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PCE Working Group                                                Q. Zhao
Internet-Draft                                                   K. Zhao
Intended status: Experimental                                      Z. Li
Expires: September 3, 2015                                      D. Dhody
                                                                U. Palle
                                                     Huawei Technologies
                                                                B. Zhang
                                                              Telus Ltd.
                                                           March 2, 2015


   PCEP Procedures and Protocol Extensions for Using PCE as a Central
                       Controller (PCECC) of LSPs
          draft-zhao-pce-pcep-extension-for-pce-controller-01

Abstract

   In certain networks deployment scenarios, service providers would
   like to keep all the existing MPLS functionalities in both MPLS and
   GMPLS while removing the complexity of existing signaling protocols
   such as LDP and RSVP-TE.  In
   [I-D.zhao-pce-central-controller-user-cases], we propose to use the
   PCE [RFC5440] as a central controller (PCECC) so that LSP can be
   calculated/ signaled/initiated and label forwarding entries are
   downloaded through a centralized PCE server to each network devices
   along the LSP path while leveraging the existing PCE technologies as
   much as possible.

   This draft specify the procedures and PCEP protocol extensions for
   using the PCE as the central controller and user cases where LSPs are
   calculated/setup/initiated and label forwarding entries are
   downloaded through extending the existing PCE architectures and PCEP.

   This document also discuss the role of PCECC in Segment Routing (SR).

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 http://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




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   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 September 3, 2015.

Copyright Notice

   Copyright (c) 2015 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
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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
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   5
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  PCECC Modes . . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  PCEP Requirements . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Procedures for Using the PCE as the Central Controller
       (PCECC) . . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     5.1.  Stateful PCE Model  . . . . . . . . . . . . . . . . . . .   7
     5.2.  New LSP Functions . . . . . . . . . . . . . . . . . . . .   7
     5.3.  PCECC Capability Advertisement  . . . . . . . . . . . . .   8
     5.4.  Label Range Reservation . . . . . . . . . . . . . . . . .   8
     5.5.  LSP Operations  . . . . . . . . . . . . . . . . . . . . .   9
       5.5.1.  Basic PCECC Mode  . . . . . . . . . . . . . . . . . .   9
         5.5.1.1.  PCECC LSP Setup . . . . . . . . . . . . . . . . .   9
         5.5.1.2.  Label Download  . . . . . . . . . . . . . . . . .  11
         5.5.1.3.  Label Cleanup . . . . . . . . . . . . . . . . . .  11
         5.5.1.4.  PCE Initiated PCECC LSP . . . . . . . . . . . . .  12
         5.5.1.5.  PCECC LSP Update  . . . . . . . . . . . . . . . .  13
         5.5.1.6.  PCECC LSP State Report  . . . . . . . . . . . . .  14
       5.5.2.  PCECC Segment Routing (SR)  . . . . . . . . . . . . .  15
         5.5.2.1.  PCECC SR-BE . . . . . . . . . . . . . . . . . . .  15
         5.5.2.2.  PCECC SR-TE . . . . . . . . . . . . . . . . . . .  16
   6.  PCEP messages . . . . . . . . . . . . . . . . . . . . . . . .  17
     6.1.  The PCLRResv message  . . . . . . . . . . . . . . . . . .  17
     6.2.  The PCLabelUpd message  . . . . . . . . . . . . . . . . .  18
   7.  PCEP Objects  . . . . . . . . . . . . . . . . . . . . . . . .  19



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     7.1.  OPEN Object . . . . . . . . . . . . . . . . . . . . . . .  19
       7.1.1.  PCECC Capability TLV  . . . . . . . . . . . . . . . .  20
     7.2.  LABEL-RANGE Object  . . . . . . . . . . . . . . . . . . .  20
     7.3.  PATH-SETUP-TYPE TLV . . . . . . . . . . . . . . . . . . .  21
     7.4.  Label Object  . . . . . . . . . . . . . . . . . . . . . .  21
       7.4.1.  NextHop TLV . . . . . . . . . . . . . . . . . . . . .  22
     7.5.  FEC Object  . . . . . . . . . . . . . . . . . . . . . . .  24
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  25
   9.  Manageability Considerations  . . . . . . . . . . . . . . . .  26
     9.1.  Control of Function and Policy  . . . . . . . . . . . . .  26
     9.2.  Information and Data Models . . . . . . . . . . . . . . .  26
     9.3.  Liveness Detection and Monitoring . . . . . . . . . . . .  26
     9.4.  Verify Correct Operations . . . . . . . . . . . . . . . .  26
     9.5.  Requirements On Other Protocols . . . . . . . . . . . . .  26
     9.6.  Impact On Network Operations  . . . . . . . . . . . . . .  26
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  26
   11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  26
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  26
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  26
     12.2.  Informative References . . . . . . . . . . . . . . . . .  27
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  28

1.  Introduction

   In certain network deployment scenarios, service providers would like
   to have the ability to dynamically adapt to a wide range of
   customer's requests for the sake of flexible network service
   delivery, Software Defined Networks(SDN) has provides additional
   flexibility in how the network is operated compared to the
   traditional network.

   The existing networking ecosystem has become awfully complex and
   highly demanding in terms of robustness, performance, scalability,
   flexibility, agility, etc.  By migrating to the SDN enabled network
   from the existing network, service providers and network operators
   must have a solution which they can evolve easily from the existing
   network into the SDN enabled network while keeping the network
   services remain scalable, guarantee robustness and availability etc.

   Taking the smooth transition between traditional network and the new
   SDN enabled network into account, especially from a cost impact
   assessment perspective, using the existing PCE components from the
   current network to function as the central controller of the SDN
   network is one choice, which not only achieves the goal of having a
   centralized controller, but also leverages the existing PCE network
   components.





