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Networking Working Group                                       Ran. Chen
Internet-Draft                                              Zheng. Zhang
Intended status: Standards Track                         ZTE Corporation
Expires: April 15, 2016                                 October 13, 2015


                        PCEP Extensions for BIER
                         draft-chen-pce-bier-00

Abstract

   Bit Index Explicit Replication (BIER) is an architecture that
   provides optimal multicast forwarding through a "BIER domain" without
   requiring intermediate routers to maintain any multicast related per-
   flow state.  BIER forwards and replicates packets based on a
   BitString in the packet header.A BIER Path can be derived from a
   variety of mechanisms, including an IGP Shortest Path Tree (SPT),
   explicit configuration, or a Path Computation Element (PCE).

   This document specifies extensions to the Path Computation Element
   Protocol (PCEP) to handle requests and responses for the computation
   of paths for BIER TE LSPs.

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
   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 15, 2016.

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



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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
   3.  Overview of PCEP Operation in BIER Networks . . . . . . . . .   3
   4.  BIER PCEP Message Extensions  . . . . . . . . . . . . . . . .   3
     4.1.  BIER Capability Advertisement . . . . . . . . . . . . . .   3
       4.1.1.  The OPEN Object . . . . . . . . . . . . . . . . . . .   3
         4.1.1.1.  The BIER PCE Capability TLV . . . . . . . . . . .   3
     4.2.  Path Computation Request/Reply Message Extensions . . . .   4
       4.2.1.  The RP/SPR Object . . . . . . . . . . . . . . . . . .   4
       4.2.2.  The New BIER END-POINT Object . . . . . . . . . . . .   5
       4.2.3.  ERO Object  . . . . . . . . . . . . . . . . . . . . .   5
         4.2.3.1.  BIER-ERO Subobject  . . . . . . . . . . . . . . .   5
       4.2.4.  RRO Object  . . . . . . . . . . . . . . . . . . . . .   7
         4.2.4.1.  RRO Processing  . . . . . . . . . . . . . . . . .   7
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
     6.1.  PCEP Objects  . . . . . . . . . . . . . . . . . . . . . .   7
     6.2.  PCEP-Error Objects and Types  . . . . . . . . . . . . . .   8
     6.3.  PCEP TLV Type Indicators  . . . . . . . . . . . . . . . .   8
     6.4.  New Path Setup Type . . . . . . . . . . . . . . . . . . .   8
   7.  Normative references  . . . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   Bit Index Explicit Replication (BIER) is an architecture that
   provides optimal multicast forwarding through a "BIER domain" without
   requiring intermediate routers to maintain any multicast related per-
   flow state.  BIER forwards and replicates packets based on a
   BitString in the packet header.A BIER Path can be derived from a
   variety of mechanisms, including an IGP Shortest Path Tree (SPT),
   explicit configuration, or a Path Computation Element (PCE).

   This document specifies extensions to the Path Computation Element
   Protocol (PCEP) to handle requests and responses for the computation
   of paths for BIER TE LSPs.






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2.  Conventions used in this document

   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.

3.  Overview of PCEP Operation in BIER Networks

   BIER forwards and replicates packets based on a BitString in the
   packet header.  In a PCEP session, An ERO object specified in
   [RFC5440] carrying a BIER-TE path consists of one or more BIER-
   subobject(s).  BIER-TE LSPs computed by a PCE can be represented in
   one of the following forms:

   o  An ordered set of BitString(s) in which each bit represents
      exactly one router that the BIER-TE paths pass through in the
      domain.

   o  An ordered set of BFR-id(s).  In this case, the PCC needs to
      convert the BFR-ID into the corresponding BitString(s).

   o  An ordered set of BFR-prefix(es).  In this case, the PCC needs to
      convert the BFR-ID into the corresponding B BitString(s).

   In this document, we define a set of PCEP protocol extensions,
   including a new PCEP capability,a new Path Setup Type (PST) ,a new
   BIER END-POINT Object, new ERO subobjects, new RRO subobjects, new
   PCEP error codes and procedures.

4.  BIER PCEP Message Extensions

   The following section describes the protocol extensions required to
   support BIER-TE path.

4.1.  BIER Capability Advertisement

4.1.1.  The OPEN Object

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

4.1.1.1.  The BIER PCE Capability TLV

   The BIER-PCE-CAPABILITY TLV is an optional TLV associated with the
   OPEN Object to exchange BIER capability of PCEP speakers.  The format
   of the BIER-PCE-CAPABILITY TLV is shown in the following figure:






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        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |            Type=TBD           |            Length=4           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |         Reserved              |         Flags                 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                                 Figure 1

   The code point for the TLV type is to be defined by IANA.

