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Versions: 00 01 02 03 04 05 06 draft-ietf-pwe3-oam-config

MPLS Working Group                                              F. Zhang
Internet-Draft                                                     B. Wu
Intended status: Standards Track                                  X. Dai
Expires: September 9, 2010                               ZTE Corporation
                                                          March 08, 2010


            LDP Extensions for MPLS-TP PW OAM configuration
                  draft-zhang-mpls-tp-pw-oam-config-01

Abstract

   This document describes a procedure for the configuration of the
   pseudowire (PW) virtual circuit connectivity verification (VCCV)
   Bidirectional Forwarding Detection (BFD) OAM mechanism through LDP
   extensions.  As the other MPLS-TP PW OAM functionalities develop, the
   procedure may be changed to cover them.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   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
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   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on September 9, 2010.

Copyright Notice

   Copyright (c) 2010 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



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   (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
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   described in the BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions used in this document  . . . . . . . . . . . . . .  3
   3.  Operation overviews  . . . . . . . . . . . . . . . . . . . . .  3
     3.1.  Establishment of OAM Entities and Functions  . . . . . . .  4
     3.2.  Deleting OAM Entities  . . . . . . . . . . . . . . . . . .  5
   4.  LDP extensions . . . . . . . . . . . . . . . . . . . . . . . .  5
     4.1.  PW OAM configuration TLV . . . . . . . . . . . . . . . . .  6
     4.2.  Local Discriminator sub-TLV  . . . . . . . . . . . . . . .  7
     4.3.  MEP_IDs  . . . . . . . . . . . . . . . . . . . . . . . . .  7
     4.4.  ME_IDs . . . . . . . . . . . . . . . . . . . . . . . . . .  7
       4.4.1.  IP Compatible ME-IDs . . . . . . . . . . . . . . . . .  8
       4.4.2.  ICC-based ME_IDs . . . . . . . . . . . . . . . . . . .  8
     4.5.  PW status TLV  . . . . . . . . . . . . . . . . . . . . . .  9
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   7.  Acknowledgement  . . . . . . . . . . . . . . . . . . . . . . .  9
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     8.1.  Normative references . . . . . . . . . . . . . . . . . . .  9
     8.2.  Informative References . . . . . . . . . . . . . . . . . .  9
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10




















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1.  Introduction

   This document describes a procedure for the configuration of the PW
   VCCV BFD OAM mechanism through LDP extensions.  As the other MPLS-TP
   PW OAM functionalities develop, the procedure may be changed to cover
   them.

   PW VCCV provides end-to-end fault detection and diagnostics for PWs,
   and currently supports the following OAM mechanisms: ICMP Ping, LSP
   Ping, and BFD, as described in [RFC5085].  BFD has been chosen to
   cover MPLS-TP CC functionality [base-BFD], and an extended version of
   BFD, as described in [BFD-CV], can accomplish both MPLS-TP CC and CV,
   even signal the AC status.  BFD for VCCV supports two modes of
   encapsulation - either IP/UDP encapsulated (with IP/UDP header) or
   PW-ACH encapsulated (with no IP/UDP header).

   The use of the VCCV control channel provides the context, based on
   the MPLS-PW label, required to bind and bootstrap the BFD session to
   a particular PW (FEC), see the analysis in [tp-oam-analysis].  But in
   order to identify certain extreme cases of misconnectivity and fill
   the requirements that the BFD mechanism MUST be the same for LSP,
   (MS-)PW and Section as well as for LSP Tandem Connection and PW
   Tandem Connection [BFD-CV], BFD still needs to use Discriminator
   values to identify the connection being verified at both ends of the
   PW.

   The discriminator values can be statically configured, or signaled
   via LSP-Ping [[tp-ping-bfd-procedure].  According to the requirements
   in [RFC5654], "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", it is naturally to
   extend LDP for setting up BFD or BFD extended version in order to
   configure MPLS-TP CC and CV OAM functionalities during the PW setup.


2.  Conventions used in this document

   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 RFC2119.


3.  Operation overviews

   Below, extension to LDP for setting up BFD or BFD extended version
   are defined in order to configure MPLS-TP CC and CV OAM
   functionalities during the PW setup.  PW signaling [RFC4447] defines



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   two FECs used to signal PWs.  Of these, FEC Type 129 along with AII
   Type 2 as defined in [RFC5003] fits the identification requirements
   of MPLS-TP, so the current version of this draft just focus on the
   P2P PW (FEC 129) along with AII type 2, P2MP PW will be studied in
   the future.

   The terms "ingress LER" and "egress LER" will not refer in this
   document to any direction in the forwarding plane, but only to the
   LER triggering the PW setup (ingress LER) and the one receiving the
   mapping message (egress LER).

   During the PW signaling, the Control Plane instance in the ingress
   and the egress LER announces the BFD OAM Configuration TLV (inside
   the interface parameters TLV carried by the mapping message,
   following the VCCV parameter field), which includes the "Local
   Discriminator" sub-TLV.

