Network Working Group                                              Z. Hu
Internet-Draft                                       Huawei Technologies
Intended status: Standards Track                                 H. Chen
Expires: 7 September 2022                                      Futurewei
                                                                  J. Yao
                                                     Huawei Technologies
                                                               C. Bowers
                                                        Juniper Networks
                                                                  Y. Zhu
                                                           China Telecom
                                                                  Y. Liu
                                                            China Mobile
                                                            6 March 2022


                      LSR for SR Proxy Forwarding
                      draft-hc-lsr-sr-proxy-fw-00

Abstract

   This document describes extensions to OSPF and IS-IS to support SR
   proxy forwarding mechanism for fast protecting the failure of a node
   with segments on a SR-TE path.  The segments of the node include
   adjacency, node or binding segments.


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."

   This Internet-Draft will expire on 7 September 2022.



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Copyright Notice

   Copyright (c) 2022 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 IGP for Proxy Forwarding  . . . . . . . . . . .   3
     2.1.  Extensions to OSPF  . . . . . . . . . . . . . . . . . . .   3
       2.1.1.  Advertising Proxy Forwarding  . . . . . . . . . . . .   3
       2.1.2.  Advertising Binding Segment . . . . . . . . . . . . .   5
     2.2.  Extensions to IS-IS . . . . . . . . . . . . . . . . . . .   8
       2.2.1.  Advertising Proxy Forwarding  . . . . . . . . . . . .   8
       2.2.2.  Advertising Binding Segment . . . . . . . . . . . . .   9
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
     4.1.  OSPFv2  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     4.2.  OSPFv3  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     4.3.  IS-IS . . . . . . . . . . . . . . . . . . . . . . . . . .  12
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  12
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  12
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   [I-D.hu-spring-segment-routing-proxy-forwarding] describes a SR proxy
   forwarding for protection.  Each neighbor of a possible failed node
   advertises its SR proxy forwarding capability when it has the
   capability.  This capability indicates that the neighbor (the Proxy
   Forwarder) will forward traffic on behalf of the failed node.  A
   router receiving the capability from the neighbors of a failed node
   will send traffic using the node-SID of the failed node to the
   nearest Proxy Forwarder after the IGP converges on the failure.






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   Once the affected traffic reaches a Proxy Forwarder, it sends the
   traffic on the post-failure shortest path to the node immediately
   following the failed node in the segment list.

   For a binding segment of a possible failed node, the node advertises
   the information about the binding segment, including the binding SID
   and the list of SIDs associated with the binding SID, to its direct
   neighbors only.  Note that the information is not advertised in the
   network domain.

   After the node fails and the IGP converges on the failure, the
   traffic with the binding SID of the failed node will reach its
   neighbor having SR Proxy Forwarding capability.  Once receiving the
   traffic, the neighbor swaps the binding SID with the list of SIDs
   associated with the binding SID and sends the traffic along the post-
   failure shortest path to the first node in the segment list.

2.  Extensions to IGP for Proxy Forwarding

   This section defines extensions to IGP for advertising the SR proxy
   forwarding capability of a node in a network domain and the
   information about each binding segment (including its binding SID and
   the list of SIDs associated) of a node to its direct neighbors.

2.1.  Extensions to OSPF

2.1.1.  Advertising Proxy Forwarding

   When a node P has the capability to do a SR proxy forwarding for its
   neighboring nodes for protecting the failures of these nodes, P
   advertises its capability for these nodes.  The mirror SID
   [RFC8402][RFC8667] for a node N (Neighbor of P) advertised by P
   indicates the capability of P for N.

   Alternatively, P advertises its capability in its router information
   opaque LSA with Router Functional Capabilities TLV [RFC7770].  One
   bit (called PF bit) in the Functional Capabilities field of the TLV
   is used to indicate node P's capability.  When this bit is set to one
   by node P, it indicates that node P is capable of doing a SR proxy
   forwarding for its neighboring nodes.

   For a node X in the network, it learns the prefix/node SID of node N,
   which is originated and advertised by node N.  It creates a proxy
   prefix/node SID of node N for node P if node P is capable of doing SR
   proxy forwarding for node N.  The proxy prefix/node SID of node N for
   node P is a copy of the prefix/node SID of node N originated by node
   N, but stored under (or say, associated with) node P.  The route to
   the proxy prefix/node SID is through proxy forwarding capable nodes.



