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Versions: (draft-leroux-pce-disco-proto-igp) 00 01 02 draft-ietf-pce-disco-proto-isis

Network Working Group                              J.L. Le Roux (Editor)
Internet Draft                                           France Telecom
Category: Standard Track                           J.P. Vasseur (Editor)
Expires: May 2006                                      Cisco System Inc.
                                                          Yuichi Ikejiri
                                                                     NTT


                                                           December 2005


  IGP protocol extensions for Path Computation Element (PCE) Discovery

               draft-ietf-pce-disco-proto-igp-00.txt


Status of this Memo

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Abstract

   In various situations it would be highly useful for a Path
   Computation Client (PCC) to be able to dynamically and automatically
   discover a set of Path Computation Element(s) (PCE), along with some
   of information relevant for PCE selection. When the PCE is an LSR
   participating to the IGP, or even a server participating passively to
   the IGP, a simple and efficient way for PCE discovery, consists of
   relying on IGP flooding. For that purpose this document defines
   simple OSPF and ISIS extensions for the advertisement of PCE
   Discovery information within and across IGP areas.


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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 RFC-2119.

Table of Contents

   1.      Note........................................................3
   2.      Terminology.................................................3
   3.      Introduction................................................4
   4.      PCE Discovery Information...................................5
   4.1.    Description.................................................5
   4.2.    Mandatory versus optional PCE information...................5
   4.3.    Flooding scope..............................................5
   4.4.    Frequency of change.........................................6
   5.      OSPF extensions.............................................6
   5.1.    The OSPF PCED TLV...........................................6
   5.1.1.  PCE-ADDRESS sub-TLV.........................................7
   5.1.2.  PATH-SCOPE sub-TLV..........................................8
   5.1.3.  PCE-DOMAINS sub-TLV.........................................9
   5.1.3.1.  IPv4 area ID DOMAIN sub-TLV..............................10
   5.1.3.2.  IPv6 area ID DOMAIN sub-TLV..............................11
   5.1.3.3.  AS Number sub-TLV........................................11
   5.1.4.  PCE-DEST-DOMAINS sub-TLV...................................11
   5.1.5.  The GENERAL-CAP sub-TLV....................................12
   5.1.6.  The PATH-COMP-CAP sub-TLV..................................13
   5.2.    Elements of Procedure......................................14
   6.      ISIS extensions............................................16
   6.1.    IS-IS PCED TLV format......................................16
   6.1.1.  PCE-ADDRESS sub-TLV........................................17
   6.1.2.  The PATH-SCOPE sub-TLV.....................................17
   6.1.3.  PCE-DOMAINS sub-TLV........................................19
   6.1.3.1.  Area ID DOMAIN sub-TLV...................................19
   6.1.3.2.  AS Number DOMAIN sub-TLV.................................19
   6.1.4.  PCE-DEST-DOMAINS sub-TLV...................................20
   6.1.5.  GENERAL-CAP sub-TLV........................................20
   6.1.6.  The PATH-COMP-CAP sub-TLV..................................21
   6.2.    Elements of procedure......................................22
   7.      Backward compatibility.....................................22
   8.      Security Considerations....................................22
   9.      IANA considerations........................................22
   9.1.    OSPF TLVs..................................................22
   9.2.    ISIS TLVs..................................................23
   9.3.    Capability bits............................................23
   10.     Security Considerations....................................24
   11.     References.................................................24
   11.1.   Normative references.......................................24
   11.2.   Informative references.....................................24
   12.     Authors' Addresses:........................................25
   13.     Intellectual Property Statement............................25

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1. Note

   This document specifies new TLVs and sub-TLVs to be carried within
   the OSPF Router information LSA ([OSPF-CAP]) and ISIS Router
   Capability TLV ([ISIS-CAP]). Because this document does not introduce
   any new element of procedure it will be discussed within the PCE
   Working Group with a review of the OSPF and ISIS Working Groups.
   Furthermore, once stabilized, it may be decided to split the document
   in two documents addressing the OSPF and ISIS aspects respectively.

2. Terminology

   Terminology used in this document

      LSR: Label Switch Router

      TE LSP: Traffic Engineered Label Switched Path

      PCE: Path Computation Element: an entity (component, application,
      or network node) that is capable of computing a network path or
      route based on a network graph, and applying computational
      constraints.

      PCC: Path Computation Client: any client application requesting a
      path computation to be performed by a Path Computation Element.

      IGP Area: OSPF Area or ISIS level

      ABR: IGP Area Border Router (OSPF ABR or ISIS L1L2 router)

      AS: Autonomous System

      ASBR: AS Border Router

      Intra-area TE LSP: A TE LSP whose path does not cross IGP area
      boundaries.

      Inter-area TE LSP: A TE LSP whose path transits through
      two or more IGP areas.

      Inter-AS MPLS TE LSP: A TE LSP whose path transits
      through two or more ASes or sub-ASes (BGP confederations).

      Domain: any collection of network elements within a common sphere
      of address management or path computational responsibility.
      Examples of domains include IGP areas and Autonomous Systems.






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3. Introduction

   [PCE-ARCH] describes the motivations and architecture for a PCE-based
   path computation model for MPLS and GMPLS TE LSPs. The model allows
   the separation of PCE from PCC (also referred to as non co-located
   PCE) and allows cooperation between PCEs. This relies on a
   communication protocol between PCC and PCE, and between PCEs, whose
   generic requirements are listed in [PCE-COM-REQ].

