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Versions: (draft-palle-pce-stateful-pce-lspdb-sync) 00 01 draft-litkowski-pce-state-sync

PCE Working Group                                               D. Dhody
Internet-Draft                                       Huawei Technologies
Intended status: Standards Track                       December 28, 2016
Expires: July 1, 2017


       Realtime Synchronization between Redundant Stateful PCEs.
          draft-dhody-pce-stateful-pce-lspdb-realtime-sync-01

Abstract

   The Path Computation Element Communication Protocol (PCEP) provides
   mechanisms for Path Computation Elements (PCEs) to perform path
   computations in response to Path Computation Clients (PCCs) requests.

   The stateful PCE further extentds PCEP to enable stateful control of
   MPLS-TE and GMPLS Label Switched Paths (LSPs) via PCEP and
   maintaining of these LSPs at the stateful PCE.  This document
   describes the mechanisms of realtime LSP Database (LSP-DB)
   synchronization between stateful PCEs.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on July 1, 2017.

Copyright Notice

   Copyright (c) 2016 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect



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   to this document.  Code Components extracted from this document must
   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
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Architectural Considerations  . . . . . . . . . . . . . . . .   4
   4.  Functions to Support LSP-DB Synchronization . . . . . . . . .   4
   5.  Operations  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     5.1.  Relatime LSP-DB Synchronization between redundant
           Stateful PCEs . . . . . . . . . . . . . . . . . . . . . .   5
     5.2.  Other Considerations  . . . . . . . . . . . . . . . . . .   8
   6.  PCEP Messages . . . . . . . . . . . . . . . . . . . . . . . .   8
     6.1.  The PCRpt Message . . . . . . . . . . . . . . . . . . . .   8
     6.2.  The PCUpd Message . . . . . . . . . . . . . . . . . . . .   8
   7.  TLVs  . . . . . . . . . . . . . . . . . . . . . . . . . . . .   8
     7.1.  Stateful PCE Capability TLV . . . . . . . . . . . . . . .   8
     7.2.  Speaker Entity Identifier TLV . . . . . . . . . . . . . .   9
     7.3.  REALTIME-SYNC TLV . . . . . . . . . . . . . . . . . . . .   9
     7.4.  PCE-CAP-FLAGS sub-TLV . . . . . . . . . . . . . . . . . .  10
   8.  Other Considerations  . . . . . . . . . . . . . . . . . . . .  10
     8.1.  PCE Initiated LSP . . . . . . . . . . . . . . . . . . . .  10
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   10. Manageability Considerations  . . . . . . . . . . . . . . . .  10
     10.1.  Control of Function and Policy . . . . . . . . . . . . .  10
     10.2.  Information and Data Models  . . . . . . . . . . . . . .  11
     10.3.  Liveness Detection and Monitoring  . . . . . . . . . . .  11
     10.4.  Verify Correct Operations  . . . . . . . . . . . . . . .  11
     10.5.  Requirements On Other Protocols  . . . . . . . . . . . .  11
     10.6.  Impact On Network Operations . . . . . . . . . . . . . .  11
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
     11.1.  STATEFUL-PCE-CAPABILITY TLV  . . . . . . . . . . . . . .  11
     11.2.  PCE-CAP-FLAGS sub-TLV  . . . . . . . . . . . . . . . . .  11
     11.3.  REALTIME-SYNC TLV  . . . . . . . . . . . . . . . . . . .  12
     11.4.  PCEP-Error Object  . . . . . . . . . . . . . . . . . . .  12
   12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  12
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  12
     13.2.  Informative References . . . . . . . . . . . . . . . . .  13
   Appendix A.  Contributor Addresses  . . . . . . . . . . . . . . .  14
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  14






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1.  Introduction

   [RFC5440] describes the Path Computation Element Protocol (PCEP) as
   the communication between a Path Computation Client (PCC) and a Path
   Computation Element (PCE), or between PCEs, enabling computation of
   Multiprotocol Label Switching (MPLS) for Traffic Engineering Label
   Switched Paths (TE LSPs).

