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Versions: (draft-dhodylee-pce-pcep-te-data-extn) 00 01 02 03 04 05 06 07 08 09 10 11

PCE Working Group                                               D. Dhody
Internet-Draft                                                    Y. Lee
Intended status: Standards Track                     Huawei Technologies
Expires: December 23, 2018                                 D. Ceccarelli
                                                                Ericsson
                                                           June 21, 2018


   PCEP Extension for Distribution of Link-State and TE Information.
                     draft-dhodylee-pce-pcep-ls-11

Abstract

   In order to compute and provide optimal paths, Path Computation
   Elements (PCEs) require an accurate and timely Traffic Engineering
   Database (TED).  Traditionally this TED has been obtained from a link
   state (LS) routing protocol supporting traffic engineering
   extensions.

   This document extends the Path Computation Element Communication
   Protocol (PCEP) with Link-State and TE Information.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on December 23, 2018.





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Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Applicability . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Requirements for PCEP extension . . . . . . . . . . . . . . .   6
   5.  New Functions to distribute link-state (and TE) via PCEP  . .   7
   6.  Overview of Extension to PCEP . . . . . . . . . . . . . . . .   7
     6.1.  New Messages  . . . . . . . . . . . . . . . . . . . . . .   7
     6.2.  Capability Advertisement  . . . . . . . . . . . . . . . .   8
     6.3.  Initial Link-State (and TE) Synchronization . . . . . . .   8
       6.3.1.  Optimizations for LS Synchronization  . . . . . . . .  11
     6.4.  LS Report . . . . . . . . . . . . . . . . . . . . . . . .  11
   7.  Transport . . . . . . . . . . . . . . . . . . . . . . . . . .  11
   8.  PCEP Messages . . . . . . . . . . . . . . . . . . . . . . . .  12
     8.1.  LS Report Message . . . . . . . . . . . . . . . . . . . .  12
     8.2.  The PCErr Message . . . . . . . . . . . . . . . . . . . .  12
   9.  Objects and TLV . . . . . . . . . . . . . . . . . . . . . . .  13
     9.1.  TLV Format  . . . . . . . . . . . . . . . . . . . . . . .  13
     9.2.  Open Object . . . . . . . . . . . . . . . . . . . . . . .  13
       9.2.1.  LS Capability TLV . . . . . . . . . . . . . . . . . .  13
     9.3.  LS Object . . . . . . . . . . . . . . . . . . . . . . . .  14
       9.3.1.  Routing Universe TLV  . . . . . . . . . . . . . . . .  16
       9.3.2.  Route Distinguisher TLV . . . . . . . . . . . . . . .  17
       9.3.3.  Virtual Network TLV . . . . . . . . . . . . . . . . .  17
       9.3.4.  Local Node Descriptors TLV  . . . . . . . . . . . . .  18
       9.3.5.  Remote Node Descriptors TLV . . . . . . . . . . . . .  18
       9.3.6.  Node Descriptors Sub-TLVs . . . . . . . . . . . . . .  19
       9.3.7.  Link Descriptors TLV  . . . . . . . . . . . . . . . .  20
       9.3.8.  Prefix Descriptors TLV  . . . . . . . . . . . . . . .  21
       9.3.9.  PCEP-LS Attributes  . . . . . . . . . . . . . . . . .  22
         9.3.9.1.  Node Attributes TLV . . . . . . . . . . . . . . .  22
         9.3.9.2.  Link Attributes TLV . . . . . . . . . . . . . . .  22



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         9.3.9.3.  Prefix Attributes TLV . . . . . . . . . . . . . .  24
       9.3.10. Removal of an Attribute . . . . . . . . . . . . . . .  25
   10. Other Considerations  . . . . . . . . . . . . . . . . . . . .  25
     10.1.  Inter-AS Links . . . . . . . . . . . . . . . . . . . . .  25
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  25
   12. Manageability Considerations  . . . . . . . . . . . . . . . .  26
     12.1.  Control of Function and Policy . . . . . . . . . . . . .  26
     12.2.  Information and Data Models  . . . . . . . . . . . . . .  26
     12.3.  Liveness Detection and Monitoring  . . . . . . . . . . .  27
     12.4.  Verify Correct Operations  . . . . . . . . . . . . . . .  27
     12.5.  Requirements On Other Protocols  . . . . . . . . . . . .  27
     12.6.  Impact On Network Operations . . . . . . . . . . . . . .  27
   13. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  27
     13.1.  PCEP Messages  . . . . . . . . . . . . . . . . . . . . .  27
     13.2.  PCEP Objects . . . . . . . . . . . . . . . . . . . . . .  28
     13.3.  LS Object  . . . . . . . . . . . . . . . . . . . . . . .  28
     13.4.  PCEP-Error Object  . . . . . . . . . . . . . . . . . . .  29
     13.5.  PCEP TLV Type Indicators . . . . . . . . . . . . . . . .  29
     13.6.  PCEP-LS Sub-TLV Type Indicators  . . . . . . . . . . . .  30
   14. TLV/Sub-TLV Code Points Summary . . . . . . . . . . . . . . .  32
   15. Implementation Status . . . . . . . . . . . . . . . . . . . .  33
     15.1.  Hierarchical Transport PCE controllers . . . . . . . . .  33
     15.2.  ONOS-based Controller (MDSC and PNC) . . . . . . . . . .  33
   16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  33
   17. References  . . . . . . . . . . . . . . . . . . . . . . . . .  34
     17.1.  Normative References . . . . . . . . . . . . . . . . . .  34
     17.2.  Informative References . . . . . . . . . . . . . . . . .  35
   Appendix A.  Reusing BGP-LS codepoints  . . . . . . . . . . . . .  38
   Appendix B.  Relevant OSPF TLV and sub-TLV  . . . . . . . . . . .  38
   Appendix C.  Examples . . . . . . . . . . . . . . . . . . . . . .  39
     C.1.  All Nodes . . . . . . . . . . . . . . . . . . . . . . . .  39
     C.2.  Designated Node . . . . . . . . . . . . . . . . . . . . .  41
     C.3.  Between PCEs  . . . . . . . . . . . . . . . . . . . . . .  41
   Appendix D.  Contributor Addresses  . . . . . . . . . . . . . . .  43
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  43

1.  Introduction

   In Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS),
   a Traffic Engineering Database (TED) is used in computing paths for
   connection oriented packet services and for circuits.  The TED
   contains all relevant information that a Path Computation Element
   (PCE) needs to perform its computations.  It is important that the
   TED be complete and accurate each time, the PCE performs a path
   computation.

   In MPLS and GMPLS, interior gateway routing protocols (IGPs) have
   been used to create and maintain a copy of the TED at each node



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   running the IGP.  One of the benefits of the PCE architecture
   [RFC4655] is the use of computationally more sophisticated path
   computation algorithms and the realization that these may need
   enhanced processing power not necessarily available at each node
   participating in an IGP.

   Section 4.3 of [RFC4655] describes the potential load of the TED on a
   network node and proposes an architecture where the TED is maintained
   by the PCE rather than the network nodes.  However, it does not
   describe how a PCE would obtain the information needed to populate
   its TED.  PCE may construct its TED by participating in the IGP
   ([RFC3630]  and [RFC5305]  for MPLS-TE; [RFC4203]  and [RFC5307] for
   GMPLS).  An alternative is offered by BGP-LS [RFC7752] .

   [RFC8231] describes a set of extensions to PCEP to provide stateful
   control.  A stateful PCE has access to not only the information
   carried by the network's Interior Gateway Protocol (IGP), but also
   the set of active paths and their reserved resources for its
   computations.  PCC can delegate the rights to modify the LSP
   parameters to an Active Stateful PCE.  This requires PCE to quickly
   be updated on any changes in the Topology and TEDB, so that PCE can
   meet the need for updating LSPs effectively and in a timely manner.
   The fastest way for a PCE to be updated on TED changes is via a
   direct interface with each network node and with incremental update
   from each network node with only the attribute that is modified.

   [RFC8281] describes the setup, maintenance and teardown of PCE-
   initiated LSPs under the stateful PCE model, without the need for
   local configuration on the PCC, thus allowing for a dynamic network
   that is centrally controlled and deployed.  This model requires
   timely topology and TED update at the PCE.

   [RFC5440] describes the specifications for the Path Computation
   Element Communication Protocol (PCEP).  PCEP specifies the
   communication between a Path Computation Client (PCC) and a Path
   Computation Element (PCE), or between two PCEs based on the PCE
   architecture [RFC4655].

   This document describes a mechanism by which Link State and TE
   information can be collected from networks and shared with PCE using
   the PCEP itself.  This is achieved using a new PCEP message format.
   The mechanism is applicable to physical and virtual links as well as
   further subjected to various policies.

   A network node maintains one or more databases for storing link-state
   and TE information about nodes and links in any given area.  Link
   attributes stored in these databases include: local/remote IP
   addresses, local/ remote interface identifiers, link metric and TE



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   metric, link bandwidth, reservable bandwidth, per CoS class
   reservation state, preemption and Shared Risk Link Groups (SRLG).
   The node's PCEP process can retrieve topology from these databases
   and distribute it to a PCE, either directly or via another PCEP
   Speaker, using the encoding specified in this document.

   Further [RFC6805] describes Hierarchical-PCE architecture, where a
   parent PCE maintains a domain topology map.  To build this domain
   topology map, the child PCE can carry the border nodes and inter-
   domain link information to the parent PCE using the mechanism
   described in this document.  Further as described in
   [I-D.ietf-pce-applicability-actn], the child PCE can also transport
   abstract Link-State and TE information from child PCE to a Parent PCE
   using the mechanism described in this document to build an abstract
   topology at the parent PCE.

   [RFC8231] describe LSP state synchronization between PCCs and PCEs in
   case of stateful PCE.  This document does not make any change to the
   LSP state synchronization process.  The mechanism described in this
   document are on top of the existing LSP state synchronization.

2.  Terminology

   The terminology is as per [RFC4655] and [RFC5440].

3.  Applicability

   The mechanism specified in this draft is applicable to deployments:

   o  Where there is no IGP or BGP-LS running in the network.

   o  Where there is no IGP or BGP-LS running at the PCE to learn link-
      state and TE information.

   o  Where there is IGP or BGP-LS running but with a need for a faster
      TE and link-state population and convergence at the PCE.