   The PCE architecture requires, of course, that a PCC be aware of the
   location of one or more PCEs in its domain, and also potentially of
   some PCEs in other domains, e.g. in case of inter-domain path
   computation.

   A network may comprise a large number of PCEs with potentially
   distinct capabilities. In such context it would be highly desirable
   to have a mechanism for automatic and dynamic PCE discovery, which
   would allow PCCs to automatically discover a set of PCEs, including
   information required for PCE selection, and to dynamically detect new
   PCEs or any modification of PCE information. This includes the
   discovery by a PCC of a set of one or more PCEs in its domain, and
   potentially in some other domains. The latter is a desirable function
   in the case of inter-domain path computation for example.
   Detailed requirements for such a PCE discovery mechanism are
   described in [PCE-DISCO-REQ].

   When PCCs are LSRs participating to the IGP (OSPF, ISIS), and PCEs
   are LSRs participating to the IGP or any network servers
   participating to the IGP, an efficient mechanism for PCE discovery
   consists of relying on IGP advertisement.

   This document defines OSPF and ISIS extensions allowing a PCE
   participating to the IGP to advertise its location along with some
   information useful for PCE selection so as to satisfy dynamic PCE
   discovery requirements set forth in [PCE-DISC-REQ].

   Generic capability mechanisms have been defined in [OSPF-CAP] and
   [ISIS-CAP] for OSPF and ISIS respectively the purpose of which is to
   allow a router to advertise its capability within an IGP area or an
   entire routing domain. This perfectly fits with the aforementioned
   dynamic PCE discovery requirements. Thus, a new TLV (named the PCE
   Discovery (PCED) TLV) is defined for ISIS and OSPF to be carried
   within the ISIS Capability TLV ([ISIS-CAP]) for ISIS and the OSPF
   Router Information LSA ([OSPF-CAP]).

   The PCE discovery information is detailed in section 3. Protocol
   extensions and procedures are defined in section 4 and 5 for ISIS and
   OSPF respectively. This document does not define any new OSPF or ISIS
   element of procedure but how the procedures defined in [OSPF-CAP] and
   [ISIS-CAP] should be used.



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   The routing extensions defined in this document allow for PCE
   discovery within and across IGP areas. Solutions for PCE discovery
   across AS boundaries are for further study.

4. PCE Discovery Information

4.1. Description

   The PCE Discovery information allows for dynamic discovery of PCEs.
   This information is advertised by means of IGP advertisements by
   PCE(s) participating to the IGP. It allows all PCCs participating to
   the IGP to dynamically discover PCEs along with information useful
   for PCE selection.

   Such dynamic PCE discovery has various advantages:
        - Simplified PCC configuration,
        - Reduces risk of misconfiguration,
        - Dynamic detection of a new PCE,
        - Dynamic detection of any change in PCE information
        - Dynamic detection of PCE aliveness (PCE liveness may require
        additional mechanisms provided by the PCC-PCE communication
        protocol)

4.2. Mandatory versus optional PCE information

   The PCE Discovery information is comprised of:

   - The PCE location: This is a set of one ore more IPv4 and or IPv6
     addresses used to reach the PCE. These are basically loopback
     addresses always reachable provided that the PCE is still alive.

   - The PCE inter-domain functions: this refers to the PCE path
     computation scope (i.e. inter-area, inter-AS, inter-layer…).

   - The PCE domain(s): This is the set domain(s) where the PCE has
     visibility and can compute paths.

   - The set of destination domain(s) towards which a PCE can compute
     paths.

   - A set of general PCE capabilities (e.g. support for request
     prioritization) and path computation specific PCE capabilities
     (e.g. supported constraints, supported objective functions…)
     These are two variable length sets of bits flags, where each bit
     represent a given PCE capability.

4.3. Flooding scope

   The PCE Discovery information can be flooded locally within the IGP
   area the PCE belongs to, or globally across the entire routing
   domain. Note that some PCEs may belong to multiple areas, in which
   case the flooding scope can correspond to these areas. This could be

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   the case of an ABR for instance that can advertise its PCE
   information within the backbone area and/or a subset of its attached
   IGP area(s).

4.4. Frequency of change

   The rate at which PCE information is advertised must be controlled so
   as to not impact by any mean the IGP scalability. Changes in PCE
   information may occur as result of PCE configuration updates, PCE
   deployment/activation or PCE deactivation/suppression. Hence, this
   information is not expected to change frequently.

5. OSPF extensions

5.1. The OSPF PCED TLV

   The OSPF PCE Discovery TLV (PCED TLV) is made of a set of non-ordered
   sub-TLVs.

   The format of the OSPF PCED TLV and its sub-TLVs is the identical as
   the TLV format used by the Traffic Engineering Extensions to OSPF
   [OSPF-TE]. That is, the TLV is composed of 2 octets for the type, 2
   octets specifying the TLV length and a value field. The Length field
   defines the length of the value portion in octets.
   The TLV is padded to four-octet alignment; padding is not included in
   the length field (so a three octet value would have a length of
   three, but the total size of the TLV would be eight octets).  Nested
   TLVs are also 32-bit aligned.  Unrecognized types are ignored.  All
   types between 32768 and 65535 are reserved for vendor-specific
   extensions.  All other undefined type codes are reserved for future
   assignment by IANA.

