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PCE Working Group                                                Q. Zhao
Internet-Draft                                                     Z. Li
Intended status: Standards Track                                D. Dhody
Expires: April 29, 2018                                   S. Karunanithi
                                                     Huawei Technologies
                                                               A. Farrel
                                                   Juniper Networks, Inc
                                                                 C. Zhou
                                                           Cisco Systems
                                                        October 26, 2017


   PCEP Procedures and Protocol Extensions for Using PCE as a Central
                     Controller (PCECC) of SR-LSPs
           draft-zhao-pce-pcep-extension-pce-controller-sr-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.  PCE has been proposed to be used as a
   central controller (PCECC) so that LSP can be calculated/setup/
   initiated and label forwarding entries are downloaded through a
   centralized PCE server to each network devices along the path while
   leveraging the existing PCE technologies as much as possible.

   This document specifies the procedures and PCEP protocol extensions
   when the PCE functions as one of the central controller components 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 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 April 29, 2018.




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Copyright Notice

   Copyright (c) 2017 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
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   4
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  PCECC SR  . . . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  PCEP Requirements . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Procedures for Using the PCE as the Central Controller
       (PCECC) in Segment Routing  . . . . . . . . . . . . . . . . .   6
     5.1.  Stateful PCE Model  . . . . . . . . . . . . . . . . . . .   6
     5.2.  New LSP Functions . . . . . . . . . . . . . . . . . . . .   6
     5.3.  PCECC Capability Advertisement  . . . . . . . . . . . . .   6
     5.4.  PCEP session IP address and TEDB Router ID  . . . . . . .   7
     5.5.  LSP Operations  . . . . . . . . . . . . . . . . . . . . .   7
       5.5.1.  PCECC Segment Routing (SR)  . . . . . . . . . . . . .   7
         5.5.1.1.  PCECC SR Node/Prefix Label allocation . . . . . .   8
         5.5.1.2.  PCECC SR Adjacency Label allocation . . . . . . .   9
         5.5.1.3.  Redundant PCEs  . . . . . . . . . . . . . . . . .  10
         5.5.1.4.  Session Termination . . . . . . . . . . . . . . .  10
         5.5.1.5.  LABEL-DB Synchronization  . . . . . . . . . . . .  10
   6.  PCEP messages . . . . . . . . . . . . . . . . . . . . . . . .  11
     6.1.  Label Operations  . . . . . . . . . . . . . . . . . . . .  11
       6.1.1.  The PCLabelUpd message  . . . . . . . . . . . . . . .  11
       6.1.2.  The PCLabelRpt message  . . . . . . . . . . . . . . .  12
   7.  PCEP Objects  . . . . . . . . . . . . . . . . . . . . . . . .  12
     7.1.  OPEN Object . . . . . . . . . . . . . . . . . . . . . . .  12
       7.1.1.  PCECC Capability TLV  . . . . . . . . . . . . . . . .  12
     7.2.  PATH-SETUP-TYPE TLV . . . . . . . . . . . . . . . . . . .  13
     7.3.  FEC Object  . . . . . . . . . . . . . . . . . . . . . . .  13
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
   9.  Manageability Considerations  . . . . . . . . . . . . . . . .  15
     9.1.  Control of Function and Policy  . . . . . . . . . . . . .  15
     9.2.  Information and Data Models . . . . . . . . . . . . . . .  15



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     9.3.  Liveness Detection and Monitoring . . . . . . . . . . . .  15
     9.4.  Verify Correct Operations . . . . . . . . . . . . . . . .  16
     9.5.  Requirements On Other Protocols . . . . . . . . . . . . .  16
     9.6.  Impact On Network Operations  . . . . . . . . . . . . . .  16
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
     10.1.  PCECC-CAPABILITY TLV . . . . . . . . . . . . . . . . . .  16
     10.2.  PCEP Object  . . . . . . . . . . . . . . . . . . . . . .  16
     10.3.  PCEP-Error Object  . . . . . . . . . . . . . . . . . . .  16
   11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  17
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  17
     12.2.  Informative References . . . . . . . . . . . . . . . . .  18
   Appendix A.  Using existing PCEP message  . . . . . . . . . . . .  21
   Appendix B.  Contributor Addresses  . . . . . . . . . . . . . . .  22
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  23

1.  Introduction

   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
   [RFC8231] 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 tear down 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-teas-pce-central-control] introduces the architecture for
   PCE as a central controller, examines the motivations and
   applicability for PCEP as a southbound interface, and introduces the
   implications for the protocol.  [I-D.ietf-teas-pcecc-use-cases]
   describes the use cases for the PCECC architecture.