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   In normal operations, node X prefers to use the prefix/node SID of
   node N.  When node N fails, node X prefers to use the proxy prefix/
   node SID of node N.  Thus node X will forward the traffic targeting
   to the prefix/node SID of node N to node P when node N fails, and
   node P will do a SR proxy forwarding for node N and forward the
   traffic towards its final destination without going through node N.

   Note that the behaviors of normal IP forwarding and routing
   convergences in a network are not changed at all by the SR proxy
   forwarding.  For example, the next hop used by BGP is an IP address
   (or prefix).  The IGP and BGP converge in normal ways for changes in
   the network.  The packet with its IP destination to this next hop is
   forwarded according to the IP forwarding table (FIB) derived from IGP
   and BGP routes.

   If node P can not do a SR proxy forwarding for all its neighboring
   nodes, but for some of them, then it advertises the node SID of each
   of the nodes as a proxy node SID, indicating that it is able to do
   proxy forwarding for the node SID.

   A new TLV, called Proxy Node SIDs TLV, is defined for node P to
   advertise the node SIDs of some of its neighboring nodes.  It has the
   format as shown in Figure 1.


     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            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        Node SID Sub-TLVs                      |
    :                                                               :
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 1: OSPF Proxy Node SIDs TLV

   The Type (TBD1) is to be assigned by IANA.  The TLV contains a number
   of Node SID Sub-TLVs.  The Length is the total size of the Node SID
   Sub-TLVs included in the TLV.  A Node SID Sub-TLV is the Prefix SID
   Sub-TLV defined in [RFC8665].

   A proxy forwarding node P originates an Extended Prefix Opaque LSA
   containing this new TLV.  The TLV includes the Node SID Sub-TLVs for
   the node SIDs of some of P's neighboring nodes.  For each of some of
   P's neighboring nodes, the Node SID Sub-TLV for its prefix/node SID
   is included the TLV.  This prefix/node SID is called a proxy prefix/
   node SID.




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   When an neighboring node fails, P maintains the LSA with the TLV
   containing the Prefix/Node SID Sub-TLV for the neighboring node for a
   given period of time.  After the given period of time, the Prefix/
   Node SID Sub-TLV for the neighboring node is removed from the TLV in
   the LSA and then after a given time the corresponding proxy
   forwarding entries for protecting the failure of the neighboring node
   is removed.

2.1.2.  Advertising Binding Segment

   For a binding segment (or binding for short) on a node A, which
   consists of a binding SID and a list of segments, node A advertises
   an LSA containing the binding (i.e., the binding SID and the list of
   the segments).  The LSA is advertised only to each of the node A's
   neighboring nodes.  For OSPFv2, the LSA is a opaque LSA of LS type 9
   (i.e., a link local scope LSA).

   A binding segment is represented by binding segment TLV of the format
   as shown in Figure 2.


     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            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           Reserved            |BindingSID Type|   SIDs Type   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ~                   Binding SID Sub-TLV/value                   ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ~                       SID Sub-TLVs/values                     ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 2: OSPF Binding Segment TLV

   It comprises a binding SID and a list of segments (SIDs).  The fields
   of this TLV are defined as follows:

   Type: 2 octets, its value (TBD2) is to be assigned by IANA.

   Length: 2 octets, its value is (4 + length of Sub-TLVs/values).

   Binding SID Type (BT): 1 octet indicates whether the binding SID is
   represented by a Sub-TLV or a value included in the TLV.  For the
   binding SID represented by a value, it indicates the type of binding
   SID.  The following BT values are defined:





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   o BT = 0: The binding SID is represented by a Sub-TLV (i.e., Binding
   SID Sub-TLV) in the TLV.  A binding SID Sub-TLV is a SID/Label Sub-
   TLV defined in [RFC8665].  BT != 0 indicates that the binding SID is
   represented by a value.

   o BT = 1: The binding SID value is a label, which is represented by
   the 20 rightmost bits.  The length of the value is 3 octets.

   o BT = 2: The binding SID value is a 32-bit SID.  The length of the
   value is 4 octets.