   The OSPF PCED TLV has the following format:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Type             |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                            sub-TLVs                          //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


         Type     To be defined by IANA (suggested value=2)
         Length   Variable
         Value    This comprises one or more sub-TLVs

   Sub-TLVs types are under IANA control.

   Currently five sub-TLVs are defined (type values to be assigned by
   IANA):

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         Sub-TLV type  Length               Name
               1      variable     PCE-ADDRESS sub-TLV
               2         4         PATH-SCOPE sub-TLV
               3      variable     PCE-DOMAINS sub-TLV
               4      variable     PCE-DEST-DOMAINS sub-TLV
               5      variable     GENERAL-CAP sub-TLV
               6      variable     PATH-COMP-CAP sub-TLV

   The sub-TLVs PCE-ADDRESS and PATH SCOPE MUST always be present within
   the PCED TLV.

   The sub-TLVs PCE-DOMAINS and DEST-DOMAINS, MUST only be present in
   some particular inter-domain cases.

   The GENERAL-CAP and PATH-COMP-CAP are optional and MAY be present in
   the PCED TLV to facilitate PCE selection.

   Any non recognized sub-TLV MUST be silently ignored.

   Additional sub-TLVs could be added in the future to advertise
   additional information.

   The PCED TLV is carried within an OSPF Router Information LSA which
   is defined in [OSPF-CAP].

5.1.1. PCE-ADDRESS sub-TLV

   The PCE-ADDRESS sub-TLV specifies the IP address to be used to reach
   the PCE. This address will typically be a loop-back address that is
   always reachable, provided that the PCE is alive.
   The PCE-ADDRESS sub-TLV is mandatory; it MUST be present within the
   PCED TLV.

   The format of the PCE-ADDRESS sub-TLV is as follows:


        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |              Type             |             Length            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     address-type              |          Reserved             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       //                       PCE IP Address                        //
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                            PCE-ADDRESS sub-TLV format

         Type     To be assigned by IANA (suggested value =1)
         Length   8 or 20

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         Address-type:
                       1   IPv4
                       2   IPv6
         PCE IP Address: The IP address to be used to reach the PCE.
                         This is the address that will be used for
                         setting up PCC-PCE communication sessions.

   The PCE-ADDRESS sub-TLV MUST appear at least once in the PCED sub-TLV
   originated by a PCE. It MAY appear multiple times, for instance when
   the PCE has both an IPv4 and IPv6 address.

5.1.2. PATH-SCOPE sub-TLV

   The PATH-SCOPE sub-TLV indicates the PCE path computation scope; in
   other words the ability of the PCE to compute or take part into the
   computation of intra-area, inter-area, inter-AS or inter-layer_TE
   LSP(s).

   The PATH-SCOPE sub-TLV is mandatory; it MUST be present within the
   PCED TLV. There MUST be exactly one PATH-SCOPE sub-TLV within each
   PCED TLV.

   The PATH-SCOPE sub-TLV contains a set of bit flags indicating the
   supported path scopes (intra-area, inter-area, inter-AS, inter-layer)
   and two fields indicating PCE preferences.

   The PATH-SCOPE sub-TLV has the following format:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Type             |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|1|2|3|4|5|   Reserved        |PrefR|PrefS|       Reserved    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


         Type     To be defined by IANA (suggested value =3)
         Length   Variable
         Value    This comprises a 2 bytes flag where each bit
                  represents a supported path scope, as well as two
                  preference fields allowing to specify PCE preferences.

         The following bits are defined:

         Bit      Path Scope

          0      L bit: Can compute intra-area path
          1      R bit: Can act as PCE for inter-area TE LSPs
                        computation
          2      Rd bit: Can act as a default PCE for inter-area TE LSPs
                         computation

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          3      S bit: Can act as PCE for inter-AS TE LSPs computation
          4      Sd bit: Can act as a default PCE for inter-AS TE LSPs
                         computation
          5      Y bit: Can compute or take part into the computation of
                        paths across layers.

   Pref field: PCE’s preference

   Pref-S field: PCE’s preference for inter-AS TE LSPs computation


   The bits L, R, S and Y bits are set when the PCE can act as a PCE for
   intra-area, inter-area, inter-AS and inter-layer TE LSPs computation
   respectively. These bits are non exclusive.

   When set the Rd bit indicates that the PCE can act as a default PCE
   for inter-area TE LSPs computation, it means that it can compute path
   for any destination area. Similarly, when set the Sd bit indicates
   that the PCE can act as a default PCE for inter-AS TE LSPs
   computation, it means that it can compute path for any destination
   AS.

   When the Rd bit is set the PCE-DEST-DOMAIN TLV (see 5.1.4) does not
   comprise any Area ID DOMAIN sub-TLV.
   When the Sd bit is set the PCE-DEST-DOMAIN TLV does not comprise any
   AS DOMAIN sub-TLV.

   The PrefR and PrefS fields are 3-bit long and allow the PCE to
   specify a preference where 7 reflects the highest preference. For the
   sake of illustration, consider the situation where N ABRs act as PCEs
   for inter-area TE LSPs computation. An operator may decide to
   configure a preference to each PCE that could be used to load balance
   the path computation load with respect to their respective CPU
   capacity. The algorithms used by a PCC to load balance its path
   computation requests according to such PCE’s preference is out of the
   scope of this document.