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   The Path Computation Element communication Protocol (PCEP) provides
   mechanisms for Path Computation Elements (PCEs) to perform route
   computations in response to Path Computation Clients (PCCs) requests.
   PCEP Extensions for PCE-initiated LSP Setup in a Stateful PCE Model
   [I-D.ietf-pce-stateful-pce] describes a set of extensions to PCEP to
   enable active control of MPLS-TE and GMPLS tunnels.

   [I-D.ietf-pce-pce-initiated-lsp] describes the setup and teardown of
   PCE-initiated LSPs under the active stateful PCE model, without the
   need for local configuration on the PCC, thus allowing for a dynamic
   MPLS network that is centrally controlled and deployed.

   [I-D.ietf-pce-remote-initiated-gmpls-lsp] complements
   [I-D.ietf-pce-pce-initiated-lsp] by addressing the requirements for
   remote-initiated GMPLS LSPs.

   Segment Routing (SR) technology leverages the source routing and
   tunneling paradigms.  A source node can choose a path without relying
   on hop-by-hop signaling protocols such as LDP or RSVP-TE.  Each path
   is specified as a set of "segments" advertised by link-state routing
   protocols (IS-IS or OSPF).  [I-D.ietf-spring-segment-routing]
   provides an introduction to SR technology.  The corresponding IS-IS
   and OSPF extensions are specified in
   [I-D.ietf-isis-segment-routing-extensions] and
   [I-D.ietf-ospf-segment-routing-extensions], respectively.

   A Segment Routed path (SR path) can be derived from an IGP Shortest
   Path Tree (SPT).  Segment Routed Traffic Engineering paths (SR-TE
   paths) may not follow IGP SPT.  Such paths may be chosen by a
   suitable network planning tool and provisioned on the source node of
   the SR-TE path.

   It is possible to use a stateful PCE for computing one or more SR-TE
   paths taking into account various constraints and objective
   functions.  Once a path is chosen, the stateful PCE can instantiate
   an SR-TE path on a PCC using PCEP extensions specified in
   [I-D.ietf-pce-pce-initiated-lsp] using the SR specific PCEP
   extensions described in [I-D.ietf-pce-segment-routing].

   PCECC may further use PCEP protocol for SR label distribution instead
   of IGP extensions with some benefits.

   Current MPLS label has local meaning.  That is, MPLS label is always
   allocated by the downstream node to the upstream node.  Then the MPLS
   label is only identified by the neighboring upstream node and
   downstream node.  The label allocation is done locally and signaled
   through the LDP/RSVP-TE/BGP protocol.  To ease the label allocation
   and signaling mechanism, PCE can be conveniently used as a central



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   controller with Label download capability.  Further PCE can also be
   used to manage the label range and SRGB etc.

   The PCECC solution introduced in
   [I-D.zhao-pce-central-controller-user-cases] allow for a dynamic MPLS
   network that is eventually controlled and deployed without the
   deployment of RSVP-TE protocol or extended IGP protocol with node/
   adjacency segment identifiers signaling capability while providing
   all the key MPLS functionalities needed by the service providers.

   This draft specify the procedures and PCEP protocol extensions for
   using the PCE as the central controller and user cases where LSPs are
   calculated/setup/initiated/downloaded through extending the existing
   PCE architectures and 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 following terminology is used in this document.

   IGP:  Interior Gateway Protocol.  Either of the two routing
      protocols, Open Shortest Path First (OSPF) or Intermediate System
      to Intermediate System (IS-IS).

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

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

   TE:  Traffic Engineering.

3.  PCECC Modes

   The following PCECC modes are supported -

   o  Basic PCECC.

   o  PCECC SR.

      *  PCECC SR-BE (Best Effort).



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      *  PCECC SR-TE (Traffic Engineered).

   In basic PCECC mode, the forwarding is similar to RSVP-TE signalled
   LSP without the RSVP-TE signaling.  The PCECC allocates and download
   the label entries along the LSP.  The rest of processing is similar
   to the existing stateful PCE mechanism.

   In case of SR, there are two modes for SR-BE and SR-TE.  For SR-BE,
   the forwarding is similar to LDP LSP without LDP signaling or IGP-SR
   extension.  The SR Node label are allocated and distributed in the
   domain centrally by the PCE via PCEP.  Each node (PCC) rely on local
   IGP for the nexthop calculation.  For SR-TE, the forwarding uses
   label stack similar to IGP based SR-TE without IGP-SR extension.  The
   SR node and adj labels are allocated and distributed in the domain
   centrally by the PCE via PCEP by PCECC.  Rest of the processing is
   similar to existing stateful PCE with SR mechanism.

4.  PCEP Requirements

   Following key requirements associated PCECC should be considered when
   designing the PCECC based solution:

   1.  PCEP speaker supporting this draft MUST have the capability to
       advertise its PCECC capability to its peers.

   2.  Path Computation Client (PCC) supporting this draft MUST have a
       capability to communicate local label range or global label range
       or both to PCE.

   3.  Path Computation Element (PCE) supporting this draft SHOULD have
       the capability to negotiate a global label range for a group of
       clients and communicate the final global label range to PCC.

   4.  PCEP speaker not supporting this draft MUST be able to reject
       PCECC related message with a reason code that indicates no
       support for PCECC.

   5.  PCEP SHOULD provide a means to identify PCECC based LSP in the
       PCEP messages.

   6.  PCEP SHOULD provide a means to update (or cleanup) the label-
       download or label-map entry to the PCC.

5.  Procedures for Using the PCE as the Central Controller (PCECC)







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5.1.  Stateful PCE Model

   Active stateful PCE is described in [I-D.ietf-pce-stateful-pce].  PCE
   as a central controller (PCECC) reuses existing Active stateful PCE
   mechanism as much as possible to control the LSP.