      *  A PCE may receive partial information (say basic TE, link-
         state) from IGP and other information (optical and impairment)
         from PCEP.

      *  A PCE may receive an incremental update (as opposed to the
         entire information of the node/link).

      *  A PCE may receive full information from both existing mechanism
         (IGP or BGP) and PCEP.





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   o  Where there is a need for transporting (abstract) Link-State and
      TE information from child PCE to a Parent PCE in H-PCE [RFC6805];
      as well as for Provisioning Network Controller (PNC) to Multi-
      Domain Service Coordinator (MDSC) in Abstraction and Control of TE
      Networks (ACTN) [I-D.ietf-teas-actn-framework].

   o  Where there is an existing PCEP session between the nodes and the
      PCE-based central controller [RFC8283], and the operator would
      like to use a single protocol between the controller and the
      nodes.

   A PCC may further choose to send only local information or both local
   and remote learned information.

   How a PCE manages the link-state (and TE) information is
   implementation specific and thus out of scope of this document.

   The prefix information in PCEP-LS can also help in determining the
   domain of the endpoints in H-PCE (and ACTN).  Section 4.5 of
   [RFC6805] describe various mechanism and procedures that might be
   used, PCEP-LS provides a simple mechanism to exchange this
   information within PCEP.  [I-D.ietf-teas-actn-framework] defines
   three types of topology abstraction - (1) Native/White Topology; (2)
   Black Topology; and (3) Grey Topology.  Based on the local policy,
   the PNC (or child PCE) would share the domain topology to the MDSC
   (or Parent PCE) based on the abstraction type.  The protocol
   extention defined in this document can carry any type of topology
   abstraction.

4.  Requirements for PCEP extension

   Following key requirements associated with link-state (and TE)
   distribution are identified for PCEP:

   1.  The PCEP speaker supporting this draft MUST be a mechanism to
       advertise the Link-State (and TE) distribution capability.

   2.  PCC supporting this draft MUST have the capability to report the
       link-state (and TE) information to the PCE.  This includes self
       originated information and remote information learned via routing
       protocols.  PCC MUST be capable to do the initial bulk sync at
       the time of session initialization as well as changes after.

   3.  A PCE MAY learn link-state (and TE) from PCEP as well as from
       existing mechanism like IGP/BGP-LS.  PCEP extension MUST have a
       mechanism to link the information learned via other means.  There
       MUST NOT be any changes to the existing link-state (and TE)
       population mechanism via IGP/BGP-LS.  PCEP extension SHOULD keep



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       the properties in a protocol (IGP or BGP-LS) neutral way, such
       that an implementation may not need to know about any OSPF or IS-
       IS or BGP protocol specifics.

   4.  It SHOULD be possible to encode only the changes in link-state
       (and TE) properties (after the initial sync) in PCEP messages.

   5.  The same mechanism should be used for both MPLS TE as well as
       GMPLS, optical and impairment aware properties.

   6.  The same mechanism should be used for PCE to PCE Link-state (and
       TE) synchronization.

5.  New Functions to distribute link-state (and TE) via PCEP

   Several new functions are required in PCEP to support distribution of
   link-state (and TE) information.  A function can be initiated either
   from a PCC towards a PCE (C-E) or from a PCE towards a PCC (E-C).
   The new functions are:

   o  Capability advertisement (E-C,C-E): both the PCC and the PCE MUST
      announce during PCEP session establishment that they support PCEP
      extensions for distribution of link-state (and TE) information
      defined in this document.

   o  Link-State (and TE) synchronization (C-E): after the session
      between the PCC and a PCE is initialized, the PCE must learn Link-
      State (and TE) information before it can perform path
      computations.  In case of stateful PCE it is RECOMENDED that this
      operation be done before LSP state synchronization.

   o  Link-State (and TE) Report (C-E): a PCC sends a LS (and TE) report
      to a PCE whenever the Link-State and TE information changes.

6.  Overview of Extension to PCEP

6.1.  New Messages

   In this document, we define a new PCEP messages called LS Report
   (LSRpt), a PCEP message sent by a PCC to a PCE to report link-state
   (and TE) information.  Each LS Report in a LSRpt message can contain
   the node or link properties.  An unique PCEP specific LS identifier
   (LS-ID) is also carried in the message to identify a node or link and
   that remains constant for the lifetime of a PCEP session.  This
   identifier on its own is sufficient when no IGP or BGP-LS running in
   the network for PCE to learn link-state (and TE) information.  Incase
   PCE learns some information from PCEP and some from the existing
   mechanism, the PCC SHOULD include the mapping of IGP or BGP-LS



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   identifier to map the information populated via PCEP with IGP/BGP-LS.
   See Section 8.1 for details.

6.2.  Capability Advertisement

   During PCEP Initialization Phase, PCEP Speakers (PCE or PCC)
   advertise their support of LS (and TE) distribution via PCEP
   extensions.  A PCEP Speaker includes the "LS Capability" TLV,
   described in Section 9.2.1, in the OPEN Object to advertise its
   support for PCEP-LS extensions.  The presence of the LS Capability
   TLV in PCC's OPEN Object indicates that the PCC is willing to send LS
   Reports whenever local link-state (and TE) information changes.  The
   presence of the LS Capability TLV in PCE's OPEN message indicates
   that the PCE is interested in receiving LS Reports whenever local
   link-state (and TE) information changes.

   The PCEP extensions for LS (and TE) distribution MUST NOT be used if
   one or both PCEP Speakers have not included the LS Capability TLV in
   their respective OPEN message.  If the PCE that supports the
   extensions of this draft but did not advertise this capability, then
   upon receipt of a LSRpt message from the PCC, it SHOULD generate a
   PCErr with error-type 19 (Invalid Operation), error-value TBD1
   (Attempted LS Report if LS capability was not advertised) and it will
   terminate the PCEP session.

   The LS reports sent by PCC MAY carry the remote link-state (and TE)
   information learned via existing means like IGP and BGP-LS only if
   both PCEP Speakers set the R (remote) Flag in the "LS Capability" TLV
   to 'Remote Allowed (R Flag = 1)'.  If this is not the case and LS
   reports carry remote link-state (and TE) information, then a PCErr
   with error-type 19 (Invalid Operation) and error-value TBD1
   (Attempted LS Report if LS remote capability was not advertised) and
   it will terminate the PCEP session.

6.3.  Initial Link-State (and TE) Synchronization

   The purpose of LS Synchronization is to provide a checkpoint-in- time
   state replica of a PCC's link-state (and TE) data base in a PCE.
   State Synchronization is performed immediately after the
   Initialization phase (see [RFC5440]).  In case of stateful PCE
   ([RFC8231]) it is RECOMENDED that the LS synchronization should be
   done before LSP state synchronization.

   During LS Synchronization, a PCC first takes a snapshot of the state
   of its database, then sends the snapshot to a PCE in a sequence of LS
   Reports.  Each LS Report sent during LS Synchronization has the SYNC
   Flag in the LS Object set to 1.  The end of synchronization marker is
   a LSRpt message with the SYNC Flag set to 0 for an LS Object with LS-



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   ID equal to the reserved value 0.  If the PCC has no link-state to
   synchronize, it will only send the end of synchronization marker.

   Either the PCE or the PCC MAY terminate the session using the PCEP
   session termination procedures during the synchronization phase.  If
   the session is terminated, the PCE MUST clean up state it received
   from this PCC.  The session re-establishment MUST be re-attempted per
   the procedures defined in [RFC5440], including use of a back-off
   timer.

   If the PCC encounters a problem which prevents it from completing the
   LS synchronization, it MUST send a PCErr message with error-type TBD2
   (LS Synchronization Error) and error-value 2 (indicating an internal
   PCC error) to the PCE and terminate the session.

   The PCE does not send positive acknowledgments for properly received
   LS synchronization messages.  It MUST respond with a PCErr message
   with error-type TBD2 (LS Synchronization Error) and error-value 1
   (indicating an error in processing the LSRpt) if it encounters a
   problem with the LS Report it received from the PCC and it MUST
   terminate the session.

   The LS reports can carry local as well as remote link-state (and TE)
   information depending on the R flag in LS capability TLV.

   The successful LS Synchronization sequences is shown in Figure 1.

























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         +-+-+                    +-+-+
         |PCC|                    |PCE|
         +-+-+                    +-+-+
           |                        |
           |-----LSRpt, SYNC=1----->| (Sync start)
           |                        |
           |-----LSRpt, SYNC=1----->|
           |            .           |
           |            .           |
           |            .           |
           |-----LSRpt, SYNC=1----->|
           |            .           |
           |            .           |
           |            .           |
           |                        |
           |-----LSRpt, SYNC=0----->| (End of sync marker
           |                        |  LS Report
           |                        |  for LS-ID=0)
           |                        | (Sync done)


                  Figure 1: Successful LS synchronization

   The sequence where the PCE fails during the LS Synchronization phase
   is shown in Figure 2.

         +-+-+                    +-+-+
         |PCC|                    |PCE|
         +-+-+                    +-+-+
           |                        |
           |-----LSRpt, SYNC=1----->|
           |                        |
           |-----LSRpt, SYNC=1----->|
           |            .           |
           |            .           |
           |            .           |
           |-----LSRpt, SYNC=1----->|
           |                        |
           |---LSRpt,SYNC=1         |
           |         \    ,-PCErr---|
           |          \  /          |
           |           \/           |
           |           /\           |
           |          /   `-------->| (Ignored)
           |<--------`              |


             Figure 2: Failed LS synchronization (PCE failure)



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   The sequence where the PCC fails during the LS Synchronization phase
   is shown in Figure 3.

         +-+-+                    +-+-+
         |PCC|                    |PCE|
         +-+-+                    +-+-+
           |                        |
           |-----LSRpt, SYNC=1----->|
           |                        |
           |-----LSRpt, SYNC=1----->|
           |            .           |
           |            .           |
           |            .           |
           |-------- PCErr--------->|
           |                        |


             Figure 3: Failed LS synchronization (PCC failure)

6.3.1.  Optimizations for LS Synchronization

   These optimizations are described in
   [I-D.kondreddy-pce-pcep-ls-sync-optimizations].