5.1.3. PCE-DOMAINS sub-TLV

   The PCE-DOMAINS sub-TLV specifies the set of domains (areas, AS)
   where the PCE has topology visibility and can compute paths. It
   contains a set of one or more sub-TLVs where each sub-TLV identifies
   a domain.

   The PCE-DOMAINS sub-TLV MUST only be present when PCE domains cannot
   be inferred by other IGP information, for instance when the PCE is
   inter-domain capable (i.e. when the R bit or S bit is set) and the
   flooding scope the entire routing domain.

   The PCE-DOMAINS sub-TLV has the following format:


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    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Type             |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                    DOMAIN sub-TLVs                          //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


         Type     To be defined by IANA (suggested value =3)
         Length   Variable
         Value    This comprises a set of one or more DOMAIN sub-TLVs
                  where each DOMAIN sub-TLV identifies a domain where
                  the PCE has topology visibility and can compute TE LSP
                  paths.

   Sub-TLVs types are under IANA control.

   Currently three DOMAIN sub-TLVs are defined (suggested type values to
   be assigned by IANA):
            Sub-TLV type  Length               Name
                1      variable     IPv4 area ID sub-TLV
                2      variable     IPv6 area ID sub-TLV
                3      variable     AS number sub-TLV

   The PCE-DOMAINS sub-TLV MUST include at least one DOMAIN sub-TLV.
   Note than when the PCE visibility is an entire AS, the PCE-DOMAINS
   sub-TLV MUST uniquely include one AS number sub-TLV.

5.1.3.1. IPv4 area ID DOMAIN sub-TLV

   The IPv4 area ID DOMAIN sub-TLV carries an IPv4 OSPF area identifier.
   It has the following format:


        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |              Type             |             Length            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                       IPv4 Area ID                            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


         Type     To be assigned by IANA (suggested value =1)
         Length   4
         IPv4 OSPF area ID: The IPv4 identifier of the OSPF area





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5.1.3.2. IPv6 area ID DOMAIN sub-TLV

   The IPv6 area ID sub-TLV carries an IPv6 OSPF area identifier. It has
   the following format:


        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |              Type             |             Length            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                       IPv6 Area ID                            |
       |                                                               |
       |                                                               |
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


         Type     To be assigned by IANA (suggested value =2)
         Length   16
         IPv6 OSPF area ID: The IPv6 identifier of the OSPF area

5.1.3.3. AS Number sub-TLV

   The AS Number sub-TLV carries an AS number. It has the following
   format:

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |              Type             |             Length            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                       AS Number                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


         Type     To be assigned by IANA (suggested value =3)
         Length   4
         AS Number:  AS number identifying an AS. When coded on two
                     bytes (which is the current defined format as the
                     time of writing this document), the AS Number field
                     MUST have its left two bytes set to 0.

5.1.4. PCE-DEST-DOMAINS sub-TLV

   The PCE-DEST-DOMAINS sub-TLV specifies the set of destination domains
   (areas, AS) toward which a PCE can compute path. It means that the
   PCE can compute or take part in the computation of inter-domain LSPs
   whose destination is located in one of these domains. It contains a
   set of one or more sub-TLVs where each sub-TLV identifies a domain.




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   The PCE-DEST-DOMAINS sub-TLV has the following format:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Type             |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                    DOMAIN sub-TLVs                          //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


         Type     To be defined by IANA (suggested value =3)
         Length   Variable
         Value    This comprises a set of one or more Area and/or AS
                  DOMAIN sub-TLVs where each DOMAIN sub-TLV identifies a
                  domain toward which a PCE can compute paths.

   The PCE-DEST-DOMAINS sub-TLV MUST include at least one DOMAIN sub-
   TLV.

   The PCE-DEST-DOMAINS sub-TLV is optional. It MUST be present only if
   the R bit is set and the Rd bit is cleared, and/or, if the S bit is
   set and the Sd bit is cleared.

   The PCE-DEST-DOMAINS sub-TLV MUST include at least one area ID sub-
   TLV, if the R bit of the PATH-SCOPE TLV is set and the Rd bit of the
   PATH-SCOPE TLV is cleared.
   Similarly, the PCE-DEST- DOMAINS sub-TLV MUST include at least one AS
   number sub-TLV if the S bit of the PATH-SCOPE TLV is set and the Sd
   bit of the PATH-SCOPE TLV is cleared.

5.1.5. The GENERAL-CAP sub-TLV

   The GENERAL-CAP sub-TLV is used to indicate general PCE capabilities.
   The GENERAL-CAP sub-TLV is optional. It MAY be carried within the
   PCED TLV.
   The value field of the GENERAL-CAP sub-TLV is made of bit flags,
   where each bit corresponds to a general PCE capability.

   The format of the GENERAL-CAP sub-TLV is as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |              Type             |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             General PCE Capabilities                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      //                    Optional sub-TLVs                         //


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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         Type     To be assigned by IANA (suggested value =1)
         Length   It is set to N x 4 octets.  N starts
                  from 1 and can be increased when there is a need.
                  Each 4 octets are referred to as a capability flag.
         Value    This comprises one or more capability flags.
                  For each 4 octets, the bits are indexed from the most
                  significant to the least significant, where each bit
                  represents one general PCE capability.  When
                  the first 32 capabilities are defined, a new
                  capability flag will be used to accommodate the next
                  capability. Optional TLVs may be defined to specify
                  more complex capabilities: there is no optional TLVs
                  currently defined.

   IANA is requested to manage the space of general PCE capability bit
   flags.

