draft-dhody-pce-pcep-extension-pce-controller-srv6-05.xml

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<rfc ipr="trust200902"
     category="std"
     docName="draft-dhody-pce-pcep-extension-pce-controller-srv6-05"
     obsoletes=""
     updates=""
     submissionType="IETF"
     xml:lang="en">
  <front>
    <title abbrev="PCECC-SRv6">PCEP Procedures and Protocol Extensions for
    Using PCE as a Central Controller (PCECC) for SRv6</title>





    <author initials="Z"
            surname="Li"
            fullname="Zhenbin Li">
      <organization>Huawei Technologies</organization>
      <address>
        <postal>
          <street>Huawei Bld., No.156 Beiqing Rd.</street>
          <city>Beijing  </city>
          <region></region>
          <code>100095</code>
          <country>China</country>
        </postal>
        <email>lizhenbin@huawei.com</email>
      </address>
    </author>

    <author initials="S" surname="Peng" fullname="Shuping Peng">
      <organization>Huawei Technologies</organization>
      <address>
        <postal>
          <street>Huawei Bld., No.156 Beiqing Rd.</street>
          <city>Beijing</city>
          <region></region>
          <code>100095</code>
          <country>China</country>
        </postal>
        <email>pengshuping@huawei.com</email>
      </address>
    </author>  

    <author initials="X"
            surname="Geng"
            fullname="Xuesong Geng">
      <organization>Huawei Technologies</organization>
      <address>
        <postal>
          <street></street>
          <city></city>
          <region></region>
          <code></code>
          <country>China</country>
        </postal>
        <email>gengxuesong@huawei.com</email>
      </address>
    </author>
 
    <author initials="M" surname="Negi" fullname="Mahendra Singh Negi">
      <organization>RtBrick India</organization>
      <address>
        <postal>
          <street>N-17L, Floor-1, 18th Cross Rd, HSR Layout Sector-3</street>
          <city>Bangalore</city>
          <region>Karnataka</region>
          <code>560102</code>
          <country>India</country>
        </postal>
        <email>mahend.ietf@gmail.com</email>
      </address>
    </author>

    <date  year="2020" />
    <area>Routing</area>
    <workgroup>PCE Working Group</workgroup>
    <abstract>
   <t>The Path Computation Element (PCE) is a core component of Software-
   Defined Networking (SDN) systems.  It can compute optimal paths for
   traffic across a network and can also update the paths to reflect
   changes in the network or traffic demands.</t>

   <t>PCE was developed to derive paths for MPLS Label Switched Paths
   (LSPs), which are supplied to the head end of the LSP using the Path
   Computation Element Communication Protocol (PCEP).  But SDN has a
   broader applicability than signaled (G)MPLS traffic-engineered (TE)
   networks, and the PCE may be used to determine paths in a range of
   use cases.  PCEP has been proposed as a control protocol for use in
   these environments to allow the PCE to be fully enabled as a central
   controller.</t>

   <t>A PCE-based Central Controller (PCECC) can simplify the processing of
   a distributed control plane by blending it with elements of SDN and
   without necessarily completely replacing it. This document specifies the procedures and PCEP protocol extensions
   when a PCE-based controller is also responsible for configuring the
   forwarding actions on the routers for Segment Routing (SR) in IPv6 (SRv6), in addition to computing the SRv6 paths
   for packet flows and telling the edge
   routers what instructions to attach to packets as they enter the
   network.   </t>

   </abstract>
  </front>
  <middle>
    <section title="Introduction"
             toc="default">
<t>The Path Computation Element (PCE) <xref target='RFC4655'/> was developed to offload
   the path computation function from routers in an MPLS traffic-engineered
   network.  Since then, the role and function of the PCE has grown to
   cover a number of other uses (such as GMPLS <xref target='RFC7025'/>) and to allow
   delegated control <xref target='RFC8231'/> and PCE-initiated use of network
   resources <xref target='RFC8281'/>.</t>

   <t>According to <xref target='RFC7399'/>, Software-Defined Networking (SDN) refers to a
   separation between the control elements and the forwarding components
   so that software running in a centralized system, called a
   controller, can act to program the devices in the network to behave
   in specific ways.  A required element in an SDN architecture is a
   component that plans how the network resources will be used and how
   the devices will be programmed.  It is possible to view this
   component as performing specific computations to place traffic flows
   within the network given knowledge of the availability of network
   resources, how other forwarding devices are programmed, and the way
   that other flows are routed.  This is the function and purpose of a
   PCE, and the way that a PCE integrates into a wider network control
   system (including an SDN system) is presented in <xref target='RFC7491'/>.</t>