   [I-D.zhao-pce-pcep-extension-for-pce-controller] specify the PCEP
   extension for the PCE as the central controller (PCECC).  This
   document extends the PCECC procedures for Segment Routing (SR).

   Segment Routing (SR) technology leverage 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



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   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.

   The [I-D.zhao-pce-pcep-extension-for-pce-controller], specifies the
   procedures and PCEP protocol extensions for using the PCE as one of
   the the central controller components and user cases where LSPs are
   calculated/setup/initiated and label forwarding entries are
   downloaded on each hop along the path, through extending the existing
   PCE architectures and PCEP.

   This draft specify the procedures and PCEP protocol extensions for
   using the PCE as the central controller for SR label distribution and
   user cases where SR 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", "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.

2.  Terminology

   Terminologies used in this document is same as described in the draft
   [I-D.ietf-teas-pcecc-use-cases].








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3.  PCECC SR

   [I-D.ietf-pce-segment-routing] specifies extensions to PCEP that
   allow a stateful PCE to compute, update or initiate SR-TE paths.  An
   ingress node of an SR-TE path appends all outgoing packets with a
   list of MPLS labels (SIDs).  This is encoded in SR-ERO subobject,
   capable of carrying a label (SID) as well as the identity of the
   node/adjacency label (SID).

   The notion of segment and SID is defined in
   [I-D.ietf-spring-segment-routing], which fits the MPLS architecture
   [RFC3031] as the label which is managed by a local allocation process
   of LSR (similarly to other MPLS signaling protocols)
   [I-D.ietf-spring-segment-routing-mpls].  The SR information such as
   node/adjacency label (SID) is flooded via IGP as specified in
   [I-D.ietf-isis-segment-routing-extensions] and
   [I-D.ietf-ospf-segment-routing-extensions].

   As per [I-D.ietf-teas-pce-central-control], PCE as a central
   controller can allocate and provision the node/adjacency label (SID)
   via PCEP.

   Rest of the processing is similar to existing stateful PCE with SR
   mechanism.

   For the purpose of this document, it is assumed that label range to
   be used by a PCE is set on both PCEP peers.  Further, a global label
   range is assumed to be set on all PCEP peers in the SR domain.

4.  PCEP Requirements

   Following key requirements for PCECC-SR should be considered when`
   designing the PCECC based solution:

   o  PCEP speaker supporting this draft MUST have the capability to
      advertise its PCECC-SR capability to its peers.

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

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

   o  PCEP SHOULD provide a means to synchronize the SR labels between
      PCE to PCC in PCEP messages.





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

5.1.  Stateful PCE Model

   Active stateful PCE is described in [RFC8231].  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 uses the same PCEP messages and its extenstions which
   are described in [I-D.zhao-pce-pcep-extension-for-pce-controller] for
   PCECC-SR as well.

   PCEP messages PCRpt, PCInitiate, PCUpd are also used to send PCECC-SR
   Reports, LSP setup and LSP update respectively.

   PCLabelUpd message described in
   [I-D.zhao-pce-pcep-extension-for-pce-controller] is used to download
   or cleanup SR Label entry.

   PCLabelRpt message described in
   [I-D.zhao-pce-pcep-extension-for-pce-controller] is also used to
   report the set of SR Label entries from PCC to PCE for which explicit
   action is required from PCE (update or cleanup or do nothing for
   these Label entries).