5.2.  New LSP Functions

   This document defines the following new PCEP messages and extends the
   existing messages to support PCECC:

   (PCLRResv):  a PCEP message sent by a PCC to a PCE to ask for the
      label range reservation or a PCE to a PCC to send the reserved
      label range.  The PCLRResv message described in Section 6.1.

   (PCLabelUpd):  a PCEP message sent by a PCE to a PCC to download or
      cleanup the Label entry.  The PCLabelUpd message described in
      Section 6.2.

   (PCRpt):  a PCEP message described in [I-D.ietf-pce-stateful-pce].
      PCRpt message MAYBE used to send PCECC LSP Reports.

   (PCInitiate):  a PCEP message described in
      [I-D.ietf-pce-pce-initiated-lsp].  PCInitiate message is used to
      setup PCE-Initiated LSP based on PCECC mechanism.

   (PCUpd):  a PCEP message described in [I-D.ietf-pce-stateful-pce].
      PCUpd message is used to send PCECC LSP Update.

   The new LSP functions defined in this document are mapped onto the
   messages as shown in the following table.


   +----------------------------------------+--------------------------+
   | Function                               | Message                  |
   +----------------------------------------+--------------------------+
   | PCECC Capability advertisement         | Open                     |
   | Label Range Reservation                | PCLRResv                 |
   | Label entry Update                     | PCLabelUpd               |
   | Label entry Cleanup                    | PCLabelUpd               |
   | PCECC Initiated LSP                    | PCInitiate               |
   | PCECC LSP Update                       | PCUpd                    |
   | PCECC LSP State Report                 | PCRpt                    |
   | PCECC LSP Delegation                   | PCRpt                    |
   +----------------------------------------+--------------------------+






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5.3.  PCECC Capability Advertisement

   During PCEP Initialization Phase, PCEP Speakers (PCE or PCC)
   advertise their support of PCECC extensions.  A PCEP Speaker includes
   the "PCECC Capability" TLV, described in Section 7.1.1 of this
   document, in the OPEN Object to advertise its support for PCECC
   extensions.

   The presence of the PCECC Capability TLV in PCC's OPEN Object
   indicates that the PCC is willing to function as a PCECC client.

   The presence of the PCECC Capability TLV in PCE's OPEN message
   indicates that the PCE is interested in function as a PCECC server.

   The PCEP protocol extensions for PCECC MUST NOT be used if one or
   both PCEP Speakers have not included the PCECC Capability TLV in
   their respective OPEN message.  If the PCEP Speakers support the
   extensions of this draft but did not advertise this capability then a
   PCErr message with Error-Type=19(Invalid Operation) and Error-
   Value=[TBD] (Attempted LSP setup/download/label-range reservation if
   PCECC capability was not advertised) will be generated and the PCEP
   session will be terminated.

   L flag and G flag defined in PCECC Capability TLV specifies the local
   and global label range reservation capability.

   A PCC or a PCE MUST include both PCECC-CAPABILITY TLV and STATEFUL-
   PCE-CAPABILITY TLV in OPEN Object to support the extensions defined
   in this document.  If PCECC-CAPABILITY TLV is advertised and
   STATEFUL-PCE-CAPABILITY TLV is not advertised in OPEN Object, it
   SHOULD send a PCErr message with Error-Type=19 (Invalid Operation)
   and Error-value=[TBD](stateful pce capability was not advertised) and
   terminate the session.

5.4.  Label Range Reservation

   After PCEP initial state synchronization, the label range is
   reserved.

   If L flag is advertised in OPEN Object by PCEP speakers, a PCC
   reserves a local label range and is communicated using PCLRResv
   message to a PCE.  The PCE maintains the local label range of each
   node and further during LSP setup, a label is assigned to each node
   from the corresponding local label range reserved.

   If G flag is advertised in OPEN Object by PCEP speakers,a PCC
   reserves a global label range and is advertised in PCLRResv message
   to a PCE.  The PCE MAY negotiate and reserves the global label range



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   and also sends the negotiated global label range in PCLRResv message
   to the PCC.  Please refer [I-D.li-mpls-global-label-framework] for
   MPLS global label allocation.

   A PCC MUST send PCLRResv message immediately after the initial LSP
   synchronization completion.  A PCE SHOULD not send PCLabelUpd message
   to a PCC before PCLRResv message received.  If the PCC received
   PCLabelUpd message and not initiated label range reservation, it
   SHOULD send a PCErr message with Error-type=[TBD] (label range not
   reserved) and Error-value=[TBD].

   The label range reservation sequence is shown below.


        +-+-+                           +-+-+
        |PCC|                           |PCE|
        +-+-+                           +-+-+
          |                               |
          |--- PCLRResv, label type=1 --->|local label range reserved
          |             (100-500)         |global label range negotiated
          |             label type=2      |
          |             (600-1000)        |
          |                               |
          |<--- PCLRResv, label type=2 ---|global label range reserved
          |             (700-1000)        |
          |                               |


   [Editor's Note: This section of the document would be updated with
   more details about Label Block Negotiation, Reservation, Adjustment
   etc in a future revision of the document.]

5.5.  LSP Operations

   The PCEP messages pertaining to PCECC MUST include PATH-SETUP-TYPE
   TLV [I-D.sivabalan-pce-lsp-setup-type] in the SRP object to clearly
   identify the PCECC LSP is intended.

5.5.1.  Basic PCECC Mode

5.5.1.1.  PCECC LSP Setup

   Inorder to setup a LSP based on PCECC mechanism, a PCC MUST delegate
   the LSP by sending a PCRpt message with Path Setup Type set for basic
   PCECC (see Section 7.3) and D (Delegate) flag (see
   [I-D.ietf-pce-stateful-pce]) set in the LSP object.





