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Network Working Group                                              Z. Hu
Internet-Draft                                       Huawei Technologies
Intended status: Standards Track                                 H. Chen
Expires: April 26, 2021                                        Futurewei
                                                                  J. Yao
                                                     Huawei Technologies
                                                               C. Bowers
                                                        Juniper Networks
                                                                  Y. Zhu
                                                           China Telecom
                                                        October 23, 2020


                     SR-TE Path Midpoint Protection
          draft-hu-spring-segment-routing-proxy-forwarding-12

Abstract

   Segment Routing Traffic Engineering (SR-TE) supports explicit paths
   using segment lists containing adjacency-SIDs, node-SIDs and binding-
   SIDs.  The current SR FRR such as TI-LFA provides fast re-route
   protection for the failure of a node along a SR-TE path by the direct
   neighbor or say point of local repair (PLR) to the failure.  However,
   once the IGP converges, the SR FRR is no longer sufficient to forward
   traffic of the path around the failure, since the non-neighbors of
   the failure will no longer have a route to the failed node.  This
   document describes a mechanism for fast re-route protection against
   the failure of a SR-TE path after the IGP converges.  It provides
   fast re-route protection for an adjacency segment, a node segment and
   a binding segment of the path.

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/.





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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on April 26, 2021.

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   Copyright (c) 2020 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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Proxy Forwarding  . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Extensions to IGP for Proxy Forwarding  . . . . . . . . . . .   4
     3.1.  Extensions to OSPF  . . . . . . . . . . . . . . . . . . .   4
       3.1.1.  Advertising Proxy Forwarding  . . . . . . . . . . . .   4
       3.1.2.  Advertising Binding Segment . . . . . . . . . . . . .   7
     3.2.  Extensions to IS-IS . . . . . . . . . . . . . . . . . . .  10
       3.2.1.  Advertising Proxy Forwarding  . . . . . . . . . . . .  10
       3.2.2.  Advertising Binding Segment . . . . . . . . . . . . .  12
   4.  Building Proxy Forwarding Table . . . . . . . . . . . . . . .  13
     4.1.  Advertising Proxy Forwarding  . . . . . . . . . . . . . .  15
     4.2.  Building Proxy Forwarding Table . . . . . . . . . . . . .  15
   5.  Node Protection for Segment List  . . . . . . . . . . . . . .  15
     5.1.  Next Segment is an Adjacency Segment  . . . . . . . . . .  16
     5.2.  Next Segment is a Node Segment  . . . . . . . . . . . . .  16
     5.3.  Next Segment is a Binding Segment . . . . . . . . . . . .  17
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  18
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  18
     7.1.  OSPFv2  . . . . . . . . . . . . . . . . . . . . . . . . .  18
     7.2.  OSPFv3  . . . . . . . . . . . . . . . . . . . . . . . . .  19
     7.3.  IS-IS . . . . . . . . . . . . . . . . . . . . . . . . . .  19
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  20
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  20
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  20



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     9.2.  Informative References  . . . . . . . . . . . . . . . . .  21
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  22

1.  Introduction

   Segment Routing Traffic Engineering (SR-TE) is a technology that
   implements traffic engineering using a segment list.  SR-TE supports
   the creation of explicit paths using adjacency-SIDs, node-SIDs,
   anycast-SIDs, and binding-SIDs.  A node-SID in the segment list
   defining an SR-TE path indicates a loose hop that the SR-TE path
   should pass through.  When the node fails, the network may no longer
   be able to properly forward traffic on that SR-TE path.

   [I-D.ietf-rtgwg-segment-routing-ti-lfa] describes an SR FRR mechanism
   that provides fast re-route protection for the failure of a node on a
   SR-TE path by the direct neighbor or say point of local repair (PLR)
   to the failure.  However, once the IGP converges, the SR FRR is no
   longer sufficient to forward traffic of the path around the failure,
   since the non-neighbors of the failure will no longer have a route to
   the failed node and drop the traffic.