   <t>In early PCE implementations, where the PCE was used to derive paths
   for MPLS Label Switched Paths (LSPs), paths were requested by network
   elements (known as Path Computation Clients (PCCs)), and the results
   of the path computations were supplied to network elements using the
   Path Computation Element Communication Protocol (PCEP) <xref target='RFC5440'/>.
   This protocol was later extended to allow a PCE to send unsolicited
   requests to the network for LSP establishment <xref target='RFC8281'/>.</t>

   <t><xref target='RFC8283'/> introduces the architecture for PCE as a central
   controller as an extension of the architecture described in <xref target='RFC4655'/>
   and assumes the continued use of PCEP as the protocol used between
   PCE and PCC. <xref target='RFC8283'/>  further examines the motivations and applicability
   for PCEP as a Southbound Interface (SBI), and introduces the implications for the
   protocol.  <xref target='I-D.ietf-teas-pcecc-use-cases'/> describes the use cases for
   the PCE-based Central Controller (PCECC) architecture.</t>
   
   <t><xref target='I-D.ietf-pce-pcep-extension-for-pce-controller'/> specify the procedures and PCEP extensions for
   using the PCE as the central controller for static LSPs, where 
   LSPs can be provisioned as explicit label instructions at each
   hop on the end-to-end path.</t>

   <t>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).  <xref target='RFC8402'/> provides an
   introduction to SR architecture. The corresponding IS-IS and OSPF extensions are
   specified in <xref target='RFC8667'/> and
   <xref target='RFC8665'/> , respectively.
   It relies on a series of
   forwarding instructions being placed in the header of a packet. 
   The list of segments forming the path is called the
   Segment List and is encoded in the packet header.  Segment Routing
   can be applied to the IPv6 architecture with the Segment Routing
   Header (SRH) <xref target='RFC8754'/>.  A segment is
   encoded as an IPv6 address.  An ordered list of segments is encoded
   as an ordered list of IPv6 addresses in the routing header.  The
   active segment is indicated by the Destination Address of the packet.
   Upon completion of a segment, a pointer in the new routing header is
   incremented and indicates the next segment.
   The segment routing architecture supports operations that can be used
   to steer packet flows in a network, thus providing a form of traffic
   engineering. <xref target='RFC8664'/> and <xref target='I-D.ietf-pce-segment-routing-ipv6'/> specify the SR specific PCEP
   extensions. 
 </t>


   <t>PCECC may further use PCEP for SR SID (Segment Identifier) distribution on the SR nodes
    with some benefits. <xref target='I-D.zhao-pce-pcep-extension-pce-controller-sr'/> specifies the procedures and PCEP extensions when 
   a PCE-based controller is also responsible for configuring
   the forwarding actions on the routers (SR-MPLS SID distribution in this case), in addition to computing
   the paths for packet flows in a segment routing network and telling the edge routers
   what instructions to attach to packets as they enter the network. This document extends this to include SRv6 SID distribution as well.
   </t>

      <!--<t>[Important Note - Note that this document achieves by extending the new PCEP message defined in <xref target='I-D.zhao-pce-pcep-extension-for-pce-controller'/>. 
    The authors and WG also debated on the use of existing PCEP messages. 
    <xref target="Procedures"/> defines the first approach where as <xref target="appendix"/>  
    defines the latter. The authors are open to either of the approach and
    will follow the direction of the WG.]</t>-->

      <section title="Requirements Language"
               toc="default">
        <t>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 <xref target="RFC2119" /> <xref target="RFC8174"/> when, and only when, they
      appear in all capitals, as shown here.</t>
      </section>
    </section>
    
    <section title="Terminology"
             toc="default">
      <t>Terminologies used in this document is the same as described in the draft 
       <xref target="RFC8283"/> and <xref target='I-D.ietf-teas-pcecc-use-cases'/>.</t>      
    </section>
    
    <section title="PCECC SRv6"
             toc="default"
             anchor="SEC_M">

