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

                                                          Yuichi Ikejiri
                                                      NTT

                                                           December 2005 Communications

                                                           Raymond Zhang
                                                              BT Infonet

                                                              March 2006

  IGP protocol extensions for Path Computation Element (PCE) Discovery

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

               draft-ietf-pce-disco-proto-igp-01.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
   groups may also distribute working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time. It is inappropriate to use Internet- Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

Abstract

   In

   There are various situations circumstances in which it would be is highly useful desirable 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 that can used 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, 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 an IGP areas. area or the entire routing
   domain.

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.      Overview....................................................5
   4.1.    PCE Information.............................................5
   4.1.1.  PCE Discovery Information...................................5
   4.1.    Description.................................................5
   4.2.    Mandatory versus optional
   4.1.2.  PCE information...................5
   4.3. Status Information......................................6
   4.2.    Flooding scope..............................................5
   4.4.    Frequency of change.........................................6 scope..............................................6
   5.      OSPF extensions.............................................6
   5.1.    The OSPF PCED TLV...........................................6
   5.1.1.  PCE-ADDRESS sub-TLV.........................................7 sub-TLV.........................................8
   5.1.2.  PATH-SCOPE sub-TLV..........................................8
   5.1.3.  PCE-DOMAINS sub-TLV.........................................9 sub-TLV........................................10
   5.1.3.1.  IPv4 area ID DOMAIN sub-TLV..............................10 sub-TLV..............................11
   5.1.3.2.  IPv6 area ID DOMAIN sub-TLV..............................11
   5.1.3.3.  AS Number sub-TLV........................................11 sub-TLV........................................12
   5.1.4.  PCE-DEST-DOMAINS sub-TLV...................................11 sub-TLV...................................12
   5.1.5.  The  GENERAL-CAP sub-TLV....................................12 sub-TLV........................................13
   5.1.6.  The PATH-COMP-CAP sub-TLV..................................13 sub-TLV..................................14
   5.2.    The OSPF PCES TLV..........................................15
   5.2.1.  The CONGESTION sub-TLV.....................................16
   5.3.    Elements of Procedure......................................14 Procedure......................................16
   5.3.1.  PCED TLV Procedure.........................................17
   5.3.2.  PCES TLV procedure.........................................17
   6.      ISIS extensions............................................16 extensions............................................19
   6.1.    IS-IS PCED TLV format......................................16 format......................................19
   6.1.1.  PCE-ADDRESS sub-TLV........................................17 sub-TLV........................................20
   6.1.2.  The PATH-SCOPE sub-TLV.....................................17 sub-TLV.....................................20
   6.1.3.  PCE-DOMAINS sub-TLV........................................19 sub-TLV........................................22
   6.1.3.1.  Area ID DOMAIN sub-TLV...................................19 sub-TLV...................................22
   6.1.3.2.  AS Number DOMAIN sub-TLV.................................19 sub-TLV.................................23
   6.1.4.  PCE-DEST-DOMAINS sub-TLV...................................20 sub-TLV...................................23
   6.1.5.  GENERAL-CAP sub-TLV........................................20 sub-TLV........................................23
   6.1.6.  The PATH-COMP-CAP sub-TLV..................................21 sub-TLV..................................24
   6.2.    The ISIS PCES TLV..........................................25
   6.2.1.  The CONGESTION sub-TLV.....................................25
   6.3.    Elements of procedure......................................22 Procedure......................................26
   6.3.1.  PCED TLV Procedure.........................................26
   6.3.2.  PCES TLV procedure.........................................27
   7.      Backward compatibility.....................................22 compatibility.....................................27
   8.      Security Considerations....................................22
   9.      IANA considerations........................................22
   9.1. considerations........................................28
   8.1.    OSPF TLVs..................................................22
   9.2. TLVs..................................................28
   8.2.    ISIS TLVs..................................................23
   9.3. TLVs..................................................28
   8.3.    Capability bits............................................23
   10. bits............................................29
   9.      Security Considerations....................................24
   11.     References.................................................24
   11.1. Considerations....................................29
   10.     References.................................................29
   10.1.  Normative references.......................................24
   11.2. references........................................29
   10.2.  Informative references.....................................24
   12. references......................................30
   11.     Authors' Addresses:........................................25
   13. Addresses:........................................30
   12.     Intellectual Property Statement............................25 Statement............................31

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]). ([ISIS-CAP]) respectively. 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) router).