   The "Reserved" (2 octets) and "Flags" (2 octet) fields are currently
   unused, and MUST be set to zero on transmission and ignored on
   reception.

4.1.1.1.1.  Exchanging BIER Capability

   This document defines a new optional BIER-PCE-CAPABILITY TLV for use
   in the OPEN object to negotiate the BIER capability.  The inclusion
   of this TLV in the OPEN message destined to a PCC indicates the PCE's
   capability to perform BIER-TE path computations, and the inclusion of
   this TLV in the OPEN message destined to a PCE indicates the PCC's
   capability to support BIER-TE Path.

   A PCE that is able to support the BIER extensions defined in this
   document SHOULD include the BIER-PCE-CAPABILITY TLV on the OPEN
   message.  If the PCE does not include the BIER-PCE-CAPABILITY TLV in
   the OPEN message and PCC does include the TLV, it is RECOMMENDED that
   the PCC indicates a mismatch of capabilities.

4.2.  Path Computation Request/Reply Message Extensions

4.2.1.  The RP/SPR Object

   In order to setup an BIER-TE LSP, a new PATH-SETUP-TYPE
   TLV([I-D.ietf-pce-lsp-setup-type]) MUST be contained in RP or SRP
   object.  This document defines a new Path Setup Type (PST) for BIER
   as follows:

   o  PST = 2: Path is setup using BIER Traffic Engineering technique.

   If a PCEP speaker does not recognize the PATH-SETUP-TYPE TLV, it MUST
   ignore the TLV in accordance with [RFC5440].  If a PCEP speaker
   recognizes the TLV but does not support the TLV, it MUST send PCErr
   with Error-Type = 2 (Capability not supported).



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4.2.2.  The New BIER END-POINT Object

   The END-POINTS object is used in a PCReq message to specify the BIER
   information of the path for which a path computation is requested.
   To represent the end points for a BIER path efficiently, we define a
   new END-POINT Object for the BIER path:

   The format of the new END-POINTS Object is as follows:


        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                        Subdomain-ID                           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                       BitStringLength                         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                        Source BFR-id                          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                      Destination BFR-id                       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ~                           ...                                 ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                      Destination BFR-id                       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                                 Figure 2

4.2.3.  ERO Object

   An BIER-TE path consists of one or more BitString/BFR-id/BFR-prefix
   where each BitString/BFR-id/BFR-prefix MAY be associated with the
   identifier that represents the node.

   The ERO object specified in [RFC5440] is used to carry BIER-TE path
   information.  In order to carry BitString/BFR-id/BFR-prefix, this
   document defines three new ERO subobjects referred to as "BIER-ERO
   subobjects" whose formats are specified in the following section.  An
   ERO object carrying a BIER-TE path consists of one or more BIER-ERO
   subobject(s).

4.2.3.1.  BIER-ERO Subobject








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        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   Type=TBD    |    Length     |     Flags     |BitStringLength|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                           BitStringLength                     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                                 Figure 3


        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     |             Flags             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                          BFR-id                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                                 Figure 4


        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     |             Flags             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                          BFR-Prefix                           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                                 Figure 5

4.2.3.1.1.  ERO Processing

   If a PCC finds a non-recognize the SR-ERO subobject, the PCC MUST
   respond with a PCErr message with Error-Type=3 ("Unknown Object") and
   Error-Value=2 ("Unrecognized object Type") or Error-Type=4 ("Not
   supported object") and Error-Value=2 ("Not supported object Type") as
   described in [RFC5440] .

   If a PCC receives an BIER-ERO subobject format 1 in which either
   BitStringLength or BitString is absent, it MUST consider the entire



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   ERO object invalid and send a PCErr message with Error-Type = 10
   ("Reception of an invalid object") and Error-Value = TBD
   ("BitStringLength is absent ") and Error-Value = TBD ("BitString is
   absent ")

   If a PCC detects that all subobjects of ERO are not identical, it
   MUST send a PCErr message with Error-Type = 10 ("Reception of an
   invalid object") and Error-Value = TBD ("Non-identical ERO
   subobjects"), as described in ([I-D.ietf-pce-segment-routing])[pce-].

   If a PCC receives an SR-ERO subobject in which BFR-ID=0, it MUST send
   a PCErr message with Error-Type = 10 ("Reception of an invalid
   object") and Error-Value = TBD ("Invalid BFR-ID").