   [I-D.ietf-pce-stateful-pce] specifies a set of extensions to PCEP to
   enable stateful control of LSPs in compliance with [RFC4655].  It
   includes mechanisms for LSP state synchronization between a PCC and a
   PCE, i.e., all stateful PCEs synchronize their LSP states from the
   network.  It further describe the handling of redundant stateful
   PCEs, where all PCEs receive the state from the network (PCCs).  When
   the primary PCE fails, another PCE can take over.

   Apart from the synchronization from the network, it is also useful if
   there is realtime synchronization mechanism between the stateful
   PCEs.  As stateful PCE make changes to its delegated LSPs, these
   changes (pending LSPs and the sticky resources) can be synchronized
   immediately to the other PCEs.  Further PCE may also synchronize any
   status change of its delegated LSPs to other PCEs.  Note that some
   synchronization issues are identified in [RFC7399].

   It should be noted that in some deployments the PCE function is part
   of the central controller architecture with multiple instances of PCE
   for load balancing and backup which uses proprietary mechanics to
   maintain consistent state between these PCE instance.  In such
   deployment PCEP MAY not used as a database synchronization mechanism.

   This document specifies the mechanisms of realtime LSP-DB
   synchronization between redundant stateful PCEs via PCEP.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

2.  Terminology

   The terminology is as per [RFC5440] and [I-D.ietf-pce-stateful-pce].

   LSP-DB:  A database of LSPs that are active in the network as
      maintained by a stateful PCE.

   Sticky Resources:  The temporarily assigned resources that are
      allocated to a pending LSP and are provisionally blocked.



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3.  Architectural Considerations

   Distributed computation model ([RFC4655]) refers to a domain or
   network that may include multiple PCEs where computation of paths is
   shared among the PCEs, this is further clarified in [RFC7399].

   When multiple stateful PCEs are operating in the network, they could
   be either -

   Primary or Backup PCE:  A backup PCE exists to perform functions in
      the network, only in the event of a failure of the primary PCE.
      In this case, all LSPs to be delegated are under primary stateful
      PCE control while other PCEs in the domain act as backup.

   Load-Balanced 'Backup' PCE:  Load-Balanced PCEs share the computation
      load at all times, as well as act backup to each other.  One PCE
      MAY serve a set of PCCs as the primary computation server, and
      only addresses requests from other PCCs in the event of the
      failure of some other PCE.  Delegated LSPs are thus distributed
      among stateful PCEs.

   In either case it is beneficial for the PCE to synchronize changes of
   its delegated LSPs to the other PCEs in realtime.  This should
   include -

   o  Any update made by the PCE to its delegated LSP.

   o  Any status change learned from the network.

   Note that the state synchronization as per
   [I-D.ietf-pce-stateful-pce] and
   [I-D.ietf-pce-stateful-sync-optimizations]remains unchanged.  This
   include initial state synchronization as well as LSP state reports.
   The mechanism described in this document are in addition to those
   already present in [I-D.ietf-pce-stateful-pce].

4.  Functions to Support LSP-DB Synchronization

   [I-D.ietf-pce-stateful-pce] specifies new functions to support a
   stateful PCE.  It also specifies that a function can be initiated
   either from a PCC towards a PCE (C-E) or from a PCE towards a PCC
   (E-C).

   o  Capability negotiation (E-C,C-E)

   o  LSP state synchronization (C-E)

   o  LSP update request (E-C)



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   o  LSP state report (C-E)

   o  LSP control delegation (C-E,E-C)

   o  Stateful PCE discovery

   This document extends some of these functions to support realtime
   LSP-DB synchronization.  These are initiated from a PCE towards
   another PCE (E-E).

   Capability negotiation (E-E):  both the PCEs must announce during
      PCEP session establishment that they support PCEP Stateful PCE
      extensions defined in [I-D.ietf-pce-stateful-pce].  It should also
      declare whether it has realtime synchronization capability between
      PCEs.  This is done via Open message.