6.4.  LS Report

   The PCC MUST report any changes in the link-state (and TE)
   information to the PCE by sending a LS Report carried on a LSRpt
   message to the PCE.  Each node and Link would be uniquely identified
   by a PCEP LS identifier (LS-ID).  The LS reports may carry local as
   well as remote link-state (and TE) information depending on the R
   flag in LS capability TLV.  In case R flag is set, It MAY also
   include the mapping of IGP or BGP-LS identifier to map the
   information populated via PCEP with IGP/BGP-LS.

   More details about LSRpt message are in Section 8.1.

7.  Transport

   A permanent PCEP session MUST be established between a PCE and PCC
   supporting link-state (and TE) distribution via PCEP.  In the case of
   session failure, session re-establishment MUST be re-attempted per
   the procedures defined in [RFC5440].








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8.  PCEP Messages

   As defined in [RFC5440], a PCEP message consists of a common header
   followed by a variable-length body made of a set of objects that can
   be either mandatory or optional.  An object is said to be mandatory
   in a PCEP message when the object must be included for the message to
   be considered valid.  For each PCEP message type, a set of rules is
   defined that specify the set of objects that the message can carry.
   An implementation MUST form the PCEP messages using the object
   ordering specified in this document.

8.1.  LS Report Message

   A PCEP LS Report message (also referred to as LSRpt message) is a
   PCEP message sent by a PCC to a PCE to report the link-state (and TE)
   information.  A LSRpt message can carry more than one LS Reports.
   The Message-Type field of the PCEP common header for the LSRpt
   message is set to [TBD3].

   The format of the LSRpt message is as follows:

   <LSRpt Message> ::= <Common Header>
                       <ls-report-list>
   Where:

   <ls-report-list> ::= <LS>[<ls-report-list>]


   The LS object is a mandatory object which carries LS information of a
   node or a link.  Each LS object has an unique LS-ID as described in
   Section 9.3.  If the LS object is missing, the receiving PCE MUST
   send a PCErr message with Error-type=6 (Mandatory Object missing) and
   Error-value=[TBD4] (LS object missing).

   A PCE may choose to implement a limit on the LS information a single
   PCC can populate.  If a LSRpt is received that causes the PCE to
   exceed this limit, it MUST send a PCErr message with error-type 19
   (invalid operation) and error-value 4 (indicating resource limit
   exceeded) in response to the LSRpt message triggering this condition
   and SHOULD terminate the session.

8.2.  The PCErr Message

   If a PCEP speaker has advertised the LS capability on the PCEP
   session, the PCErr message MAY include the LS object.  If the error
   reported is the result of an LS report, then the LS-ID number MUST be
   the one from the LSRpt that triggered the error.




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   The format of a PCErr message from [RFC5440] is extended as follows:

   The format of the PCErr message is as follows:

   <PCErr Message> ::= <Common Header>
                     ( <error-obj-list> [<Open>] ) | <error>
                     [<error-list>]

   <error-obj-list>::=<PCEP-ERROR>[<error-obj-list>]

   <error>::=[<request-id-list> | <ls-id-list>]
              <error-obj-list>

   <request-id-list>::=<RP>[<request-id-list>]

   <ls-id-list>::=<LS>[<ls-id-list>]

   <error-list>::=<error>[<error-list>]

9.  Objects and TLV

   The PCEP objects defined in this document are compliant with the PCEP
   object format defined in [RFC5440].  The P flag and the I flag of the
   PCEP objects defined in this document MUST always be set to 0 on
   transmission and MUST be ignored on receipt since these flags are
   exclusively related to path computation requests.

9.1.  TLV Format

   The TLV and the sub-TLV format (and padding) in this document, is as
   per section 7.1 of [RFC5440].

9.2.  Open Object

   This document defines a new optional TLV for use in the OPEN Object.

9.2.1.  LS Capability TLV

   The LS-CAPABILITY TLV is an optional TLV for use in the OPEN Object
   for link-state (and TE) distribution via PCEP capability
   advertisement.  Its format is shown in the following figure:










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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Type=[TBD5]     |            Length=4           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Flags                           |R|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The type of the TLV is [TBD5] and it has a fixed length of 4 octets.

   The value comprises a single field - Flags (32 bits):

   o  R (remote allowed - 1 bit): if set to 1 by a PCC, the R Flag
      indicates that the PCC allows reporting of remote LS information
      learned via other means like IGP and BGP-LS; if set to 1 by a PCE,
      the R Flag indicates that the PCE is capable of receiving remote
      LS information (from the PCC point of view).  The R Flag must be
      advertised by both a PCC and a PCE for LSRpt messages to report
      remote as well as local LS information on a PCEP session.  The
      TLVs related to IGP/BGP-LS identifier MUST be encoded when both
      PCEP speakers have the R Flag set.

   Unassigned bits are considered reserved.  They MUST be set to 0 on
   transmission and MUST be ignored on receipt.

   Advertisement of the LS capability implies support of local link-
   state (and TE) distribution, as well as the objects, TLVs and
   procedures defined in this document.

9.3.  LS Object

   The LS (link-state) object MUST be carried within LSRpt messages and
   MAY be carried within PCErr messages.  The LS object contains a set
   of fields used to specify the target node or link.  It also contains
   a flag indicating to a PCE that the LS synchronization is in
   progress.  The TLVs used with the LS object correlate with the IGP/
   BGP-LS encodings.

   LS Object-Class is [TBD6].

   Four Object-Type values are defined for the LS object so far:

   o  LS Node: LS Object-Type is 1.

   o  LS Link: LS Object-Type is 2.

   o  LS IPv4 Topology Prefix: LS Object-Type is 3.




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   o  LS IPv6 Topology Prefix: LS Object-Type is 4.

   The format of all types of LS object 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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Protocol-ID  |          Flag                             |R|S|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                          LS-ID                                |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     //                         TLVs                                //
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Protocol-ID (8-bit): The field provide the source information.  The
   protocol could be an IGP, BGP-LS or an abstraction algorithm.  Incase
   PCC only provides local information of the PCC, it MUST use Protocol-
   ID as Direct.  The following values are defined (some of them are
   same as [RFC7752]):

            +-------------+----------------------------------+
            | Protocol-ID | Source protocol                  |
            +-------------+----------------------------------+
            |      1      | IS-IS Level 1                    |
            |      2      | IS-IS Level 2                    |
            |      3      | OSPFv2                           |
            |      4      | Direct                           |
            |      5      | Static configuration             |
            |      6      | OSPFv3                           |
            |      7      | BGP                              |
            |      8      | PCEP                             |
            |      9      | Abstraction                      |
            |      10     | Unspecified                      |
            +-------------+----------------------------------+

   Flags (24-bit):

   o  S (SYNC - 1 bit): the S Flag MUST be set to 1 on each LSRpt sent
      from a PCC during LS Synchronization.  The S Flag MUST be set to 0
      in other LSRpt messages sent from the PCC.

   o  R (Remove - 1 bit): On LSRpt messages the R Flag indicates that
      the node/link/prefix has been removed from the PCC and the PCE
      SHOULD remove from its database.  Upon receiving an LS Report with
      the R Flag set to 1, the PCE SHOULD remove all state for the




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      node/link/prefix identified by the LS Identifiers from its
      database.

   LS-ID(64-bit): A PCEP-specific identifier for the node or link or
   prefix information.  A PCC creates an unique LS-ID for each
   node/link/prefix that is constant for the lifetime of a PCEP session.
   The PCC will advertise the same LS-ID on all PCEP sessions it
   maintains at a given times.  All subsequent PCEP messages then
   address the node/link/prefix by the LS-ID.  The values of 0 and
   0xFFFFFFFFFFFFFFFF are reserved.

   Unassigned bits are considered reserved.  They MUST be set to 0 on
   transmission and MUST be ignored on receipt.

   TLVs that may be included in the LS Object are described in the
   following sections.

9.3.1.  Routing Universe TLV

   In case of remote link-state (and TE) population when existing IGP/
   BGP-LS are also used, OSPF and IS-IS may run multiple routing
   protocol instances over the same link as described in [RFC7752].  See
   [RFC8202] and [RFC6549] for more information.  These instances define
   independent "routing universes".  The 64-Bit 'Identifier' field is
   used to identify the "routing universe" where the LS object belongs.
   The LS objects representing IGP objects (nodes or links or prefix)
   from the same routing universe MUST have the same 'Identifier' value;
   LS objects with different 'Identifier' values MUST be considered to
   be from different routing universes.

   The format of the optional ROUTING-UNIVERSE TLV is shown in the
   following figure:

      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=[TBD7]         |           Length=8            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           Identifier                          |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Below table lists the 'Identifier' values that are defined as well-
   known in this draft (same as [RFC7752]).







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            +------------+-----------------------------------+
            | Identifier | Routing Universe                  |
            +------------+-----------------------------------+
            |     0      | Default Layer 3 Routing topology  |
            +------------+-----------------------------------+

   If this TLV is not present the default value 0 is assumed.

9.3.2.  Route Distinguisher TLV

   To allow identification of VPN link, node and prefix information in
   PCEP-LS, a Route Distinguisher (RD) [RFC4364] is used.  The LS
   objects from the same VPN MUST have the same RD; LS objects with
   different RD values MUST be considered to be from different VPNs.

   The format of the optional ROUTE-DISTINGUISHER TLV is shown in the
   following figure:

      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=[TBD15]        |           Length=8            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                     Route Distinguisher                       |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The format of RD is as per [RFC4364].

9.3.3.  Virtual Network TLV

   To realize ACTN, the MDSC needs to build an multi-domain topology.
   This topology is best served, if this is an abstracted view of the
   underlying network resources of each domain.  It is also important to
   provide a customer view of network slice for each customer.  There is
   a need to control the level of abstraction based on the deployment
   scenario and business relationship between the controllers.

   Virtual service coordination function in ACTN incorporates customer
   service-related knowledge into the virtual network operations in
   order to seamlessly operate virtual networks while meeting customer's
   service requirements.  [I-D.ietf-teas-actn-requirements] describes
   various VN operations initiated by a customer/application.  In this
   context, there is a need for associating the abstracted link state
   and TE topology with a VN "construct" to facilitate VN operations in
   PCE architecture.