   To solve this problem,
   [I-D.ietf-spring-segment-protection-sr-te-paths] proposes that a hold
   timer should be configured on every router in a network.  After the
   IGP converges on the event of a node failure, if the node-SID of the
   failed node becomes unreachable, the forwarding changes should not be
   communicated to the forwarding planes on all configured routers
   (including PLRs for the failed node) until the hold timer expires.
   This solution may not work for some cases such as some of nodes in
   the network not supporting this solution.

   This document describes a proxy protection/forwarding mechanism,
   which provides more protection coverages.  It considers the fast re-
   route protection capability of every node in the network and supports
   the fast re-route protection of the binding-SIDs on a failed node.

2.  Proxy Forwarding

   In the proxy forwarding mechanism, each neighbor of a possible failed
   node advertises its SR proxy forwarding capability in its network
   domain 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 SR Proxy Forwarding
   capability from 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 event of 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.

3.  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.

3.1.  Extensions to OSPF

3.1.1.  Advertising Proxy Forwarding

   When a node P has the capability to do a SR proxy forwarding for all
   its neighboring nodes for protecting the failures of these nodes,
   node P advertises its SR proxy forwarding capability in its router
   information opaque LSA, which contains a Router Functional
   Capabilities TLV of 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             |             Length            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                     Functional Capabilities                   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 1: Router Functional Capabilities TLV

   One bit (called PF bit) in the Functional Capabilities field of the
   TLV is used to indicate node P's SR proxy forwarding 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.



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   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.

   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 forwarding the
   traffic to its final destination without going through node N.  After
   node N fails, node X will keep the FIB entry to the proxy prefix/node
   SID of node N for a given period of time.

   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 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 (TBD1)           |             Length            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        Node SID Sub-TLVs                      |
    :                                                               :
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 2: 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 [I-D.ietf-ospf-segment-routing-extensions].



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   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.

   A proxy forwarding node will originate an Extended Prefix Opaque LSA,
   which includes a Proxy Node SIDs TLV.  The format of the LSA is shown
   in Figure 3.

   For a proxy forwarding node P, having a number of neighboring nodes,
   P originates and maintains an Extended Prefix Opaque LSA, which
   includes a Proxy Node SIDs TLV.  The TLV contains the Prefix/Node SID
   Sub-TLV for each of some of the neighboring nodes after node P
   creates the corresponding proxy forwarding entries for protecting the
   failure of some of the neighboring nodes.

     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     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Opaque Type(7)|                 Opaque ID                     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                     Advertising Router                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                     LS sequence number                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         LS checksum           |             Length            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    :                             TLVs                              :
    :                (including Proxy Node SIDs TLV)                :
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 3: OSPFv2 Extended Prefix Opaque LSA

   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.





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   For a node X in the network, it learns the prefix/node SID of node N
   and the proxy prefix/node SID of node N.  The former is originated
   and advertised by node N, and the latter is originated and advertised
   by the proxy forwarding node P of node N.  Note that the proxy
   Prefix/Node SID Sub-TLV for node N does not contain a prefix of node
   N, and the prefix is the prefix associated with the prefix/node SID
   of node N originated by node N.

   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 node N to node P when node N fails, and node P will do a proxy
   forwarding for node N and forwarding the traffic to its destination
   without going through node N.

3.1.2.  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 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 (TBD2)          |             Length            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           Reserved            |BindingSID Type|   SIDs Type   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ~                   Binding SID Sub-TLV/value                   ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ~                       SID Sub-TLVs/values                     ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 4: 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).




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   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:

   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 [I-D.ietf-ospf-segment-routing-extensions].  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
   [I-D.ietf-ospf-segment-routing-extensions].  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 5.  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 5: 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 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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |            LS age             |0|0|0|       BS-LSA (TBD3)     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        Link State ID                          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      Advertising Router                       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      LS Sequence Number                       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         LS checksum           |           Length              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    :                      Binding Segment TLVs                     :
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 6: 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.

3.2.  Extensions to IS-IS

3.2.1.  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 them, node P
   advertises its SR proxy forwarding capability in its LSP, which
   contains a Router Capability TLV of Type 242 including a SR
   capabilities sub-TLV of sub-Type 2.