   The following bits in the first capability flag are to be assigned by
   IANA:


     Bit       Capabilities

      0      P bit: Support for Request prioritization.
      1      M bit: Support for multiple messages within the same
                    request message.

     2-31    Reserved for future assignments by IANA.

5.1.6. The PATH-COMP-CAP sub-TLV

   The PATH-COMP-CAP sub-TLV is used to indicate path computation
   specific capabilities of a PCE.
   The PATH-COMP-CAP sub-TLV is optional. It MAY be carried within the
   PCED TLV.
   This is a series of bit flags, where each bit correspond to a path
   computation capability.

   The format of the PATH-COMP-CAP sub-TLV is as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |              Type             |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             Path Computation Capabilities                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      //                    Optional sub-TLVs                         //


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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



         Type     To be assigned by IANA (suggested value =1)
         Length   It is set to N x 4 octets.  N starts
                  from 1 and can be increased when there is a need.
                  Each 4 octets are referred to as a capability flag.
         Value    This comprises one or more capability flags.
                  For each 4 octets, the bits are indexed from the most
                  significant to the least significant, where each bit
                  represents one path computation PCE capability.  When
                  the first 32 capabilities are defined, a new
                  capability flag will be used to accommodate the next
                  capability. Optional TLVs may be defined to specify
                  more complex capabilities: there is no optional TLVs
                  currently defined.

   IANA is requested to manage the space of PCE path commutation
   capability bit flags.

   The following bits in the first capability flag are to be assigned by
   IANA:


     Bit       Capabilities

      0      M bit: Capability to compute P2P paths in MPLS-TE networks
      1      G bit: Capability to compute P2P paths in GMPLS networks
      2      D bit: Capability to compute link/node/SRLG diverse paths
      3      L bit: Capability to compute load-balanced paths
      4      S bit: Capability to compute a set of paths in a
                    synchronized Manner
      5      O bit: Support for multiple objective functions


     6-31    Reserved for future assignments by IANA.

   The M, G, D, L, S and O bits are not exclusive.

5.2. Elements of Procedure

   The PCED TLV is carried within an OSPF Router information opaque LSA
   (opaque type of 4, opaque ID of 0) which is defined in [OSPF-CAP].

   A router MUST originate a new OSPF router information LSA whenever
   the content of any of the carried TLVs changes or whenever
   required by the regular OSPF procedure (LSA refresh (every
   LSRefreshTime)).

   The PCED TLV may be carried within a type 10 or 11 router information
   LSA depending on the flooding scope of the PCE information.

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   If the flooding scope is local to an area then it MUST be carried
   within a type 10 router information LSA.
   If the flooding scope is the entire domain then it MUST be carried
   within type 11 router information LSA.
   Note that when the L bit of the PATH-SCOPE TLV is set and the R bit
   and S bit are cleared, the flooding scope MUST be local, and the PCED
   TLV MUST be carried within a type 10 Router Information LSA.

   PCED TLVs are OPTIONAL. When an OSPF LSA does not contain any PCED
   TLV, this means that the PCE information of that node is unknown.

   Note that a change in PCED information MUST not trigger normal SPF
   computation.








































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6. ISIS extensions

6.1. IS-IS PCED TLV format

   The IS-IS PCED TLV is made of various non ordered sub-TLVs.

   The format of the IS-IS PCED TLV and its sub-TLVs is the same as the
   TLV format used by the Traffic Engineering Extensions to IS-IS [ISIS-
   TE]. That is, the TLV is composed of 1 octet for the
   type, 1 octet specifying the TLV length and a value field.

   The IS-IS PCED TLV has the following format:

      TYPE: To be assigned by IANA
      LENGTH: Variable
      VALUE: set of sub-TLVs

   Sub-TLVs types are under IANA control.

   Currently five sub-TLVs are defined (suggested type values to be
   assigned by IANA):
            Sub-TLV type  Length               Name
                1      variable     PCE-ADDRESS sub-TLV
                2         2         PATH-SCOPE sub-TLV
                3      variable     PCE-DOMAINS sub-TLV
                4      variable     PCE-DEST-DOMAINS sub-TLV
                5      variable     GENERAL-CAP sub-TLV
                6      variable     PATH-COMP-CAP sub-TLV


   The sub-TLVs PCE-ADDRESS and PATH-SCOPE MUST always be present within
   the PCED TLV.

   The sub-TLVs PCE-DOMAINS and DEST-DOMAINS, MUST only be present in
   some particular inter-domain cases.

   The GENERAL-CAP and PATH-COMP-CAP are optional and MAY be present in
   the PCED TLV to facilitate PCE selection.

   Any non recognized sub-TLV MUST be silently ignored.

   Additional sub-TLVs could be added in the future to advertise
   additional PCE information.

   The PCED TLV is carried within an ISIS CAPABILITY TLV which is
   defined in [ISIS-CAP].







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6.1.1. PCE-ADDRESS sub-TLV

   The PCE-ADDRESS sub-TLV specifies the IP address to be used to reach
   the PCE. This address will typically be a loop-back address that is
   always reachable, provided the PCE is alive.
   The PCE-ADDRESS sub-TLV is mandatory; it MUST be present within the
   PCED TLV.