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   VIRTUAL-NETWORK-TLV as per [I-D.leedhody-pce-vn-association] can be
   included in LS object to identify the link, node and prefix
   information belongs to a particular VN.

9.3.4.  Local Node Descriptors TLV

   As described in [RFC7752], each link is anchored by a pair of Router-
   IDs that are used by the underlying IGP, namely, 48 Bit ISO System-ID
   for IS-IS and 32 bit Router-ID for OSPFv2 and OSPFv3.  Incase of
   additional auxiliary Router-IDs used for TE, these MUST also be
   included in the link attribute TLV (see Section 9.3.9.2).

   It is desirable that the Router-ID assignments inside the Node
   Descriptor are globally unique.  Some considerations for globally
   unique Node/Link/Prefix identifiers are described in [RFC7752].

   The Local Node Descriptors TLV contains Node Descriptors for the node
   anchoring the local end of the link.  This TLV MUST be included in
   the LS Report when during a given PCEP session a node/link/prefix is
   first reported to a PCE.  A PCC sends to a PCE the first LS Report
   either during State Synchronization, or when a new node/link/prefix
   is learned at the PCC.  The value contains one or more Node
   Descriptor Sub-TLVs, which allows specification of a flexible key for
   any given node/link/prefix information such that global uniqueness of
   the node/link/prefix is ensured.

   This TLV is applicable for all LS Object-Type.

      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=[TBD8]         |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     //              Node Descriptor Sub-TLVs (variable)            //
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The value contains one or more Node Descriptor Sub-TLVs defined in
   Section 9.3.6.

9.3.5.  Remote Node Descriptors TLV

   The Remote Node Descriptors contains Node Descriptors for the node
   anchoring the remote end of the link.  This TLV MUST be included in
   the LS Report when during a given PCEP session a link is first
   reported to a PCE.  A PCC sends to a PCE the first LS Report either
   during State Synchronization, or when a new link is learned at the



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   PCC.  The length of this TLV is variable.  The value contains one or
   more Node Descriptor Sub-TLVs defined in Section 9.3.6.

   This TLV is applicable for LS Link Object-Type.

      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=[TBD9]         |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     //              Node Descriptor Sub-TLVs (variable)            //
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

9.3.6.  Node Descriptors Sub-TLVs

   The Node Descriptor Sub-TLV type Type and lengths are listed in the
   following table:

       +----------+-------------------+----------+----------------+
       | Sub-TLV  | Description       |   Length |Value defined in|
       +----------+-------------------+----------+----------------+
       |        0 | Reserved          |        - |        -       |
       |        1 | Autonomous System |        4 |  [RFC7752]     |
       |        2 | BGP-LS Identifier |        4 |  / section     |
       |        3 | OSPF Area-ID      |        4 |    3.2.1.4     |
       |        4 | Router-ID         | Variable |                |
       +----------+-------------------+----------+----------------+

   The sub-TLV values in Node Descriptor TLVs are defined as follows
   (similar to [RFC7752]):

   o  Autonomous System: opaque value (32 Bit AS Number)

   o  BGP-LS Identifier: opaque value (32 Bit ID).  In conjunction with
      ASN, uniquely identifies the BGP-LS domain as described in
      [RFC7752].  This sub-TLV is present only if the node implements
      BGP-LS and the ID is set by the operator.

   o  OSPF Area ID: It is used to identify the 32 Bit area to which the
      LS object belongs.  Area Identifier allows the different LS
      objects of the same node to be discriminated.

   o  Router ID: opaque value.  Usage is described in [RFC7752] as IGP
      Router ID.  In case this is not learned from IGP, it SHOULD
      contain the unique router ID, such as TE router ID.




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9.3.7.  Link Descriptors TLV

   The Link Descriptors TLV contains Link Descriptors for each link.
   This TLV MUST be included in the LS Report when during a given PCEP
   session a link is first reported to a PCE.  A PCC sends to a PCE the
   first LS Report either during State Synchronization, or when a new
   link is learned at the PCC.  The length of this TLV is variable.  The
   value contains one or more Link Descriptor Sub-TLVs.

   The 'Link descriptor' TLVs uniquely identify a link among multiple
   parallel links between a pair of anchor routers similar to [RFC7752].

   This TLV is applicable for LS Link Object-Type.

      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=[TBD10]        |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     //              Link Descriptor Sub-TLVs (variable)            //
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Link Descriptor Sub-TLV type and lengths are listed in the
   following table:

   +-----------+---------------------+---------------+-----------------+
   |  Sub-TLV  | Description         |   IS-IS TLV   | Value defined   |
   |           |                     |    /Sub-TLV   | in:             |
   +-----------+---------------------+---------------+-----------------+
   |    6      | Link Local/Remote   |      22/4     | [RFC5307]/1.1   |
   |           | Identifiers         |               |                 |
   |    7      | IPv4 interface      |      22/6     | [RFC5305]/3.2   |
   |           | address             |               |                 |
   |    8      | IPv4 neighbor       |      22/8     | [RFC5305]/3.3   |
   |           | address             |               |                 |
   |    9      | IPv6 interface      |     22/12     | [RFC6119]/4.2   |
   |           | address             |               |                 |
   |    10     | IPv6 neighbor       |     22/13     | [RFC6119]/4.3   |
   |           | address             |               |                 |
   |    5      | Multi-Topology      |       -       | [RFC7752]/      |
   |           | identifier          |               | 3.2.1.5         |
   +-----------+---------------------+---------------+-----------------+

   The format and semantics of the 'value' fields in most 'Link
   Descriptor' sub-TLVs correspond to the format and semantics of value
   fields in IS-IS Extended IS Reachability sub-TLVs, defined in



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   [RFC5305], [RFC5307] and [RFC6119].  Although the encodings for 'Link
   Descriptor' TLVs were originally defined for IS-IS, the TLVs can
   carry data sourced either by IS-IS or OSPF or direct.

   The information about a link present in the LSA/LSP originated by the
   local node of the link determines the set of sub-TLVs in the Link
   Descriptor of the link as described in [RFC7752].

9.3.8.  Prefix Descriptors TLV

   The Prefix Descriptors TLV contains Prefix Descriptors uniquely
   identify an IPv4 or IPv6 Prefix originated by a Node.  This TLV MUST
   be included in the LS Report when during a given PCEP session a
   prefix is first reported to a PCE.  A PCC sends to a PCE the first LS
   Report either during State Synchronization, or when a new prefix is
   learned at the PCC.  The length of this TLV is variable.

   This TLV is applicable for LS Prefix Object-Types for both IPv4 and
   IPv6.

      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=[TBD11]        |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     //             Prefix Descriptor Sub-TLVs (variable)           //
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The value contains one or more Prefix Descriptor Sub-TLVs defined
   below -


   +--------------+-----------------------+----------+-----------------+
   |   TLV Code   | Description           |  Length  | Value defined   |
   |    Point     |                       |          | in:             |
   +--------------+-----------------------+----------+-----------------+
   |   5          | Multi-Topology        | variable | [RFC7752]       |
   |              | Identifier            |          | /3.2.1.5        |
   |   11         | OSPF Route Type       |    1     | [RFC7752]       |
   |              |                       |          | /3.2.3.1        |
   |   12         | IP Reachability       | variable | [RFC7752]       |
   |              | Information           |          | /3.2.3.2        |
   +--------------+-----------------------+----------+-----------------+






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9.3.9.  PCEP-LS Attributes

9.3.9.1.  Node Attributes TLV

   This is an optional attribute that is used to carry node attributes.
   This TLV is applicable for LS Node Object-Type.

      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=[TBD12]        |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     //              Node Attributes Sub-TLVs (variable)            //
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Node Attributes Sub-TLV type and lengths are listed in the
   following table:

   +--------------+-----------------------+----------+-----------------+
   |   Sub TLV    | Description           |   Length | Value defined   |
   |              |                       |          | in:             |
   +--------------+-----------------------+----------+-----------------+
   |     5        | Multi-Topology        | variable | [RFC7752]       |
   |              | Identifier            |          | /3.2.1.5        |
   |     13       | Node Flag Bits        |        1 | [RFC7752]       |
   |              |                       |          | /3.3.1.1        |
   |     14       | Opaque Node           | variable | [RFC7752]       |
   |              | Properties            |          | /3.3.1.5        |
   |     15       | Node Name             | variable | [RFC7752]       |
   |              |                       |          | /3.3.1.3        |
   |     16       | IS-IS Area Identifier | variable | [RFC7752]       |
   |              |                       |          | /3.3.1.2        |
   |     17       | IPv4 Router-ID of     |        4 | [RFC5305]/4.3   |
   |              | Local Node            |          |                 |
   |     18       | IPv6 Router-ID of     |       16 | [RFC6119]/4.1   |
   |              | Local Node            |          |                 |
   +--------------+-----------------------+----------+-----------------+

9.3.9.2.  Link Attributes TLV

   This TLV is applicable for LS Link Object-Type.  The format and
   semantics of the 'value' fields in some 'Link Attribute' sub-TLVs
   correspond to the format and semantics of value fields in IS-IS
   Extended IS Reachability sub-TLVs, defined in [RFC5305], [RFC5307]
   and [RFC7752].  Although the encodings for 'Link Attribute' TLVs were




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   originally defined for IS-IS, the TLVs can carry data sourced either
   by IS-IS or OSPF or direct.

