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Networking Working Group                                       Ran. Chen
Internet-Draft                                              Zheng. Zhang
Intended status: Standards Track                         ZTE Corporation
Expires: May 7, 2020                                   Senthil. Dhanaraj
                                                                  Huawei
                                                            Fengwei. Qin
                                                            China Mobile
                                                        November 4, 2019


                      PCEP Extensions for BIER-TE
                         draft-chen-pce-bier-06

Abstract

   Bit Index Explicit Replication (BIER)-TE shares architecture and
   packet formats with BIER as described in [RFC8279].  BIER-TE forwards
   and replicates packets based on a BitString in the packet header, but
   every BitPosition of the BitString of a BIER-TE packet indicates one
   or more adjacencies as described in [I-D.ietf-bier-te-arch].BIER-TE
   Path can be derived from a Path Computation Element (PCE).

   This document specifies extensions to the Path Computation Element
   Protocol (PCEP) that allow a PCE to compute and initiate the path for
   the BIER-TE.

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 May 7, 2020.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.




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   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
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
   3.  Overview of PCEP Operation in BIER Networks . . . . . . . . .   3
   4.  Object Formats  . . . . . . . . . . . . . . . . . . . . . . .   3
     4.1.  The OPEN Object . . . . . . . . . . . . . . . . . . . . .   3
       4.1.1.  The BIER-TE PCE Capability sub-TLV  . . . . . . . . .   3
     4.2.  The RP/SRP Object . . . . . . . . . . . . . . . . . . . .   4
     4.3.  END-POINTS object . . . . . . . . . . . . . . . . . . . .   4
     4.4.  ERO Object  . . . . . . . . . . . . . . . . . . . . . . .   4
       4.4.1.  BIER-ERO Subobject  . . . . . . . . . . . . . . . . .   5
       4.4.2.  BIER-ERO Processing . . . . . . . . . . . . . . . . .   6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  PCEP Objects  . . . . . . . . . . . . . . . . . . . . . .   6
       6.1.1.  BIER-TE-PCE-CAPABILITY Sub-TLV Type Indicators  . . .   7
       6.1.2.  New Path Setup Type . . . . . . . . . . . . . . . . .   7
       6.1.3.  BIER-ERO Subobject  . . . . . . . . . . . . . . . . .   7
       6.1.4.  PCEP-Error Objects and Types  . . . . . . . . . . . .   7
   7.  Normative references  . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   Bit Index Explicit Replication (BIER)-TE shares architecture and
   packet formats with BIER as described in [RFC8279].  BIER-TE forwards
   and replicates packets based on a BitString in the packet header, but
   every BitPosition of the BitString of a BIER-TE packet indicates one
   or more adjacencies as described in [I-D.ietf-bier-te-arch].BIER-TE
   Path can be derived from a Path Computation Element (PCE).

   [RFC8231] specifies a set of extensions to PCEP that allow a PCE to
   compute and recommend network paths in compliance with [RFC4657] and
   defines objects and TLVs for MPLS-TE LSPs.

   This document uses a PCE for computing one or more BIER-TE paths
   taking into account various constraints and objective functions.



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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-TE forwards and replicates packets based on a BitString in the
   packet header, and every BitPosition of the BitString of a BIER-TE
   packet indicates one or more adjacencies as described in
   [I-D.ietf-bier-te-arch].  In a PCEP session, An ERO object specified
   in [RFC5440] can be extended to carry a BIER-TE path consists of one
   or more BIER-ERO subobject(s).  BIER-TE computed by a PCE can be
   represented in the following forms:

   o  An ordered set of adjacencies BitString(s) in which each bit
      represents that the adjacencies to which the BFR should replicate
      packets to in the domain.

   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 PCEP error codes and
   procedures.

4.  Object Formats

4.1.  The OPEN Object

4.1.1.  The BIER-TE PCE Capability sub-TLV

   [RFC8408]defines the PATH-SETUP-TYPE-CAPABILITY TLV for use in the
   OPEN object.  The PATH-SETUP-TYPE-CAPABILITY TLV contains an optional
   list of sub-TLVs which are intended to convey parameters that are
   associated with the path setup types supported by a PCEP speaker.

   This document defines a new Path Setup Type (PST) for BIER as
   follows:

   o  PST = TBD2: Path is setup using BIER Traffic Engineering
      technique.