   SIDs Type (ST): 1 octet indicates whether the list of segments (SIDs)
   are represented by Sub-TLVs or values included in the TLV.  For the
   SIDs represented by values, it indicates the type of SIDs.  The
   following ST values are defined:

   o ST = 0: The SIDs are represented by Sub-TLVs (i.e., SID Sub-TLVs)
   in the TLV.  A SID Sub-TLV is an Adj-SID Sub-TLV, a Prefix-SID Sub-
   TLV or a SID/Label Sub-TLV defined in [RFC8665].  ST != 0 indicates
   that the SIDs are represented by values.

   o ST = 1: Each of the SID values is a label, which is represented by
   the 20 rightmost bits.  The length of the value is 3 octets.

   o ST = 2: Each of the SID values is a 32-bit SID.  The length of the
   value is 4 octets.

   The opaque LSA of LS Type 9 containing the binding segment (i.e., the
   binding SID and the list of the segments) has the format as shown in
   Figure 3.  It may have Opaque Type of x (the exact type is to be
   assigned by IANA) for Binding Segment Opaque LSA.




















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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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |            LS age             |     Options   |  LS Type (9)  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Opaque Type(x)|                 Opaque ID                     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                     Advertising Router                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                     LS sequence number                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         LS checksum           |             Length            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    :                      Binding Segment TLVs                     :
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 3: OSPFv2 Binding Segment Opaque LSA

   For every binding on a node A, the LSA originated by A contains a
   binding segment TLV for it.

   For node A running OSPFv3, it originates a link-local scoping LSA of
   a new LSA function code (TBD3) containing binding segment TLVs for
   the bindings on it.  The format of the LSA 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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |            LS age             |0|0|0|       BS-LSA (TBD3)     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        Link State ID                          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      Advertising Router                       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      LS Sequence Number                       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         LS checksum           |           Length              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    :                      Binding Segment TLVs                     :
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 4: OSPFv3 Binding Segment Opaque LSA



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   The U-bit is set to 0, and the scope is set to 00 for link-local
   scoping.

2.2.  Extensions to IS-IS

2.2.1.  Advertising Proxy Forwarding

   When a node P has the capability to do a SR proxy forwarding for its
   neighboring nodes, P advertises its capability in its LSP with a
   Router Capability TLV of Type 242 including a SR capabilities sub-TLV
   of sub-Type 2.

   One bit (called PF bit) in the Flags field of the SR capabilities
   sub-TLV is defined to indicate node P's capability.  When this bit is
   set to one by node P, it indicates that node P is capable of doing a
   SR proxy forwarding for its neighboring nodes.

   If node P can not do a SR proxy forwarding for all its neighboring
   nodes, but for some of them, then it advertises the node SID of each
   of the nodes as a proxy node SID, indicating that it is able to do
   proxy forwarding for the node SID.

   The IS-IS SID/Label Binding TLV (suggested value 149) is defined in
   [RFC8667].  A Proxy Forwarder uses the SID/Label Binding TLV to
   advertise the node SID of its neighboring node.  The Flags field of
   the SID/Label Binding TLV is extended to include a P flag as shown in
   Figure 5.  The prefix/node SID in prefix/node SID Sub-TLV included in
   SID/Label Binding TLV is identified as a proxy forwarding prefix/node
   SID.

       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     |     Length    |     Flags     |     RESERVED  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            Range              | Prefix Length |     Prefix    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      //               Prefix (continued, variable)                  //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    SubTLVs (variable)                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                       0 1 2 3 4 5 6 7
                                      +-+-+-+-+-+-+-+-+
                                      |F|M|S|D|A|P|   |
                                      +-+-+-+-+-+-+-+-+
                                            Flags




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                      Figure 5: SID/Label Binding TLV

   Where:

   P-Flag: Proxy forwarding flag.  If set, this prefix/node SID is
   advertised by the proxy node.  This TLV is used to announce that the
   node has the ability to proxy forward the prefix/node SID.

   When the P-flag is set in the SID/Label Binding TLV, the following
   usage rules apply.

   The Range, Prefix Length and Prefix field are not used.  They should
   be set to zero on transmission and ignored on receipt.

   SID/Label Binding TLV contains a number of prefix/node SID Sub-TLVs.
   The TLV advertised by a proxy forwarding node P contains prefix/node
   SID Sub-TLVs for the node SIDs of P's neighbor nodes.  Each of the
   Sub-TLVs is a prefix/node SID Sub-TLV defined in [RFC8667].  From the
   SID in a prefix/node SID Sub-TLV advertised by the Proxy Forwarding
   node, its prefix can be obtained through matching corresponding
   prefix/node SID advertised by the neighbor/protected node using
   TLV-135 (or 235, 236, or 237) together with the prefix/node SID Sub-
   TLV.