   If a PCC receives an SR-ERO subobject in which BitStringLength values
   are not chosen from: 64, 128, 256, 512, 1024, 2048, and 4096, as it
   described in ([I-D.ietf-bier-architecture]).  The PCC MUST send a
   PCErr message with Error-Type = 10 ("Reception of an invalid object")
   and Error-Value = TBD ("Invalid BitStringLength").

4.2.4.  RRO Object

   A PCC can record BIER-TE LSP and report the LSP to a PCE via RRO.  An
   RRO object contains one or more subobjects called "BIER-RRO
   subobjects" whose formats are the same as that of SR-ERO subobject.

4.2.4.1.  RRO Processing

   Processing rules of SR-RRO subobject are identical to those of SR-ERO
   subobject defined in section 4.2.3.1.1 in this document.

5.  Security Considerations

   TBD.

6.  IANA Considerations

6.1.  PCEP Objects

   As discussed in Section 4.2.2, a new END-POINTS Object-Type is
   defined.  IANA has made the following Object-Type allocations from
   the "PCEP Objects" sub-registry:

                Object                          Object-Class Value
          ---------------------               --------------------------
            BIER END-POINT Object                      TBD





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   As discussed in Section 4.2.3 and 4.2.4, a new sub-object type for
   the PCEP explicit route object (ERO), and a new sub-object type for
   the PCEP record route object (RRO) are defined.

   IANA has made the following sub-objects allocation from the RSVP
   Parameters registry:

               Object                Sub-Object                 Sub-Object Type
          --------------------- -------------------------- --------------------------
               EXPLICIT_ROUTE        BIER-ERO (PCEP-specific)          TBD
               ROUTE_RECORD          BIER-RRO (PCEP-specific)          TBD


6.2.  PCEP-Error Objects and Types

   As described in Section 4.2.3.1.1, a number of new PCEP-ERROR Object
   Error Values have been defined.


             Error-Type           Meaning                                  Reference
             ---------- ----------------------------------- ---------------------------------
                10        Reception of an invalid object.                   RFC5540
                          Error-value = TBD:  BitStringLength is absent     This document
                          Error-value = TBD:  BitString is absent           This document
                          Error-value = TBD:  invalid BFR-ID                This document
                          Error-value = TBD:  Invalid BitStringLength       This document


6.3.  PCEP TLV Type Indicators

   IANA is requested to allocate a new code point in the PCEP TLV Type
   Indicators registry, as follows:


             Value                     Meaning                      Reference
     -------------------- ---------------------------- -----------------------------------
             TBD               BIER-PCE-CAPABILITY TLV             This document


6.4.  New Path Setup Type

   IANA is requested to allocate a new code point in the PCEP
   PATH_SETUP_TYPE TLV PST field registry, as follows:








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              Value                     Description                  Reference
       ----------------   ------------------------------------ ----------------------------
                2             Path is setup using BIER Traffic      This document
                              Engineering technique


7.  Normative references

   [I-D.ietf-bier-architecture]
              Wijnands, I., Rosen, E., Dolganow, A., Przygienda, T., and
              S. Aldrin, "Multicast using Bit Index Explicit
              Replication", draft-ietf-bier-architecture-02 (work in
              progress), July 2015.

   [I-D.ietf-pce-lsp-setup-type]
              Sivabalan, S., Medved, J., Minei, I., Crabbe, E., Varga,
              R., Tantsura, J., and J. Hardwick, "Conveying path setup
              type in PCEP messages", draft-ietf-pce-lsp-setup-type-03
              (work in progress), June 2015.

   [I-D.ietf-pce-segment-routing]
              Sivabalan, S., Medved, J., Filsfils, C., Crabbe, E.,
              Lopez, V., Tantsura, J., Henderickx, W., and J. Hardwick,
              "PCEP Extensions for Segment Routing", draft-ietf-pce-
              segment-routing-06 (work in progress), August 2015.

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

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

Authors' Addresses

   Ran Chen
   ZTE Corporation
   No.50 Software Avenue,Yuhuatai District
   Nanjing, Jiangsu Province  210012
   China

   Phone: +86 025 88014636
   Email: chen.ran@zte.com.cn





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   Zheng Zhang
   ZTE Corporation
   No.50 Software Avenue,Yuhuatai District
   Nanjing, Jiangsu Province  210012
   China

   Email: zhang.zheng@zte.com.cn












































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