   A PCEP speaker MUST indicate its support of the function described in
   this document by sending a PATH-SETUP-TYPE-CAPABILITY TLV in the OPEN
   object with this new PST included in the PST list.

   This document also defines the BIER-TE-PCE-CAPABILITY sub-TLV.  PCEP
   speakers use this sub-TLV to exchange BIER capability.  If a PCEP



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   speaker includes PST=TBD1 in the PST List of the PATH-SETUP-TYPE-
   CAPABILITY TLV then it MUST also include the BIER-TE-PCE- CAPABILITY
   sub-TLV inside the PATH-SETUP-TYPE-CAPABILITY TLV.

   The format of the BIER-TE-PCE-CAPABILITY sub-TLV is shown in the
   following figure:


         0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |         Type=TBD1             |            Length             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |         Reserved              |            Flags              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 1 BIER-TE-PCE-CAPABILITY sub-TLV format

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

   Length: 4 bytes.

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

4.2.  The RP/SRP Object

   In order to setup an BIER-TE, a new PATH-SETUP-TYPE TLV MUST be
   contained in RP/SRP object.  This document defines a new Path Setup
   Type (PST=TBD2) for BIER-TE.

4.3.  END-POINTS object

   The END-POINTS object which is defined in [RFC8306]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 reuse the P2MP END-POINTS object body for
   IPv4(Object-Type 3) and END-POINTS object body for IPv6 (Object-Type
   4) which is defined in [RFC8306].

4.4.  ERO Object

   BIER-TE consists of one or more adjacencies BitStrings where every
   BitPosition of the BitString indicates one or more adjacencies, as
   described in([RFC8279]).





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   The ERO object specified in [RFC5440] is used to encode the path of a
   TE LSP through the network.The ERO is carried within a PCRep message
   to provide the computed TE LSP if the path computation was
   successful.In order to carry BIER-TE explicit paths, this document
   defines a new ERO subobjects referred to as "BIER-ERO subobjects"
   whose formats are specified in the following section.  An BIER-ERO
   subobjects carrying a adjacencies BitStrings consists of one or more
   BIER-ERO subobject(s).

4.4.1.  BIER-ERO Subobject



      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |L|   Type=TBD3 |      Length   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    BS Length  | subdomain-id  |       SI      |   Reserved    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |             Adjacency BitString  (first 32 bits)              ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~            Adjacency BitString  (last 32 bits)                |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                                 Figure 3

   The 'L' Flag: Indicates whether the subobject represents a loose-hop
   in the LSP[RFC3209].  If the bit is not set, the subobject represents
   a strict hop in the explicit route.

   Type: TBD3

   Length: 1 octet ([RFC3209]).  Contains the total length of the
   subobject in octets.  The Length MUST be at least 8, and MUST be a
   multiple of 4.

   BS Length: A 1 octet field encodes the length in bits of the
   BitString as per [RFC8296], the maximum length of the BitString is 5,
   it indicates the length of BitString is 1024.It is used to refer to
   the number of bits in the BitString.

   subdomain-id: Unique value identifying the BIER subdomain. 1 octet.





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   SI: Set Identifier (Section 1 of [RFC8279] used in the encapsulation
   for this BIER subdomain for this BitString length, 1 octet.

   The "Reserved" (1 octets) fields are currently unused, and MUST be
   set to zero on transmission and ignored on reception.

   Adjacency BitString: a variable length field encoding the Adjacency
   BitString where every BitPosition of the BitString indicates one or
   more adjacencies.the length of this field is according the BS length.
   The minimum value of this field is 64 bits, and the maximum value of
   this field is 1024 bits.

   Notice:

   The maximum value of BS Length is limited to the 1024 bits, in case
   the BIER-ERO Subobject is too long.

4.4.2.  BIER-ERO Processing

   The ERO and SR-ERO subobject processing remains as per [RFC5440].

   If a PCC receives an BIER-ERO subobject in which either
   BitStringLength or Adjacency BitString or SI is absent, it MUST
   consider the entire BIER-ERO subobject invalid and send a PCErr
   message with Error-Type = 10 ("Reception of an invalid object"),
   Error-Value = TBD5 ("BitStringLength is absent ") or Error-Value =
   TBD6 ("Adjacency BitString is absent")or Error-Value = TBD7("SI is
   absent ").