    <t><xref target='RFC8664'/> specifies extensions to 
    PCEP that allow a stateful PCE to
   compute, update, or initiate SR-TE paths for MPLS dataplane. 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). <xref target='I-D.ietf-pce-segment-routing-ipv6'/> extends the procedure
   to include support for SRv6 paths.</t>         
   
   <t>As per <xref target='RFC8754'/>, an SRv6 Segment is a
   128-bit value.  "SRv6 SID" or simply "SID" are often used as a
   shorter reference for "SRv6 Segment".  Further details are in an
   illustration provided in
   <xref target='I-D.ietf-spring-srv6-network-programming'/>.
The SR is applied to IPV6 data
   plane using SRH.  An SR path can be derived from an IGP Shortest Path
   Tree (SPT), but SR-TE paths may not follow IGP SPT.  Such paths may
   be chosen by a suitable network planning tool, or a PCE and
   provisioned on the ingress node. <xref target='I-D.ietf-pce-segment-routing-ipv6'/> specify 
   the SRv6-ERO subobject capable of carrying an SRv6 SID as well as the identity
   of the node/adjacency represented by the SID.</t>

   <t>As per <xref target='RFC8283'/>, 
   PCECC can allocate and provision the node/prefix/adjacency label (SID) via PCEP. 
  As per <xref target='I-D.ietf-teas-pcecc-use-cases'/> this is also applicable to SRv6 SIDs.</t> 
   <t>The rest of the
   processing is similar to existing stateful PCE for SRv6 <xref target='I-D.ietf-pce-segment-routing-ipv6'/>.</t>

   </section>
   
    <section title="PCEP Requirements"
             toc="default"
             anchor="SEC_R">
   <t>Following key requirements for PCECC-SRv6 should be considered when
   designing the PCECC-based solution:</t>
      <t>
        <list style="symbols">
   <t>A PCEP speaker supporting this draft needs to have the capability to
       advertise its PCECC-SRv6 capability to its peers.</t>
   <t>PCEP procedures need to allow for PCC-based SRv6 SID allocations.</t>  

   <!--<t>PCEP speaker not supporting this draft needs to be able to reject
       PCECC-SRv6 related message with a reason code that indicates no
       support for it.</t>-->

   <t>PCEP procedures need means to update (or clean up) the SRv6 SID to the PCC.</t>

   <t>PCEP procedures need to provide a mean to synchronize the SRv6 SID allocations between
       the PCE to the PCC in the PCEP messages.</t>

        </list>
      </t>
    </section>
    
    
    <section title="Procedures for Using the PCE as a Central Controller (PCECC) in SRv6"
             toc="default" anchor="Procedures">
             
    <section title="Stateful PCE Model"
             toc="default">
    <t>Active stateful PCE is described in <xref target='RFC8231'/>. PCE
    as a Central Controller (PCECC) reuses the existing active stateful PCE
    mechanism as much as possible to control the LSPs.</t>
    </section>
    
    <section title="New Functions"
             toc="default">
   <t>This document uses the same PCEP messages and its extensions which
   are described in <xref target='I-D.ietf-pce-pcep-extension-for-pce-controller'/> and <xref target='I-D.zhao-pce-pcep-extension-pce-controller-sr'/> for
   PCECC-SRv6 as well.</t>
   
   <t>The PCEP messages PCRpt, PCInitiate, PCUpd are used to send
   LSP Reports, LSP setup, and LSP update respectively. The extended PCInitiate message described in
   <xref target='I-D.ietf-pce-pcep-extension-for-pce-controller'/> is used to download
   or clean up central controller's instructions (CCIs) (SRv6 SID in the scope of this document). The extended PCRpt message described in
   <xref target='I-D.ietf-pce-pcep-extension-for-pce-controller'/> is also used to report
   the CCIs (SRv6 SIDs) from PCC to PCE.</t>

    <!--<t>[Editor's Note: <xref target='I-D.zhao-pce-pcep-extension-for-pce-controller'/> defines new messages PCLabelUpd and 
      PCLabelRpt. The authors and WG also debated on the use of existing PCEP 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 <xref target="appendix"/> 
      to see the extension of existing message for PCECC-SR functionality.]</t>-->
        