      AS: Autonomous System System.

      ASBR: AS Border Router Router.

      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.

      IGP Area: OSPF Area or ISIS level.

      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:

      LSR: Label Switch Router.

      PCC: Path Computation Client: any collection of network elements within client application requesting a common sphere
      of address management or
      path computational responsibility.
      Examples computation to be performed by a Path Computation Element.

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

      PCECP: Path Computation Element Communication Protocol.

      TE LSP: Traffic Engineered Label Switched Path

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]. PCEs. The PCE architecture requires,
   requirements for such communication protocol can be found in [PCECP-
   REQ] and the communication protocol is defined in [PCEP].

   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 TE LSP
   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 along with
   additional 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].

   Moreover, it may also be useful to discover when a PCE experiences
   some processing congestion state and exits such state in order for
   the PCCs to take some appropriate actions (e.g. redirect to another
   PCE). Note that the PCE selection algorithm is out of the scope of
   this document.

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

   This document defines OSPF and ISIS extensions allowing a PCE
   participating to in 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]. This document
   also defines extensions allowing a PCE participating to the IGP to
   advertise its potential processing congestion state.

   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 Such IGP extensions fully satisfy the
   aforementioned dynamic PCE discovery requirements. Thus, a

   This document defines two new TLV TLVs (named the PCE Discovery (PCED)
   TLV and the PCE Status (PCES) 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 advertised is detailed in section 3. 4. Protocol
   extensions and procedures are defined in section 4 and 5 and 6 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.

   The routing extensions defined in this document allow for PCE
   discovery within and across an IGP areas. Routing domain. Solutions for PCE discovery
   across AS boundaries are beyond the scope of this document, and for
   further study.

4. Overview

4.1. 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 within 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 includes PCE information
        - Dynamic detection of Discovery
   Information and PCE aliveness (PCE liveness may require
        additional mechanisms provided by the PCC-PCE communication
        protocol)

4.2. Mandatory versus optional Status information.

4.1.1. PCE information Discovery Information

   The PCE Discovery information is comprised of:

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

   - 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 PCE Destination domain(s): This is the set of destination
     domain(s) towards which a PCE can compute paths.

   - A set of general PCE PCECP capabilities (e.g. support for request
     prioritization) and path computation specific PCE capabilities
     (e.g. supported constraints, supported objective functions…) functions…).

     These are two variable length sets of bits flags, where each bit
     represent a given PCE capability.

4.3.

   It may also contain optional elements to describe more complex
   capabilities.

   PCE Discovery information is by nature a static information that does
   not change with PCE activity. Changes in PCE Discovery information
   may occur as a result of PCE configuration updates, PCE
   deployment/activation or PCE deactivation/suppression. Hence, this
   information is not expected to change frequently.

4.1.2. PCE Status Information

   The PCE Status is optional information that can be used to report a
   PCE processing congested state along with an estimated congestion
   duration. This dynamic information may change with PCE activity.

   Procedures for a PCE to move from a processing congested state to a
   non congested state are beyond the scope of this document, but the
   rate at which a PCE Status change is advertised MUST not impact by
   any mean the IGP scalability. Particular attention should be given on
   procedures to avoid state oscillations.