   One bit (called PF bit as shown in Figure 7) in the Flags field of
   the SR capabilities sub-TLV is defined to indicate node P's SR proxy
   forwarding 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.

     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 (2)    |     Length    |    Flags      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                     Range                     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    //                SID/Label Sub-TLV (variable)                 //
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                0  1  2  3  4  5  6  7
                               +--+--+--+--+--+--+--+--+
                               | I| V|PF|              |
                               +--+--+--+--+--+--+--+--+
                                         Flags

                     Figure 7: SR Capabilities sub-TLV

   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
   [I-D.ietf-isis-segment-routing-extensions].  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 8.  The prefix/node




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   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

                      Figure 8: 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
   [I-D.ietf-isis-segment-routing-extensions].  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.







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3.2.2.  Advertising Binding Segment

   [I-D.ietf-spring-segment-routing-policy] has defined the usage of
   binding-SID.  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 may be
   advertised in IS-IS Hello (IIH) PDUs, LSPs, or in Circuit Scoped Link
   State PDUs (CS-LSP) [RFC7356].  Its format is shown in Figure 9.

      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 9: 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).

   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:

   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 [I-D.ietf-isis-segment-routing-extensions].  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 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:




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   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
   [I-D.ietf-isis-segment-routing-extensions].  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.

4.  Building Proxy Forwarding Table

   Figure 10 is used to illustrate the SR proxy forwarding approach.
   Each node N has SRGB = [N000-N999].  RT1 is an ingress node of SR
   domain.  RT3 is a failure node.  RT2 is a Point of Local Repair (PLR)
   node, i.e., a proxy forwarding node.  Three label stacks are shown in
   the figure.  Label Stack 1 uses only adjacency-SIDs and represents
   the path RT1->RT2->RT3->RT4->RT5.  Label Stack 2 uses only node-SIDs
   and represents the ECMP-aware path RT1->RT3->RT4->RT5.  Label Stack 3
   uses a node-SID and a binding SID.  The Binding-SID with label=100 at
   RT3 represents the ECMP-aware path RT3->RT4->RT5.  So Label Stack 3,
   which consists of the node-SID for RT3 following by Binding-SID=100,
   represents the ECMP-aware path RT1->RT3->RT4->RT5.


























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             Node SID:2      Node SID:3
             +-----+          +-----+
             |     |----------+     |
           / |RT2  |          | RT3 |\
          /  +-----+          +-----+ \
         /      | \             /|     \
        /       |  \           / |      \
       /        |   \         /  |       \
      /         |    \       /   |        \
     /          |     \     /    |         \
 Node SID:1     |      \   /     |          \Node SID:4    Node SID:5
+-----+         |       \ /      |           +-----+       +-----+
|     |         |        X       |           |     |-------|     |
| RT1 |         |       / \      |           | RT4 |       | RT5 |
+-----+         |      /   \     |           +-----+       +-----+
   \            |     /     \    |           /
    \           |    /       \   |          /
     \          |   /         \  |         /
      \         |  /           \ |        /
       \        | /             \|       /
        \       |/               |      /
         \   +-----+           +-----+ /
          \  |     |           |     |/
           \ | RT6 |-----------| RT7 |
             +-----+           +-----+
             Node SID:6        Node SID:7

+-----------------+  +--------------+
|    Node SRGB    |  | Adj-SID      |  +-------+  +-------+  +-------+
+-----------------+  +--------------+  |Label  |  |Label  |  |Label  |
| RT1:[1000-1999] |  |RT1->RT2:10012|  |Stack 1|  |Stack 2|  |Stack 3|
+-----------------+  +--------------+  +-------+  +-------+  +-------+
| RT2:[2000-2999] |  |RT2->RT3:20023|  | 10012 |  | 1003  |  | 1003  |
+-----------------+  +--------------+  +-------+  +-------+  +-------+
| RT3:[3000-3999] |  |RT3->RT6:30036|  | 20023 |  | 3004  |  | 100   |
+-----------------+  +--------------+  +-------+  +-------+  +-------+
| RT4:[4000=4999] |  |RT3->RT7:30037|  | 30034 |  | 4005  |   100 is
+-----------------+  +--------------+  +-------+  +-------+  binding SID
| RT5:[5000-5999] |  |RT3->RT4:30034|  | 40045 |             to
+-----------------+  +--------------+  +-------+            {30034,40045}
| RT6:[6000-6999] |  |RT7->RT4:70074|
+-----------------+  +--------------+
| RT7:[7000-7999] |  |RT4->RT5:40045|
+-----------------+  +--------------+