   LSP state report (E-E):  a PCE sends an LSP state report to a PCE
      whenever the state of an delegated LSP changes.  This is usually
      triggered on receiving the state report from the PCC.  This is
      done via PCRpt message.

   LSP update request (E-E):  When a PCE requests modification of
      attributes of a delegated LSP, this information should also be
      sent to other PCEs.  This is done via PCUpd message.  This is
      needed to synchronize the pending LSPs and sticky resources.

   Stateful PCE discovery:  PCE can advertise its realtime
      synchronization capability between PCEs via IGP.

5.  Operations

5.1.  Relatime LSP-DB Synchronization between redundant Stateful PCEs

   PCE (including redundant stateful PCEs) learn LSP state from the
   PCCs.  Apart from that, for each LSP delegated to a stateful PCE -

   o  When it sends an LSP Update (PCUpd message) to the PCC for the
      delegated LSP, it also sends an LSP update to other stateful PCEs.

   o  When it receives an LSP report (LSRpt message) from the PCC for
      the delegated LSP, it also sends an LSP report to other stateful
      PCEs.

   Thus a PCE may learn LSP state from both the PCC as well as the PCE
   to which LSP is delegated.

   In Figure 1, PCE1 is the primary stateful PCE and PCE2 is the backup
   stateful PCE (all LSPs are delegated to PCE1).  PCC1 and PCC2



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   synchronize the LSP-DB with PCE1 and PCE2 after session
   initialization phase.

   PCC1 and PCC2 delegates LSP1 and LSP2 to the primary PCE1.  Whenever
   there is an update in LSP, PCE1 sends a PCUpd message to
   corresponding PCC and also to backup PCE2.  This is LSP update
   request as described in Section 4 and uses PCUpd message.  This makes
   sure that the pending LSP changes and sticky resources are backed up.
   The PCC sends a PCRpt message to the primary PCE, indicating the
   LSP's status, the primary PCE further synchronizes the state with
   backup PCEs via PCRpt message.

   +----+            +----+             +----+              +----+
   |PCC1|            |PCC2|             |PCE1|              |PCE2|
   +-+--+            +-+--+             +-+--+              +-+--+
     |                 |                  |                   |
     |---- LSP SYNC ---+----------------->|                   |
     |                 |---- LSP SYNC --->|                   |
     |                 |                  |                   |
     |                 |---- LSP SYNC ----+------------------>|
     |---- LSP SYNC ---+------------------+------------------>|
     |                 |                  |                   |
     |-- PCRpt,lsp1,D -+----------------->|                   |
     |<----------------+----PCUpd,lsp1 ---|                   |
     |                 |                  |--- PCUpd,lsp1 --->|
     |-- PCRpt,lsp1,up-+----------------->|                   |
     |-- PCRpt,lsp1,up-+------------------+------------------>|
     |                 |                  |----PCRpt,lsp1,up->|
     |                 |                  |                   |
     |                 |-- PCRpt,lsp2,D ->|                   |
     |                 |<---PCUpd,lsp2 ---|                   |
     |                 |                  |--- PCUpd,lsp2---->|
     |                 |-- PCRpt,lsp2,up->|                   |
     |                 |-- PCRpt,lsp2,up--+------------------>|
     |                 |                  |----PCRpt,lsp2,up->|
     |                 |                  |                   |


   Figure 1: Relatime LSP-DB synchronization between primary and backup
                               stateful PCEs

   The backup PCE is used only in case the primary PCE fails.  At the
   time of failure of primary PCE (PCE1), the backup PCE (PCE2) act as a
   primary.

   In Figure 2, PCE1 and PCE2 are load-balanced stateful PCEs and share
   the computation load as well as act as backup to each other.  PCC1




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   and PCC2 synchronize their LSP-DB with both PCEs after session
   initialization phase as per [I-D.ietf-pce-stateful-pce].