4.2. Flooding scope

   The flooding scope for PCE Discovery information Information can be flooded locally within the limited to
   one or more IGP
   area areas the PCE belongs to, to or globally can be extended across
   the entire routing domain.
   Note that some PCEs may belong to multiple areas, in which case the
   flooding scope can correspond to may comprise these areas. This could be the case of an
   ABR for instance that can advertise advertising 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):
         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, PCE-DEST-DOMAINS are optional. They MUST only
   be present only in some particular specific inter-domain cases.

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

   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]. [OSPF-CAP], the opaque type of which is determined by the
   desired flooding scope.

5.1.1. PCE-ADDRESS sub-TLV

   The PCE-ADDRESS sub-TLV specifies the IP address to that MUST be used to
   reach the PCE. This address will typically be It is RECOMMENDED to make use of 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 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.

   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   4 (IPv4) or 20 16 (IPv6)

         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 scope(s),
   which refers to the PCE ability 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 four 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        |PrefL|PrefR|PrefS|PrefY| Res   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         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 four
                  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
          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

   Pref-L field: PCE's preference for intra-area TE LSPs computation.

   Pref-R field: PCE’s preference for inter-area TE LSPs computation.

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

   Pref-Y field: PCE's preference for inter-layer TE LSPs computation.

   Res: Reserved for future usage.

   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 computation (the PCE can compute path for any
   destination area. 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 computation (the
   PCE can compute path for any destination
   AS. AS).

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

   Similarly, when the Sd bit is set the PCE-DEST-DOMAIN TLV does not comprise
   contain any AS DOMAIN sub-TLV.

   The PrefR and PrefL, PrefR, PrefS and PrefY fields are 3-bit long and allow the
   PCE to specify a preference for each computation scope, where 7
   reflects the highest preference. For the
   sake of illustration, consider the situation where N ABRs act as PCEs Such preference can be used for inter-area TE LSPs computation.
   weighted load balancing of requests. An operator may decide to
   configure a preference to each PCE that could be used so as to load balance the path
   computation load among them, 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. Same or distinct preferences may be used for
   different scopes. For instance an operator that wants a PCE capable
   of both inter-area and inter-AS computation to be used preferably for
   inter-AS computation may configure a PrefS higher than the PrefR.

   When the L bit, R bit, S or Y bit are cleared the PrefL, PrefR,
   PrefS, PrefY bit MUST respectively be set to 0.

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 is the entire routing domain.

   The PCE-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 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

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 destinations are located in within one of these domains. It
   contains a set of one or more sub-TLVs where each sub-TLV identifies
   a domain.

   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 DOMAIN sub-
   TLV. It MUST include at least one area ID sub-
   TLV, 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 it 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 PATH-
   SCOPE TLV is cleared.

5.1.5. The GENERAL-CAP sub-TLV

   The GENERAL-CAP sub-TLV is an optional TLV used to indicate general PCE PCECP
   related 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. It MAY also
   include optional sub-TLVs to encode more complex capabilities.

   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                         //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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

   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                         //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         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      G bit: Capability to compute P2P paths in MPLS-TE networks handle GMPLS contraints
      1      G      B bit: Capability to compute P2P bidirectional 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, B, D, L, S and O bits are not exclusive.

5.2. Elements of Procedure The PCED OSPF PCES TLV

   The OSPF PCE Status TLV (PCES TLV) carries information related to PCE
   processing congestion state.
   The PCES TLV is carried within an OSPF Router information opaque Information 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 OSPF PCES TLV may 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            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //                      PCE ADDRESS sub-TLV                     //
   //                     CONGESTION sub-TLV                     //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         Type     To be carried within defined by IANA (suggested value=3)
         Length   Variable
         Value    This comprises a type 10 or 11 router information
   LSA depending on the flooding scope of PCE ADDRESS sub-TLV, identifying the
                  PCE and a CONGESTION sub-TLV that contains congestion
                  information.

   If the flooding scope is local

   Sub-TLV types are under IANA control.