        <t><xref target='I-D.ietf-pce-pcep-extension-for-pce-controller'/> specify an object called CCI for the encoding of the central controller's instructions. <xref target='I-D.zhao-pce-pcep-extension-pce-controller-sr'/> defined a CCI object-type for segment routing. This document further defines a new CCI object-type for SRv6.
      </t>
    </section>
    
    <section title="PCECC Capability Advertisement"
             toc="default">
   <t>During PCEP Initialization Phase, PCEP Speakers (PCE or PCC)
   advertise their support of PCECC extensions.  A PCEP Speaker includes
   the "PCECC Capability" sub-TLV, described in 
   <xref target='I-D.ietf-pce-pcep-extension-for-pce-controller'/>.</t>

   <t>A new S-bit is added in the PCECC-CAPABILITY sub-TLV to indicate support for 
   PCECC-SR in <xref target='I-D.zhao-pce-pcep-extension-pce-controller-sr'/>. This document adds another I-bit to indicate support for SR in IPv6. A PCC MUST set the I-bit in the PCECC-CAPABILITY sub-TLV and include 
   the SRv6-PCE-CAPABILITY sub-TLV (<xref target='I-D.ietf-pce-segment-routing-ipv6'/>) in the OPEN Object 
   (inside the PATH-SETUP-TYPE-CAPABILITY TLV)
   to support the PCECC SRv6 extensions defined in this document.  If
   I-bit is set in PCECC-CAPABILITY sub-TLV and the SRv6-PCE-CAPABILITY sub-TLV is not
   advertised in the OPEN Object, PCE SHOULD send a PCErr message with
   Error-Type=19 (Invalid Operation) and Error-value=TBD4 (SRv6 capability
   was not advertised) and terminate the session.</t>

    <t>The rest of the processing is as per  
     <xref target='I-D.ietf-pce-pcep-extension-for-pce-controller'/>.</t>
   </section>
   
   <section title="PCEP session IP address and TED Router ID"
             toc="default" anchor="SEC_SESSION">
   <t>As described in <xref target='I-D.zhao-pce-pcep-extension-pce-controller-sr'/>, it is important to link the session IP address with the
   Router ID in TED for successful PCECC-SRv6 operations.</t>
   </section>

   
    <section title="SRv6 Path Operations"
             toc="default">
            <t><xref target='RFC8664'/> specify the PCEP extension 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. <xref target='I-D.ietf-pce-segment-routing-ipv6'/> extends it to support SRv6.</t>         
                <t>The Path Setup Type for SRv6 (PST=TBD) is used on the PCEP session with the Ingress as per 
        <xref target='I-D.ietf-pce-segment-routing-ipv6'/>.</t>

    <!--<t> The PCEP messages pertaining to PCECC-SRv6 MUST include PATH-SETUP-TYPE
   TLV <xref target='RFC8408'/> with PST=TBD2 in the SRP object
   to clearly identify the PCECC-SRv6 setup is intended.</t>-->
   
    <section title="PCECC Segment Routing in IPv6 (SRv6)"
             toc="default"
             anchor="SEC_SR_SETUP">
   <t>Segment Routing (SR) as described in
   <xref target='RFC8402'/> depends on "segments" that are
   advertised by Interior Gateway Protocols (IGPs).  The SR-node
   allocates and advertises the SID (node, adj, etc) and floods them via the
   IGP.  This document proposes a new mechanism where PCE allocates the
   SRv6 SID centrally and uses PCEP to advertise them.  In some
   deployments, PCE (and PCEP) are better suited than IGP because of
   the centralized nature of PCE and direct TCP based PCEP sessions to the
   node.</t>
   
       <section title="PCECC SRv6 Node/Prefix SID allocation"
             toc="default"
             anchor="SEC_NODE_ALLOC">
        <t>Each node (PCC) is allocated a node SRv6 SID by the PCECC.  The
         PCECC sends the PCInitiate message to update the SRv6 SID table of each node.  
         The TE router ID is determined from the
         TED or from "IPv4/IPv6 Router-ID" Sub-TLV
         <xref target='I-D.dhodylee-pce-pcep-ls'/>, in the OPEN Object.</t>

         <!--<t>Note: See <xref target="appendix"/> for how
   we could use PCInitiate message instead.]</t>-->

        <!--<t>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 (<xref target="SEC_SESSION"/>).</t>-->

