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Versions: 00 01 draft-ietf-pwe3-pw-typed-wc-fec

Network Working Group                                       Kamran Raza
Internet Draft                                            Cisco Systems
Intended Status: Standards Track
Expiration Date: December 1, 2011                          Sami Boutros
                                                          Cisco Systems

                                                       Carlos Pignataro
                                                          Cisco Systems

                                                           June 2, 2011



                   LDP Typed Wildcard FEC for the PW FEC Elements

                  draft-raza-pwe3-pw-typed-wc-fec-01.txt


Status of this Memo

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   This Internet-Draft will expire on December 1, 2011.

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   Copyright (c) 2011 IETF Trust and the persons identified as the
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   respect to this document. Code Components extracted from this
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Abstract

   The "Typed Wildcard Forwarding Equivalence Class (FEC) Element"
   defines an extension to the Label Distribution Protocol (LDP) that
   can be used when it is desired to request or withdraw or release all
   label bindings for a given FEC Element type.  However, a typed
   wildcard FEC element must be individually defined for each FEC
   element type.  This specification defines the typed wildcard FEC
   elements for the PWid (0x80), Generalized PWid (0x81), and P2MP PW
   (0x82) FEC element types.

Conventions used in this document

   The keywords "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].

Table of Contents

  1. Introduction                                                    3
  2. Typed Wildcard for PW FEC Elements                              3
  3. Applicability Statement                                         4
  4. Operation                                                       5
     4.1. PW Consistency Check                                       5
     4.2. PW Graceful Shutdown                                       5
     4.3. Wildcard PW Status                                         6
  5. Security Considerations                                         6
  6. IANA Considerations                                             6
  7. Acknowledgments                                                 6
  8. References                                                      6
     8.1. Normative References                                       6
     8.2. Informative References                                     7
  Author's Address                                                   7







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1. Introduction

   An extension [RFC5918] to the Label Distribution Protocol (LDP)
   [RFC5036] defines the general notion of a "Typed Wildcard Forwarding
   Equivalence Class (FEC) Element".  This can be used when it is
   desired to request all label bindings for a given type of FEC
   Element, or to release or withdraw all label bindings for a given
   type of FEC element.  However, a typed wildcard FEC element must be
   individually defined for each type of FEC element.

   [RFC4447] defines the "PWid FEC Element" and "Generalized PWid FEC
   Element", and [P2MP-PW] defines the "P2MP PW FEC Element". These
   specifications, however, do not specify the Typed Wildcard format
   for these elements. This document specifies the format of the Typed
   Wildcard FEC Element for the "PWid FEC Element", "Generalized PWid
   FEC Element", and "P2MP FEC Element". The procedures for Typed
   Wildcard processing for PWid, Generalized PWid, and P2MP FEC
   Elements are same as described in [RFC5918] for any typed wildcard
   FEC Element type.

2. Typed Wildcard for PW FEC Elements

   The format of the Typed Wildcard FEC Element for PWid, Generalized
   PWid, and P2MP PW FEC Elements is specified as:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Typed Wcard=0x5| Type=PW FEC   |   Len = 2     |R|   PW type   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    . . .      |
   +-+-+-+-+-+-+-+-+

   Figure 1: Format of Typed Wildcard FEC Element for PW FEC Elements

   Where:

      Typed Wcard (one octet): Typed Wildcard FEC element type (0x05)
           as specified in [RFC5918]

      [FEC Element] Type (one octet): PW FEC Element type:

        PWid: (type 0x80 [RFC4447])
        Generalized PWid: (type 0x81 [RFC4447])
        P2MP PW: (type 0x82, [P2MP-PW]


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      Len [FEC Type Info] (one octet):  Two. (i.e. there is additional
           FEC info to scope the Typed Wildcard)

      Reserved bit: Must be set to ZERO on transmit and ignored on
           receipt.

      PW type (15-bits): PW type as specified in [RFC4447]. This field
           is used to scope the PWid wildcard FEC operation to limit to
           all PWs of a given type. This MUST be set to 0x7FFF
           (Wildcard PW [IANA-PWE3]) when referring PWs of all types
           (see Section 7).

  [RFC4447] defines "PW Grouping ID TLV" that can be used for wildcard
  withdrawal or status messages related to Generalized PWid and P2MP PW
  FECs. When Typed Wildcard FEC for Generalized PWid or P2MP PW FEC
  element is in use, "PW Grouping ID TLV" MUST NOT be present in the
  same message. If found present, receiving LSR MUST silently ignore
  Grouping ID TLV and process rest of the message.

3. Applicability Statement

   The Typed wildcard FEC Elements defined in this document for the
   PWid, Generalized PWid, and P2MP PW FEC Elements provide a finer
   degree of granularity when compared to the Wildcard FEC mechanics
   defined in [RFC5036].

   The PWid FEC Element as defined in [RFC4447] contains a Group ID
   field. This field is defined as an arbitrary 32-bit value that
   represents a group of PWs, and is used to create groups in the PW
   space, including potentially a single group of all PWs for a given
   FEC Element. This grouping enables an LSR to send wildcard label
   withdrawals and/or status notification messages corresponding to a
   PW group upon physical port failures. Similarly, [RFC4447] defines
   the "PW Grouping ID TLV" used in the same fashion for the
   Generalized PWid and P2MP PW FEC Elements.