   The PCE-ADDRESS sub-TLV has the following format:

      TYPE: To be assigned by IANA (Suggested value =1)
      LENGTH: 4 for IPv4 address and 16 for IPv6 address
      VALUE: This comprises one octet indicating the address-type and 4
             or 16 octets encoding the IPv4 or IPv6 address to be used
             to reach the PCE

   Address-type:
                  1   IPv4
                  2   IPv6

   The PCE-ADDRESS sub-TLV MUST appear at least once in the PCED sub-LTV
   originated by a PCE. It MAY appear multiple times, for instance when
   the PCE has both an IPv4 and IPv6 address.

6.1.2. The PATH-SCOPE sub-TLV

   The PATH-SCOPE sub-TLV indicates the PCE path computation scope; in
   other words the ability of the PCE to compute or take part into the
   computation of intra-area, inter-area, inter-AS or inter-layer_TE
   LSP(s).

   The PATH-SCOPE sub-TLV is mandatory; it MUST be present within the
   PCED TLV. There MUST be exactly one PATH-SCOPE sub-TLV within each
   PCED TLV.

   The PATH-SCOPE sub-TLV contains a set of bit flags indicating the
   supported path scopes (intra-area, inter-area, inter-AS, inter-layer)
   and two fields indicating PCE preferences.

   The PATH-SCOPE sub-TLV has the following format:

   TYPE: To be assigned by IANA (Suggested value =2)
   LENGTH: Variable
   VALUE: This comprises a one-byte flag of bits where each bit
          represents a supported path scope, followed by a one-byte
          preference field indicating PCE preferences.







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   Here is the structure of the bits flag:


    0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+
   |0|1|2|3|4|5|Res|
   +-+-+-+-+-+-+-+-+

   Bit      Path Scope

   0      L bit: Can compute intra-area path
   1      R bit: Can act as PCE for inter-area TE LSPs
                 computation
   2      Rd bit: Can act as a default PCE for inter-area TE LSPs
                  computation
   3      S bit: Can act as PCE for inter-AS TE LSPs computation
   4      Sd bit: Can act as a default PCE for inter-AS TE LSPs
                  computation
   5      Y bit: Can compute or take part into the computation of
                 paths across layers


   Here is the structure of the preference field

    0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+
   |PrefR|PrefS|Res|
   +-+-+-+-+-+-+-+-+

   PrefR field: PCE’s preference for inter-area TE LSPs computation

   PrefS field: PCE’s preference for inter-AS TE LSPs computation


   The bits L, R, S and Y bits are set when the PCE can act as a PCE for
   intra-area, inter-area, inter-AS and inter-layer TE LSPs computation
   respectively. These bits are non exclusive.

   When set the Rd bit indicates that the PCE can act as a default PCE
   for inter-area TE LSPs computation, it means that it can compute path
   for any destination area. Similarly, when set the Sd bit indicates
   that the PCE can act as a default PCE for inter-AS TE LSPs
   computation, it means that it can compute path for any destination
   AS.

   When the Rd bit is set the PCE-DEST-DOMAINS TLV (see 6.1.4) does not
   comprise any Area ID DOMAIN sub-TLV. When the Sd bit is set the PCE-
   DEST-DOMAINS TLV does not comprise any AS DOMAIN sub-TLV.

   The PrefR and PrefS fields are 3-bit long and allow the PCE to
   specify a preference where 7 reflects the highest preference. For the
   sake of illustration, consider the situation where N ABRs act as PCEs

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   for inter-area TE LSPs computation. An operator may decide to
   configure a preference to each PCE that could be used to load balance
   the path computation load with respect to their respective CPU
   capacity. The algorithms used by a PCC to load balance its path
   computation requests according to such PCE’s preference is out of the
   scope of this document

6.1.3. PCE-DOMAINS sub-TLV

   The PCE-DOMAINS sub-TLV specifies the set of domains (areas, AS)
   where the PCE has topology visibility and can compute paths. It
   contains a set of one or more sub-TLVs where each sub-TLV identifies
   a domain.

   The PCE-DOMAINS sub-TLV MUST only be present when PCE domains cannot
   be inferred by other IGP information, for instance when the PCE is
   inter-domain capable (i.e. when the R bit or S bit is set) and the
   flooding scope is the entire routing domain.

   The PCE-DOMAINS sub-TLV has the following format:

   TYPE: To be assigned by IANA (Suggested value =2)
   LENGTH: Variable
   VALUE: This comprises a set of one or more DOMAIN sub-TLVs where
          each DOMAIN sub-TLV identifies a domain where the PCE has
          topology visibility and can compute paths

   DOMAIN Sub-TLVs types are under IANA control.

   Currently two DOMAIN sub-TLVs are defined (suggested type values to
   be assigned by IANA):
            Sub-TLV type  Length               Name
                1      variable     Area ID sub-TLV
                2      variable     AS number sub-TLV

   At least one DOMAIN sub-TLV MUST be present in the PCE-DOMAINS sub-
   TLV.

6.1.3.1. Area ID DOMAIN sub-TLV

   This sub-TLV carries an ISIS area ID. It has the following format

   TYPE: To be assigned by IANA (Suggested value =1)
   LENGTH: Variable
   VALUE: This comprises a variable length ISIS area ID. This is the
          combination of an Initial Domain Part (IDP) and High Order
          part of the Domain Specific part (HO-DPS)

6.1.3.2. AS Number DOMAIN sub-TLV

   The AS Number sub-TLV carries an AS number. It has the following
   format:

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   TYPE: To be assigned by IANA (Suggested value =2)
   LENGTH: 4
   VALUE: AS number identifying an AS. When coded on two
          bytes (which is the current defined format as the
          time of writing this document), the AS Number field
          MUST have its left two bytes set to 0.

