009 MPLS Generic Associated Channel draft-ietf-mpls-tp-gach-gal-00draft-ietf-mpls-tp-gach-gal-01 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or sheThis Internet-Draft is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed,submitted to IETF in accordancefull conformance with Section 6the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts.Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress".progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txthttp://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.htmlhttp://www.ietf.org/shadow.html. This Internet-Draft will expire on April 27,July 10, 2009. Copyright Notice Copyright (C) The(c) 2009 IETF Trust (2008).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. 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 AlertAssociated channel header Label (GAL)', to be used as a label based exception mechanism. Conventions used in this documentRequirements 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 . Table of Contents 1. Introduction................................................3Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Contributing Authors....................................4Authors . . . . . . . . . . . . . . . . . . . 5 1.2. Objectives.............................................4Objectives . . . . . . . . . . . . . . . . . . . . . . . . 5 1.3. Scope..................................................4Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.4. Terminology............................................5Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 2. Generic Associated Channel...................................5Channel 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.....6Mechanisms . . . 8 3.2. GAL Applicability and Usage.............................7Usage . . . . . . . . . . . . . . . 8 3.2.1. GAL Processing.....................................7 184.108.40.206. MPLS Section..................................7 220.127.116.11. Label Switched Paths..........................8 18.104.22.168. Tandem Connection Monitoring Entity...........9Processing . . . . . . . . . . . . . . . . . . . . 8 3.3. Relationship withwth RFC 3429.............................103429 . . . . . . . . . . . . . . . . 11 4. Compatibility..............................................10Compatability . . . . . . . . . . . . . . . . . . . . . . . . 11 5. Congestion Considerations...................................10Considerations . . . . . . . . . . . . . . . . . . 12 6. Security Considerations.....................................11Consderations . . . . . . . . . . . . . . . . . . . . 12 7. IANA Considerations........................................11Considerations . . . . . . . . . . . . . . . . . . . . . 12 8. Acknowledgments............................................12Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 9. References.................................................12References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 9.1. Normative References...................................12References . . . . . . . . . . . . . . . . . . . 13 9.2. Informative References.................................13 Authors' Addresses............................................14 ContributingReferences . . . . . . . . . . . . . . . . . . 14 Authors' Addresses................................14 Intellectual Property Statement................................15 Disclaimer of Validity........................................15Addresses . . . . . . . . . . . . . . . . . . . . . . . . 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 ana LSP or PW or an MPLS section ),) fault detection, diagnostics, maintenance and other functions for a PseudowirePW and ana LSP. Some of these functions can be supported using tools such as VCCV ,, BFD ,, or LSP-Ping .. 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 . TheseExamples 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  is used with additional code points to support additional MPLS OAMmaintenance 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 AlertAssociated 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  and BFD for MPLS LSPs  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 )) particularly when IP based demultiplexing cannot be used. This document proposes an OPTIONAL mechanism that is RECOMMENDED for identifying and demultiplexing MPLS OAM packetsand other maintenance messages when IP based mechanisms such as those in  and  are not available. The G-ACH and GAL mechanisms are defined to work together. Note that, in this document, OAMmaintenace functions and packets should be understood in the broad sense, that is, as a set of FCAPS mechanisms that alsoinclude OAM, Automatic Protection Switching (APS), Signalling ControlCommunication Channel (SCC) and Management ControlCommunication 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  and .. 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 OAMmaintenance needs of emerging applications for MPLS. It creates a generic OAMcontrol 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, ornor 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 AlertAssociated 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  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 labelMPLS 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 routersrouter 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 arefield is set to 0, as specified in RFC 4385 .. 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 channelControl Channel and connectivity verificationConnectivity Verification (i.e. OAM functions) typesTypes between PEs. TheseIt is anticipated that similar mechanisms need towill be extended when a Generalisedapplied 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 andnot used. For G-ACH packets where IP is outsidenot used as the multiplexer, the scope of this document. 2.1. Allocation ofChannel TypesType 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 .. 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 OAMmaintenace packets onto a PW, LSP or sectionSection and provides information on the type of OAMfunction 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 theA special case of an MPLS LSP or section, therethe control word (the G-ACH) is a needused to notify an LSR of the presence of anidentify packets belonging to a PW associated channel packet i.e.channel. Generalizing the ACH mechanism to MPLS LSPs and sections requireMPLS Sections also requires a mechanismmethod 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 proposesspecifies that a label be used and calls this special label the 'Generic AlertAssociated channel header Label (GAL)'. One of the reserved label values defined in RFC 3032  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 AlertAssociated 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  and BFD for MPLS LSPs  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 AlertAssociated channel header Label (GAL)' MUST only be used with Label Switched Paths (LSPs), with their associated Tandem Connection Monitoring Entities (see  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. TheGAL 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 OAMpackets 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 .. The Time-To-Live (TTL) field of the label stack entry that contains the GAL follows the definition and processing rules specified in .. 