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Versions: (draft-thomas-mpls-ldp-typed-wildcard) 00 01 02 03 04 05 06 07 RFC 5918

MPLS Working Group                                           Bob Thomas
Internet Draft
Intended status: Standards Track
Expires: Feb 2010                                             Ina Minei
                                                       Juniper Networks

                                                            Rajiv Asati
                                                           Cisco Systems

                                                      September 5, 2009


                          LDP Typed Wildcard FEC
                 draft-ietf-mpls-ldp-typed-wildcard-04.txt


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Copyright Notice

   Copyright (c) 2009 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 in effect on the date of
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   Please review these documents carefully, as they describe your rights
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Abstract

   The LDP specification [RFC5036] for the Wildcard FEC element has
   several deficiencies.  This document corrects those deficiencies. In
   addition, it specifies the Typed Wildcard FEC for the Prefix FEC
   Element Type defined in RFC5036.



Table of Contents


   1. Introduction...................................................3
   2. Specification Language.........................................4
   3. The Typed Wildcard FEC Element.................................4
   4. Procedures for the Typed Wildcard FEC Element..................5
   5. Typed Wildcard FEC Capability..................................6
   6. Typed Wildcard FEC Element for Prefix FEC Element..............7
   7. Typed Wildcard FEC Element for Host and Wildcard FEC Elements..8
   8. IANA Considerations............................................8
   9. Security Considerations........................................8
   10. Acknowledgments...............................................8
   11. References....................................................9
      11.1. Normative References.....................................9
      11.2. Informative References...................................9
   Author's Addresses...............................................10






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1. Introduction

   LDP [RFC5036] distributes labels for Forwarding Equivalence Classes
   (FECs).  LDP uses FEC TLVs in LDP messages to specify FECs.  An LDP
   FEC TLV includes 1 or more FEC Elements.  A FEC element includes a
   FEC type and an optional type-dependent value.

   RFC5036 specifies two FEC types (Prefix and Wildcard), and other
   documents specify additional FEC types; e.g., see [RFC4447] [MLDP].

   As specified by RFC5036 the Wildcard FEC Element refers to all FECs
   relative to an optional constraint.  The only constraint RFC5036
   specifies is one that limits the scope of the Wildcard FEC Element to
   "all FECs bound to a given label".

   The RFC5036 specification of the Wildcard FEC Element has the
   following deficiencies which limit its utility:

   1) The Wildcard FEC Element is untyped. There are situations where
      it would be useful to be able to refer to all FECs of a given
      type.

   2) Use of the Wildcard FEC Element is limited to Label Withdraw and
      Label Release messages only. There are situations where it would
      be useful in Label Request messages.

   This document:

      - Addresses the above deficiencies by defining a Typed Wildcard
        FEC Element and procedures for its use.

      - Specifies use of the LDP capability mechanism [RFC5561] at
        session establishment time for informing a peer that an LDP
        speaker is capable of handling the Typed Wildcast FEC.

      - Specifies the Typed Wildcard FEC Element for the Prefix FEC
        Element specified by RFC5036.

   Note that this document does not change procedures specified for the
   LDP Wildcard FEC Element by RFC5036.









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2. Specification 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 [RFC2119].



3. The Typed Wildcard FEC Element

   The Typed Wildcard FEC Element refers to all FECs of a given type
   relative to an optional constraint.  The constraint, if present, is
   determined from the context in which the Typed Wildcard FEC Element
   appears.

   The format of the Typed Wildcard FEC Element is:



   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 2
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Typed  (IANA) | FEC Element   | Len FEC Type  |               |
   | Wildcard      | Type          | Info          |               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               |
   |                                                               |
   ~          Additional FEC Type-specific Information             ~
   |                                                               |
   |                                               +-+-+-+-+-+-+-+-+
   |                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 1 Typed Wildcard FEC Element



   where:

     Typed Wildcard:  One octet FEC Element Type (to be assigned by
     IANA).

     FEC Element Type:  One octet FEC Element Type that specifies the
     FEC Element Type to be wildcarded.