  The PW Typed Wildcard FEC elements defined in this document help us
  achieve the similar functionality as "Group ID" field or "PW Grouping
  ID TLV" for label withdrawal and status notification messages;
  Additionally, the Typed Wildcard procedures [RFC5918] also provide
  more generalized and comprehensive solution by allowing:
  1. Typed-Wildcard Label Request message





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  2. Label TLV to further constraint the wildcard to all FECs of the
      specified FEC type [and its specific filter] that are also bound
      to the specified label.

4. Operation

   The use of Typed Wildcard FEC elements for PW can be useful under
   several scenarios. This section describes two use cases to
   illustrate their usage. The following use cases consider two LSR
   nodes, A and B, with LDP session between them to exchange L2VPN PW
   bindings.

4.1. PW Consistency Check

   A user may request a control plane consistency check at LSR A for
   the PWid FEC and Generalized PWid FEC bindings that it had learnt
   from LSR B over LDP session.  To perform this consistency check, LSR
   A marks all its learnt PW bindings from LSR B as stale, and then
   send a Label Request message towards LSR B with Typed Wildcard FEC
   element for PWid FEC element (PW type = 0x7FFF) and Generalized PWid
   FEC element (PW type = 0x7FFF). Upon receipt of such request, LSR B
   replays its database related to PWid FEC elements and Generalized
   PWid FEC element in Label Mapping message. As a PW binding is
   received at LSR A, the associated binding state is marked as
   refreshed (no stale).  When replay completes for a given type of
   FEC, LSR B sends End-of-LIB Notification [RFC5919] to mark the end
   of update for the given FEC type. Upon receipt of this Notification
   at LSR A, any remaining stale PW binding of given FEC type learnt
   from the peer LSR B, is cleaned up and removed from the database.
   This completes consistency check with LSR B at LSR A for given FEC
   type.

4.2. PW Graceful Shutdown

   It may be desirable to perform shutdown/removal of existing PW
   bindings advertised towards a peer in a graceful manner -- i.e. all
   advertised PW bindings to be removed from a peer without session
   flap.  For example, to request a graceful delete of the PWid FEC and
   Generalized PWid FEC bindings at LSR A learnt from LSR B, LSR A
   would send a Label Withdraw message towards LSR B with Typed
   Wildcard FEC elements pertaining to PWid FEC element (PW type =
   0x7FFF) and Generalized PWid FEC element (PW type = 0x7FFF). Upon
   receipt of such message, LSR B will delete all PWid and Generalized
   PWid bindings learnt from LSR A. Afterwards, LSR B would send Label
   Release message corresponding to received Label Withdraw with Typed
   FEC element.


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4.3. Wildcard PW Status

  The Typed Wildcard FEC Elements for PW FECs can be very useful when
  used to convey PW status amongst LSRs. The PE devices can send "PW
  Status TLV" in an LDP Notification message to indicate status (i.e.,
  a Pseudowire Status Code denoting for example a particular fault) to
  their remote peers [RFC4447]. In case of a global failure affecting
  all PWs, an LSR typically sends one PW Status Notification message
  per PW. Using Typed Wildcard FEC Element for given type of PW FEC
  Element, the LSR will need to send only one PW Status Notification
  message with Typed Wildcard PW FEC specified to notify about the
  common status applicable to all PWs as scoped by the PW Typed
  Wildcard FEC.

5. Security Considerations

  No new security considerations beyond that apply to the base LDP
  specification [RFC5036], [RFC4447] and [MPLS_SEC] apply to the use of
  the PW Typed Wildcard FEC Element types described in this document.

6. IANA Considerations

  None.

7. Acknowledgments

  The authors would like to thank Eric Rosen, Siva Sivabalan, and Zafar
  Ali for their valuable comments.

  This document was prepared using 2-Word-v2.0 template.dot.

8. References

8.1. Normative References

[RFC5036] Andersson, L., Menei, I., and Thomas, B., Editors, "LDP
          Specification", RFC 5036, September 2007.

[RFC5918] Asati, R., Minei, I., and Thomas, B., "LDP Typed Wildcard
         Forwarding Equivalence Class", RFC 5918, August 2010.

[RFC5919] Asati, R., Mohapatra, P., Chen, E., and Thomas, B.,
         "Signaling LDP Label Advertisement Completion", RFC 5919,


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         August 2009.

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

[P2MP-PW] Boutros, S., Martini, L., Sivabalan, S., Del Vecchio, G.,
          Kamite, Jin, L.,  "Signaling Root-Initiated P2MP PWs using
          LDP", draft-ietf-pwe3-p2mp-pw-02.txt, Work in Progress, March
          2011.

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

8.2.  Informative References

[MPLS_SEC] Fang, L. et al., "Security Framework for MPLS and GMPLS
         Networks", draft-ietf-mpls-mpls-and-gmpls-security-framework-
         05.txt, Work in Progress, March 2009.

[IANA-PWE3] Internet Assigned Numbers Authority, "Pseudo Wires Name
          Spaces (PWE3)", http://www.iana.org/assignments/pwe3-
         parameters, May 2011.


Author's Address

  Kamran Raza
  Cisco Systems, Inc.,
  2000 Innovation Drive,
  Kanata, ON K2K-3E8, Canada.
  E-mail: skraza@cisco.com

  Sami Boutros
  Cisco Systems, Inc.,
  3750 Cisco Way,
  San Jose, CA 95134, USA.
  E-mail: sboutros@cisco.com

  Carlos Pignataro
  Cisco Systems, Inc.,



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  7200 Kit Creek Road,
  Research Triangle Park, NC 27709-4987, USA.
  Email: cpignata@cisco.com












































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