   [Editor's Note: [I-D.zhao-pce-pcep-extension-for-pce-controller]
   defines new messages PCLabelUpd and PCLabelRpt.  Questions where
   raised on the need for the new messages.  Further the document also
   includes an appendix on how the existing messages can be extended to
   add this functionality.  WG needs to decide the final direction i.e.
   new specific messages are needed or existing PCEP messages can be
   extended.  See See Appendix A to see the extension of existing
   message for PCECC-SR functionality.]

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
   [I-D.zhao-pce-pcep-extension-for-pce-controller].

   A new S-bit is added in PCECC-CAPABILITY TLV to indicate support for
   PCECC-SR.  A PCC MUST set S-bit in PCECC-CAPABILITY TLV and include
   SR-PCE-CAPABILITY TLV ([I-D.ietf-pce-segment-routing]) in OPEN Object
   to support the PCECC SR extensions defined in this document.  If



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   S-bit is set in PCECC-CAPABILITY TLV and SR-PCE-CAPABILITY TLV is not
   advertised in OPEN Object, PCE SHOULD send a PCErr message with
   Error-Type=19 (Invalid Operation) and Error-value=TBD(SR capability
   was not advertised) and terminate the session.

5.4.  PCEP session IP address and TEDB Router ID

   PCE may construct its TEDB by participating in the IGP ([RFC3630] and
   [RFC5305] for MPLS-TE; [RFC4203] and [RFC5307] for GMPLS).  An
   alternative is offered by BGP-LS [RFC7752] and
   [I-D.dhodylee-pce-pcep-ls].

   PCEP [RFC5440] speaker MAY use any IP address while creating a TCP
   session.  It is important to link the session IP address with the
   Router ID in TEDB for successful PCECC operations.

   During PCEP Initialization Phase, PCC SHOULD advertise the TE mapping
   information.  Thus a PCC includes the "Node Attributes TLV"
   [I-D.dhodylee-pce-pcep-ls] with "IPv4/IPv6 Router-ID of Local Node",
   in the OPEN Object for this purpose.  [RFC7752] describes the usage
   as auxiliary Router-IDs that the IGP might be using, e.g., for TE
   purposes.  If there are more than one auxiliary Router-ID of a given
   type, then multiple TLVs are used to encode them.

   If "IPv4/IPv6 Router-ID" TLV is not present, the TCP session IP
   address is directly used for the mapping purpose.

5.5.  LSP Operations

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

5.5.1.  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
   allocates and advertises the SID (node, adj etc) and flood via the
   IGP.  This document proposes a new mechanism where PCE allocates 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.







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5.5.1.1.  PCECC SR Node/Prefix Label allocation

   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.  The TE router ID is determined from the
   TEDB or from "IPv4/IPv6 Router-ID" Sub-TLV
   [I-D.dhodylee-pce-pcep-ls], in the OPEN Object Section 5.4.

   It is RECOMMENDED that PCEP session with PCECC SR capability to use a
   different session IP address during TCP session establishment than
   the node Router ID in TEDB, to make sure that the PCEP session does
   not get impacted by the SR Node/Prefix Label maps (Section 5.4).

   If a node (PCC) receives a PCLabelUpd message with a Label, out of
   the range set aside for the global label, it MUST send a PCErr
   message with Error-type=TBD (label download failure) and Error-
   value=TBD (Label out of range) and MUST include the SRP object to
   specify the error is for the corresponding label update
   [I-D.zhao-pce-pcep-extension-for-pce-controller].

   On receiving the label map, each node (PCC) uses the local
   information to determine 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  |
                  |192.0.2.3|                           +-------+
           +------|         |                               |
           | PCC  +---------+                               |
           | 192.0.2.2| |                                   |
    +------|          | |                                   |
    |PCC   +----------+ |                                   |
    |192.0.2.1| |       |                                   |
    +---------+ |       |                                   |
        |       |       |                                   |
        |<------- PCLabelUpd, FEC=192.0.2.1---------------- | Label Map
        |       |       |      Label=X                      | update
        |Find   |       |                                   |
        |Nexthop|<------- PCLabelUpd, FEC=192.0.2.1-------- | Label Map
        |locally|       |             Label=X               | update
        |       |       |                                   |
        |       |       |<--- PCLabelUpd, FEC=192.0.2.1---- | Label Map
        |       |       |                 Label=X           | update
        |       |       |                                   |





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   The forwarding behaviour 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.

