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PCE for Mirror Binding
draft-chen-pce-mbinding-02

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This is an older version of an Internet-Draft whose latest revision state is "Expired".
Authors Huaimo Chen , Bruno Decraene , Gyan Mishra , Aijun Wang , Xufeng Liu , Lei Liu
Last updated 2023-10-08 (Latest revision 2023-04-16)
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draft-chen-pce-mbinding-02
Network Working Group                                            H. Chen
Internet-Draft                                                 Futurewei
Intended status: Standards Track                             B. Decraene
Expires: 10 April 2024                                            Orange
                                                               G. Mishra
                                                                 Verizon
                                                                 A. Wang
                                                           China Telecom
                                                                  X. Liu
                                                         IBM Corporation
                                                                  L. Liu
                                                                 Fujitsu
                                                          8 October 2023

                         PCE for Mirror Binding
                       draft-chen-pce-mbinding-02

Abstract

   PCE is used to distribute a binding to a node.  The binding includes
   a binding SID and a path represented by a list of SIDs.  This
   document describes extensions to PCEP for distributing the
   information about the binding to a protecting node.  For an SR path
   via the node with the binding SID, when the node fails, the
   protecting node such as the upstream neighbor on the path uses the
   information to protect the binding SID of the failed node.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

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."

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   This Internet-Draft will expire on 10 April 2024.

Copyright Notice

   Copyright (c) 2023 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 carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Extensions to PCEP  . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Binding Protection Information Distribution Capability  .   3
     2.2.  Extensions to RP/SRP Object . . . . . . . . . . . . . . .   5
   3.  Procedure for Updating Information  . . . . . . . . . . . . .   6
   4.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     4.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     4.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   [I-D.ietf-pce-binding-label-sid] specifies how PCE may be used to
   distribute a Segment Routing (SR) Policy to a node in a network.  An
   SR Policy may contain a binding, which includes a binding SID and a
   path associated with the binding SID.  The path is represented by a
   list of SIDs.

   After a PCE as a controller distributes the binding to the node, the
   node forwards the packet with the binding SID according to the first
   SID in the list.  It replaces the binding SID in the packet with the
   list of SIDs and forwards the packet using the FIB entry for the top
   SID (i.e., the first SID) in the packet.

   When the node fails, suppose that the upstream neighbor (as PLR) of
   the node has the corresponding binding protection information for
   protecting the binding SID of the node.  The information includes the
   binding SID, the list of SIDs and an identifier of the node.  After
   the upstream neighbor as PLR detects the failure of the node, for a

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   packet with the node SID of the failed node received, it protects the
   binding SID of the failed node.  It pops the node SID, replaces the
   binding SID in the packet with the list of SIDs, forwards the packet
   without going through the failed node towards the top SID (i.e., the
   first SID, assuming it is a node SID for simplicity here).  How a
   upstream node protect the binding SID of the failed node is out of
   scope of this document and described in
   [I-D.ietf-spring-segment-protection-sr-te-paths] and
   [I-D.hu-spring-segment-routing-proxy-forwarding] (Note: the second
   reference will be removed after the first one includes enough text
   for protecting binding SIDs of a node).

   This document proposes some procedures and extensions to PCEP for
   distributing the binding protection information to the possible
   protecting nodes, which are the nodes that may protect the failed
   node.

2.  Extensions to PCEP

   A PCC may run on each node in a network.  A PCE runs on a server as a
   controller to communicate with PCCs.  The PCE and the PCCs work
   together to distribute the binding protection information about a
   binding SID on a node to the possible protecting nodes for protecting
   the binding SID of the node when the node fails.

2.1.  Binding Protection Information Distribution Capability

   When a PCE and a PCC running on a network node establish a PCEP
   session between them, they exchange their capabilities of Binding
   Protection Information Distribution in Open messages.  An Open
   message includes an Open object.  The object contains a
   PATH_SETUP_TYPE_CAPABILITY TLV with Path Setup Type (PST) = TBD1 and
   a new sub-TLV, called Binding Protection Information Distribution
   Capability (BSID-D for short) sub-TLV.

   PST = TBD1 indicates Binding Protection Information Distribution.

   BSID-D sub-TLV contains parameters used for Binding Protection
   Information distribution.

   The format of BSID-D sub-TLV is shown in Figure 1.

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     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |          Type = TBD2          |          Length = 4           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           Reserved            |          Flags                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         Figure 1: BSID_PROTECTION_DISTRIBUTION_CAPABILITY sub-TLV

   Type:  TBD2 is to be assigned by IANA.