         <!--<t>If a node (PCC) receives a PCInitiate message with a CCI encoding a SID, out
      of the range set aside for the SRGB, it MUST send a PCErr message with Error-type=TBD
   (PCECC failure) and Error-value=TBD (SID out of range) and MUST include the
   SRP object to specify the error is for the corresponding label update via PCInitiate message.</t>-->

        <t>On receiving the SRv6 node SID allocation, each node (PCC) uses the local
         routing information to determine the next-hop and download the 
         forwarding instructions accordingly.  The PCInitiate message uses the FEC object <xref target='I-D.zhao-pce-pcep-extension-pce-controller-sr'/>.</t>


         <t>On receiving the SRv6 node SID allocation:<list>

  <t>For the local SID, the node (PCC) needs to update SID with associated 
  function (END function in this case) in "My Local SID Table" (<xref target="I-D.ietf-spring-srv6-network-programming"/>).</t>
  
  <t>For the non-local SID, the node (PCC) uses the local routing information
  to determine the next-hop and download the forwarding instructions accordingly.  </t></list></t>
  
  <!--<t>The PCInitiate message in this
  case MUST have FEC object.</t>-->         
        

        <t>The forwarding behavior and the end result is similar to IGP based
        "Node-SID" in SRv6.  Thus, from anywhere in the domain, it enforces the
        ECMP-aware shortest-path forwarding of the packet towards the related
        node as per <xref target='RFC8402'/>.</t>

        <t>PCE relies on the Node/Prefix SRv6 SID clean  up using the same PCInitiate
        message as per <xref target='RFC8281'/>.</t>             

       </section>
       
       <section title="PCECC SRv6 Adjacency SID allocation"
             toc="default"
             anchor="SEC_ADJ_ALLOC">
             
        <!--<t><xref target='RFC8664'/> 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.</t>-->

        <t>For PCECC-SRv6, apart from node-SID, Adj-SID is used where each adjacency
         is allocated an Adj-SID by the PCECC.  The PCECC sends
         PCInitiate message to update the SRv6 SID entry for each adjacency to the corresponding
         nodes in the domain.  Each node (PCC) download the SRv6 SID
         instructions accordingly.  Similar to SRv6 Node/Prefix Label allocation, the
         PCInitiate message in this case uses
         the FEC object. </t>
        
        <t>The forwarding behavior and the end result is similar to IGP based
        "Adj-SID" in SRv6 as per <xref target='RFC8402'/>.</t>

<t>The handling of adjacencies on the LAN subnetworks is specified in <xref target="RFC8402"/>. PCECC MUST assign Adj-SID for every pair of routers in the LAN. The rest of the protocol mechanism remains the same.</t>

        <!--<t>The Path Setup Type for segment routing MUST be set for PCECC SRv6 = TBD2
         (see <xref target="SEC_PATH"/>).  All PCEP procedures and mechanism are similar to
        <xref target='RFC8664'/>.</t>-->

        <t>PCE relies on the Adj label clean up using the same PCInitiate
        message as per <xref target='RFC8281'/>.</t>

       </section>

        <section title="Redundant PCEs "
             toc="default"
             anchor="SEC_REDUND">

       <t><xref target='I-D.litkowski-pce-state-sync'/> describes the synchronization
       mechanism between the stateful PCEs. The SRv6 SIDs allocated by a PCE MUST also be 
       synchronized among PCEs for PCECC-SRv6 state synchronization. Note that the SRv6 SIDs
       are independent of the SRv6 paths, and remains intact till any topology 
       change. The redundant PCEs MUST have a common view of all SRv6 SIDs allocated in the
       domain.
     </t>
    
       </section>     
       
       <section title="Re-Delegation and Clean up"
             toc="default"
             anchor="SEC_SES_TERMIN">
        <t><xref target='I-D.ietf-pce-pcep-extension-for-pce-controller'/> describes the action
        needed for CCIs for the static LSPs on a terminated
        session. Same holds true for the CCI for SRv6 SID as well.</t>
       </section>

       <section title="Synchronization of SRv6 SID Allocations"
             toc="default"
             anchor="SEC_DB_SYNC">
        <t><xref target='I-D.ietf-pce-pcep-extension-for-pce-controller'/> describes the synchronization of Central Controller's Instructions (CCI) via the LSP state synchronization 
   as described in <xref target='RFC8231'/> and 
   <xref target='RFC8232'/>.  
        Same procedures are applied for the CCI for the SRv6 SIDs as well.</t>    
        <!--<t>See <xref target="I-D.palle-pce-controller-labeldb-sync"/> for the optimizations for LABEL-DB synchronization procedure.</t>          -->
       </section>       
       