   Currently two sub-TLVs are defined (type values 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 assigned by
   IANA):
         Sub-TLV type  Length               Name
               1      variable     PCE-ADDRESS sub-TLV
               2         4         CONGESTION sub-TLV

   The PCE-ADDRESS and CONGESTION sub-TLVs MUST be carried
   within type 11 router information LSA.
   Note that when the L bit present once
   in a PCES TLV. The PCE-ADDRESS sub-TLV is defined in section 5.1.1.
   It carries one of the PATH-SCOPE TLV is set PCE IP addresses and is used to identify the R bit
   and S bit are cleared,
   PCE the flooding scope MUST be local, and processing congestion state information is applied to. This
   is required as the PCES and PCED
   TLV MUST TLVs may be carried within a type 10 in separate
   Router Information LSA.

   PCED TLVs are OPTIONAL. When an OSPF LSA does not contain any PCED
   TLV, this means that LSAs.

   Any non recognized sub-TLV MUST be silently ignored.

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

5.2.1. The CONGESTION sub-TLV

   The CONGESTION sub-TLV is unknown.

   Note that used to indicate whether a change in PCED information MUST PCE experiences
   a processing congestion state or not trigger normal SPF
   computation.

6. ISIS extensions

6.1. IS-IS PCED TLV format along with optionally the
   expected PCE congestion duration.
   The IS-IS PCED TLV CONGESTION sub-TLV is made of various non ordered sub-TLVs. mandatory. It MUST be carried once within
   the PCES TLV.

   The format of the IS-IS PCED TLV and its sub-TLVs CONGESTION sub-TLV 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 follows:

       0                   1 octet for the
   type,                   2                   3
       0 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 2 3 4 5 6 7 8 9 0 1      variable     PCE-ADDRESS sub-TLV 2 3 4 5 6 7 8 9 0 1 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 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |              Type             |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |C|       Reserved              |      Congestion Duration      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         Type     To be present within assigned by IANA (suggested value =2)
         Length   4

         Value
           -C bit: When set this indicates that the PCED TLV.

   The sub-TLVs PCE-DOMAINS PCE experiences
                   congestion and DEST-DOMAINS, MUST only be present cannot support any new request. When
                   cleared this indicates that the PCE does not
                   experiences congestion an can support a new request.

            -Congestion Duration: 2-bytes, the estimated PCE congestion
                                  duration in
   some particular inter-domain cases.

   The GENERAL-CAP and PATH-COMP-CAP are optional seconds.

   When C is set and MAY be present in the PCED TLV Congestion Duration field is equal to facilitate PCE selection.

   Any non recognized sub-TLV 0, this
   means that the Congestion Duration is unknown.
   When C is cleared the Congestion Duration MUST be silently ignored.

   Additional sub-TLVs could be added in the future set to advertise
   additional PCE information. 0.

5.3. Elements of Procedure

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

6.1.1. PCE-ADDRESS sub-TLV

   The PCE-ADDRESS sub-TLV specifies the IP address to be used to reach
   [OSPF-CAP]. As the PCE. This address will typically be a loop-back address that PCES information is
   always reachable, provided likely to change more
   frequently than the PCE is alive.
   The PCE-ADDRESS sub-TLV is mandatory; PCED information, 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 is RECOMMENDED to be used carry PCES
   and PCED TLVs in separate Router Information LSAs, so as not to reach carry
   all PCED information each time the PCE

   Address-type:
                  1   IPv4
                  2   IPv6

   The PCE-ADDRESS sub-TLV status changes.

5.3.1. PCED TLV Procedure

   A router MUST appear at least once in originate a new OSPF router information LSA whenever
   the content of the PCED sub-LTV
   originated TLV changes or whenever required 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
   regular OSPF procedure (LSA refresh (every LSRefreshTime)).

   The PATH-SCOPE sub-TLV indicates the PCE path computation scope; in
   other words PCED TLV may be carried within a type 10 or 11 router information
   LSA depending on the ability flooding scope of the PCE to compute or take part into information.
   If the
   computation of intra-area, inter-area, inter-AS or inter-layer_TE
   LSP(s).