6.1.4. PCE-DEST-DOMAINS sub-TLV

   The PCE-DEST-DOMAINS sub-TLV specifies the set of destination domains
   (areas, AS) toward which a PCE can compute path. It means that the
   PCE can compute or take part in the computation of inter-domain LSPs
   whose destination is located in one of these domains. It contains a
   set of one or more DOMAIN sub-TLVs where each DOMAIN sub-TLV
   identifies a domain.

   The PCE-DEST-DOMAINS sub-TLV has the following format:

   TYPE: To be assigned by IANA (Suggested value =2)
   LENGTH: Variable
   VALUE: This comprises a set of one or more Area or/and AS DOMAIN sub-
          TLVs where each sub-TLV identifies a destination domain toward
          which a PCE can compute path.

   At least one DOMAIN sub-TLV MUST be present in the PCE-DEST-DOMAINS
   sub-TLV.

   The PCE-DEST-DOMAINS sub-TLV is optional. It MUST be present only if
   the R bit is set and the Rd bit is cleared, and/or, if the S bit is
   set and the Sd bit is cleared.

   The PCE-DEST-DOMAINS sub-TLV MUST include at least one area ID sub-
   TLV, if the R bit of the PATH-SCOPE TLV is set and the Rd bit of the
   PATH-SCOPE TLV is cleared. Similarly, the PCE-DEST-DOMAINS sub-TLV
   MUST include at least one AS number sub-TLV if the S bit of the PATH-
   SCOPE TLV is set and the Sd bit of the PATH-SCOPE TLV is cleared.

6.1.5. GENERAL-CAP sub-TLV

   The GENERAL-CAP sub-TLV is used to indicate general PCE capabilities.
   The GENERAL-CAP sub-TLV is optional. It MAY be carried within the
   PCED TLV.
   This is a series of bits flags, where each bit corresponds to a
   general PCE capability.

   The GENERAL-CAP sub-TLV has the following format:

      TYPE: To be assigned by IANA (Suggested value =4)
      LENGTH: It is set to N. N starts from 1 and can be increased when
              there is a need. Each octet is referred to as a
              capability flag.

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      VALUE: This comprises one or more general PCE capability
             flags.

   The following bits in the first capability flag are to be assigned by
   IANA:

    0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+
   |P|M| Reserved  |
   +-+-+-+-+-+-+-+-+

   P bit: Support for request prioritization.
   M bit: Support for multiple messages within the same request message.

   Reserved bits are for future assignment by IANA.

6.1.6. The PATH-COMP-CAP sub-TLV

   The PATH-COMP-CAP sub-TLV is used to indicate path computation
   specific capabilities of a PCE.
   The PATH-COMP-CAP sub-TLV is optional. It MAY be carried within the
   PCED TLV.
   This is a series of bit flags, where each bit correspond to a path
   computation capability.

   The PATH-COMP-CAP sub-TLV has the following format:

      TYPE: To be assigned by IANA (suggested value = 5)
      LENGTH: It is set to N. N starts from 1 and can be increased
              when there is a need. Each octet is referred to as a
              capability flag.
      VALUE: This comprises one or more Path Computation specific PCE
             capability flags.

   The following bits in the first capability flag are to be assigned by
   IANA.

    0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+
   |M|G|D|L|S|0|Res|
   +-+-+-+-+-+-+-+-+

      M bit: Capability to compute P2P paths in MPLS-TE networks
      G bit: Capability to compute P2P paths in GMPLS networks
      D bit: Capability to compute link/node/SRLG diverse paths
      L bit: Capability to compute load-balanced paths
      S bit: Capability to compute a set of paths in a
             synchronized Manner
      O bit: Support for multiple objective functions

     Reserved bits are for future assignment by IANA.


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6.2. Elements of procedure

   The PCED TLV is carried within an IS-IS CAPABILITY TLV defined in
   [IS-IS-CAP].

   An IS-IS router MUST originate a new IS-IS LSP whenever the content
   of any of the PCED TLV changes or whenever required by the regular
   IS-IS procedure (LSP refresh).

   When the scope of the PCED TLV is area local it MUST be carried
   within an ISIS CAPABILITY TLV having the S bit cleared.
   When the scope of the PCED TLV is the entire domain, the PCED TLV
   MUST be carried within an ISIS CAPABILITY TLV having the S bit set.
   Note that when the L bit of the PATH-SCOPE sub-TLV is set and the R
   and S bits are cleared the flooding scope MUST be local.

   PCED TLVs are OPTIONAL. When an IS-IS LSP does not contain any PCED
   TLV, this means that the PCE information of that node is unknown.

   Note that a change in PCED information MUST not trigger normal SPF
   computation.

7. Backward compatibility

   The PCED TLVs defined in this document do not introduce any
   interoperability issue. For OSPF, a router not supporting the PCED
   TLV SHOULD just silently ignore the TLV as specified in RFC2370. For
   IS-IS a router not supporting the PCED TLV SHOULD just silently
   ignore the TLV.

8. Security Considerations

   No new security issues are raised in this document.

9. IANA considerations

9.1. OSPF TLVs

   IANA will assign a new codepoint for the OSPF PCED TLV defined in
   this document and carried within the Router Information LSA.