       </section>
    </section>
    </section>

    
    <section title="PCEP Messages"
             toc="default">
    <t>The PCEP messages are as per  <xref target='I-D.zhao-pce-pcep-extension-pce-controller-sr'/>.</t>
   
    
    </section>

    
    <section title="PCEP Objects"
             toc="default">

    <section title="OPEN Object"
             toc="default">

    <section title="PCECC Capability sub-TLV"
             toc="default"
             anchor="SEC_PCECC_CAP_TLV">
    <t><xref target='I-D.ietf-pce-pcep-extension-for-pce-controller'/> defined
    the PCECC-CAPABILITY sub-TLV.</t>
    <t>A new I-bit is defined in PCECC-CAPABILITY sub-TLV for PCECC-SRv6:</t>
<figure align="left"
                alt=""
                height=""
                suppress-title="true"
                title=""
                width=""
                anchor="SEC_CAP">
          <artwork align="left"
         alt=""
         height=""
         name=""
         type=""
         width=""
         xml:space="preserve">
<![CDATA[
    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                       |I|S|L|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]>
        </artwork>
        </figure>
        <t>[Editor's Note - The above figure is included for ease of the reader but should be removed before publication.]</t>

    <t>I (PCECC-SRv6-CAPABILITY - 1 bit - TBD1):  If set to 1 by a PCEP speaker, it
      indicates that the PCEP speaker is capable of PCECC-SRv6 capability
      and the PCE allocates the Node and Adj SRv6 SID on this session.</t>
    </section>

    </section>
    
    <section title="SRv6 Path Setup"
             toc="default"
             anchor="SEC_PATH">
             
    <t>The PATH-SETUP-TYPE TLV is defined in <xref target='RFC8408'/>. A PST value of TBD is used
   when Path is setup via SRv6 mode as per <xref target='I-D.ietf-pce-segment-routing-ipv6'/>. The procedure for SRv6 path setup as specified in <xref target='I-D.ietf-pce-segment-routing-ipv6'/> remians unchanged.</t>

   <!--<t>On a PCRpt/PCUpd/PCInitiate message, the PST=TBD2 indicates that this 
   path was setup via a PCECC-SRv6 based mechanism where either the SIDs were 
   allocated/instructed by PCE via PCECC mechanism.</t>-->


    </section>
    <section title="CCI Object"
             toc="default"
             anchor="SEC_CCI">
    <t>The Central Control Instructions (CCI) Object is used by the PCE to specify the cntroller instructions is defined in <xref target='I-D.ietf-pce-pcep-extension-for-pce-controller'/>. 
    This document defines another object-type for SRv6 purpose. </t>
    <t>CCI Object-Type is TBD3 for SRv6 as below - 
      <figure align="left"
                alt=""
                height=""
                suppress-title="true"
                title=""
                width=""
                anchor="SEC_FIG9">
          <artwork align="left"
         alt=""
         height=""
         name=""
         type=""
         width=""
         xml:space="preserve">
<![CDATA[
 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                            CC-ID                              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      MT-ID    |    Algorithm  |    Flags      |B|P|G|C|N|E|V|L|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|           Reserved            |   SRv6 Endpoint Function      | 
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
|                      SRv6 Identifier                          |
|                         (128-bit)                             |
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
//                        Optional TLV                         //
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]>
        </artwork>
        </figure>
       </t>                 
       <t>The field CC-ID is as described in <xref target='I-D.ietf-pce-pcep-extension-for-pce-controller'/>. The field MT-ID, Algorithm, Flags are defined in 
       <xref target='I-D.zhao-pce-pcep-extension-pce-controller-sr'/>.</t>
      <t>Reserved: MUST be set to 0 while sending and ignored on receipt.</t>
      <t>SRv6 Endpoint Function: 16-bit field representing supported
      functions associated with SRv6 SIDs.</t>
      <t>SRv6 Identifier: 128-bit IPv6 addresses representing SRv6
      segment.</t>
      <t>[Editor's Note - It might be useful to separate the LOC:FUNC part in the SRv6 SID (future study)]</t>
     </section>   
    <section title="FEC Object"
             toc="default"
             anchor="SEC_FEC">
    <t>The FEC Object is used to specify the FEC information and MAY be
   carried within PCInitiate or PCRpt message.</t>
    <t>FEC Object (and various Object-Types) are described in <xref target='I-D.zhao-pce-pcep-extension-pce-controller-sr'/>. SRv6 Node SID MUST includes the FEC Object-Type 2 for IPv6 Node. 
    SRv6 Adjacency SID MUST include the FEC Object-Type=4 for IPv6 adjacency. Further FEC object types could be added in future extensions.</t>  
    