      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=[TBD13]        |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     //              Link Attributes Sub-TLVs (variable)            //
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The following 'Link Attribute' sub-TLVs are valid :

   +-----------+---------------------+--------------+------------------+
   |  Sub-TLV  | Description         |  IS-IS TLV   | Defined in:      |
   |           |                     |   /Sub-TLV   |                  |
   |           |                     |  BGP-LS TLV  |                  |
   +-----------+---------------------+--------------+------------------+
   |    17     | IPv4 Router-ID of   |   134/---    | [RFC5305]/4.3    |
   |           | Local Node          |              |                  |
   |    18     | IPv6 Router-ID of   |   140/---    | [RFC6119]/4.1    |
   |           | Local Node          |              |                  |
   |    19     | IPv4 Router-ID of   |   134/---    | [RFC5305]/4.3    |
   |           | Remote Node         |              |                  |
   |    20     | IPv6 Router-ID of   |   140/---    | [RFC6119]/4.1    |
   |           | Remote Node         |              |                  |
   |    6      | Link Local/Remote   |     22/4     | [RFC5307]/1.1    |
   |           | Identifiers         |              |                  |
   |    22     | Administrative      |     22/3     | [RFC5305]/3.1    |
   |           | group (color)       |              |                  |
   |    23     | Maximum link        |     22/9     | [RFC5305]/3.3    |
   |           | bandwidth           |              |                  |
   |    24     | Max. reservable     |    22/10     | [RFC5305]/3.5    |
   |           | link bandwidth      |              |                  |
   |    25     | Unreserved          |    22/11     | [RFC5305]/3.6    |
   |           | bandwidth           |              |                  |
   |    26     | TE Default Metric   |    22/18     | [RFC7752]        |
   |           |                     |              | /3.3.2.3         |
   |    27     | Link Protection     |    22/20     | [RFC5307]/1.2    |
   |           | Type                |              |                  |
   |    28     | MPLS Protocol Mask  |     1094     | [RFC7752]        |
   |           |                     |              | /3.3.2.2         |
   |    29     | IGP Metric          |     1095     | [RFC7752]        |
   |           |                     |              | /3.3.2.4         |
   |    30     | Shared Risk Link    |     1096     | [RFC7752]        |
   |           | Group               |              | /3.3.2.5         |



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   |    31     | Opaque link         |     1097     | [RFC7752]        |
   |           | attributes          |              | /3.3.2.6         |
   |    32     | Link Name attribute |     1098     | [RFC7752]        |
   |           |                     |              | /3.3.2.7         |
   |    33     | Unidirectional      |     22/33    | [RFC7810]/4.1    |
   |           | Link Delay          |              |                  |
   |    34     | Min/Max             |     22/34    | [RFC7810]/4.2    |
   |           | Unidirectional Link |              |                  |
   |           | Delay               |              |                  |
   |    35     | Unidirectional      |     22/35    | [RFC7810]/4.3    |
   |           | Delay Variation     |              |                  |
   |    36     | Unidirectional      |     22/36    | [RFC7810]/4.4    |
   |           | Link Loss           |              |                  |
   |    37     | Unidirectional      |     22/37    | [RFC7810]/4.5    |
   |           | Residual Bandwidth  |              |                  |
   |    38     | Unidirectional      |     22/38    | [RFC7810]/4.6    |
   |           | Available Bandwidth |              |                  |
   |    39     | Unidirectional      |     22/39    | [RFC7810]/4.7    |
   |           | Bandwidth           |              |                  |
   |           | Utilization         |              |                  |
   |    40     | Extended Admin      |     22/14    | [RFC7308]/2.1    |
   |           | Group (EAG)         |              |                  |
   +-----------+---------------------+--------------+------------------+

9.3.9.3.  Prefix Attributes TLV

   This TLV is applicable for LS Prefix Object-Types for both IPv4 and
   IPv6.  Prefixes are learned from the IGP (IS-IS or OSPF) or BGP
   topology with a set of IGP attributes (such as metric, route tags,
   etc.).  This section describes the different attributes related to
   the IPv4/IPv6 prefixes.  Prefix Attributes TLVs SHOULD be encoded in
   the LS Prefix Object.

      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=[TBD14]        |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     //            Prefix Attributes Sub-TLVs (variable)            //
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The following 'Prefix Attribute' sub-TLVs are valid :







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   +-----------+---------------------+--------------+------------------+
   |  Sub-TLV  | Description         |  BGP-LS TLV  | Defined in:      |
   +-----------+---------------------+--------------+------------------+
   |    41     | IGP Flags           |     1152     | [RFC7752]        |
   |           |                     |              | /3.3.3.1         |
   |    42     | Route Tag           |     1153     | [RFC7752]        |
   |           |                     |              | /3.3.3.2         |
   |    43     | Extended Tag        |     1154     | [RFC7752]        |
   |           |                     |              | /3.3.3.3         |
   |    44     | Prefix Metric       |     1155     | [RFC7752]        |
   |           |                     |              | /3.3.3.4         |
   |    45     | OSPF Forwarding     |     1156     | [RFC7752]        |
   |           | Address             |              | /3.3.3.5         |
   |    46     | Opaque Prefix       |     1157     | [RFC7752]        |
   |           | Attribute           |              | /3.3.3.6         |
   +-----------+---------------------+--------------+------------------+

9.3.10.  Removal of an Attribute

   One of a key objective of PCEP-LS is to encode and carry only the
   impacted attributes of a Node, a Link or a Prefix.  To accommodate
   this requirement, incase of a removal of an attribute, the sub-TLV
   MUST be included with no 'value' field and length=0 to indicate that
   the attribute is removed.  On receiving a sub-TLV with zero length,
   the receiver removes the attribute from the database.

10.  Other Considerations

10.1.  Inter-AS Links

   The main source of LS (and TE) information is the IGP, which is not
   active on inter-AS links.  In some cases, the IGP may have
   information of inter-AS links ([RFC5392], [RFC5316]).  In other
   cases, an implementation SHOULD provide a means to inject inter-AS
   links into PCEP.  The exact mechanism used to provision the inter-AS
   links is outside the scope of this document.

11.  Security Considerations

   This document extends PCEP for LS (and TE) distribution including a
   new LSRpt message with new object and TLVs.  Procedures and protocol
   extensions defined in this document do not effect the overall PCEP
   security model.  See [RFC5440], [RFC8253].  Tampering with the LSRpt
   message may have an effect on path computations at PCE.  It also
   provides adversaries an opportunity to eavesdrop and learn sensitive
   information and plan sophisticated attacks on the network
   infrastructure.  The PCE implementation SHOULD provide mechanisms to
   prevent strains created by network flaps and amount of LS (and TE)



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   information.  Thus it is suggested that any mechanism used for
   securing the transmission of other PCEP message be applied here as
   well.  As a general precaution, it is RECOMMENDED that these PCEP
   extensions only be activated on authenticated and encrypted sessions
   belonging to the same administrative authority.

   Further, as stated in [RFC6952], PCEP implementations SHOULD support
   the TCP-AO [RFC5925] and not use TCP MD5 because of TCP MD5's known
   vulnerabilities and weakness.  PCEP also support Transport Layer
   Security (TLS) [RFC8253] as per the recommendations and best current
   practices in [RFC7525].

12.  Manageability Considerations

   All manageability requirements and considerations listed in [RFC5440]
   apply to PCEP protocol extensions defined in this document.  In
   addition, requirements and considerations listed in this section
   apply.

12.1.  Control of Function and Policy

   A PCE or PCC implementation MUST allow configuring the PCEP-LS
   capabilities as described in this document.

   A PCC implementation SHOULD allow configuration to suggest if remote
   information learned via routing protocols should be reported or not.

   An implementation SHOULD allow the operator to specify the maximum
   number of LS data to be reported.

   An implementation SHOULD also allow the operator to create abstracted
   topologies that are reported to the peers and create different
   abstractions for different peers.

   An implementation SHOULD allow the operator to configure a 64-bit
   Instance-ID for Routing Universe TLV.

12.2.  Information and Data Models

   An implementation SHOULD allow the operator to view the LS
   capabilities advertised by each peer.  To serve this purpose, the
   PCEP YANG module [I-D.ietf-pce-pcep-yang]" can be extended to include
   advertised capabilities.

   An implementation SHOULD also provide the statistics:

   o  Total number of LSRpt sent/received, as well as per neighbor




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   o  Number of error received for LSRpt, per neighbor

   o  Total number of locally originated Link-State Information

   These statistics should be recorded as absolute counts since system
   or session start time.  An implementation MAY also enhance this
   information by recording peak per-second counts in each case.

   An operator SHOULD define an import policy to limit inbound LSRpt to
   "drop all LSRpt from a particular peers" as well provide means to
   limit inbound LSRpts.

12.3.  Liveness Detection and Monitoring

   Mechanisms defined in this document do not imply any new liveness
   detection and monitoring requirements in addition to those already
   listed in [RFC5440]".

12.4.  Verify Correct Operations

   Mechanisms defined in this document do not imply any new operation
   verification requirements in addition to those already listed in
   [RFC5440] .

12.5.  Requirements On Other Protocols

   Mechanisms defined in this document do not imply any new requirements
   on other protocols.

12.6.  Impact On Network Operations

   Mechanisms defined in this document do not have any impact on network
   operations in addition to those already listed in [RFC5440].

13.  IANA Considerations

   This document requests IANA actions to allocate code points for the
   protocol elements defined in this document.

13.1.  PCEP Messages

   IANA created a registry for PCEP messages.  Each PCEP message has a
   message type value.  This document defines a new PCEP message value.

           Value     Meaning                          Reference
            TBD3     LSRpt                            [This I-D]





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13.2.  PCEP Objects

   This document defines the following new PCEP Object-classes and
   Object-values:

          Object-Class Value  Name                    Reference
               TBD6           LS Object               [This I-D]
                              Object-Type=1
                              (LS Node)
                              Object-Type=2
                              (LS Link)
                              Object-Type=3
                              (LS IPv4 Prefix)
                              Object-Type=4
                              (LS IPv6 Prefix)

13.3.  LS Object

   This document requests that a new sub-registry, named "LS Object
   Protocol-ID Field", is created within the "Path Computation Element
   Protocol (PCEP) Numbers" registry to manage the Flag field of the LSP
   object.  New values are to be assigned by Standards Action [RFC8126].