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   The LSP-ID in LSP-IDENTIFIER TLV (which usually corresponds to the
   RSVP-TE LSP-ID) for PCECC LSP MUST always be generated by the PCE.
   In the first PCRpt message of PCECC LSP, LSP ID of LSP-IDENTIFIER TLV
   is set to zero.

   When a PCE received PCRpt message with P and D flags set, it
   generates LSP ID; calculates the path and assign labels along the
   path; and setup the path by sending PCLabelUpd message to each node
   along the path of the LSP.

   The PCE SHOULD send the PCUpd message with the same PLSP-ID to the
   Ingress PCC in response to the delegate PCRpt message.

   The PCECC LSPs MUST be delegated to a PCE at all times.

   LSP deletion operation for PCECC LSP is same as defined in
   [I-D.ietf-pce-stateful-pce].  If the PCE received PCRpt message for
   LSP deletion then it does Label cleanup operation as described in
   Section 5.5.1.3 for the corresponding LSP.

   The Basic PCECC LSP setup sequence is as shown below.


                 +-------+                           +-------+
                 |PCC    |                           |  PCE  |
                 |Ingress|                           +-------+
          +------|       |                               |
          | PCC  +-------+                               |
          | Transit| |                                   |
   +------|        | |--- PCRpt,PLSP-ID=1, P=1, D=1  --->| PCECC LSP
   |PCC   +--------+ |       (LSP ID=0)                  |(LSPID=1)
   |Egress  |  |     |                                   |
   +--------+  |     |                                   |
       |       |     |                                   |
       |<------ PCLabelUpd,PLSP-ID=1  ------------------ | Label
       |       |     |       (LSP ID=1)                  | download
       |       |     |                                   |
       |       |<----- PCLabelUpd,PLSP-ID=1  ----------- | Label
       |       |     |      (LSP ID=1)                   | download
       |       |     |                                   |
       |       |     |<--- PCLabelUpd,PLSP-ID=1  ------- | Label
       |       |     |      (LSP ID=1)                   | download
       |       |     |                                   |
       |       |     |<-- PCUpd,PLSP-ID=1, P=1, D=1 ---- | PCECC LSP
       |       |     |      (LSP ID=1)                   | Update
       |       |     |                                   |





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   The PCECC LSP are considered to be 'up' by default.  The Ingress MAY
   further choose to deploy a data plane check mechanism and report the
   status back to the PCE via PCRpt message.

5.5.1.2.  Label Download

   Inorder to setup an LSP based on PCECC, the PCE sends a PCLabelUpd
   message to each node of the LSP to download the Label entry as
   described in Section 5.5.1.1.

   The LSP object in PCLabelUpd MUST include the LSP-IDENTIFIER TLV.

   If a node (PCC) received a PCLabelUpd message but failed to download
   the Label entry, it MUST send a PCErr message with Error-type=[TBD]
   (label download failed) and Error-value=[TBD].

5.5.1.3.  Label Cleanup

   Inorder to delete an LSP based on PCECC, the PCE sends a PCLabelUpd
   message to each node along the path of the LSP to cleanup the Label
   entry.

   If the PCC received a PCLabelUpd message but does not recognize the
   label, the PCC MUST generate a PCErr message with Error-Type
   19(Invalid operation) and Error-Value=3, "Unknown Label".

   The R flag in SRP object defined in [I-D.ietf-pce-pce-initiated-lsp]
   specifies the deletion of Label Entry in the PCLabelUpd message.























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                 +-------+                           +-------+
                 |PCC    |                           |  PCE  |
                 |Ingress|                           +-------+
          +------|       |                               |
          | PCC  +-------+                               |
          | Transit| |                                   |
   +------|        | |--- PCRpt,PLSP-ID=1,P=1,D=1,R=1--->| PCECC LSP
   |PCC   +--------+ |       (LSP ID=1)                  | remove
   |Egress  |  |     |                                   |
   +--------+  |     |                                   |
       |       |     |                                   |
       |<------ PCLabelUpd, PLSP-ID=1 ------------------ | Label
       |       |     |       (LSP ID=1, R=1)             | cleanup
       |       |     |                                   |
       |       |<----- PCLabelUpd, PLSP-ID=1 ----------- | Label
       |       |     |       (LSP ID=1, R=1)             | cleanup
       |       |     |                                   |
       |       |     |<--- PCLabelUpd, PLSP-ID=1 ------- | Label
       |       |     |       (LSP ID=1, R=1)             | cleanup
       |       |     |                                   |


5.5.1.4.  PCE Initiated PCECC LSP

   The LSP Instantiation operation is same as defined in
   [I-D.ietf-pce-pce-initiated-lsp].

   Inorder to setup a PCE Initiated LSP based on PCECC mechanism, a PCE
   sends PCInitiate message with Path Setup Type set for basic PCECC
   (see Section 7.3) to the Ingress PCC.

   The Ingress PCC MUST also set D (Delegate) flag (see
   [I-D.ietf-pce-stateful-pce]) and C (Create) flag (see
   [I-D.ietf-pce-pce-initiated-lsp]) in LSP object of PCRpt message.
   The PCC responds with first PCRpt message with the status as "GOING-
   UP" and assigned PLSP-ID.

   The rest of the PCECC LSP setup operations are same as those
   described in Section 5.5.1.1.

   The LSP deletion operation for PCE Initiated PCECC LSP is same as
   defined in [I-D.ietf-pce-pce-initiated-lsp].  The PCE should further
   perform Label entry cleanup operation as described in Section 5.5.1.3
   for the corresponding LSP.

   The PCE Initiated PCECC LSP setup sequence is shown below.