    </section>
    </section>    

  
    <section title="Security Considerations"
             toc="default">
    <t>The security considerations described in 
     <xref target='I-D.ietf-pce-pcep-extension-for-pce-controller'/> apply to the
     extensions described in this document.</t>

      <t>As per <xref target="RFC8231"/>, it is RECOMMENDED that these PCEP extensions only be activated on authenticated and encrypted sessions across PCEs and PCCs belonging to the same administrative authority, using Transport Layer Security (TLS) <xref target="RFC8253"/> as per the recommendations and best current practices in <xref target="RFC7525"/> (unless explicitly set aside in <xref target="RFC8253"/>).</t>
    </section>
    
    <section title="Manageability Considerations"
             toc="default">
      <section title="Control of Function and Policy"
               toc="default">
        <t> A PCE or PCC implementation SHOULD allow to configure to
   enable/disable PCECC SRv6 capability as a global configuration.</t>
      </section>
      <section title="Information and Data Models"
               toc="default">
        <t><xref target="RFC7420"/> describes the PCEP MIB, this MIB can be extended to get the
           PCECC SRv6 capability status.</t>
   
        <t>The PCEP YANG module <xref target="I-D.ietf-pce-pcep-yang"/> could be extended
           to enable/disable PCECC SRv6 capability.</t>
      </section>
      <section title="Liveness Detection and Monitoring"
               toc="default">
        <t>Mechanisms defined in this document do not imply any new liveness
           detection and monitoring requirements in addition to those already
           listed in <xref target="RFC5440"/>.</t>
      </section>
      <section title="Verify Correct Operations"
               toc="default">
        <t>Mechanisms defined in this document do not imply any new operation
   verification requirements in addition to those already listed in
   <xref target="RFC5440"/> and <xref target="RFC8231"/>.</t>
      </section>
      <section title="Requirements On Other Protocols"
               toc="default">
        <t>PCEP extensions defined in this document do not put new requirements
   on other protocols.</t>
      </section>
      <section title="Impact On Network Operations"
               toc="default">
        <t>PCEP implementation SHOULD allow a limit to be placed on the rate
   of PCInitiate/PCUpd messages (as per <xref target="RFC8231"/>) sent by PCE and processed by PCC.
   It SHOULD also allow sending a notification when a rate threshold is
   reached.</t>
      </section>
    </section>

    
    <section title="IANA Considerations"
             toc="default">

      <section title="PCECC-CAPABILITY sub-TLV" toc="default">
      <t><xref target='I-D.ietf-pce-pcep-extension-for-pce-controller'/> defines the
      PCECC-CAPABILITY sub-TLV and requests that IANA creates a registry to
      manage the value of the PCECC-CAPABILITY sub-TLV's Flag field.  IANA
      is requested to allocate a new bit in the PCECC-CAPABILITY sub-TLV Flag
      Field registry, as follows:</t>
     <texttable anchor="CAP-TLV" style="none" suppress-title="true" title="" align="center">
      <ttcol align="left" width="20%">Bit</ttcol>
      <ttcol align="left" width="30%">Description</ttcol>
      <ttcol align="left" width="20%">Reference</ttcol>
       <c>TBD1</c>
       <c>SRv6</c>
       <c>This document</c>
     </texttable>         
      </section>