           Value       Meaning                        Reference
           0           Reserved                       [This I-D]
           1           IS-IS Level 1                  [This I-D]
           2           IS-IS Level 2                  [This I-D]
           3           OSPFv2                         [This I-D]
           4           Direct                         [This I-D]
           5           Static configuration           [This I-D]
           6           OSPFv3                         [This I-D]
           7           BGP-LS                         [This I-D]
           8           PCEP-LS                        [This I-D]
           9           Abstraction                    [This I-D]
           10          Unspecified                    [This I-D]


   Further, this document also requests that a new sub-registry, named
   "LS Object Flag Field", is created within the "Path Computation
   Element Protocol (PCEP) Numbers" registry to manage the Flag field of
   the LSP object.New values are to be assigned by Standards Action
   [RFC8126].  Each bit should be tracked with the following qualities:

   o  Bit number (counting from bit 0 as the most significant bit)

   o  Capability description

   o  Defining RFC



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   The following values are defined in this document:

                 Bit     Description           Reference
                 0-21    Unassigned
                 22      R (Remove bit)        [This I-D]
                 23      S (Sync bit)          [This I-D]

13.4.  PCEP-Error Object

   IANA is requested to make the following allocation in the "PCEP-ERROR
   Object Error Types and Values" registry.

           Error-Type Meaning                        Reference
           6          Mandatory Object missing       [RFC5440]
                      Error-Value=TBD4               [This I-D]
                      (LS object missing)

           19         Invalid Operation              [RFC8231]
                      Error-Value=TBD1               [This I-D]
                      (Attempted LS Report if LS
                      remote capability was not
                      advertised)

           TBD2       LS Synchronization Error       [This I-D]
                      Error-Value=1
                      (An error in processing the
                      LSRpt)
                      Error-Value=2
                      (An internal PCC error)



13.5.  PCEP TLV Type Indicators

   This document defines the following new PCEP TLVs.

            Value     Meaning                        Reference
             TBD5     LS-CAPABILITY TLV              [This I-D]
             TBD7     ROUTING-UNIVERSE TLV           [This I-D]
             TBD15    ROUTE-DISTINGUISHER TLV        [This I-D]
             TBD8     Local Node Descriptors TLV     [This I-D]
             TBD9     Remote Node Descriptors TLV    [This I-D]
             TBD10    Link Descriptors TLV           [This I-D]
             TBD11    Prefix Descriptors TLV         [This I-D]
             TBD12    Node Attributes TLV            [This I-D]
             TBD13    Link Attributes TLV            [This I-D]
             TBD14    Prefix Attributes TLV          [This I-D]




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13.6.  PCEP-LS Sub-TLV Type Indicators

   This document specifies the PCEP-LS Sub-TLVs.  IANA is requested to
   create an "PCEP-LS Sub-TLV Types" sub-registry in the "PCEP TLV Type
   Indicators" for the sub-TLVs carried in the PCEP-LS TLV (Local and
   Remote Node Descriptors TLV, Link Descriptors TLV, Prefix Descriptors
   TLV, Node Attributes TLV, Link Attributes TLV and Prefix Attributes
   TLV.  This document defines the following types:

   +-----------+---------------------+---------------+-----------------+
   |  Sub-TLV  | Description         |     Ref       | Value defined   |
   |           |                     |     Sub-TLV   | in:             |
   +-----------+---------------------+---------------+-----------------+
   |    1      | Autonomous System   |      512      | [RFC7752]       |
   |           |                     |               | /3.2.1.4        |
   |    2      | BGP-LS Identifier   |      513      | [RFC7752]       |
   |           |                     |               | /3.2.1.4        |
   |    3      | OSPF Area-ID        |      514      | [RFC7752]       |
   |           |                     |               | /3.2.1.4        |
   |    4      | Router-ID           |      515      | [RFC7752]       |
   |           |                     |               | /3.2.1.4        |
   |    5      | Multi-Topology-ID   |      263      | [RFC7752]       |
   |           |                     |               | /3.2.1.5        |
   |    6      | Link Local/Remote   |      22/4     | [RFC5307]/1.1   |
   |           | Identifiers         |               |                 |
   |    7      | IPv4 interface      |      22/6     | [RFC5305]/3.2   |
   |           | address             |               |                 |
   |    8      | IPv4 neighbor       |      22/8     | [RFC5305]/3.3   |
   |           | address             |               |                 |
   |    9      | IPv6 interface      |     22/12     | [RFC6119]/4.2   |
   |           | address             |               |                 |
   |    10     | IPv6 neighbor       |     22/13     | [RFC6119]/4.3   |
   |           | address             |               |                 |
   |    11     | OSPF Route Type     |      264      | [RFC7752]       |
   |           |                     |               | /3.2.3.1        |
   |    12     | IP Reachability     |      265      | [RFC7752]       |
   |           | Information         |               | /3.2.3.2        |
   |    13     | Node Flag Bits      |      1024     | [RFC7752]       |
   |           |                     |               | /3.3.1.1        |
   |    14     | Opaque Node         |      1025     | [RFC7752]       |
   |           | Properties          |               | /3.3.1.5        |
   |    15     | Node Name           |      1026     | [RFC7752]       |
   |           |                     |               | /3.3.1.3        |
   |    16     | IS-IS Area          |      1027     | [RFC7752]       |
   |           | Identifier          |               | /3.3.1.2        |
   |    17     | IPv4 Router-ID of   |      134/--   | [RFC5305]/4.3   |
   |           | Local Node          |               |                 |
   |    18     | IPv6 Router-ID of   |      140/--   | [RFC6119]/4.1   |



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   |           | Local Node          |               |                 |
   |    19     | IPv4 Router-ID of   |      134/--   | [RFC5305]/4.3   |
   |           | Remote Node         |               |                 |
   |    20     | IPv6 Router-ID of   |      140/--   | [RFC6119]/4.1   |
   |           | Remote Node         |               |                 |
   |    22     | Administrative      |     22/3      | [RFC5305]/3.1   |
   |           | group (color)       |               |                 |
   |    23     | Maximum link        |     22/9      | [RFC5305]/3.3   |
   |           | bandwidth           |               |                 |
   |    24     | Max. reservable     |    22/10      | [RFC5305]/3.5   |
   |           | link bandwidth      |               |                 |
   |    25     | Unreserved          |    22/11      | [RFC5305]/3.6   |
   |           | bandwidth           |               |                 |
   |    26     | TE Default Metric   |    22/18      | [RFC7752]       |
   |           |                     |               | /3.3.2.3        |
   |    27     | Link Protection     |    22/20      | [RFC5307]/1.2   |
   |           | Type                |               |                 |
   |    28     | MPLS Protocol Mask  |     1094      | [RFC7752]       |
   |           |                     |               | /3.3.2.2        |
   |    29     | IGP Metric          |     1095      | [RFC7752]       |
   |           |                     |               | /3.3.2.4        |
   |    30     | Shared Risk Link    |     1096      | [RFC7752]       |
   |           | Group               |               | /3.3.2.5        |
   |    31     | Opaque link         |     1097      | [RFC7752]       |
   |           | attributes          |               | /3.3.2.6        |
   |    32     | Link Name attribute |     1098      | [RFC7752]       |
   |           |                     |               | /3.3.2.7        |
   |    33     | Unidirectional      |     22/33     | [RFC7810]/4.1   |
   |           | Link Delay          |               |                 |
   |    34     | Min/Max             |     22/34     | [RFC7810]/4.2   |
   |           | Unidirectional Link |               |                 |
   |           | Delay               |               |                 |
   |    35     | Unidirectional      |     22/35     | [RFC7810]/4.3   |
   |           | Delay Variation     |               |                 |
   |    36     | Unidirectional      |     22/36     | [RFC7810]/4.4   |
   |           | Link Loss           |               |                 |
   |    37     | Unidirectional      |     22/37     | [RFC7810]/4.5   |
   |           | Residual Bandwidth  |               |                 |
   |    38     | Unidirectional      |     22/38     | [RFC7810]/4.6   |
   |           | Available Bandwidth |               |                 |
   |    39     | Unidirectional      |     22/39     | [RFC7810]/4.7   |
   |           | Bandwidth           |               |                 |
   |           | Utilization         |               |                 |
   |    40     | Extended Admin      |     22/14     | [RFC7308]/2.1   |
   |           | Group (EAG)         |               |                 |
   |    41     | IGP Flags           |     1152      | [RFC7752]       |
   |           |                     |               | /3.3.3.1        |
   |    42     | Route Tag           |     1153      | [RFC7752]       |



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   |           |                     |               | /3.3.3.2        |
   |    43     | Extended Tag        |     1154      | [RFC7752]       |
   |           |                     |               | /3.3.3.3        |
   |    44     | Prefix Metric       |     1155      | [RFC7752]       |
   |           |                     |               | /3.3.3.4        |
   |    45     | OSPF Forwarding     |     1156      | [RFC7752]       |
   |           | Address             |               | /3.3.3.5        |
   |    46     | Opaque Prefix       |     1157      | [RFC7752]       |
   |           | Attribute           |               | /3.3.3.6        |
   +-----------+---------------------+---------------+-----------------+

   New values are to be assigned by Standards Action [RFC8126].

14.  TLV/Sub-TLV Code Points Summary

   This section contains the global table of all TLVs/Sub-TLVs in LS
   object defined in this document.

   +-----------+---------------------+---------------+-----------------+
   |    TLV    | Description         |     Ref TLV   | Value defined   |
   |           |                     |               | in:             |
   +-----------+---------------------+---------------+-----------------+
   |    TBD7   | Routing Universe    |      --       | Sec 9.2.1       |
   |    TBD15  | Route               |      --       | Sec 9.2.2       |
   |           | Distinguisher       |               |                 |
   |     *     | Virtual Network     |      --       | [leedhody-pce-  |
   |           |                     |               | vn-association] |
   |    TBD8   | Local Node          |      256      | [RFC7752]       |
   |           | Descriptors         |               | /3.2.1.2        |
   |    TBD9   | Remote Node         |      257      | [RFC7752]       |
   |           | Descriptors         |               | /3.2.1.3        |
   |    TBD10  | Link Descriptors    |      --       | Sec 9.2.8       |
   |    TBD11  | Prefix Descriptors  |      --       | Sec 9.2.9       |
   |    TBD12  | Node Attributes     |      --       | Sec 9.2.10.1    |
   |    TBD13  | Link Attributes     |      --       | Sec 9.2.10.2    |
   |    TBD14  | Prefix Attributes   |      --       | Sec 9.2.10.3    |
   +-----------+---------------------+---------------+-----------------+

   * this TLV is defined in a different PCEP document

                                 TLV Table

   Refer Section 13.6 for the table of Sub-TLVs.