   PCC1 delegates LSP1 to PCE1.  Whenever there is an update in LSP1,
   PCE1 sends the PCUpd message to PCC1 and other stateful PCEs (PCE2).
   Similarly, PCC2 delegates LSP2 to PCE2.  Whenever there is an update
   in LSP2, PCE2 sends the PCUpd message to PCC2 and other stateful PCEs
   (PCE1).  This is LSP update request as described in Section 4 and it
   makes sure that the pending LSP changes and sticky resources are
   synchronized.  The PCC sends an PCRpt message to the all load-
   balanced PCEs as per [I-D.ietf-pce-stateful-pce], indicating the
   LSP's status.  The PCE to which LSP is delegated, also sends report
   message to other PCEs.

   +----+            +----+             +----+              +----+
   |PCC1|            |PCC2|             |PCE1|              |PCE2|
   +-+--+            +-+--+             +-+--+              +-+--+
     |                 |                  |                   |
     |---- LSP SYNC ---+----------------->|                   |
     |---- LSP SYNC ---+------------------+------------------>|
     |                 |---- LSP SYNC --->|                   |
     |                 |---- LSP SYNC ----+------------------>|
     |                 |                  |                   |
     |-- PCRpt,lsp1,D -+----------------->|                   |
     |                 |-- PCRpt,lsp2,D --+------------------>|
     |                 |                  |                   |
     |                 |                  |                   |
     |<----------------+----PCUpd, lsp1---|                   |
     |                 |                  |--- PCUpd, lsp1--->|
     |-- PCRpt,lsp1,up-+----------------->|                   |
     |-- PCRpt,lsp1,up-+------------------+------------------>|
     |                 |                  |----PCRpt,lsp1,up->|
     |                 |                  |                   |
     |                 |                  |                   |

     |                 |<---PCUpd, lsp2---|-------------------|
     |                 |                  |<--- PCUpd, lsp2 --|
     |                 |-- PCRpt,lsp2,up--+------------------>|
     |                 |                  |<---PCRpt,lsp1,up--|
     |                 |-- PCRpt,lsp2,up->|                   |
     |                 |                  |                   |


      Figure 2: Relatime LSP-DB synchronization between load-balanced
                               stateful PCEs

   At the time of failure of one of the PCEs (say PCE1), the other PCE
   (PCE2) may take up the load.



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5.2.  Other Considerations

   o  The computation mechanism and how PCE chooses to handle the sticky
      resources during computation is out of scope of this document.

   o  This document does not tackle the issue about TED synchronization
      which is described in detail in [RFC7399].

6.  PCEP Messages

   [Editor's Note: There are ongoing discussions to come up with a
   singular extention for inter-stateful-PCE communications.  This
   section will be updated based on the outcome of the discussion.]

6.1.  The PCRpt Message

   The format of PCRpt message is defined in
   [I-D.ietf-pce-stateful-pce].  It specifies the PCRpt message is sent
   from PCC to PCE in reporting the LSP state.  This document extends
   the usage of PCRpt message between redundant stateful PCEs for
   realtime LSP synchronization as described in Section 5.1.  A unique
   PLSP-ID needs to be generated at the PCE and should also carry the
   PCC generated PLSP-ID along in a REALTIME-SYNC TLV in the LSP object.

6.2.  The PCUpd Message

   The format of PCUpd Message is defined in
   [I-D.ietf-pce-stateful-pce].  It specifies the PCUpd message is sent
   from PCE to PCC to request changes in LSP attributes.  This document
   extends the usage of PCUpd message between stateful PCEs for realtime
   LSP synchronization as described in Section 5.1.  Whenever there is a
   PCUpd message sent from PCE to PCC, PCE should also send it to other
   PCEs along with the PCC generated PLSP-ID in a REALTIME-SYNC TLV in
   the LSP object.

7.  TLVs

7.1.  Stateful PCE Capability TLV

   As per [I-D.ietf-pce-stateful-pce], STATEFUL-PCE-CAPABILITY TLV can
   be used in the OPEN object for stateful PCE capability negotiation.
   A stateful PCE must announce during PCEP session establishment that
   they support PCEP stateful PCE extensions defined in
   [I-D.ietf-pce-stateful-pce].  A new flag is added -

   R (REALTIME-SYNC-PCE - 1 bit):  if set to 1 by PCE, the PCE has the
      capability for realtime synchronization between PCEs.  In case of
      PCC, this bit has no meaning and is simply ignored.