      <!--<section title="New Path Setup Type Registry" toc="default">
        <t>IANA is requested to allocate new PST Field in PATH-
           SETUP-TYPE TLV.  The allocation policy for this new registry should
           be by IETF Consensus. The new registry should contain the following value:</t>
     <texttable anchor="PCEP-PATH-TYPE" style="none" suppress-title="true" title="" align="center">
      <ttcol align="left" width="20%">Value</ttcol>
      <ttcol align="left" width="30%">Description</ttcol>
      <ttcol align="left" width="20%">Reference</ttcol>
       <c>TBD2</c>
       <c>Path is</c>
       <c>This document</c>
       <c> </c>
       <c>setup using PCECC-SRv6 mode</c>
       <c> </c>       
     </texttable>      
      </section>-->
<section title="PCEP Object" toc="default">
        <t>IANA is requested to allocate a new code-point for the new CCI object-type in "PCEP Objects" sub-registry as follows:</t>
     <texttable anchor="PCEP-OBJECT" style="none" suppress-title="true" title="" align="center">
      <ttcol align="left" width="10%">Object-Class Value</ttcol>
      <ttcol align="left" width="10%">Name</ttcol>
      <ttcol align="left" width="40%">Object-Type</ttcol>
      <ttcol align="left" width="20%">Reference</ttcol>

       
       <c>TBD</c>
       <c>CCI</c>
       <c> </c>
       <c> </c>
       
       <c> </c>
       <c> </c>
       <c>TBD3: SRv6</c> 
       <c>This document</c>       
     </texttable>            
      </section>
      
      <section title="PCEP-Error Object" toc="default">
      <t>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:

        <vspace blankLines="1" /> 
        
        <?rfc subcompact="yes"?>

        <list style="hanging" hangIndent="13">

          <t hangText="Error-Type">Meaning</t>
          <t hangText="----------   -------"></t>
          <t hangText="19">Invalid operation.
          <list style="hanging" hangIndent="37">
            <t hangText=" Error-value = TBD4 :">SRv6 capability was not advertised</t>
          </list>
          </t>            
        </list>
        </t>         
      </section>      
      
    </section>


    
    <section title="Acknowledgments"
             toc="default">

    </section>
  </middle>
  <back>
    <references title="Normative References">
      <?rfc include="reference.RFC.2119.xml" ?>
      
      
      
      
      <?rfc include="reference.RFC.5440.xml" ?>
      
      
      
      
      <?rfc include="reference.RFC.8174.xml"?>
      <?rfc include="reference.RFC.8231.xml"?>
      <?rfc include="reference.RFC.8281.xml"?>

      <?rfc include="reference.RFC.8664.xml"?>

      <?rfc include="reference.I-D.ietf-pce-segment-routing-ipv6"?>
       <?rfc include="reference.I-D.ietf-pce-pcep-extension-for-pce-controller"?>
        <?rfc include="reference.I-D.zhao-pce-pcep-extension-pce-controller-sr"?>

      </references>

    <references title="Informative References">

    <?rfc include="reference.RFC.4655.xml"?>
      <?rfc include="reference.RFC.7025.xml"?>
      <?rfc include="reference.RFC.7399.xml"?>
      <?rfc include="reference.RFC.7420.xml" ?>
      <?rfc include="reference.RFC.7491.xml"?>
      <?rfc include="reference.RFC.7525.xml"?>
    <?rfc include="reference.RFC.8232.xml"?>
    <?rfc include="reference.RFC.8253.xml"?>
    <?rfc include="reference.RFC.8283.xml"?>
    <?rfc include="reference.RFC.8402.xml"?>
    <?rfc include="reference.RFC.8408.xml"?>
    
    <?rfc include="reference.RFC.8665.xml"?>
    <?rfc include="reference.RFC.8667.xml"?>
    <?rfc include="reference.RFC.8754.xml"?>
    
    <?rfc include="reference.I-D.ietf-teas-pcecc-use-cases"?>
    
    <?rfc include="reference.I-D.ietf-pce-pcep-yang"?>
   
    
    
    <?rfc include="reference.I-D.litkowski-pce-state-sync"?>
    <?rfc include="reference.I-D.dhodylee-pce-pcep-ls"?>
    
    
    <?rfc include="reference.I-D.ietf-spring-srv6-network-programming"?>
    
    <!--<?rfc include="reference.I-D.palle-pce-controller-labeldb-sync"?>-->

      </references>
    
<section title="Contributor Addresses" toc="default">
    <t>
    <figure title="" suppress-title="false" align="left" alt="" width="" height="">
       <artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[


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

EMail: dhruv.ietf@gmail.com

      
        ]]></artwork>
        </figure>
      </t>
    </section>

  </back>
</rfc>