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15.  Implementation Status

   The PCEP-LS protocol extension as described in this I-D were
   implemented and tested for a variety of applications.  Apart from the
   below implementation, there exist other experimental implementations
   done for optical networks.

15.1.  Hierarchical Transport PCE controllers

   The PCEP-LS has been implemented as part of IETF97 Hackathon and
   Bits-N-Bites demonstration.  The use-case demonstrated was DCI use-
   case of ACTN architecture in which to show the following scenarios:

      - connectivity services on the ACTN based recursive hierarchical
      SDN/PCE platform that has the three tier level SDN controllers
      (two-tier level MDSC and PNC) on the top of the PTN systems
      managed by EMS.

      - Integration test of two tier-level MDSC: The SBI of the low
      level MDSC is the YANG based Korean national standards and the one
      of the high level MDSC the PCEP-LS based ACTN protocols.

      - Performance test of three types of SDN controller based recovery
      schemes including protection, reactive and proactive restoration.
      PCEP-LS protocol was used to demonstrate quick report of failed
      network components.

15.2.  ONOS-based Controller (MDSC and PNC)

   Huawei (PNC, MDSC) and SKT (MDSC) implemented PCEP-LS during
   Hackathon and IETF97 Bits-N-Bites demonstration.  The demonstration
   was ONOS-based ACTN architecture in which to show the following
   capabilities:

      Both packet PNC and optical PNC (with optical PCEP-LS extension)
      implemented PCEP-LS on its SBI and well as its NBI (towards MDSC).

      SKT orchestrator (acting as MDSC) also supported PCEP-LS (as well
      as RestConf) towards packet and optical PNCs on its SBI.

   Further description can be found at <ONOS-PCEP> and the code at
   <ONOS-PCEP-GITHUB>.

16.  Acknowledgments

   This document borrows some of the structure and text from the
   [RFC7752].




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   Thanks to Eric Wu, Venugopal Kondreddy, Mahendra Singh Negi,
   Avantika, and Zhengbin Li for the reviews.

   Thanks to Ramon Casellas for his comments and suggestions based on
   his implementation experience.

17.  References

17.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, DOI 10.17487/RFC5305, October
              2008, <https://www.rfc-editor.org/info/rfc5305>.

   [RFC5307]  Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS Extensions
              in Support of Generalized Multi-Protocol Label Switching
              (GMPLS)", RFC 5307, DOI 10.17487/RFC5307, October 2008,
              <https://www.rfc-editor.org/info/rfc5307>.

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,
              <https://www.rfc-editor.org/info/rfc5440>.

   [RFC6119]  Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic
              Engineering in IS-IS", RFC 6119, DOI 10.17487/RFC6119,
              February 2011, <https://www.rfc-editor.org/info/rfc6119>.

   [RFC7752]  Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
              S. Ray, "North-Bound Distribution of Link-State and
              Traffic Engineering (TE) Information Using BGP", RFC 7752,
              DOI 10.17487/RFC7752, March 2016,
              <https://www.rfc-editor.org/info/rfc7752>.

   [RFC7810]  Previdi, S., Ed., Giacalone, S., Ward, D., Drake, J., and
              Q. Wu, "IS-IS Traffic Engineering (TE) Metric Extensions",
              RFC 7810, DOI 10.17487/RFC7810, May 2016,
              <https://www.rfc-editor.org/info/rfc7810>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.




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17.2.  Informative References

   [RFC3630]  Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
              (TE) Extensions to OSPF Version 2", RFC 3630,
              DOI 10.17487/RFC3630, September 2003,
              <https://www.rfc-editor.org/info/rfc3630>.

   [RFC4203]  Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in
              Support of Generalized Multi-Protocol Label Switching
              (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005,
              <https://www.rfc-editor.org/info/rfc4203>.

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
              2006, <https://www.rfc-editor.org/info/rfc4364>.

   [RFC4655]  Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
              Element (PCE)-Based Architecture", RFC 4655,
              DOI 10.17487/RFC4655, August 2006,
              <https://www.rfc-editor.org/info/rfc4655>.

   [RFC5316]  Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in
              Support of Inter-Autonomous System (AS) MPLS and GMPLS
              Traffic Engineering", RFC 5316, DOI 10.17487/RFC5316,
              December 2008, <https://www.rfc-editor.org/info/rfc5316>.

   [RFC5392]  Chen, M., Zhang, R., and X. Duan, "OSPF Extensions in
              Support of Inter-Autonomous System (AS) MPLS and GMPLS
              Traffic Engineering", RFC 5392, DOI 10.17487/RFC5392,
              January 2009, <https://www.rfc-editor.org/info/rfc5392>.

   [RFC5925]  Touch, J., Mankin, A., and R. Bonica, "The TCP
              Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
              June 2010, <https://www.rfc-editor.org/info/rfc5925>.

   [RFC6549]  Lindem, A., Roy, A., and S. Mirtorabi, "OSPFv2 Multi-
              Instance Extensions", RFC 6549, DOI 10.17487/RFC6549,
              March 2012, <https://www.rfc-editor.org/info/rfc6549>.

   [RFC6805]  King, D., Ed. and A. Farrel, Ed., "The Application of the
              Path Computation Element Architecture to the Determination
              of a Sequence of Domains in MPLS and GMPLS", RFC 6805,
              DOI 10.17487/RFC6805, November 2012,
              <https://www.rfc-editor.org/info/rfc6805>.







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   [RFC6952]  Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
              BGP, LDP, PCEP, and MSDP Issues According to the Keying
              and Authentication for Routing Protocols (KARP) Design
              Guide", RFC 6952, DOI 10.17487/RFC6952, May 2013,
              <https://www.rfc-editor.org/info/rfc6952>.

   [RFC7525]  Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
              2015, <https://www.rfc-editor.org/info/rfc7525>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8202]  Ginsberg, L., Previdi, S., and W. Henderickx, "IS-IS
              Multi-Instance", RFC 8202, DOI 10.17487/RFC8202, June
              2017, <https://www.rfc-editor.org/info/rfc8202>.

   [RFC8231]  Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
              Computation Element Communication Protocol (PCEP)
              Extensions for Stateful PCE", RFC 8231,
              DOI 10.17487/RFC8231, September 2017,
              <https://www.rfc-editor.org/info/rfc8231>.

   [RFC8253]  Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
              "PCEPS: Usage of TLS to Provide a Secure Transport for the
              Path Computation Element Communication Protocol (PCEP)",
              RFC 8253, DOI 10.17487/RFC8253, October 2017,
              <https://www.rfc-editor.org/info/rfc8253>.

   [RFC8281]  Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path
              Computation Element Communication Protocol (PCEP)
              Extensions for PCE-Initiated LSP Setup in a Stateful PCE
              Model", RFC 8281, DOI 10.17487/RFC8281, December 2017,
              <https://www.rfc-editor.org/info/rfc8281>.

   [RFC8283]  Farrel, A., Ed., Zhao, Q., Ed., Li, Z., and C. Zhou, "An
              Architecture for Use of PCE and the PCE Communication
              Protocol (PCEP) in a Network with Central Control",
              RFC 8283, DOI 10.17487/RFC8283, December 2017,
              <https://www.rfc-editor.org/info/rfc8283>.







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   [I-D.ietf-pce-pcep-yang]
              Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A
              YANG Data Model for Path Computation Element
              Communications Protocol (PCEP)", draft-ietf-pce-pcep-
              yang-07 (work in progress), March 2018.

   [I-D.ietf-pce-applicability-actn]
              Dhody, D., Lee, Y., and D. Ceccarelli, "Applicability of
              Path Computation Element (PCE) for Abstraction and Control
              of TE Networks (ACTN)", draft-ietf-pce-applicability-
              actn-06 (work in progress), June 2018.

   [I-D.ietf-teas-actn-framework]
              Ceccarelli, D. and Y. Lee, "Framework for Abstraction and
              Control of Traffic Engineered Networks", draft-ietf-teas-
              actn-framework-15 (work in progress), May 2018.

   [I-D.ietf-teas-actn-requirements]
              Lee, Y., Ceccarelli, D., Miyasaka, T., Shin, J., and K.
              Lee, "Requirements for Abstraction and Control of TE
              Networks", draft-ietf-teas-actn-requirements-09 (work in
              progress), March 2018.

   [I-D.kondreddy-pce-pcep-ls-sync-optimizations]
              Kondreddy, V. and M. Negi, "Optimizations of PCEP Link-
              State(LS) Synchronization Procedures", draft-kondreddy-
              pce-pcep-ls-sync-optimizations-00 (work in progress),
              October 2015.

   [I-D.leedhody-pce-vn-association]
              Lee, Y., Dhody, D., Zhang, X., and D. Ceccarelli, "PCEP
              Extensions for Establishing Relationships Between Sets of
              LSPs and Virtual Networks", draft-leedhody-pce-vn-
              association-05 (work in progress), June 2018.

   [ONOS-PCEP]
              "Support for PCEP in ONOS",
              <https://wiki.onosproject.org/display/ONOS/PCEP+Protocol>.

   [ONOS-PCEP-GITHUB]
              "Github for PCEP code in ONOS",
              <https://github.com/opennetworkinglab/onos/tree/master/
              protocols/pcep>.








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Appendix A.  Reusing BGP-LS codepoints

   This document creates a new registry for the PCEP-LS sub-TLVs
   (Section 13.6) and define new sub-TLV codepoints.  Another approach
   could be to use the BGP-LS registry which is already defined for use
   in BGP.  This is possible because the "BGP-LS Node Descriptor, Link
   Descriptor, Prefix Descriptor, and Attribute TLVs" registry marks
   0-255 as reserved.  Thus the space of the sub-TLV values for the Type
   field can be partitioned as shown below -

   Range          |
   ---------------+---------------------------------------------
   0              | Reserved - must not be allocated.
                  |
   1 .. 255       | New PCEP sub-TLV allocated according to the
                  | registry defined in this document.
                  |
   256 ..   65535 | Per BGP registry defined by [RFC7752].
                  | Not to be allocated in this registry.

   [Editor's Note - If this approach is agreed by the WG, the document
   would be updated with new sub-TLV type values.]