   The PATH-SCOPE sub-TLV flooding scope is mandatory; local to an area then it MUST be present carried
   within a type 10 router information LSA.
   If the
   PCED TLV. There flooding scope is the entire domain then it MUST be exactly one PATH-SCOPE sub-TLV carried
   within each
   PCED TLV.

   The type 11 router information LSA.
   Note that when the L bit of the PATH-SCOPE sub-TLV contains a TLV is set of bit flags indicating and the
   supported path scopes (intra-area, inter-area, inter-AS, inter-layer) R bit
   and two fields indicating PCE preferences. 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 sub-TLVs are OPTIONAL. When an OSPF LSA does not contain
   any PCED sub-TLV, this means that the PCE information of that
   node is unknown.

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

   The way PCEs retrieve their own information is out of the scope of
   this document. Some information may be configured on the PCE (e.g.
   address, preferences, scope) and other information may be
   automatically retrieved by the PCE (e.g. areas of visibility).

5.3.2. PCES TLV procedure

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

   When a PCE enters into a processing congestion state, the conditions
   of which are implementation dependent, it SHOULD originate a Router
   Information LSA with a PCES TLV with the C bit set, and optionally a
   non-null expected congestion duration.

   When a PCE leaves the processing congestion state, the conditions of
   which are implementation dependent, there are two cases:
        - If the congestion duration in the previously originated PCES
   TLV was null, it SHOULD originate a PCES TLV with the C bit cleared
   and a null congestion duration;
        - If the congestion duration in the previously originated PCES
   TLV was non null, it MAY not originate a PCES TLV. Note that in some
   particular cases it may be desired to originate a PCES TLV with the C
   bit cleared if the saturation duration was over estimated.

   The congestion duration allows reducing the amount of OSPF flooding,
   as only uncongested-congested state transitions are flooded.

   It is expected that a proper implementation will support dampening
   algorithms so as to dampen OSPF flooding in order to not impact the
   OSPF scalability. It is recommended to introduce some hysteresis for
   saturation state transition, so as to avoid state oscillations that
   may impact OSPF performances. For instance two thresholds could be
   configured: A resource saturation upper-threshold and a resource
   saturation lower-threshold. An LSR enters the congested state when
   the CPU load reaches the upper threshold and leaves the congested
   state when the CPU load goes under the lower threshold.

   Upon receipt of an updated PCES TLV a PCC should take appropriate
   actions. In particular, the PCC should stop sending requests to a
   congested PCE, and should gradually start sending again requests to a
   no longer congested PCE. Such PCC procedures are out of the scope of
   this document.

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         3         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 PCE-DEST-DOMAINS are optional. They MUST
   be present only in some specific inter-domain cases.

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

   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 defined in
   [ISIS-CAP], whose S bit is determined by the desired flooding scope.

6.1.1. PCE-ADDRESS sub-TLV

   The PCE-ADDRESS sub-TLV specifies the IP address that MUST be used to
   reach the PCE. It is RECOMMENDED to make use of a loop-back addresse
   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 which
   refers to the PCE ability 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 four fields indicating PCE preferences.

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

   TYPE: To be assigned by IANA (Suggested value =2)
   LENGTH: Variable 3
   VALUE: This comprises a one-byte flag of bits where each bit
          represents a supported path scope, followed by a one-byte
          preference 2-bytes
          preferences field indicating PCE preferences.

   Here is the structure of the bits bit 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
   6-7          Reserved for future usage.

   Here is the structure of the preference preferences field

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

   PrefR

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |PrefL|PrefR|PrefS|PrefY| Res   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Pref-L field: PCE's preference for intra-area TE LSPs computation.

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

   PrefS computation.

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

Pref-Y field: PCE's preference for inter-layer TE LSPs computation.

Res: Reserved for future usage.

   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 computation (the PCE can compute path for any
   destination area. 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 computation (the
   PCE can compute path for any destination
   AS. AS).