   PCE relies on the Node/Prefix Label cleanup using the same PCLabelUpd
   message.

5.5.1.2.  PCECC SR Adjacency Label allocation

   [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 PCECC SR, 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 Node/Prefix
   Label allocation, the PCLabelUpd message in this case MUST NOT have
   LSP object but uses new FEC object.


                    +---------+                         +-------+
                    |PCC      |                         |  PCE  |
                    |192.0.2.3|                         +-------+
             +------|         |                             |
             | PCC  +---------+                             |
             | 192.0.2.2| |                                 |
      +------|          | |                                 |
      |PCC   +----------+ |                                 |
      |192.0.2.1|  |      |                                 |
      +---------+  |      |                                 |
          |        |      |                                 |
          |<------ PCLabelUpd, FEC=192.0.2.1 / ------------ | Label Map
          |        |      |          192.0.2.2              | update
          |        |      |      Label=A                    |
          |        |      |                                 |
          |        |<----- PCLabelUpd, FEC=192.0.2.2------- | Label Map
          |        |      |                 192.0.2.1       | 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 for segment routing MUST be set for PCECC SR (see
   Section 7.2).  All PCEP procedures and mechanism are similar to
   [I-D.ietf-pce-segment-routing].

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

5.5.1.3.  Redundant PCEs

   [I-D.litkowski-pce-state-sync] describes synchronization mechanism
   between the stateful PCEs.  The SR Labels allocated by a PCE should
   also be synchronized among PCEs for PCECC SR state synchronization.
   Note that the SR labels are downloaded independent to the PCECC LSP,
   and remains intact till any topology change.  The redundant PCEs MUST
   have a common view of all SR labels allocated in the domain.

   Incase the session to the PCE that allocated the SR labels is down,
   similar to the LSP re-delegation mechanims, the SR labels are re-
   delegated to a redundant PCE using the PCLabelRpt message.  This is
   done so that the SR labels remains intact and cosntant in case of
   session disconnect.

5.5.1.4.  Session Termination

   [I-D.zhao-pce-pcep-extension-for-pce-controller] describes the action
   needed for label provisioned for the Basic PCECC LSP on this
   terminated session.  Similarly actions should be applied for SR
   Labels as well.

   Additionally, if PCC has any alternate PCEP session with another PCE,
   then PCC MUST deligate the SR labels of this session to this
   alternate PCE in a sequence of PCLabelRpt message.  PCE can accept it
   and can send PCLabelUpd message to update or clean the label.

   Extensions for PCLabelUpd and PCLabelRpt message for SR label are
   described in Section 6.1.

5.5.1.5.  LABEL-DB Synchronization

   [I-D.zhao-pce-pcep-extension-for-pce-controller] describes LABEL-DB
   Synchronization procedures needed for the labels provisioned for the
   Basic PCECC LSP.  Same procedures should be applied for SR labels as
   well.

   See [I-D.palle-pce-controller-labeldb-sync] for the optimizations for
   LABEL-DB synchronization procedure.





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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.  Label Operations

   [Editor's Note: [I-D.zhao-pce-pcep-extension-for-pce-controller]
   defines new messages PCLabelUpd and PCLabelRpt.  Questions where
   raised on the need for the new messages.  Further the document also
   includes an appendix on how the existing messages can be extended to
   add this functionality.  WG needs to decide the final direction i.e.
   new specific messages are needed or existing PCEP messages can be
   extended.  See See Appendix A to see the extension of existing
   message for PCECC-SR functionality.]

6.1.1.  The PCLabelUpd message

   Label Update Message (PCLabelUpd) defined in
   [I-D.zhao-pce-pcep-extension-for-pce-controller] is extended to
   update the label map at the PCC.

   The format of the extended 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-map> ::= <SRP>
                          <LABEL>
                          <FEC>

      <pce-label-download> is defined in
      [I-D.zhao-pce-pcep-extension-for-pce-controller].