2.2.2.  Advertising Binding Segment

   For supporting binding SID proxy forwarding, a new IS-IS TLV, called
   Binding Segment TLV, is defined.  It contains a binding SID and a
   list of segments (SIDs).  This TLV is advertised in Circuit Scoped
   Link State PDUs (CS-LSP) [RFC7356].  Its format is shown in Figure 6.

      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     |     Length    |BindingSID Type|   SIDs Type   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                   Binding SID value/Sub-TLV                   ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                      SID values/Sub-TLVs                      ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 6: IS-IS Binding Segment TLV

   The fields of this TLV are defined as follows:

   Type: 1 octet Suggested value 152 (to be assigned by IANA)

   Length: 1 octet (2 + length of Sub-TLVs/values).



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   The other fields are the same as those in Figure 2.

3.  Security Considerations

   The extensions to OSPF and IS-IS described in this document result in
   two types of behaviors in data plane when a node in a network fails.
   One is that for a node, which is a upstream (except for the direct
   upstream) node of the failed node along a SR-TE path, it continues to
   send the traffic to the failed node along the SR-TE path for an
   extended period of time.  The other is that for a node, which is the
   direct upstream node of the failed node, it fast re-routes the
   traffic around the failed node to the direct downstream node of the
   failed node along the SR-TE path.  These behaviors are internal to a
   network and should not cause extra security issues.

4.  IANA Considerations

4.1.  OSPFv2

   Under Subregistry Name "OSPF Router Functional Capability Bits"
   within the "Open Shortest Path First v2 (OSPFv2) Parameters"
   [RFC7770], IANA is requested to assign one bit for Proxy Forwarding
   Capability as follows:


     +============+==================+===================+
     | Bit number | Capability Name  |  Reference        |
     +============+==================+===================+
     |     31     | Proxy Forwarding |  This document    |
     +------------+------------------+-------------------+

   Under Registry Name "OSPFv2 Extended Prefix Opaque LSA TLVs"
   [RFC7684], IANA is requested to assign one new TLV value for OSPF
   Proxy Node SIDs as follows:


     +============+=====================+================+
     | TLV Value  |    TLV Name         | Reference      |
     +============+=====================+================+
     |    2       | Proxy Node SIDs TLV | This document  |
     +------------+---------------------+----------------+

   Under Registry Name "Opaque Link-State Advertisements (LSA) Option
   Types" [RFC5250], IANA is requested to assign new Opaque Type
   registry values for Binding Segment LSA as follows:






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     +================+==================+================+
     | Registry Value |  Opaque Type     | Reference      |
     +================+==================+================+
     |     10         |  Binding Segment | This document  |
     +----------------+------------------+----------------+

   IANA is requested to create and maintain new registries:

   o  OSPFv2 Binding Segment Opaque LSA TLVs

   Initial values for the registry are given below.  The future
   assignments are to be made through IETF Review [RFC5226].


       Value          TLV Name                  Definition
       -----         -----------------------    ----------
       0             Reserved
       1             Binding Segment TLV        This Document
       2-32767       Unassigned
       32768-65535   Reserved

4.2.  OSPFv3

   Under Registry Name "OSPFv3 LSA Function Codes", IANA is requested to
   assign new registry values for Binding Segment LSA as follows:

     +========+========================+================+
     | Value  | LSA Function Code Name | Reference      |
     +========+========================+================+
     |  16    | Binding Segment LSA    | This document  |
     +--------+------------------------+----------------+

   IANA is requested to create and maintain new registries:

   o  OSPFv3 Binding Segment LSA TLVs

   Initial values for the registry are given below.  The future
   assignments are to be made through IETF Review [RFC5226].