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7.2.  Speaker Entity Identifier TLV

   [I-D.ietf-pce-stateful-sync-optimizations] describes 'Speaker Entity
   Identifier TLV' to be included in OPEN object.  This document uses
   the same TLV in the LSP object for realtime sync between redundant
   stateful PCEs.

   For a PCE that supports realtime sync (REALTIME-SYNC-PCE R flag in
   Stateful PCE Capability TLV), the PCC MUST include 'Speaker Entity
   Identifier TLV' in the OPEN message.  Note a PCC may have to bring
   down the current session and include the TLV in the subsequent open
   message.

   Any realtime state synchronization (PCRpt or PCUpd message between
   PCEs) MUST include 'Speaker Entity Identifier TLV' in LSP object with
   the PCC's speaker identity.  If the TLV is missing, the PCE will
   generate an error with error-type 6 (mandatory object missing) and
   error-value TBD1 (Speaker Entity Identifier TLV missing) and close
   the session.

   The format of Speaker Entity Identifier is defined in
   [I-D.ietf-pce-stateful-sync-optimizations].

7.3.  REALTIME-SYNC TLV

   PCC uses the PLSP-ID in LSP object to uniquely identify an LSP.  For
   PCE to PCE realtime sync, another unique PLSP-ID needs to be
   generated at the PCE and should also carry the PCC's generated PLSP-
   ID in the REALTIME-SYNC TLV.  This way redundant PCE can correlate
   the LSP from the state received from the PCCs.

   This TLV MUST be encoded in the PCRpt and PCUpd message between
   redundant stateful PCEs.  If the TLV is missing, the PCE will
   generate an error with error-type 6 (mandatory object missing) and
   error-value TBD2 (REALTIME-SYNC TLV missing) and close the session.

   The format of the REALTIME-SYNC 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=TBD3           |           Length=4            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           PCC's PLSP-ID               |     reserved          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 3: REALTIME-SYNC TLV format




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   The type of the TLV is to be assigned by IANA and it has a fixed
   length of 4 octets.  The value contains the following fields:

   PCC's PLSP-ID (20 bits):  The PCC's original PLSP-ID as received in
      the PCRpt message from the PCC.  This along with Speaker Entity
      Identifier TLV can be used to co-relate information received from
      the network (PCCs).

7.4.  PCE-CAP-FLAGS sub-TLV

   [RFC5088] and [RFC5089] describe the mechanism to advertise the PCE
   Discovery information via OSPF and IS-IS respectively along with
   processing rules for the sub-TLVs.  [I-D.ietf-pce-stateful-pce]
   further enhances the optional PCE-CAP-FLAGS sub-TLV used to advertise
   PCE stateful capabilities.

   Further a new bit is added -

         Bit       Capabilities

         TBD4      Realtime Sync between PCEs

   If this bit is set to 1, the PCE has the capability for realtime
   synchronization between PCEs.

8.  Other Considerations

8.1.  PCE Initiated LSP

   [I-D.ietf-pce-pce-initiated-lsp] describes the setup and teardown of
   PCE-initiated LSPs under the active stateful PCE model.  As the PCE
   sends PCInitiate message to PCC to create or delete LSP, the PCE
   should also send PCUpd message to other PCEs.  For the initiation,
   the PCUpd message should have PCC's PLSP-ID as zero.  The rest of the
   processing remains unchanged.

9.  Security Considerations

   This document does not introduce any new security concerns besides
   those in [I-D.ietf-pce-stateful-pce].

10.  Manageability Considerations

10.1.  Control of Function and Policy

   A PCE may be deployed to act only as a backup (Section 5.1), an
   operator SHOULD be able to configure a PCE as backup.




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10.2.  Information and Data Models

   [RFC7420] describes the PCEP MIB, there are no new MIB Objects for
   this document.

10.3.  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].

10.4.  Verify Correct Operations

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

10.5.  Requirements On Other Protocols

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

10.6.  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].