   Length:  4.

   Reserved:  2 octets.  Must be set to zero in transmission and ignored
      on reception.

   Flags:  2 octets.  No flag bits are defined.

   A PCC, which supports the capability of Binding Protection
   Information Distribution, sends a PCE an Open message containing a
   PATH_SETUP_TYPE_CAPABILITY TLV with Path Setup Type (PST) = TBD1 and
   a BSID_PROTECTION_DISTRIBUTION_CAPABILITY sub-TLV.  PST = TBD1
   indicates that the PCC is capable of receiving and processing the
   binding protection information about a binding SID on a node from the
   PCE for protecting the binding SID of the node when the node fails.

   A PCE, which supports the capability of Binding Protection
   Information Distribution, sends a PCC an Open message containing a
   PATH_SETUP_TYPE_CAPABILITY TLV with Path Setup Type (PST) = TBD1 and
   a BSID_PROTECTION_DISTRIBUTION_CAPABILITY sub-TLV.  PST = TBD1
   indicates that the PCE supports the capability of Binding Protection
   Information Distribution.

   If both a PCC and a PCE support the capability of Binding Protection
   Information Distribution, each of the Open messages sent by the PCC
   and PCE contains a PATH-SETUP-TYPE-CAPABILITY TLV with a PST list
   containing PST = TBD1 and a BSID_PROTECTION_DISTRIBUTION_CAPABILITY
   sub-TLV.

   If a PCE receives an Open message without a PATH-SETUP-TYPE-
   CAPABILITY TLV containing PST = TBD1 from a PCC, then the PCE MUST
   not send the PCC any binding protection information.

   If a PCC receives an Open message without a PATH-SETUP-TYPE-
   CAPABILITY TLV containing PST = TBD1 from a PCE, then the PCC MUST
   ignore any binding protection information from the PCE.

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   When PCECC is used, a PCC and PCE exchange capability of binding
   protection information distribution using PCECC-CAPABILITY Sub-TLV
   which is included in the PATH_SETUP_TYPE_CAPABILITY TLV in an Open
   message.

   A new flag bit B is defined in the Flags field of the PCECC-
   CAPABILITY sub-TLV as shown in Figure 2.  B flag (for Binding SID
   Protection): if set to 1 by a PCEP speaker (PCE or PCC), the B flag
   indicates that the PCEP speaker supports and is willing to handle the
   PCECC based central controller instructions for Binding SID
   protection.  The bit MUST be set to 1 by both a PCC and a PCE for the
   PCECC Binding SID protection instruction download/report on a PCEP
   session.

     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 = 1            |          Length = 4           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         Flags                             |B|L|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                 Figure 2: PCECC-Capability sub-TLV with B

2.2.  Extensions to RP/SRP Object

   After sending the binding to a node (i.e., the PCC running on the
   node), a PCE sends the corresponding binding protection information
   to the possible protecting nodes of the node in a PCEP message such
   as a Path Computation LSP Update Request (PCUpd) message.  The
   message contains a Request Parameters (RP) object or Stateful PCE
   Request Parameters (SRP) object.  The object includes:

   *  A PATH-SETUP-TYPE TLV with PST = TBD1 indicating binding
      protection information for a Binding SID of a node.

   *  A Node ID TLV containing the identifier of the node.

   The format of PATH-SETUP-TYPE TLV is shown in Figure 3.

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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 = 28           |          Length = 4           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                  Reserved                     |   PST = TBD1  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 3: PATH-SETUP-TYPE TLV with PST = TBD1

   The format of Node ID TLV is illustrated in 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 = TBDa           |         Length (4)            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Node ID (4 octets)                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                        Figure 4: Node ID TLV Format

   Type:  Its value (TBDa) is to be assigned by IANA.

   Length:  Its value indicates the length of the value field of the TLV
      is 4.

   Node ID:  4-octet field contains the 4-octet TE router identifier
      (ID) of the (protected) node.

3.  Procedure for Updating Information

   When a PCE sends a binding to node N (i.e., PCC running on N) in a
   first Path Computation LSP Update Request (PCUpd) message, the PCE
   sends the corresponding binding protection information to the
   possible protecting nodes such as neighbors of node N in a second
   PCUpd message.

   The first message contains an RP/SRP object and an LSP object with a
   TE-PATH-BINDING TLV.  The RP/SRP object does not include any PATH-
   SETUP-TYPE TLV with PST = TBD1.  The TLV includes a binding SID and R
   bit set to zero.