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   The FEC object is defined in Section 7.3.  Either FEC object or LSP
   object defined in [I-D.zhao-pce-pcep-extension-for-pce-controller] is
   mandatory in PCLabelUpd message.  The FEC object encodes the Node and
   Adjacency information of the Label Map.

6.1.2.  The PCLabelRpt message

   Label Report Message (PCLabelRpt) defined in
   [I-D.zhao-pce-pcep-extension-for-pce-controller] is extended to
   report or delegate the label map to PCE.

   The format of the PCLabelRpt message is as follows:


      <PCLabelRpt Message> ::= <Common Header>
                               <pce-label-report-list>
      Where:
      <pce-label-report-list> ::= <pce-label-report>
                         [<pce-label-report-list>]

      <pce-label-report> ::= (<pce-label-delegate>|<pce-label-map>)

      Where:

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

      <pce-label-delegate> is defined in



   [I-D.zhao-pce-pcep-extension-for-pce-controller].

   The FEC object is defined in Section 7.3.  Either FEC object or LSP
   object defined in [I-D.zhao-pce-pcep-extension-for-pce-controller] is
   mandatory in PCLabelRpt message.  The FEC object encodes the Node and
   Adjacency information of the Label Map.

7.  PCEP Objects

7.1.  OPEN Object

7.1.1.  PCECC Capability TLV

   [I-D.zhao-pce-pcep-extension-for-pce-controller] defined the PCECC-
   CAPABILITY TLV.




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   A new S-bit is defined in PCECC-CAPABILITY TLV for PCECC-SR:


       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                           |S|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   S (PCECC-SR-CAPABILITY - 1 bit): If set to 1 by a PCEP speaker, it
   indicates that the PCEP speaker is capable for PCECC-SR capability
   and PCE would allocate node and Adj label on this session.

7.2.  PATH-SETUP-TYPE TLV

   The PATH-SETUP-TYPE TLV is defined in [I-D.ietf-pce-lsp-setup-type].
   PST = 1 (defined in [I-D.ietf-pce-segment-routing]) can be reused
   when Path is setup via PCECC SR mode.

   On a PCRpt/PCUpd/PCInitiate message, the PST=1 indicates that this
   LSP was setup via a SR based mechanism where either the labels are
   allocated by PCE via PCECC mechanism or advertised by IGP.

7.3.  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'.


      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



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       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      //                      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)                //
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      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:




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   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

   The security considerations described in
   [I-D.zhao-pce-pcep-extension-for-pce-controller] apply to the
   extensions described in this document.

9.  Manageability Considerations

9.1.  Control of Function and Policy

   A PCE or PCC implementation SHOULD allow to configure to enable/
   disable PCECC SR capability as a global configuration.

9.2.  Information and Data Models

   [RFC7420] describes the PCEP MIB, this MIB can be extended to get the
   PCECC SR capability status.

   The PCEP YANG module [I-D.ietf-pce-pcep-yang] could be extended to
   enable/disable PCECC SR capability.

9.3.  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].





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9.4.  Verify Correct Operations

   Mechanisms defined in this document do not imply any new operation
   verification requirements in addition to those already listed in
   [RFC5440] and [RFC8231].

9.5.  Requirements On Other Protocols

   PCEP extensions defined in this document do not put new requirements
   on other protocols.

9.6.  Impact On Network Operations

   PCEP implementation SHOULD allow a limit to be placed on the rate of
   PCLabelUpd messages sent by PCE and processed by PCC.  It SHOULD also
   allow sending a notification when a rate threshold is reached.

10.  IANA Considerations

10.1.  PCECC-CAPABILITY TLV

   [I-D.zhao-pce-pcep-extension-for-pce-controller] defines the PCECC-
   CAPABILITY TLV and requests that IANA creates a registry to manage
   the value of the PCECC-CAPABILITY TLV's Flag field.  IANA is
   requested to allocate a new bit in the PCECC-CAPABILITY TLV Flag
   Field registry, as follows:

           Bit            Description              Reference
           31             S((PCECC-SR-CAPABILITY)) This document

10.2.  PCEP Object

   IANA is requested to allocate new registry for FEC PCEP object.