     Len FEC Type Info:  One octet that specifies the length of the FEC
     Type Specific information field.  MUST be 0 if there is no
     Additional FEC Type-specific Information.


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     Additional FEC Type-specific Information:  Additional information
     specific to the FEC Element Type required to fully specify the
     Typed Wildcard.

     Specification of the length and format of Additional FEC Type
     Specific Information for particular FEC Element Types is outside of
     the scope of this document.  It is the responsibility of the
     designer of the FEC Element Type to specify the length and format
     of any Additional FEC Type Specific Information.

   This document discusses two instances of Typed Wildcard FEC Elements
   in section 6 and 7.



4. Procedures for the Typed Wildcard FEC Element

   It is the responsibility of the designer of the FEC Element Type to
   determine whether typed wildcarding makes sense the FEC Element Type.
   If typed wildcarding does make sense the specification for the FEC
   Element Type MUST include support for it.

   When typed wildcarding is supported for a FEC Element Type it is the
   responsibility of the designer to specify the length and format of
   any Additional FEC Type Specific Information.

   When a FEC TLV contains a Typed Wildcard FEC Element the Typed
   Wildcard FEC Element MUST be the only FEC Element in the TLV.

   An LDP implementation that supports the Typed Wildcard FEC Element
   MUST support its use in Label Request, Label Withdraw and Label
   Release messages.

   An LDP implementation that supports the Typed Wildcard FEC Element
   MUST support it for every FEC Element Type implemented for which it
   is defined.

   Receipt of a Label Request message with a FEC TLV containing a Typed
   Wildcard FEC Element is interpreted as a request to send a Label
   Mapping for all FECs of the type specified by the FEC Element Type
   field in the Typed Wildcard FEC Element encoding.

   An LDP implementation that supports the Typed Wildcard FEC Element
   MUST support the following constraints whenever a Typed Wildcard FEC
   appears in a Label Withdraw or Label Release message:




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   1) If the message carries an optional Label TLV the Typed Wildcard
      FEC Element refers to all FECs of the specified FEC type bound to
      the specified label.

   2) If the message has no Label TLV the Typed Wildcard FEC Element
      refers to all FECs of the specified FEC type.

   Backwards compatibility with a router not supporting the Typed
   Wildcard FEC element is ensured by the FEC procedures defined in
   RFC5036. Quoting from RFC5036:

     "If it" [an LSR] "encounters a FEC Element type it cannot decode,
     it SHOULD stop decoding the FEC TLV, abort processing the message
     containing the TLV, and send an "Unknown FEC" Notification message
     to its LDP peer signaling an error."

   A router receiving a FEC TLV containing a Typed Wildcard FEC element
   for a FEC Element Type that it either doesn't support or for a FEC
   Element Type that doesn't support the use of wildcarding MUST stop
   decoding the FEC TLV, abort processing the message containing the
   TLV, and send an "Unknown FEC" Notification message to its LDP peer
   signaling an error.



5. Typed Wildcard FEC Capability

   As noted above, RFC5056 FEC procedures provide for backward
   compatibility with a LSR not supporting the Typed Wildcard FEC
   Element.  However, they don't provide means for LSR wishing to use
   the Typed Wildcard FEC Element to determine whether a peer supports
   it other than to send a message that uses the FEC Element and to wait
   and see how the peer responds.

   An LDP speaker that supports the Typed Wildcard FEC Element MUST
   inform its peers of the support by including a Typed Wildcard FEC
   Element Capability Parameter [RFC5561] in its Initialization
   messages.

   The Capability Parameter for the Typed Wildcard FEC capability is a
   TLV with the following format:








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   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |U|F| Typed WCard FEC Cap (IANA)|            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |S| Reserved    |
   +-+-+-+-+-+-+-+-+

               Figure 2 Typed Wildcard FEC Capability format

   Where:

     U and F bits          : MUST be 1 and 0 respectively as per section
     3 of LDP Capabilities [RFC5561].

     Typed WCard FEC Cap   : TLV code point to be assigned by IANA.

     S-bit                 : MUST be 1 (indicates that capability is
     being advertised).