   The second message contains an RP/SRP object and an LSP object with a
   TE-PATH-BINDING TLV.  The RP/SRP object includes a PATH-SETUP-TYPE
   TLV with PST = TBD1 and a Node ID TLV indicating node N.  TE-PATH-
   BINDING TLV includes the binding SID and R bit set to zero.

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   After a PCE sends the binding to node N, if the PCE removes the
   binding from node N through sending a third PCUpd message to node N,
   the PCE removes the corresponding binding protection information from
   the nodes through sending a fourth PCUpd message to the nodes.

   The third message contains an RP/SRP object and an LSP object with a
   TE-PATH-BINDING TLV.  The RP/SRP object does not include any PATH-
   SETUP-TYPE TLV with PST = TBD1.  The TLV includes a binding SID and R
   bit set to one (1).

   The fourth message contains an RP/SRP object and an LSP object with a
   TE-PATH-BINDING TLV.  The RP/SRP object includes a PATH-SETUP-TYPE
   TLV with PST = TBD1 and a Node ID TLV indicating node N.  TE-PATH-
   BINDING TLV includes the binding SID and R bit set to one (1).

   After a PCE sends the binding to node N, if the PCE changes the
   binding in node N through sending a fifth PCUpd message to node N,
   the PCE changes the corresponding binding protection information in
   the nodes through sending a sixth PCUpd message to the them.

   The fifth message contains an RP/SRP object and an LSP object with a
   TE-PATH-BINDING TLV.  The RP/SRP object does not include any PATH-
   SETUP-TYPE TLV with PST = TBD1.  The LSP object includes a (changed)
   path.  The TLV includes a binding SID and R bit set to zero.

   The sixth message contains an RP/SRP object and an LSP object with a
   TE-PATH-BINDING TLV.  The RP/SRP object includes a PATH-SETUP-TYPE
   TLV with PST = TBD1 and a Node ID TLV indicating node N.  The LSP
   object includes the (changed) path.  TE-PATH-BINDING TLV includes the
   binding SID and R bit set to zero.

4.  References

4.1.  Normative References

   [I-D.ietf-spring-segment-protection-sr-te-paths]
              Hegde, S., Bowers, C., Litkowski, S., Xu, X., and F. Xu,
              "Segment Protection for SR-TE Paths", Work in Progress,
              Internet-Draft, draft-ietf-spring-segment-protection-sr-
              te-paths-05, 27 September 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-spring-
              segment-protection-sr-te-paths-05>.

   [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>.

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4.2.  Informative References

   [I-D.hu-spring-segment-routing-proxy-forwarding]
              Hu, Z., Chen, H., Yao, J., Bowers, C., Zhu, Y., and Y.
              Liu, "SR-TE Path Midpoint Restoration", Work in Progress,
              Internet-Draft, draft-hu-spring-segment-routing-proxy-
              forwarding-24, 21 August 2023,
              <https://datatracker.ietf.org/doc/html/draft-hu-spring-
              segment-routing-proxy-forwarding-24>.

   [I-D.ietf-pce-binding-label-sid]
              Sivabalan, S., Filsfils, C., Tantsura, J., Previdi, S.,
              and C. Li, "Carrying Binding Label/Segment Identifier
              (SID) in PCE-based Networks.", Work in Progress, Internet-
              Draft, draft-ietf-pce-binding-label-sid-16, 27 March 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-pce-
              binding-label-sid-16>.

Acknowledgments

   The authors would like to thank Andrew Stone, and Dhruv Dhody for
   their comments to this work.

Authors' Addresses

   Huaimo Chen
   Futurewei
   Boston, MA,
   United States of America
   Email: huaimo.chen@futurewei.com

   Bruno Decraene
   Orange
   France
   Email: bruno.decraene@orange.com

   Gyan S. Mishra
   Verizon
   13101 Columbia Pike
   Silver Spring,  MD 20904
   United States of America
   Phone: 301 502-1347
   Email: gyan.s.mishra@verizon.com

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   Aijun Wang
   China Telecom
   Beiqijia Town, Changping District
   Beijing
   102209
   China
   Email: wangaj3@chinatelecom.cn

   Xufeng Liu
   IBM Corporation
   United States of America
   Email: xufeng.liu.ietf@gmail.com

   Lei Liu
   Fujitsu
   United States of America
   Email: liulei.kddi@gmail.com

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