   Five sub-TLVs types are defined for this TLV and should be assigned
   by IANA:
        -PCE-ADDRESS sub-TLV (suggested value = 1)
        -PATH-SCOPE sub-TLV (suggested value = 2)
        -PCE-DOMAINS sub-TLV (suggested value = 3)
        -PCE-DEST-DOMAINS sub-TLV (suggested value =4)
        -GENERAL-CAP sub-TLV (suggested value = 5)
        -PATH-COMP-CAP sub-TLV (suggested value = 6)



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   Three sub-TLVs types are defined for the PCE-DOMAINS and PCE-DEST-
   DOMAINS TLVs and should be assigned by IANA:
        -IPv4 area ID sub-TLV (suggested value = 1)
        -IPv6 area ID sub-TLV (suggested value = 2)
        -AS number sub-TLV (suggested value = 3)


9.2. ISIS TLVs

   IANA will assign a new codepoint for the PCED TLV defined in this
   document and carried within the ISIS CAPABILITY TLV.

   Five sub-TLVs types are defined for the PCED TLV and should be
   assigned by IANA:
        -PCE-ADDRESS sub-TLV (suggested value = 1)
        -PATH-SCOPE sub-TLV (suggested value = 2)
        -PCE-DOMAINS sub-TLV (suggested value = 3)
        -GENERAL-CAP sub-TLV (suggested value = 4)
        -PATH-COMP-CAP sub-TLV (suggested value = 5)

   Two sub-TLVs types are defined for the PCE-DOMAINS and PCE-DEST-
   DOMAINS TLVs and should be assigned by IANA:
        -Area ID sub-TLV (suggested value = 1)
        -AS number sub-TLV (suggested value = 2)


9.3. Capability bits

   IANA is requested to manage the space of general and path computation
   specific PCE capability bits flags, numbering them in the usual IETF
   notation starting at zero and continuing at least through 31.
   New bit numbers may be allocated only by an IETF Consensus action.
   Each bit should be tracked with the following qualities:
      - Bit number
      - Defining RFC
      - Name of bit

   Currently two bits are defined in the first general PCE capability
   flag. Here are the suggested values:
      -0: Support for Request prioritization.
      -1: Support for multiple messages within the same request message

   Currently six bits are defined in the first path computation specific
   PCE capability flag. Here are the suggested values:

      -0: Capability to compute P2P paths in MPLS-TE networks
      -1: Capability to compute P2P paths in GMPLS networks
      -2: Capability to compute link/node/SRLG diverse paths
      -3: Capability to compute load-balanced paths
      -4: Capability to compute a set of paths in a
          synchronized Manner
      -5: Support for multiple objective functions

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10. Security Considerations

   No new security issues are raised in this document.

11. References

11.1. Normative references

   [OSPF-v2] Moy, J., "OSPF Version 2", RFC 2328, April 1998.

   [IS-IS] "Intermediate System to Intermediate System Intra-Domain
   Routing Exchange Protocol " ISO 10589.

   [IS-IS-IP] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
   dual environments", RFC 1195, December 1990.

   [OSPF-TE] Katz, D., Yeung, D., Kompella, K., "Traffic Engineering
   Extensions to OSPF Version 2", RFC 3630, September 2003.

   [IS-IS-TE] Li, T., Smit, H., "IS-IS extensions for Traffic
   Engineering", RFC 3784, June 2004.

   [OSPF-CAP] Lindem, A., Shen, N., Aggarwal, R., Shaffer, S., Vasseur,
   J.P., "Extensions to OSPF for advertising Optional Router
   Capabilities", draft-ietf-ospf-cap, work in progress.

   [IS-IS-CAP] Vasseur, J.P. et al., "IS-IS extensions for advertising
   router information", draft-ietf-isis-caps, work in progress.

   [PCE-ARCH] Farrel, A., Vasseur, J.P., Ash, J., "Path Computation
   Element (PCE) Architecture", draft-ietf-pce-architecture, work in
   progress.

   [PCE-DISCO-REQ] Le Roux, J.L., et al. "Requirements for PCE
   discovery", draft-ietf-pce-discovery-reqs, work in progress


11.2. Informative references

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

   [RFC3667] Bradner, S., "IETF Rights in Contributions", BCP 78, RFC
   3667, February 2004.

   [RFC3668] Bradner, S., "Intellectual Property Rights in IETF
   Technology", BCP 79, RFC 3668, February 2004.



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   [PCE-COM-REQ] Ash, J., Le Roux, J.L., " PCE Communication Protocol
   Generic Requirements", draft-ietf-pce-comm-protocol-gen-reqs, work in
   progress.


12. Authors' Addresses:

   Jean-Louis Le Roux
   France Telecom
   2, avenue Pierre-Marzin
   22307 Lannion Cedex
   FRANCE
   Email: jeanlouis.leroux@francetelecom.com

   Jean-Philippe Vasseur
   Cisco Systems, Inc.
   300 Beaver Brook Road
   Boxborough , MA - 01719
   USA
   Email: jpv@cisco.com

   Yuichi Ikejiri
   NTT Communications Corporation
   1-1-6, Uchisaiwai-cho, Chiyoda-ku
   Tokyo 100-8019
   JAPAN
   Email: y.ikejiri@ntt.com


13. Intellectual Property Statement

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at
   ietf-ipr@ietf.org.

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   Disclaimer of Validity

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
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