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                 +-------+                           +-------+
                 |PCC    |                           |  PCE  |
                 |Ingress|                           +-------+
          +------|       |                               |
          | PCC  +-------+                               |
          | Transit| |                                   |
   +------|        | |<---PCInitiate,PLSP-ID=0,P=1,D=1---| PCECC LSP
   |PCC   +--------+ |                                   | Initiate
   |Egress  |  |     |--- PCRpt,PLSP-ID=2,P=1,D=1,C=1--->| PCECC LSP
   +--------+  |     |       (LSP ID=0,GOING-UP)         |(LSPID=2
       |       |     |                                   | assigned)
       |<------ PCLabelUpd, PLSP-ID=2 ------------------ | Label
       |       |     |       (LSP ID=2)                  | download
       |       |     |                                   |
       |       |<----- PCLabelUpd, PLSP-ID=2 ----------- | Label
       |       |     |       (LSP ID=2)                  | download
       |       |     |                                   |
       |       |     |<--- PCLabelUpd, PLSP-ID=2 ------- | Label
       |       |     |       (LSP ID=2)                  | download
       |       |     |                                   |
       |       |     |<-- PCUpd, PLSP-ID=2, P=1, D=1---- | PCECC LSP
       |       |     |       (LSP ID=2)                  | Update
       |       |     |                                   |


5.5.1.5.  PCECC LSP Update

   Incase of a modification of PCECC LSP with a new path, a PCE sends a
   PCUpd message to the Ingress PCC.

   When a PCC received a PCUpd message for an existing LSP, a PCC MUST
   follow the make-before-break procedure.  On successful traffic switch
   over to the new LSP, PCC sends a PCRpt message to the PCE for the
   deletion of old LSP.  Further the PCE does cleanup operation for the
   old LSP described in Section 5.5.1.3.

   The PCECC LSP Update and make-before-break sequence is shown below.














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                 +-------+                           +-------+
                 |PCC    |                           |  PCE  |
                 |Ingress|                           +-------+
          +------|       |                               |
          | PCC  +-------+                               |
          | Transit| |                                   |
   +------|        | |                                   |
   |PCC   +--------+ |                                   |
   |Egress  |  |     |                                   |
   +--------+  |     |                                   |
       |       |     |                                   | Modify LSP
       |<------ PCLabelUpd, PLSP-ID=1 ------------------ | (LSPID=3
       |       |     |       (LSP ID=3)                  | assigned)
       |       |     |                                   |
       |       |<----- PCLabelUpd, PLSP-ID=1 ----------- | Label
       |       |     |      (LSP ID=3)                   | download
       |       |     |                                   |
       |       |     |<--- PCLabelUpd, PLSP-ID=1 ------- | Label
       |       |     |      (LSP ID=3)                   | download
       |       |     |                                   |
       |       |     |<-- PCUpd, PLSP-ID=1, P=1, D=1---- | PCECC
       |       |     |       (LSP ID=3)                  | LSP Update
       |       |     |                                   |
       |       |     |--- PCRpt,PLSP-ID=1,P=1,D=1,R=1--->| Delete
       |       |     |       (LSP ID=1)                  | old LSP
       |       |     |                                   |
       |<------ PCLabelUpd, PLSP-ID=1 ------------------ | Label
       |       |     |       (LSP ID=1, R=1)             | cleanup
       |       |     |                                   |
       |       |<----- PCLabelUpd, PLSP-ID=1 ----------- | Label
       |       |     |      (LSP ID=1, R=1)              | cleanup
       |       |     |                                   |
       |       |     |<--- PCLabelUpd, PLSP-ID=1 ------- | Label
       |       |     |      (LSP ID=1, R=1)              | cleanup


   The modified PCECC LSP are considered to be 'up' by default.  The
   Ingress MAY further choose to deploy a data plane check mechanism and
   report the status back to the PCE via PCRpt message.

5.5.1.6.  PCECC LSP State Report

   As mentioned before, an Ingress PCC MAY choose to apply any OAM
   mechanism to check the status of LSP in the Data plane and MAY
   further send its status in PCRpt message to the PCE.






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5.5.2.  PCECC Segment Routing (SR)

   Segment Routing (SR) as described in
   [I-D.ietf-spring-segment-routing] depends on "segments" that are
   advertised by Interior Gateway Protocols (IGPs).  The SR-node
   allocate and advertise the SID (node, adj etc) and flood via the IGP.
   This document proposes a new mechanism where PCE allocate the SID
   (label) centrally and uses PCEP to advertise the SID.  In some
   deployments PCE (and PCEP) are better suited than IGP because of
   centralized nature of PCE and direct TCP based PCEP session to the
   node.

5.5.2.1.  PCECC SR-BE

   Each node (PCC) is allocated a node-SID (label) by the PCECC.  The
   PCECC sends PCLabelUpd to update the label map of each node to all
   the nodes in the domain.  Each node (PCC) uses the local information
   to determines the next-hop and download the label forwarding
   instructions accordingly.  The PCLabelUpd message in this case MUST
   not have LSP object but uses new FEC object.


                 +-------+                           +-------+
                 |PCC    |                           |  PCE  |
                 |3.3.3.3|                           +-------+
          +------|       |                               |
          | PCC  +-------+                               |
          | 2.2.2.2| |                                   |
   +------|        | |                                   |
   |PCC   +--------+ |                                   |
   |1.1.1.1 |  |     |                                   |
   +--------+  |     |                                   |
       |       |     |                                   |
       |<------ PCLabelUpd, FEC=1.1.1.1----------------- | Label Map
       |       |     |      Label=X                      | update
       |Find   |     |                                   |
       |Nexthop|<----- PCLabelUpd, FEC=1.1.1.1---------- | Label Map
       |locally|     |             Label=X               | update
       |       |     |                                   |
       |       |     |<--- PCLabelUpd, FEC=1.1.1.1------ | Label Map
       |       |     |                 Label=X           | update
       |       |     |                                   |


   The forwarding behavior and the end result is similar to IGP based
   "Node-SID" in SR.  Thus, from anywhere in the domain, it enforces the
   ECMP-aware shortest- path forwarding of the packet towards the
   related node.