Appendix B.  Relevant OSPF TLV and sub-TLV

   This section list the relevant TLVs and sub-TLVs defined for OSPF.

   +-----------+---------------------+---------------+-----------------+
   |  Sub-TLV  | Description         |     OSPF-TE   | Value defined   |
   |           |                     |     Sub-TLV   | in:             |
   +-----------+---------------------+---------------+-----------------+
   |    6      | Link Local/Remote   |      11       | [RFC4203]/1.1   |
   |           | Identifiers         |               |                 |
   |    7      | IPv4 interface      |      3        | [RFC3630]/2.5.3 |
   |           | address             |               |                 |
   |    8      | IPv4 neighbor       |      4        | [RFC3630]/2.5.4 |
   |           | address             |               |                 |
   |    9      | IPv6 interface      |      19       | [RFC5329]/4.3   |
   |           | address             |               |                 |
   |    10     | IPv6 neighbor       |      20       | [RFC5329]/4.4   |
   |           | address             |               |                 |
   |    17     | IPv4 Router-ID of   |      1        | [RFC3630]/2.4.1 |
   |           | Local Node          |               |                 |
   |    18     | IPv6 Router-ID of   |      3        | [RFC5329]/3     |
   |           | Local Node          |               |                 |
   |    19     | IPv4 Router-ID of   |      1        | [RFC3630]/2.4.1 |
   |           | Remote Node         |               |                 |
   |    20     | IPv6 Router-ID of   |      3        | [RFC5329]/3     |



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   |           | Remote Node         |               |                 |
   |    22     | Administrative      |      9        | [RFC3630]/2.5.9 |
   |           | group (color)       |               |                 |
   |    23     | Maximum link        |      6        | [RFC3630]/2.5.6 |
   |           | bandwidth           |               |                 |
   |    24     | Max. reservable     |      7        | [RFC3630]/2.5.7 |
   |           | link bandwidth      |               |                 |
   |    25     | Unreserved          |      8        | [RFC3630]/2.5.8 |
   |           | bandwidth           |               |                 |
   |    27     | Link Protection     |      14       | [RFC4203]/1.2   |
   |           | Type                |               |                 |
   |    30     | Shared Risk Link    |      16       | [RFC4203]/1.3   |
   |           | Group               |               |                 |
   |    33     | Unidirectional      |      27       | [RFC7471]/4.1   |
   |           | Link Delay          |               |                 |
   |    34     | Min/Max             |      28       | [RFC7471]/4.2   |
   |           | Unidirectional Link |               |                 |
   |           | Delay               |               |                 |
   |    35     | Unidirectional      |      29       | [RFC7471]/4.3   |
   |           | Delay Variation     |               |                 |
   |    36     | Unidirectional      |      30       | [RFC7471]/4.4   |
   |           | Link Loss           |               |                 |
   |    37     | Unidirectional      |      31       | [RFC7471]/4.5   |
   |           | Residual Bandwidth  |               |                 |
   |    38     | Unidirectional      |      32       | [RFC7471]/4.6   |
   |           | Available Bandwidth |               |                 |
   |    39     | Unidirectional      |      33       | [RFC7471]/4.7   |
   |           | Bandwidth           |               |                 |
   |           | Utilization         |               |                 |
   |    40     | Extended Admin      |      26       | [RFC7308]/2.1   |
   |           | Group (EAG)         |               |                 |
   +-----------+---------------------+---------------+-----------------+

Appendix C.  Examples

   These examples are for illustration purposes only to show how the new
   PCEP-LS message could be encoded.  They are not meant to be an
   exhaustive list of all possible use cases and combinations.

C.1.  All Nodes

   Each node (PCC) in the network chooses to provide its own local node
   and link information, and in this way PCE can build the full link
   state and TE information.

   +--------------------+                    +--------------------+
   |                    |                    |                    |
   |     RTA            |10.1.1.1            |     RTB            |



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   |     1.1.1.1        |--------------------|     2.2.2.2        |
   |     Area 0         |            10.1.1.2|     Area 0         |
   |                    |                    |                    |
   +--------------------+                    +--------------------+
   RTA
   ---
   LS Node
      TLV - Local Node Descriptors
          Sub-TLV - 3: OSPF Area-ID: 0.0.0.0
          Sub-TLV - 4: Router-ID: 1.1.1.1
      TLV - Node Attributes TLV
          Sub-TLV(s)


   LS Link
      TLV - Local Node Descriptors
          Sub-TLV - 3: OSPF Area-ID: 0.0.0.0
          Sub-TLV - 4: Router-ID: 1.1.1.1
      TLV - Remote Node Descriptors
          Sub-TLV - 3: OSPF Area-ID: 0.0.0.0
          Sub-TLV - 4: Router-ID: 2.2.2.2
      TLV - Link Descriptors
          Sub-TLV - 7: IPv4 interface: 10.1.1.1
          Sub-TLV - 8: IPv4 neighbor: 10.1.1.2
      TLV - Link Attributes TLV
          Sub-TLV(s)

   RTB
   ---
   LS Node
      TLV - Local Node Descriptors
          Sub-TLV - 3: OSPF Area-ID: 0.0.0.0
          Sub-TLV - 4: Router-ID: 2.2.2.2
      TLV - Node Attributes TLV
          Sub-TLV(s)

   LS Link
      TLV - Local Node Descriptors
          Sub-TLV - 3: OSPF Area-ID: 0.0.0.0
          Sub-TLV - 4: Router-ID: 2.2.2.2
      TLV - Remote Node Descriptors
          Sub-TLV - 3: OSPF Area-ID: 0.0.0.0
          Sub-TLV - 4: Router-ID: 1.1.1.1
      TLV - Link Descriptors
          Sub-TLV - 7: IPv4 interface: 10.1.1.2
          Sub-TLV - 8: IPv4 neighbor: 10.1.1.1
      TLV - Link Attributes TLV
          Sub-TLV(s)



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C.2.  Designated Node

   A designated node(s) in the network will provide its own local node
   as well as all learned remote information, and in this way PCE can
   build the full link state and TE information.

   As described in Appendix C.1, the same LS Node and Link objects will
   be generated with a difference that it would be a designated router
   say RTA that generate all this information.

C.3.  Between PCEs

   As per Hierarchical-PCE [RFC6805], Parent PCE builds an abstract
   domain topology map with each domain as an abstract node and inter-
   domain links as an abstract link.  Each child PCE may provide this
   information to the parent PCE.  Considering the example in figure 1
   of [RFC6805], following LS object will be generated:


































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   PCE1
   ----
   LS Node
      TLV - Local Node Descriptors
          Sub-TLV - 1: Autonomous System: 100 (Domain 1)
          Sub-TLV - 4: Router-ID: 11.11.11.11 (abstract)

   LS Link
      TLV - Local Node Descriptors
          Sub-TLV - 1: Autonomous System: 100
          Sub-TLV - 4: Router-ID: 11.11.11.11 (abstract)
      TLV - Remote Node Descriptors
          Sub-TLV - 1: Autonomous System: 200 (Domain 2)
          Sub-TLV - 4: Router-ID: 22.22.22.22 (abstract)
      TLV - Link Descriptors
          Sub-TLV - 7: IPv4 interface: 11.1.1.1
          Sub-TLV - 8: IPv4 neighbor: 11.1.1.2
      TLV - Link Attributes TLV
          Sub-TLV(s)

   LS Link
      TLV - Local Node Descriptors
          Sub-TLV - 1: Autonomous System: 100
          Sub-TLV - 4: Router-ID: 11.11.11.11 (abstract)
      TLV - Remote Node Descriptors
          Sub-TLV - 1: Autonomous System: 200
          Sub-TLV - 4: Router-ID: 22.22.22.22 (abstract)
      TLV - Link Descriptors
          Sub-TLV - 7: IPv4 interface: 12.1.1.1
          Sub-TLV - 8: IPv4 neighbor: 12.1.1.2
      TLV - Link Attributes TLV
          Sub-TLV(s)

   LS Link
      TLV - Local Node Descriptors
          Sub-TLV - 1: Autonomous System: 100
          Sub-TLV - 4: Router-ID: 11.11.11.11 (abstract)
      TLV - Remote Node Descriptors
          Sub-TLV - 1: Autonomous System: 400 (Domain 4)
          Sub-TLV - 4: Router-ID: 44.44.44.44 (abstract)
      TLV - Link Descriptors
          Sub-TLV - 7: IPv4 interface: 13.1.1.1
          Sub-TLV - 8: IPv4 neighbor: 13.1.1.2
      TLV - Link Attributes TLV
          Sub-TLV(s)

   * similar information will be generated by other PCE
     to help form the abstract domain topology.



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   Further the exact border nodes and abstract internal path between the
   border nodes may also be transported to the Parent PCE to enable ACTN
   as described in [I-D.ietf-pce-applicability-actn] using the similar
   LS node and link objects encodings.

Appendix D.  Contributor Addresses

   Udayasree Palle
   Huawei Technologies
   Divyashree Techno Park, Whitefield
   Bangalore, Karnataka  560066
   India

   EMail: udayasreereddy@gmail.com

   Sergio Belotti
   Alcatel-Lucent
   Italy

   EMail: sergio.belotti@alcatel-lucent.com

   Veerendranatha Reddy Vallem
   Huawei Technologies
   Divyashree Techno Park, Whitefield
   Bangalore, Karnataka  560066
   India

   Email: veerendranatharv@huawei.com

   Satish Karunanithi
   Huawei Technologies
   Divyashree Techno Park, Whitefield
   Bangalore, Karnataka  560066
   India

   Email: satishk@huawei.com

Authors' Addresses

   Dhruv Dhody
   Huawei Technologies
   Divyashree Techno Park, Whitefield
   Bangalore, Karnataka  560066
   India

   EMail: dhruv.ietf@gmail.com





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   Young Lee
   Huawei Technologies
   5340 Legacy Drive, Building 3
   Plano, TX  75023
   USA

   EMail: leeyoung@huawei.com


   Daniele Ceccarelli
   Ericsson
   Torshamnsgatan,48
   Stockholm
   Sweden

   EMail: daniele.ceccarelli@ericsson.com



































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