11.  IANA Considerations

11.1.  STATEFUL-PCE-CAPABILITY TLV

   As discussed in Section 7.1, a new STATEFUL-PCE-CAPABILITY TLV Flag
   Field has been defined.  IANA has made the following allocation from
   the PCEP "STATEFUL-PCE-CAPABILITY TLV Flag Field" sub-registry:

         Bit    Description                               Reference

         TBD    REALTIME-SYNC-PCE                         [This I.D.]

11.2.  PCE-CAP-FLAGS sub-TLV

   As discussed in Section 7.1, a new bit is added, IANA is requested to
   allocate a new bit in "PCE Capability Flags" registry for backup
   stateful PCE capability as follows:

         Bit    Description                               Reference

         TBD4   Realtime Sync between PCEs                [This I.D.]



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11.3.  REALTIME-SYNC TLV

   This document defines the following new PCEP TLV:

           Value      Meaning               Reference
           TBD3       REALTIME-SYNC TLV     This document

11.4.  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= TBD2                 This document
                 Speaker Entity Identifier TLV
                 missing
                 Error-Value= TBD3                 This document
                 REALTIME-SYNC TLV missing



12.  Acknowledgments

   Thanks to Adrian Farrel and Daniel King for writing [RFC7399].

   We would like to thank Avantika Kumar for her useful comments and
   suggestions.

13.  References

13.1.  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,
              <http://www.rfc-editor.org/info/rfc2119>.

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

   [I-D.ietf-pce-stateful-pce]
              Crabbe, E., Minei, I., Medved, J., and R. Varga, "PCEP
              Extensions for Stateful PCE", draft-ietf-pce-stateful-
              pce-18 (work in progress), December 2016.




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   [I-D.ietf-pce-stateful-sync-optimizations]
              Crabbe, E., Minei, I., Medved, J., Varga, R., Zhang, X.,
              and D. Dhody, "Optimizations of Label Switched Path State
              Synchronization Procedures for a Stateful PCE", draft-
              ietf-pce-stateful-sync-optimizations-07 (work in
              progress), December 2016.

13.2.  Informative References

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

   [RFC5088]  Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
              Zhang, "OSPF Protocol Extensions for Path Computation
              Element (PCE) Discovery", RFC 5088, DOI 10.17487/RFC5088,
              January 2008, <http://www.rfc-editor.org/info/rfc5088>.

   [RFC5089]  Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
              Zhang, "IS-IS Protocol Extensions for Path Computation
              Element (PCE) Discovery", RFC 5089, DOI 10.17487/RFC5089,
              January 2008, <http://www.rfc-editor.org/info/rfc5089>.

   [RFC7399]  Farrel, A. and D. King, "Unanswered Questions in the Path
              Computation Element Architecture", RFC 7399,
              DOI 10.17487/RFC7399, October 2014,
              <http://www.rfc-editor.org/info/rfc7399>.

   [RFC7420]  Koushik, A., Stephan, E., Zhao, Q., King, D., and J.
              Hardwick, "Path Computation Element Communication Protocol
              (PCEP) Management Information Base (MIB) Module",
              RFC 7420, DOI 10.17487/RFC7420, December 2014,
              <http://www.rfc-editor.org/info/rfc7420>.

   [I-D.ietf-pce-pce-initiated-lsp]
              Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP
              Extensions for PCE-initiated LSP Setup in a Stateful PCE
              Model", draft-ietf-pce-pce-initiated-lsp-07 (work in
              progress), July 2016.











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Appendix A.  Contributor Addresses

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

   EMail: udayasree.palle@huawei.com

   Xian Zhang
   Huawei Technologies
   Bantian, Longgang District
   Shenzhen  518129
   P.R.China

   EMail: zhang.xian@huawei.com

   Venugopal Reddy Kondreddy
   Huawei Technologies
   Divyashree Techno Park, Whitefield
   Bangalore, Karnataka  560066
   India

   EMail: venugopalreddyk@huawei.com

Author's Address

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

   EMail: dhruv.ietf@gmail.com
















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