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   PCE rely on the Node label cleanup using the same PCLabelUpd message.

5.5.2.2.  PCECC SR-TE

   A Segment Routed Best Effort path (SR-BE path) can be derived from an
   IGP Shortest Path Tree (SPT) as explained above.  On the other hand,
   SR-TE paths may not follow IGP SPT.  Such paths may be chosen by a
   PCE and provisioned on the source node of the SR-TE path.

   [I-D.ietf-pce-segment-routing] extends PCEP to allow a stateful PCE
   to compute and initiate SR-TE paths, as well as a PCC to request a
   path subject to certain constraint(s) and optimization criteria in SR
   networks.

   For SR-TE, apart from node-SID, Adj-SID is used where each adjacency
   is allocated an Adj-SID (label) by the PCECC.  The PCECC sends
   PCLabelUpd to update the label map of each Adj to the corresponding
   nodes in the domain.  Each node (PCC) download the label forwarding
   instructions accordingly.  Similar to SR-BE, the PCLabelUpd message
   in this case MUST not have LSP object but uses new FEC object.


                 +-------+                           +-------+
                 |PCC    |                           |  PCE  |
                 |3.3.3.3|                           +-------+
          +------|       |                               |
          | PCC  +-------+                               |
          | 2.2.2.2| |                                   |
   +------|        | |                                   |
   |PCC   +--------+ |                                   |
   |1.1.1.1 |  |     |                                   |
   +--------+  |     |                                   |
       |       |     |                                   |
       |<------ PCLabelUpd, FEC=10.1.1.1 / ------------- | Label Map
       |       |     |          10.1.1.2                 | update
       |       |     |      Label=A                      |
       |       |     |                                   |
       |       |<----- PCLabelUpd, FEC=10.1.1.2--------- | Label Map
       |       |     |                 10.1.1.1          | update
       |       |     |             Label=B               |
       |       |     |                                   |


   The forwarding behavior and the end result is similar to IGP based
   "Adj-SID" in SR.






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   The Path Setup Type MUST be set for PCECC SR-TE (see Section 7.3).
   The rest of the PCEP procedures and mechanism are similar to
   [I-D.ietf-pce-segment-routing].

   PCE rely on the Adj label cleanup using the same PCLabelUpd message.

6.  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.

6.1.  The PCLRResv message

   A Label Range Reservation message (also referred to as PCLRResv
   message) is a PCEP message sent by a PCC to a PCE for the reservation
   of label range or by PCE to PCC to send reserved label range for the
   network.  The Message-Type field of the PCEP common header for the
   PCLRResv message is set to [TBD].

   The format of a PCLRResv message is as follows:


   PCLRResv Message>::= <Common Header>
                                <label-range>
      Where:

       <label-range> ::= <SRP>
                         <labelrange-list>

      Where
   <labelrange-list>::=<LABEL-RANGE>[<labelrange-list>]


   There are two mandatory objects that MUST be included within each
   <label-range> in the PCLRResv message: the SRP Object and LABEL-RANGE
   object.

   SRP object is defined in [I-D.ietf-pce-stateful-pce] and this
   document extends the use of SRP object in PCLRResv message.  If the
   SRP object is missing, the receiving PCE MUST send a PCErr message
   with Error-type=6 (Mandatory Object missing) and Error-value=10 (SRP
   object missing).



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   PCC generates the value of SRP-ID-number in SRP object of PCLRResv
   message send to a PCE.  The PCE MUST include the same SRP-ID-number
   in SRP object of PCLRResv message sent to the PCC in response to
   PCLRResv message.

   LABEL-RANGE object is defined in Section 7.2.  If the LABEL-RANGE
   object is missing, the receiving PCE MUST send a PCErr message with
   Error-type=6 (Mandatory Object missing) and Error-value=[TBD] (Label
   object missing).

   [Editor's Note: This section of the document would be updated with
   more details about Label Block Negotiation, Reservation, Adjustment
   etc in a future revision of the document.]

6.2.  The PCLabelUpd message

   The Label Update Message (also referred to as PCLabelUpd) is a PCEP
   message sent by a PCE to a PCC to download label or update the label
   map.  The same message is also used to cleanup the Label entry.  The
   Message-Type field of the PCEP common header for the PCLabelUpd
   message is set to [TBD].

   The format of the PCLabelUpd message is as follows:


   <PCLabelUpd Message> ::= <Common Header>
                                    <pce-label-update-list>
   Where:
   <pce-label-update-list> ::= <pce-label-update>
                              [<pce-label-update-list>]

   <pce-label-update> ::= (<pce-label-download>|<pce-label-map>)

   Where:
   <pce-label-download> ::= <SRP>
                                    <LSP>
                            <label-list>

   <pce-label-map> ::= <SRP>
                           <LABEL>
                           <FEC>

   <label-list > ::=  <LABEL>
                             [<label-list>]







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   The PCLabelUpd message is used to download label along the path of
   the LSP for the basic PCECC mode, as well as to update the label map
   for the Node and Adjacency Label in case of SR.

   The SRP object is defined in [I-D.ietf-pce-stateful-pce] and this
   document extends the use of SRP object in PCLabelUpd message.  The
   SRP object is mandatory and MUST be included in PCLabelUpd message.
   If the SRP object is missing, the receiving PCC MUST send a PCErr
   message with Error-type=6 (Mandatory Object missing) and Error-
   value=10 (SRP object missing).