       Object-Class Value Name                  Reference
       TBD                FEC                   This document
                          Object-Type : 1       IPv4 Node ID
                          Object-Type : 2       IPv6 Node ID
                          Object-Type : 3       IPv4 Adjacency
                          Object-Type : 4       IPv6 Adjacency
                          Object-Type : 5       Unnumbered Adjacency
                                                with IPv4 NodeID

10.3.  PCEP-Error Object

   IANA is requested to allocate new error types and error values within
   the "PCEP-ERROR Object Error Types and Values" sub-registry of the
   PCEP Numbers registry for the following errors:



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   Error-Type   Meaning
   ----------   -------
   19           Invalid operation.

                 Error-value = TBD :                 SR capability was
                                                     not advertised

11.  Acknowledgments

   We would like to thank Robert Tao, Changjing Yan, Tieying Huang and
   Avantika 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,
              DOI 10.17487/RFC2119, March 1997,
              <https://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,
              <https://www.rfc-editor.org/info/rfc5440>.

   [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,
              <https://www.rfc-editor.org/info/rfc7420>.

   [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>.

   [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>.






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   [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>.

   [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>.

   [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>.

   [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>.

   [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-11 (work in
              progress), October 2017.

12.2.  Informative References

   [RFC3031]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
              Label Switching Architecture", RFC 3031,
              DOI 10.17487/RFC3031, January 2001,
              <https://www.rfc-editor.org/info/rfc3031>.

   [I-D.ietf-teas-pce-central-control]
              Farrel, A., Zhao, Q., Li, Z., and C. Zhou, "An
              Architecture for Use of PCE and PCEP in a Network with
              Central Control", draft-ietf-teas-pce-central-control-05
              (work in progress), September 2017.

   [I-D.ietf-teas-pcecc-use-cases]
              Zhao, Q., Li, Z., Khasanov, B., Ke, Z., Fang, L., Zhou,
              C., Communications, T., and A. Rachitskiy, "The Use Cases
              for Using PCE as the Central Controller(PCECC) of LSPs",
              draft-ietf-teas-pcecc-use-cases-01 (work in progress), May
              2017.





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   [I-D.ietf-pce-lsp-setup-type]
              Sivabalan, S., Tantsura, J., Minei, I., Varga, R., and J.
              Hardwick, "Conveying path setup type in PCEP messages",
              draft-ietf-pce-lsp-setup-type-04 (work in progress), April
              2017.

   [I-D.ietf-pce-pcep-yang]
              Dhody, D., Hardwick, J., Beeram, V., and j.
              jefftant@gmail.com, "A YANG Data Model for Path
              Computation Element Communications Protocol (PCEP)",
              draft-ietf-pce-pcep-yang-05 (work in progress), June 2017.

   [I-D.zhao-pce-pcep-extension-for-pce-controller]
              Zhao, Q., Li, Z., Dhody, D., Karunanithi, S., Farrel, A.,
              and C. Zhou, "PCEP Procedures and Protocol Extensions for
              Using PCE as a Central Controller (PCECC) of LSPs", draft-
              zhao-pce-pcep-extension-for-pce-controller-05 (work in
              progress), June 2017.

   [I-D.ietf-pce-segment-routing]
              Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
              and J. Hardwick, "PCEP Extensions for Segment Routing",
              draft-ietf-pce-segment-routing-10 (work in progress),
              October 2017.

   [I-D.ietf-isis-segment-routing-extensions]
              Previdi, S., Filsfils, C., Bashandy, A., Gredler, H.,
              Litkowski, S., Decraene, B., and j. jefftant@gmail.com,
              "IS-IS Extensions for Segment Routing", draft-ietf-isis-
              segment-routing-extensions-13 (work in progress), June
              2017.

   [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-21 (work in progress), October 2017.

   [I-D.litkowski-pce-state-sync]
              Litkowski, S., Sivabalan, S., and D. Dhody, "Inter
              Stateful Path Computation Element communication
              procedures", draft-litkowski-pce-state-sync-02 (work in
              progress), August 2017.