       Value          TLV Name                  Definition
       -----         -----------------------    ----------
       0             Reserved
       1             Binding Segment TLV        This Document
       2-32767       Unassigned
       32768-65535   Reserved





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4.3.  IS-IS

   Under Registration "Segment Routing Capability" in the "sub-TLVs for
   TLV 242" registry [RFC8667], IANA is requested to assign one bit flag
   for Proxy Forwarding Capability as follows:


     +============+=======================+===============+
     | Bit number | Capability Name       | Reference     |
     +============+=======================+===============+
     |     2      | Proxy Forwarding (PF) | This document |
     +------------+-----------------------+---------------+

   Under Registration "Segment Identifier/Label Binding TLV 149"
   [RFC8667], IANA is requested to assign one bit P-Flag as follows:


     +============+=================+===============+
     | Bit number | Flag Name       | Reference     |
     +============+=================+===============+
     |     5      | P-Flag          | This document |
     +------------+-----------------+---------------+

   Under Registry Name: IS-IS TLV Codepoints, IANA is requested to
   assign one new TLV value for IS-IS Binding Segment as follows:

     +========+======================+===============+
     | Value  | TLV Name             | Reference     |
     +========+======================+===============+
     |  152   | Binding Segment TLV  | This Document |
     +--------+----------------------+---------------+

5.  Acknowledgements

   The authors would like to thank Peter Psenak, Acee Lindem, Les
   Ginsberg, Bruno Decraene and Jeff Tantsura for their comments to this
   work.

6.  References

6.1.  Normative References

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





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   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <https://www.rfc-editor.org/info/rfc5226>.

   [RFC5250]  Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The
              OSPF Opaque LSA Option", RFC 5250, DOI 10.17487/RFC5250,
              July 2008, <https://www.rfc-editor.org/info/rfc5250>.

   [RFC7356]  Ginsberg, L., Previdi, S., and Y. Yang, "IS-IS Flooding
              Scope Link State PDUs (LSPs)", RFC 7356,
              DOI 10.17487/RFC7356, September 2014,
              <https://www.rfc-editor.org/info/rfc7356>.

   [RFC7684]  Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
              Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
              Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
              2015, <https://www.rfc-editor.org/info/rfc7684>.

   [RFC7770]  Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
              S. Shaffer, "Extensions to OSPF for Advertising Optional
              Router Capabilities", RFC 7770, DOI 10.17487/RFC7770,
              February 2016, <https://www.rfc-editor.org/info/rfc7770>.

   [RFC8665]  Psenak, P., Ed., Previdi, S., Ed., Filsfils, C., Gredler,
              H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
              Extensions for Segment Routing", RFC 8665,
              DOI 10.17487/RFC8665, December 2019,
              <https://www.rfc-editor.org/info/rfc8665>.

   [RFC8667]  Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C.,
              Bashandy, A., Gredler, H., and B. Decraene, "IS-IS
              Extensions for Segment Routing", RFC 8667,
              DOI 10.17487/RFC8667, December 2019,
              <https://www.rfc-editor.org/info/rfc8667>.

6.2.  Informative References

   [I-D.hu-spring-segment-routing-proxy-forwarding]
              Hu, Z., Chen, H., Yao, J., Bowers, C., Yongqing, and
              Yisong, "SR-TE Path Midpoint Restoration", Work in
              Progress, Internet-Draft, draft-hu-spring-segment-routing-
              proxy-forwarding-18, 28 February 2022,
              <https://www.ietf.org/archive/id/draft-hu-spring-segment-
              routing-proxy-forwarding-18.txt>.






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   [I-D.ietf-spring-segment-routing-policy]
              Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and
              P. Mattes, "Segment Routing Policy Architecture", Work in
              Progress, Internet-Draft, draft-ietf-spring-segment-
              routing-policy-18, 17 February 2022,
              <https://www.ietf.org/archive/id/draft-ietf-spring-
              segment-routing-policy-18.txt>.

   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

Authors' Addresses

   Zhibo Hu
   Huawei Technologies
   Huawei Bld., No.156 Beiqing Rd.
   Beijing
   100095
   China
   Email: huzhibo@huawei.com


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


   Junda Yao
   Huawei Technologies
   Huawei Bld., No.156 Beiqing Rd.
   Beijing
   100095
   China
   Email: yaojunda@huawei.com


   Chris Bowers
   Juniper Networks
   1194 N. Mathilda Ave.
   Sunnyvale, CA,  94089
   United States of America
   Email: cbowers@juniper.net





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   Yongqing
   China Telecom
   109, West Zhongshan Road, Tianhe District
   Guangzhou
   510000
   China
   Email: zhuyq8@chinatelecom.cn


   Yisong
   China Mobile
   510000
   China
   Email: liuyisong@chinamobile.com





































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