   The LSP object is defined in [I-D.ietf-pce-stateful-pce] and this
   document extends the use of LSP object in PCLabelUpd message.  The
   LSP is an optional object and used in the basic PCECC mode in
   PCLabelUpd message.  LSP Identifiers TLV is defined in
   [I-D.ietf-pce-stateful-pce], it MUST be included in the LSP object in
   PCLabelUpd message.  If the TLV is missing, the PCC will generate a
   PCErr message with Error-Type=6 (mandatory object missing) and Error-
   Value=11 (LSP-IDENTIFIERS TLV missing) and close the session.

   The LABEL object is defined in Section 7.4.  The LABEL is the
   mandatory object and MUST be included in PCLabelUpd message.  If the
   LABEL object is missing, the receiving PCC MUST send a PCErr message
   with Error-type=6 (Mandatory Object missing) and Error-value=[TBD]
   (LABEL object missing).  More than one LABEL object MAY be included
   in the PCLabelUpd message for the transit LSR.

   The FEC object is defined in Section 7.5.  The FEC is an optional
   object and used in PCECC SR mode in PCLabelUpd message.  The FEC
   object encodes the Node and Adjacency information of the Label Map.

   To cleanup the SRP object must set the R (remove) bit.

7.  PCEP Objects

   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.

7.1.  OPEN Object

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







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7.1.1.  PCECC Capability TLV

   The PCECC-CAPABILITY TLV is an optional TLV for use in the OPEN
   Object for PCECC capability advertisement.  Advertisement of the
   PCECC capability implies support of LSPs that are setup through PCECC
   as per PCEP extensions defined in this document.

   Its format 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=[TBD]      |            Length=4           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Flags                         |G|L|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


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

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

   L (LOCAL-LABEL-RANGE-CAPABILITY - 1 bit):  If set to 1 by a PCEP
      speaker, it indicates that the PCEP speaker is capable for local
      label range reservation.

   G (GLOBAL-LABEL-RANGE-CAPABILITY - 1 bit):  If set to 1 by a PCEP
      speaker, it indicates that the PCEP speaker capable for global
      label range reservation.

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

7.2.  LABEL-RANGE Object

   The LABEL-RANGE object MUST be carried within PCLRResv message.  The
   LABEL-RANGE object is used to carry the label range information based
   on the label type.

   LABEL-RANGE Object-Class is TBD.

   LABEL-RANGE Object-Type is 1.








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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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  label type  |                 range size                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           label  base                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                      Optional TLVs                          //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   label type (8 bit):  The values defined for label type are label type
      1 specifies the local label.  It means the label range is non
      negotiable.  label type 2 specifies the global label.  It means
      the label range is negotiable.  Refer
      [I-D.li-mpls-global-label-framework] for global label.

   Range size (24 bit):  It specifies the size of label range.

   Label base (32 bit):  It specifies the minimum label of label range.

7.3.  PATH-SETUP-TYPE TLV

   The PATH-SETUP-TYPE TLV is defined in
   [I-D.sivabalan-pce-lsp-setup-type]; this document defines following
   new PST value:

   o  PST = 2: Path is setup via Basic PCECC mode.

   o  PST = 3: Path is setup via PCECC SR-TE mode.

   On a PCRpt or PCInitiate message, the PST=2 in PATH-SETUP-TYPE TLV in
   SRP object indicates that this LSP was setup via a basic PCECC based
   mechanism; the PST=3 indicates that this LSP was setup via a PCECC
   SR-TE based mechanism.

7.4.  Label Object

   The LABEL Object is used to specify the Label information and MUST be
   carried within PCLabelUpd message.

   LABEL Object-Class is TBD.

   LABEL Object-Type is 1.





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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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Reserved            |              Flags           |O|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              Label                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                        Optional TLV                         //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The fields in the LABEL object are as follows:

   Flags:  is used to carry any additional information pertaining to the
      label.  Currently, the following flag bit is defined:

      *  O bit(Out-label) : if the bit is set it specifies the label is
         the OUT label and it is mandatory to encode the nexthop
         information (via NEXTHOP-IPV4-ADDRESS TLV or NEXTHOP-
         IPV6-ADDRESS TLV or NEXTHOP-UNNUMBERED-IPV4-ID TLV in LABEL
         object).

   Label (32-bit):  The Label information encoded such that the 20
      rightmost bits represent a label.

7.4.1.  NextHop TLV

   This document defines the following TLV for the LABEL object to
   associate the nexthop information incase of an outgoing label.




















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   NEXTHOP-IPV4-ADDRESS TLV:

    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=TBD          |  Length = 8                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       nexthop IPv4 address                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   NEXTHOP-IPV6-ADDRESS TLV:

    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=TBD          |   Length = 20                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //               nexthop IPv6 address (16 bytes)               //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   NEXTHOP-UNNUMBERED-IPV4-ID TLV:

    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=TBD          |   Length = 12                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                            Node-ID                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Interface ID                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The NextHop TLVs are as follows:

   NEXTHOP-IPV4-ADDRESS TLV:  where Nexthop IPv4 address is specified as
      an IPv4 address of the Nexthop.

   NEXTHOP-IPV6-ADDRESS TLV:  where Nexthop IPv6 address is specified as
      an IPv6 address of the Nexthop.

   NEXTHOP-UNNUMBERED-IPV4-ID TLV:  where a pair of Node ID / Interface
      ID tuples is used for the Nexthop.






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7.5.  FEC Object

   The FEC Object is used to specify the FEC information and MAY be
   carried within PCLabelUpd message.


   FEC Object-Class is TBD.