   [I-D.dhodylee-pce-pcep-ls]
              Dhody, D., Lee, Y., and D. Ceccarelli, "PCEP Extension for
              Distribution of Link-State and TE Information.", draft-
              dhodylee-pce-pcep-ls-08 (work in progress), June 2017.



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   [I-D.ietf-spring-segment-routing]
              Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
              and R. Shakir, "Segment Routing Architecture", draft-ietf-
              spring-segment-routing-12 (work in progress), June 2017.

   [I-D.ietf-spring-segment-routing-mpls]
              Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
              Litkowski, S., and R. Shakir, "Segment Routing with MPLS
              data plane", draft-ietf-spring-segment-routing-mpls-10
              (work in progress), June 2017.

   [I-D.palle-pce-controller-labeldb-sync]
              Palle, U., Dhody, D., and S. Karunanithi, "LABEL-DB
              Synchronization Procedures for a PCE as a central
              controller(PCECC)", draft-palle-pce-controller-labeldb-
              sync-01 (work in progress), June 2017.



































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Appendix A.  Using existing PCEP message

   This is a temporary section added to this document, till the time a
   decision on the use of new messages v/s extending existing message is
   resolved.  This section should be removed before the final
   publication of the document.

   The PCInitiate message can be used to download or remove the labels -

        <PCInitiate Message> ::= <Common Header>
                                 <PCE-initiated-lsp-list>
     Where:
        <Common Header> is defined in [RFC5440]

        <PCE-initiated-lsp-list> ::= <PCE-initiated-lsp-request>
                                     [<PCE-initiated-lsp-list>]

        <PCE-initiated-lsp-request> ::=
                             (<PCE-initiated-lsp-instantiation>|
                              <PCE-initiated-lsp-deletion>|
                              <PCE-initiated-lsp-label-download>|
                              <PCE-initiated-label-map>)

        <PCE-initiated-lsp-label-download> ::= <SRP>
                                               <LSP>
                                               <label-list>

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

       <PCE-initiated-label-map> ::= <SRP>
                                     <LABEL>
                                     <FEC>

     Where:
         <PCE-initiated-lsp-instantiation> and
         <PCE-initiated-lsp-deletion> are as per
         [I-D.ietf-pce-pce-initiated-lsp].

        The LSP and SRP object is defined in [RFC8231].


   The PCRpt message can be used to report the labels that were
   allocated by the PCE, to be used during the state synchronization
   phase.






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   The format of the PCRpt message is as follows:

         <PCRpt Message> ::= <Common Header>
                             <state-report-list>
      Where:

         <state-report-list> ::= <state-report>[<state-report-list>]

         <state-report> ::= (<lsp-state-report>|
                             <pce-label-report>)

         <lsp-state-report> ::= [<SRP>]
                                <LSP>
                                <path>

         <pce-label-report> ::= (<pce-label-delegate>|
                                 <pce-label-map>)

         <pce-label-delegate> ::= <SRP>
                                  <LSP>
                                  <label-list>

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

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


       Where:
         <path> is as per [RFC8231] and the LSP and SRP object are
         also defined in [RFC8231].

   The procedure for LSP-DB synchronization would also change, in-case
   we use the existing message.  It will be the PCCs that would first
   report all the labels downloaded by the PCE during the state
   synchronization from PCC towards PCE, and then in case of any
   discrepancies PCE would use the PCInitiate message to add/remove
   labels.

Appendix B.  Contributor Addresses









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

   EMail: udayasreereddy@gmail.com

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

   EMail: katherine.zhao@huawei.com

   Boris Zhang
   Telus Ltd.
   Toronto
   Canada

   EMail: boris.zhang@telus.com


Authors' Addresses

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

   EMail: quintin.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  560066
   India

   EMail: dhruv.ietf@gmail.com


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

   EMail: satishk@huawei.com


   Adrian Farrel
   Juniper Networks, Inc
   UK

   EMail: adrian@olddog.co.uk


   Chao Zhou
   Cisco Systems

   EMail: choa.zhou@cisco.com






















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