22.214.171.124. MPLS Section The following figure (Figure 2) depicts two MPLS LSRs immediately adjacent at the MPLS layer. +---+ +---+ | A |-------------| Z | +---+ +---+ Figure 2 : MPLS-TP OAM2: Maintenance over aan MPLS Section Associated Channel With regards to the MPLS Section, both LERs containare Maintenance End Points (see  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 packetMaintenance Message . . | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3 : Labelled MPLS-TP OAM packet3: Maintenance Packet Format for MPLS Section OAMTo send ana MPLS-TP OAMmaintenance packet on an associated channel of the MPLS Section, the head-end LSR (A) of the MPLS Section generates a OAMmaintenance 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 OAMmaintenance 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. 126.96.36.199. 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 OAM4: Maintenance over aan LSP Associated Channel LERs A and D containare Maintenance End Points (MEPs) with respect to this LSP. Furthermore, LSRs B and C could also containbe Maintenance Intermediate Points (MIPs) with respect to this LSP (see  for definitions of MEPs and MIPs). The following figure (Figure 5) depicts the format of a labelled MPLS-TP OAMmaintenance 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 packetMaintenance Message . . | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5 : Labelled MPLS-TP OAM packet5: Maintenance Packet Format for MPLS-TP LSP OAMNote that it is possible that the LSP MAY also be tunnelled in another LSP (e.g. if ana 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 OAMa maintenance packet on the LSP,LSP associated channel, the head-endhead- end LSR (A) generates a MPLS-TPOAM packetmessage 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. 188.8.131.52. Tandem Connection Monitoring Entity Tandem Connection Monitoring will be specified in a separate document. 3.3. Relationship withwth RFC 3429 RFC 3429  describes the assignment of one of the reserved label values, defined in RFC 3032 ,, 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  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- TP3429 , 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 .. o The set of OAMmaintenance functions potentially operated in the context of the generic associated channel is wider than the set of OAM functions referenced in RFC 3429.3429 . o It has been reported that there are existing implementations and running deployments using the 'OAM Alert Label' as described in RFC 3429.3429 . 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. CompatibilityCompatability 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  apply. Further generic associated channel-specific congestion considerations will be detailed in a future revision of this document. 6. Security ConsiderationsConsderations The security considerations detailed in RFC 5085 ,, the MPLS architecture ,, the PWE3 architecture  and the MPLS-TP framework apply. 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 .. The PW Associated Channel Type registry is currently allocated based on the IETF consensus process, described in .in. 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 ) 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 .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 . 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  Bradner, S., "Key words for use in RFCs to Indicate Requirement  Rosen, E., Viswanathan, A., Callon, R., "Multiprotocol Label Switching Architecture", RFC 3031, January 2001  Rosen, E., et al., "MPLS Label Stack Encoding", RFC 3032, January 2001  Agarwal, P., Akyol, B., "Time To Live (TTL) Processing in Multi-Protocol Label Switching (MPLS) Networks", RFC 3443, January 2003  Bryant, S., Pate, P., "Pseudo Wire Emulation Edge-to-Edge  Kompella, K., Swallow, G., "Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures", RFC 4379, February 2006  Swallow, G., Bryant, S., Andersson, L., "Avoiding Equal Cost Multipath Treatmenttype 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  Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 128,14, RFC 4928, June 2007 2119, March 1997.  Nadeau, T.,T. and C. Pignataro, S.,"Pseudowire Virtual Circuit Connectivity Verification (VCCV): A Control Channel for Pseudowires", RFC 5085, December 2007 2007.  Aggarwal, R., Kompella, K., Swallow, G.,Nadeau, T., and G. Swallow, "BFD For  Andersson, L., ""EXP field" renamed to "CoS Field"", draft- MPLS LSPs", draft-ietf-bfd-mpls-07 (work in progress), June 2008.  Kompella, K. and G. Swallow, "Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures", RFC 4379, February 2006.  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 2006.  Martini, L., "IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)", BCP 116, RFC 4446, April 2006.  Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack Encoding", RFC 3032, January 2001.  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.  Agarwal, P. and B. Akyol, "Time To Live (TTL) Processing in Multi-Protocol Label Switching (MPLS) Networks", RFC 3443, January 2003.  Swallow, G., Bryant, S., and L. Andersson, "Avoiding Equal Cost Multipath Treatment in MPLS Networks", BCP 128, RFC 4928, June 2007.  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol Label Switching Architecture", RFC 3031, January 2001.  Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture", RFC 3985, March 2005.  Narten, T.,T. and H. Alvestrand, H., " Guidelines"Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 19981998.  Narten, T., "Assigning Experimental and Testing Numbers Considered Useful", RFC 3692, January 2004 9.2. Informative References Testing Numbers Considered Useful", BCP 82, RFC 3692, January 2004. 9.2. Informative References  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.  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.  Busi, I. and B. Niven-Jenkins, "MPLS-TP OAM Framework and Overview", draft-busi-mpls-tp-oam-framework-00 (work in progress), October 2008.  Ohta, H., "Assignment of the 'OAM Alert Label' for Multiprotocol Label Switching Architecture (MPLS) Operation and Maintenance (OAM) Functions", RFC 3429, November 2002  Vigoureux, M., Betts, M., Ward, D., "Requirements for OAM in MPLS Transport Networks", draft-vigoureux-mpls-tp-oam-  Bryant, S., Bocci, M., Lasserre, M., "A Framework for MPLS in Transport Networks", draft-ietf-mpls-tp-framework-00.txt, November 2008  Busi, I., Niven-Jenkins B., "MPLS-TP OAM Framework and Overview", draft-busi-mpls-tp-oam-framework-00, October 20082002. Authors' Addresses Martin Vigoureux (Editor) Alcatel-Lucent Email: email@example.comMatthew Bocci (Editor)(editor) Alcatel-Lucent Email: firstname.lastname@example.org David Ward (Editor) Cisco Systems, Inc.Martin Vigoureux (editor) Alcatel-Lucent Email: email@example.com@alcatel-lucent.com George Swallow (Editor)Cisco Systems, Inc.Email: firstname.lastname@example.org David Ward Cisco Email: email@example.com Rahul Aggarwal (Editor)Juniper Networks Email: firstname.lastname@example.org Contributing Authors' Addresses Stewart Bryant Cisco Systems, Inc. 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