   FEC Object-Type is 1 'IPv4 Node ID'.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      IPv4 Node ID                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   FEC Object-Type is 2 'IPv6 Node ID'.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                      IPv6 Node ID (16 bytes)                //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   FEC Object-Type is 3 'IPv4 Adjacency'.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Local IPv4 address                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Remote IPv4 address                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   FEC Object-Type is 4 'IPv6 Adjacency'.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //               Local IPv6 address (16 bytes)                 //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //               Remote IPv6 address (16 bytes)                //



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   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   FEC Object-Type is 5 'Unnumbered Adjacency with IPv4 NodeIDs'.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Local Node-ID                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Local Interface ID                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Remote Node-ID                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Remote Interface ID                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The FEC objects are as follows:

   IPv4 Node ID:  where IPv4 Node ID is specified as an IPv4 address of
      the Node.  FEC Object-type is 1, and the Object-Length is 4 in
      this case.

   IPv6 Node ID:  where IPv6 Node ID is specified as an IPv6 address of
      the Node.  FEC Object-type is 2, and the Object-Length is 16 in
      this case.

   IPv4 Adjacency:  where Local and Remote IPv4 address is specified as
      pair of IPv4 address of the adjacency.  FEC Object-type is 3, and
      the Object-Length is 8 in this case.

   IPv6 Adjacency:  where Local and Remote IPv6 address is specified as
      pair of IPv6 address of the adjacency.  FEC Object-type is 4, and
      the Object-Length is 32 in this case.

   Unnumbered Adjacency with IPv4 NodeID:  where a pair of Node ID /
      Interface ID tuples is used.  FEC Object-type is 5, and the
      Object-Length is 16 in this case.

8.  Security Considerations

   TBD








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9.  Manageability Considerations

9.1.  Control of Function and Policy

   TBD.

9.2.  Information and Data Models

   TBD.

9.3.  Liveness Detection and Monitoring

   TBD.

9.4.  Verify Correct Operations

   TBD.

9.5.  Requirements On Other Protocols

   TBD.

9.6.  Impact On Network Operations

   TBD.

10.  IANA Considerations

   TBD

11.  Acknowledgments

   We would like to thank Robert Tao, Changjing Yan, Tieying Huang for
   their useful comments and suggestions.

12.  References

12.1.  Normative References

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

   [RFC5440]  Vasseur, JP. and JL. Le Roux, "Path Computation Element
              (PCE) Communication Protocol (PCEP)", RFC 5440, March
              2009.






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   [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-10 (work in progress), October 2014.

   [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-02 (work in
              progress), October 2014.

12.2.  Informative References

   [I-D.li-mpls-global-label-framework]
              Li, Z., Zhao, Q., Chen, X., Yang, T., and R. Raszuk, "A
              Framework of MPLS Global Label", draft-li-mpls-global-
              label-framework-02 (work in progress), July 2014.

   [I-D.zhao-pce-central-controller-user-cases]
              Zhao, Q., Zhao, K., and Z. Ke, "The Use Cases for Using
              PCE as the Central Controller(PCECC) of LSPs", draft-zhao-
              pce-central-controller-user-cases-01 (work in progress),
              July 2014.

   [I-D.ietf-pce-remote-initiated-gmpls-lsp]
              Ali, Z., Sivabalan, S., Filsfils, C., Varga, R., Lopez,
              V., Dios, O., and X. Zhang, "Path Computation Element
              Communication Protocol (PCEP) Extensions for remote-
              initiated GMPLS LSP Setup", draft-ietf-pce-remote-
              initiated-gmpls-lsp-00 (work in progress), March 2014.

   [I-D.ietf-spring-segment-routing]
              Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
              Litkowski, S., Horneffer, M., Shakir, R., Tantsura, J.,
              and E. Crabbe, "Segment Routing Architecture", draft-ietf-
              spring-segment-routing-01 (work in progress), February
              2015.

   [I-D.ietf-isis-segment-routing-extensions]
              Previdi, S., Filsfils, C., Bashandy, A., Gredler, H.,
              Litkowski, S., Decraene, B., and J. Tantsura, "IS-IS
              Extensions for Segment Routing", draft-ietf-isis-segment-
              routing-extensions-03 (work in progress), October 2014.








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   [I-D.ietf-ospf-segment-routing-extensions]
              Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
              Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
              Extensions for Segment Routing", draft-ietf-ospf-segment-
              routing-extensions-04 (work in progress), February 2015.

   [I-D.ietf-pce-segment-routing]
              Sivabalan, S., Medved, J., Filsfils, C., Crabbe, E.,
              Raszuk, R., Lopez, V., and J. Tantsura, "PCEP Extensions
              for Segment Routing", draft-ietf-pce-segment-routing-00
              (work in progress), October 2014.

   [I-D.sivabalan-pce-lsp-setup-type]
              Sivabalan, S., Medved, J., Minei, I., Crabbe, E., and R.
              Varga, "Conveying path setup type in PCEP messages",
              draft-sivabalan-pce-lsp-setup-type-02 (work in progress),
              June 2014.

Authors' Addresses

   Quintin Zhao
   Huawei Technologies
   125 Nagog Technology Park
   Acton, MA  01719
   USA

   EMail: quintin.zhao@huawei.com


   Katherine Zhao
   Huawei Technologies
   2330 Central Expressway
   Santa Clara, CA  95050
   USA

   EMail: katherine.zhao@huawei.com


   Zhenbin Li
   Huawei Technologies
   Huawei Bld., No.156 Beiqing Rd.
   Beijing    100095
   China

   EMail: lizhenbin@huawei.com






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   Dhruv Dhody
   Huawei Technologies
   Divyashree Techno Park, Whitefield
   Bangalore, Karnataka  560037
   India

   EMail: dhruv.ietf@gmail.com


   Udayasree Palle
   Huawei Technologies
   Divyashree Techno Park, Whitefield
   Bangalore, Karnataka  560037
   India

   EMail: udayasree.palle@huawei.com


   Boris Zhang
   Telus Ltd.
   Toronto
   Canada

   EMail: boris.zhang@telus.com



























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