6. Typed Wildcard FEC Element for Prefix FEC Element

   RFC5036 defines the Prefix FEC Element but it does not specify a
   Typed Wildcard for it.  This section specifies the Typed Wildcard FEC
   Element for Prefix FEC Elements.

   The format of the Prefix FEC Typed Wildcard FEC ("Prefix FEC
   Wildcard" for short) is:



   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 2
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Typed Wcard   | Prefix (2)    |      2        |  Address...   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | ...Family     |
   +-+-+-+-+-+-+-+-+

        Figure 3 Format of Prefix FEC Element using Typed Wildcard

   Where:

   Address Family:  Two octet quantity containing a value from ADDRESS
   FAMILY NUMBERS in [IANA-AF].


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   The procedures of Section 4 apply to the Prefix FEC Wildcard.



7. Typed Wildcard FEC Element for Host and Wildcard FEC Elements

   There is no need to specify Typed Wildcard FEC Elements for the Host
   FEC Element specified by [RFC3036], nor for the Wildcard FEC Element
   specified by RFC5036. The [RFC3036] Host FEC Element has been removed
   from RFC5036, and the Wildcard FEC Element is untyped by definition.



8. IANA Considerations

   This draft introduces a new LDP FEC Element Type and a new LDP
   Capability both of which require IANA assignment -

      The 'Typed Wildcard' FEC Element requires a code point from the
      LDP FEC Type Name Space.  [RFC5036] partitions the FEC Type Name
      Space into 3 regions:  IETF Consensus region, First Come First
      Served region, and Private Use region.  The authors recommend that
      the code point 0x05 from the IETF Consensus range be assigned to
      the 'Typed Wildcard' FEC Element.

      The 'Typed Wildcard FEC' Capability requires a code point from the
      TLV Type name space.  [RFC5036] partitions the TLV TYPE name space
      into 3 regions:  IETF Consensus region, First Come First Served
      region, and Private Use region.  The authors recommend that a code
      point from the IETF Consensus range be assigned to the 'Typed
      Wildcard FEC' Capability.



9. Security Considerations

   No security considerations beyond those that apply to the base LDP
   specification [RFC5036] and further described in [MPLSsec] apply to
   use of the Typed Wildcard FEC Elements as described in this document.

10. Acknowledgments

   The authors would like to thank Yakov Rekhter for suggesting that the
   deficiencies of the Wildcard FEC be addressed.

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



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11. References

11.1. Normative References

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

   [RFC5036] Andersson, L., Minei, I., and Thomas, B., "LDP
             Specification", RFC 5036, October 2007.

   [RFC5561] Thomas, B., Aggarwal, S., Aggarwal, R., Le Roux, J.L., "LDP
             Capabilities", RFC5561, May 2007.



11.2. Informative References

   [RFC3036] Andersson, L., Doolan, P., Feldman, N., Fredette, A. and
             Thomas, B., "LDP Specification", RFC 3036, January 2001.

   [RFC4447] Martini, L., Editor, "Pseudowire Setup and Maintenance
             Using the label Distribution Protocol (LDP)", RFC4447,
             April 2006.

   [MLDP]    Minei, I., Wijnands, I., Editors, "Label Distribution
             Protocol Extensions for Point-to-Multipoint and Multipoint-
             to-Multipoint Label Switched Paths", draft-ietf-mpls-ldp-
             p2mp-07.txt, Work in Progress, July 2009.

   [MPLSsec] Fang, L., "Security Framework for MPLS and GMPLS Networks",
             draft-ietf-mpls-mpls-and-gmpls-security-framework-06, Work
             in Progress, July 13 2009.

   [IANA-AF] http://www.iana.org/assignments/address-family-numbers.













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Author's Addresses

   Ina Minei
   Juniper Networks
   1194 North Mathilda Ave.
   Sunnyvale, CA 94089
   Email: ina@juniper.net


   Bob Thomas
   Email: bobthomas@alum.mit.edu


   Rajiv Asati
   Cisco Systems,
   7025-6 Kit Creek Rd, RTP, NC, 27709-4987
   Email: rajiva@cisco.com
































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