   When the Rd bit is set the PCE-DEST-DOMAINS PCE-DEST-DOMAIN TLV (see 6.1.4) 5.1.4) does not
   comprise
   contain any Area ID DOMAIN sub-TLV. When

   Similarly, when the Sd bit is set the PCE-
   DEST-DOMAINS PCE-DEST-DOMAIN TLV does not comprise
   contain any AS DOMAIN sub-TLV.

   The PrefR and PrefL, PrefR, PrefS and PrefY 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. each computation scope, where 7
   reflects the highest preference. Such preference can be used for
   weighted load balancing of requests. An operator may decide to
   configure a preference to each PCE that could be used so as to load balance the path
   computation load among them, 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 document. Same or distinct preferences may be used for
   different scopes. For instance an operator that wants a PCE capable
   of both inter-area and inter-AS computation to be used preferably for
   inter-AS computation may configure a PrefS higher than the PrefR.

   When the L bit, R bit, S or Y bit are cleared the PrefL, PrefR,
   PrefS, PrefY bit MUST respectively be set to 0.

6.1.3. PCE-DOMAINS sub-TLV

   The PCE-DOMAINS sub-TLV specifies the set of domains (areas, (areas or 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:

   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 destinations are located in within one of these domains. It
   contains a set of one or more DOMAIN sub-TLVs where each DOMAIN sub-TLV sub-
   TLV identifies a domain.

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

   TYPE: To be assigned by IANA (Suggested value =2) =3)
   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 DOMAIN sub-
   TLV. It MUST include at least one area ID sub-
   TLV, 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 it MUST include at least one AS number sub-TLV if
   the S bit of the PATH-
   SCOPE PATH-SCOPE TLV is set and the Sd bit of the PATH-SCOPE PATH-
   SCOPE TLV is cleared.

6.1.5. GENERAL-CAP sub-TLV

   The GENERAL-CAP GENERAL-CAP sub-TLV is an optional TLV used to indicate PCECP
   related capabilities.
   This is a series of bits flags, where each bit corresponds to a
   general PCE capability. It MAY also include optional sub-TLVs to
   encode more complex capabilities.

   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.
      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 an optional TLV used to indicate general PCE capabilities.
   The GENERAL-CAP sub-TLV is optional. It MAY be carried within the
   PCED TLV. path
   computation specific capabilities of a PCE.
   This is a series of bits bit flags, where each bit corresponds correspond to a
   general PCE path
   computation capability. It MAY also include optional sub-TLVs to
   encode more complex capabilities.

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

      TYPE: To be assigned by IANA (Suggested (suggested value =4) = 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 general Path Computation specific PCE
             capability flags.

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

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

      G bit: Capability to handle GMPLS constraints
      B bit: Capability to compute bidirectional paths
      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.

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

6.2. The ISIS PCES TLV

   The ISIS PCE Status TLV (PCES TLV) carries information related to PCE
   processing congestion state.
   The PCES TLV is carried within an ISIS Capability TLV which is
   defined in [ISIS-CAP].

   The ISIS PCES 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 two sub-TLVs are defined (suggested type values to be
   assigned by IANA):
            Sub-TLV type  Length               Name
                1      variable     PCE-ADDRESS sub-TLV
                2         3         CONGESTION sub-TLV

   The PCE-ADDRESS and CONGESTION sub-TLVs MUST be present once
   in a PCES TLV. The PCE-ADDRESS sub-TLV is defined in section 6.1.1.
   It carries one of the PCE IP addresses and is used to identify the
   PCE the processing congestion state information is applied to. This
   is required as the PCES and PCED TLVs may 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 carried in separate
   ISIS Capability TLVs.

   Any non recognized sub-TLV MUST be silently ignored.

   Additional sub-TLVs could be added in the same request message.

   Reserved bits are for future assignment by IANA.

6.1.6. to advertise
   additional congestion information.