   If a PCC receives an BIER-ERO subobject in which BitStringLength
   values are not chosen from: 64, 128, 256, 512, 1024, as it described
   in ( [RFC8279]).  The PCC MUST send a PCErr message with Error-Type
   =10 ("Reception of an invalid object") and Error-Value = TBD8
   ("Invalid BitStringLength").

5.  Security Considerations

   TBD.

6.  IANA Considerations

6.1.  PCEP Objects

   IANA has made the following Object-Type allocations from the "PCEP
   Objects" sub-registry.






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6.1.1.  BIER-TE-PCE-CAPABILITY Sub-TLV Type Indicators


                vlaue             Meaning                  Reference
             --------------  -----------------------      -------------
                TBD1         BIER-TE-PCE-CAPABILITY       This Document



6.1.2.  New Path Setup Type


           vlaue             Meaning                         Reference
          --------------  -----------------------         -------------
             TBD2         Path is setup using BIER
                         Traffic Engineering technique    This Document



6.1.3.  BIER-ERO Subobject

   This document defines a new subobject type for the BIER explicit
   route object (ERO),The code points for subobject types of these
   objects is maintained in the RSVP parameters registry.



               Object            Sub-Object            Sub-Object Type
          -----------------  -----------------------   -----------------
           EXPLICIT_ROUTE    BIER-ERO (PCEP-specific)          TBD3


6.1.4.  PCEP-Error Objects and Types

   IANA is requested to allocate code-points in the "PCEP-ERROR Object
   Error Types and Values" subregistry for the following new error-types
   and error-values:














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   Error-Type           Meaning                    Reference
    ---------   ---------------------------    ----------------
       10      Reception of an invalid object      RFC5440

                   Error-value = TBD4                 This document
                           BitStringLength is absent

               Error-value = TBD5                 This document
                           Adjacency BitString is absent

               Error-value = TBD6                 This document
                           SI is absent

                           Error-value = TBD7                This document
               Invalid BitStringLength


7.  Normative references

   [I-D.ietf-bier-te-arch]
              Eckert, T., Cauchie, G., and M. Menth, "Traffic
              Engineering for Bit Index Explicit Replication (BIER-TE)",
              draft-ietf-bier-te-arch-05 (work in progress), November
              2019.

   [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>.

   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
              <https://www.rfc-editor.org/info/rfc3209>.

   [RFC4657]  Ash, J., Ed. and J. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol Generic
              Requirements", RFC 4657, DOI 10.17487/RFC4657, September
              2006, <https://www.rfc-editor.org/info/rfc4657>.

   [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>.







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   [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>.

   [RFC8279]  Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
              Przygienda, T., and S. Aldrin, "Multicast Using Bit Index
              Explicit Replication (BIER)", RFC 8279,
              DOI 10.17487/RFC8279, November 2017,
              <https://www.rfc-editor.org/info/rfc8279>.

   [RFC8296]  Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
              Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation
              for Bit Index Explicit Replication (BIER) in MPLS and Non-
              MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January
              2018, <https://www.rfc-editor.org/info/rfc8296>.

   [RFC8306]  Zhao, Q., Dhody, D., Ed., Palleti, R., and D. King,
              "Extensions to the Path Computation Element Communication
              Protocol (PCEP) for Point-to-Multipoint Traffic
              Engineering Label Switched Paths", RFC 8306,
              DOI 10.17487/RFC8306, November 2017,
              <https://www.rfc-editor.org/info/rfc8306>.

   [RFC8408]  Sivabalan, S., Tantsura, J., Minei, I., Varga, R., and J.
              Hardwick, "Conveying Path Setup Type in PCE Communication
              Protocol (PCEP) Messages", RFC 8408, DOI 10.17487/RFC8408,
              July 2018, <https://www.rfc-editor.org/info/rfc8408>.

Authors' Addresses

   Ran Chen
   ZTE Corporation

   Email: chen.ran@zte.com.cn


   Zheng Zhang
   ZTE Corporation

   Email: zhang.zheng@zte.com.cn


   Senthil Dhanaraj
   Huawei

   Email: senthil.dhanaraj.ietf@gmail.com



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   Fengwei Qin
   China Mobile

   Email: qinfengwei@chinamobile.com















































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