   During the BFD session the ingress LER will use as "MyDiscriminator"
   the value announced in the "Local Discriminator" (Mapping message
   sent) and as YourDiscriminator" the value received in the "Local
   Discriminator" (Mapping message received).

   The interval value of BFD control packets both in transmission and
   reception can be negotiated through BFD session itself, so the
   mapping message does not need to carry these time values.  In the
   case BFD extended version should be configured, the ME ID and MEP ID
   do not need to be carried also, for they can be deduced from the
   advertised FEC(129) TLV, as described in the following sections.

3.1.  Establishment of OAM Entities and Functions

   Assuming there is one PW needs to be setup between LSR1 and LSR2.

   (1) LSR1 MUST setup the OAM sink function to be prepared to receive
   OAM messages but MUST suppress any OAM alarms (e.g., due to missing
   or unidentified OAM messages).  The Mapping message MUST be sent with
   the "OAM Alarms Enabled" cleared, "OAM MEP Entities desired" set,
   "OAM MIP Entities desired" set in the PW status code.

   (2) When the Mapping message arrives at the receiver LSR2, it MUST
   establish and configure OAM entities according to the OAM information
   provided in mapping message.  If this is not possible, a Label
   Release message SHOULD be sent and neither the OAM entities nor the
   PW SHOULD be established.  If OAM entities are established
   successfully, the OAM Source function MUST be prepared to Send OAM
   messages.  At the same time, LSR2 needs to setup the OAM sink
   function to be prepared to receive OAM messages but MUST suppress any
   OAM alarms (e.g., due to missing or unidentified OAM messages).  The



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   Mapping message MUST be sent with the "OAM Alarms Enabled" cleared,
   "OAM MEP Entities desired" set, "OAM MIP Entities desired" set in the
   PW status code.

   (3) When LSR1 receives the Mapping message, it completes any pending
   OAM configuration and enables the OAM source function to send OAM
   messages.

   After this round, OAM entities are established and configured for the
   PW and OAM messages MAY already be exchanged.  OAM alarms can now be
   enabled.  The LSR1, while still keeping OAM alarms disabled sends a
   LDP Notification message with "OAM Alarms Enabled" PW status flag
   set.  LSR2 enables the OAM alarms after processing the LDP
   Notification message.  LSR1 enables OAM alarms after it receives the
   LDP Notification message from LSR2.  Data plane OAM is now fully
   functional.

3.2.  Deleting OAM Entities

   In some cases it may be useful to remove some or all OAM entities and
   functions from one PW without actually tearing down the connection.

   To avoid any spurious alarm, the following procedure should be
   followed:

   (1) LSR1/LSR2 SHOULD send Notification message with "OAM Alarms"
   cleared but unchanged OAM configuration.

   After that,

   (2) LSR1 SHOULD delete OAM source functions, then send Notification
   message with "OAM MEP Entities desired" and "OAM MIP Entities
   desired" cleared.

   (3) LSR2 SHOULD delete OAM source and sink functions, and then send
   Notification message with "OAM MEP Entities desired" and "OAM MIP
   Entities desired" cleared.

   Then, LSR1 SHOULD delete OAM sink functions.


4.  LDP extensions









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4.1.  PW OAM configuration TLV


             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|        Type     (IANA)     |           Length             |
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            |Vers.| PHB |                                               |V|C|
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            |                                                               |
            ~                           sub TLVs                            ~
            |                                                               |
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                    Figure 1: PW OAM configuration TLV

   Type: indicates a new type, the "PW OAM Configuration TLV" (IANA to
   define).

   Length: indicates the total length including sub-TLVs.

   Version: identifies the BFD protocol version.

   PHB: Identifies the Per-Hop Behavior (PHB) to be used for periodic
   continuity monitoring messages.

   C: BFD CC OAM functon should be configured

   V: BFD CV OAM function should be configured (C MUST be set at the
   same time).

   The BFD CC OAM Configuration MUST include the following sub-TLVs in
   the Mapping message:

   Local Discriminator" sub-TLV (described in paragraph 4.2)

   The BFD CV OAM Configuration May include the following sub-TLVs
   except the "Local Discriminator" sub-TLV during the Mapping message:

   "ICC based ME-IDs" sub-TLV (described in paragraph 4.4.2)

   If the receiving LER does not support this PW OAM configuration TLV,
   it must be ignored and return a Notification message.






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4.2.  Local Discriminator sub-TLV

   The Local Discriminator sub-TLV is depicted 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|         Type   (IANA)     |           Length              |
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            |                      Local Discriminator                      |
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                   Figure 2: Local Discriminator sub-TLV

   Type: indicates a new type, the Local Discriminator sub TLV (1) (IANA
   to define)

   Length: indicates the total length of the TLV including padding.

   Local Discriminator: A unique, nonzero discriminator value generated
   by the transmitting system and referring to itself, used to
   demultiplex multiple BFD sessions between the same pair of systems.

   This Discriminator will be signaled both by the ingress LSR and the
   egress LSR in the Mapping message respectively.