6.2.1. The PATH-COMP-CAP CONGESTION sub-TLV

   The PATH-COMP-CAP CONGESTION sub-TLV is used to indicate path computation
   specific capabilities of whether a PCE. PCE experiences
   a processing congestion state or not along with optionally the PCE
   expected congestion duration.
   The PATH-COMP-CAP CONGESTION sub-TLV is optional. mandatory. It MAY MUST be carried once within
   the
   PCED PCES TLV.
   This is a series of bit flags, where each bit correspond to a path
   computation capability.

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

   TYPE: To be assigned by IANA (suggested (Suggested value = 5) =2)
   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. 3
   VALUE: This comprises one or more Path Computation specific PCE
             capability flags.

   The following a one-byte flag of bits in indicating the first capability flag are to be assigned
          congestion status, followed by
   IANA.

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

      M a 2-bytes field indicating the
          congestion duration.

   Here is the TLV structure

  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |C|       Reserved|      Congestion Duration      |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         Value
           -C bit: Capability When set this indicates that the PCE experiences
                   congestion and cannot support any new request. When
                   cleared this indicates that the PCE does not
                   experiences congestion an can support a new request.

           -Congestion Duration: 2-bytes, the estimated PCE congestion
                                 duration in seconds.

   When C is set and the Congestion Duration field is equal to compute P2P paths in MPLS-TE networks
      G bit: Capability 0, this
   means that the Congestion Duration is unknown.
   When C is cleared the Congestion Duration MUST be set to compute P2P paths in GMPLS networks
      D bit: 0.

6.3. Elements of Procedure

   The PCED and PCES TLV are carried within an ISIS Capability TLV which
   is defined in [ISIS-CAP]. As PCES information is likely to compute link/node/SRLG diverse paths
      L bit: Capability change
   more frequently than the PCED information, it is RECOMMENDED to compute load-balanced paths
      S bit: carry
   PCES and PCED TLVs in separate ISIS Capability TLVs, so as not to compute
   carry all PCED information each time the PCE status changes.

6.3.1. PCED TLV Procedure

   An ISIS router MUST originate a set new ISIS LSP whenever the content
   of paths in a
             synchronized Manner
      O bit: Support for multiple objective functions

     Reserved bits are for future assignment by IANA.

6.2. Elements any of the PCED TLV changes or whenever required by the regular
   ISIS procedure

   The (LSP refresh).

   When the scope of the PCED TLV is area local it MUST be carried
   within an IS-IS 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 defined in
   [IS-IS-CAP]. having the S bit set.
   Note that when only the L bit of the PATH-SCOPE sub-TLV is set and
   the flooding scope MUST be local.

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

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

   The way PCEs retrieve their own information is out of the scope of
   this document. Some information may be configured (e.g. address,
   preferences, scope) and other information may be automatically
   retrieved (e.g. areas of visibility).

6.3.2. PCES TLV procedure

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

   When a PCE enters into a processing congestion state, the scope conditions
   of the PCED TLV is area local which are implementation dependent, it MUST be carried
   within an SHOULD originate a new ISIS CAPABILITY
   LSP with a Capability TLV having carrying a PCES TLV with the S C bit cleared. set and
   optionally a non-null expected congestion duration.

   When a PCE leaves the scope of processing congestion state, the PCED TLV is conditions of
   which are implementation dependent, there are two cases:
        - If the entire domain, congestion duration in the PCED previously originated PCES
   TLV
   MUST be carried within an ISIS CAPABILITY was null, it SHOULD originate a PCES TLV having with the S C bit set. cleared
   and a null congestion duration;
        - If the congestion duration in the previously originated PCES
   TLV was non null, it MAY not originate a PCES TLV. Note that when in some
   particular cases it may be desired to originate a PCES TLV with the L C
   bit cleared if the saturation duration was over estimated.

   The congestion duration allows reducing the amount of ISIS flooding,
   as only uncongested-congested state transitions are flooded.