   If the receiving LER does not support this Local Discriminator
   format, it must be ignored and return a Notification message.

4.3.  MEP_IDs

   In order to automatically generate MEP_IDs for MPLS-TP PWs, this
   draft is apt to use the AII associated with that end of the PW.  The
   AII is composed of three fields.  These are the Global_ID, the
   Prefix, and the AC_ID.  The Global_ID used in this document is
   identical to the Global_ID defined in [RFC5003].  The Node_ID is used
   as the Prefix.  The AC_ID is as defined in [RFC5003].  In this way,
   the definition is in accordance with the suggestion in the draft
   [tp-identifier], and there is no need to carry MEP_ID in the mapping
   message.

4.4.  ME_IDs







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4.4.1.  IP Compatible ME-IDs

   In order to automatically generate ME_IDs for MPLS-TP PWs, it is
   convenient to use the corresponding PW identifier.  In an MPLS-TP
   environment, a PW is identified by a set of identifiers which can be
   mapped directly to the elements required by FEC 129 and AII Type 2,
   so there is no need to carry ME_IDs in the mapping messages also.

4.4.2.  ICC-based ME_IDs

   ME ID for PWs MAY use the globally unique ICC-based format.  This ME
   ID format MAY be used to identify SME, LME, LTCME, PME and PTCME
   independently on LER/T-PE addressing schemes as well as of the FECs
   used to identify the PW.


             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|      ME ID Type           |       Length = 20             |
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            |                                                               |
            +                                                               +
            |                       MEG ID                                  |
            +                     (13 bytes)                                +
            |                                                               |
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            |               |0 0 0 0 0 0 0 0|0 0 0 0 0 0 0 0|0 0 0 0 0 0 0 0|
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                       Figure 3: ICC-based ME_ID TLV

   ME ID Type: it identifies the specific format, value = TBD.

   Length: indicates the total length and it is set to 20.

   ME ID value: the ME ID is a string of up to thirteen characters, each
   character being either alphabetic (i.e.  A-Z) or numeric (i.e. 0-9)
   characters.  It consists of two subfields: the ICC (as defined in
   section 3) followed by a unique ME ID code (UMC).  The UMC MUST be
   unique within the organization identified by the ICC.

   If the receiving LER does not support this ME ID format, it must be
   ignored and return a Notification message.






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4.5.  PW status TLV

   In this document, three new PW status flags are defined: "OAM Alarms
   Enabled", "OAM MEP Entities desired", "OAM MIP Entities desired".


5.   IANA Considerations

   TBD.


6.  Security Considerations

   TBD.


7.  Acknowledgement

   The author would like to thank Hongbo Wei for his useful discussion.


8.  References

8.1.  Normative references

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4447]  Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G.
              Heron, "Pseudowire Setup and Maintenance Using the Label
              Distribution Protocol (LDP)", RFC 4447, April 2006.

   [RFC5003]  Metz, C., Martini, L., Balus, F., and J. Sugimoto,
              "Attachment Individual Identifier (AII) Types for
              Aggregation", RFC 5003, September 2007.

   [RFC5085]  Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit
              Connectivity Verification (VCCV): A Control Channel for
              Pseudowires", RFC 5085, December 2007.

   [RFC5654]  Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N.,
              and S. Ueno, "Requirements of an MPLS Transport Profile",
              RFC 5654, September 2009.

8.2.  Informative References

   [BFD-CV]   Fulignoli, A., Boutros, S., and M. Vigoureux, "MPLS-TP BFD
              for Proactive CC-CV and RDI", July 2009.



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   [base-BFD]
              Katz, D. and D. Ward, "Bidirectional Forwarding
              Detection", January 2010.

   [tp-identifier]
              Bocci, M. and G. Swallow, "MPLS-TP Identifiers",
              July 2009.

   [tp-oam-analysis]
              Sprecher, N., Van Helvoort, H., Bellagamba, E., and Y.
              Weingarten, "MPLS-TP OAM Analysis", March 2010.

   [tp-ping-bfd-procedure]
              Bahadur, N., Aggarwal, R., Nadeau, T., Sprecher, N., and
              Y. Weingarten, "LSP-Ping and BFD for MPLS-TP", July 2009.


Authors' Addresses

   Fei Zhang
   ZTE Corporation
   4F,RD Building 2,Zijinghua Road
   Yuhuatai District,Nanjing 210012
   P.R.China

   Phone: +86 025 52877612
   Email: zhang.fei3@zte.com.cn


   Bo Wu
   ZTE Corporation
   4F,RD Building 2,Zijinghua Road
   Yuhuatai District,Nanjing 210012
   P.R.China

   Phone: +86 025 52877276
   Email: wu.bo@zte.com.cn


   Xuehui Dai
   ZTE Corporation
   4F,RD Building 2,Zijinghua Road
   Yuhuatai District,Nanjing 210012
   P.R.China

   Phone: +86 025 52877612
   Email: dai.xuehui@zte.com.cn




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