   It is expected that a proper implementation will support dampening
   algorithms so as to dampen ISIS flooding in order to not impact the PATH-SCOPE sub-TLV
   ISIS scalability. It is set recommended to introduce some hysteresis for
   congestion state transition, so as to avoid state oscillations that
   may impact ISIS performances. For instance two thresholds could be
   configured: A resource saturation upper-threshold and a resource
   saturation lower-threshold. An LSR enters the R congested state when
   the CPU load reaches the upper threshold and S bits are cleared leaves the flooding scope MUST be local.

   PCED TLVs are OPTIONAL. When an IS-IS LSP does not contain any PCED
   TLV, this means that congested
   state when the PCE information CPU load goes under the lower threshold.

   Upon receipt of that node is unknown.

   Note that an updated PCES TLV a change in PCED information MUST not trigger normal SPF
   computation. PCC should take appropriate
   actions. In particular, the PCC should stop sending requests to a
   congested PCE, and should gradually start sending again requests to a
   no longer congested PCE. Such PCC procedures are out of the scope of
   this document.

7. Backward compatibility

   The PCED and PCEs TLVs defined in this document do not introduce any
   interoperability issue.
   For OSPF, a router not supporting the PCED
   TLV PCED/PCES TLVs SHOULD just
   silently ignore the TLV TLVs as specified in RFC2370. [RFC2370].

   For
   IS-IS ISIS a router not supporting the PCED TLV PCED/PCES TLVs SHOULD just
   silently ignore the TLV.

8. Security Considerations

   No new security issues are raised in this document.

9. IANA considerations

9.1.

8.1. 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)

   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.

   IANA will assign a new codepoint for the OSPF PCES TLV defined in
   this document and carried within the Router Information LSA.
   Two sub-TLVs types are defined for this TLV and should be assigned by
   IANA:
        -PCE-ADDRESS sub-TLV (suggested value = 1)
        -CONGESTION sub-TLV (suggested value = 2)

8.2. 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
        -PCE-DEST-DOMAINS sub-TLV (suggested value = 3)
        -GENERAL-CAP
        -PCE-DOMAINS sub-TLV (suggested value = 4)
        -PATH-COMP-CAP
        -GENERAL-CAP sub-TLV (suggested value = 5)
        -PATH-COMP-CAP sub-TLV (suggested value = 6)

   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.

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

   Two sub-TLVs types are defined for this TLV and should be assigned by
   IANA:
        -PCE-ADDRESS sub-TLV (suggested value = 1)
        -CONGESTION sub-TLV (suggested value = 2)

8.3. 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 handle GMPLS Constraints
      -1: Capability to compute P2P bidirectional 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

10.

9. Security Considerations

   No new security issues are raised

   To be completed in this document.

11. further revisions.

10. References

11.1.

10.1. Normative 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.

   [BCP79] Bradner, S., "Intellectual Property Rights in IETF
   Technology", RFC 3979, March 2005.

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

   [RFC2370] Coltun, R., “The OSPF Opaque LSA Option”, RFC 2370, July
   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.

10.2. 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.

   [PCE-COM-REQ]

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

12.

   [PCEP] Vasseur et al., “Path Computation Element (PCE) communication
   Protocol (PCEP) - Version 1”, draft-ietf-pce-pcep-01.txt, work in
   progress.

11. Authors' Addresses:

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

   Jean-Philippe Vasseur (Editor)
   Cisco Systems, Inc.
   300 Beaver Brook Road
   1414 Massachusetts avenue
   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.

   Raymond Zhang
   BT Infonet
   2160 E. Grand Ave.
   El Segundo, CA 90025
   USA
   Email: raymond_zhang@infonet.com

12. 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.

   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,
   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

   Copyright Statement
   Copyright (C) The Internet Society (2005). (2006).  This document is subject
   to the rights, licenses and restrictions contained in BCP 78, and
   except as set forth therein, the authors retain all their rights.