                     Figure 10: Topology of SR-TE Path





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4.1.  Advertising Proxy Forwarding

   If the Point of Local Repair (PLR), for example, RT2, has the
   capability to do a SR proxy forwarding for all its neighboring nodes,
   it must advertise this capability.  If the PLR can not do a SR proxy
   forwarding for all its neighboring nodes, but for some of them, for
   example, RT3, then it uses proxy Node SIDs TLV to advertise the
   prefix-SID learned from RT3.  The TLV contains the Sub-TLV/value for
   the prefix/node SID of RT3 as a proxy SID.  When RT3 fails, RT2 needs
   to maintain the Sub-TLV/value for a period of time.  When the proxy
   forwarding table corresponding to the fault node is deleted (see
   section 3.2), the Sub-TLV/value is withdrawn.  The nodes in the
   network (for example, RT1) learn the prefix/node SID TLV advertised
   by RT3 and the proxy Node SIDs TLV advertised by RT2.  When RT3 is
   normal, the nodes prefer prefix/node SID TLV.  When the RT3 fails,
   the proxy prefix/node SIDs TLV advertised by RT2 is preferred.

4.2.  Building Proxy Forwarding Table

   A SR proxy node P needs to build an independent proxy forwarding
   table for each neighbor N.  The proxy forwarding table for node N
   contains the following information:

   1: Node N's SRGB range and the difference between the SRGB start
   value of node P and that of node N;

   2: All adjacency-SID of N and Node-SID of the node pointed to by node
   N's adjacency-SID.

   3: The binding-SID of N and the label stack associated with the
   binding-SID.

   Node P (PLR) uses a proxy forwarding table based on the next segment
   to find a node N as a backup forwarding entry to the adj-SID and
   Node-SID of node N.  When node N fails, the proxy forwarding table
   needs to be maintained for a period of time, which is recommended for
   30 minutes.

   Node RT3 in the topology of Figure 1 is node N, and node RT2 is node
   P (PLR).  RT2 builds the proxy forwarding table for RT3.  The
   structure of the table and how to build the table is a local
   implementation issue.

5.  Node Protection for Segment List

   Segment Routing Traffic Engineering supports the creation of explicit
   paths using adjacency-SIDs, node-SIDs, and binding-SIDs.  The label
   stack is a combination of one or more of adjacency-SIDs, node-SIDs,



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   and binding-SIDs.  This Section shows how a proxy node uses the SR
   proxy forwarding mechanism to protect traffic to the destination node
   when the next segment of label stack is adjacency-SIDs, node-SIDs, or
   binding-SIDs, respectively.

5.1.  Next Segment is an Adjacency Segment

   As shown in Figure 1, Label Stack 1 {10012, 20023, 30034, 40045}
   represents SR-TE strict explicit path RT1->RT2->RT3->RT4->RT5.  When
   RT3 fails, node RT2 acts as a PLR, and uses next adj-SID (30034) of
   the label stack to lookup the proxy forwarding table built by RT2
   locally for RT3.  The path returned is the label forwarding path to
   RT3's next hop node RT4, which bypasses RT3.  The specific steps are
   as follows:

   a.  RT1 pops top adj-SID 10012, and forwards the packet to RT2;

   b.  RT2 uses the label 20023 to identify the next hop node RT3, which
   has failed.  RT2 pops label 20023 and queries the Proxy Forwarding
   Table corresponding to RT3 with label 30034.  The Proxy Forwarding
   Table corresponding to RT3 returns an outgoing interface and label
   stack representing a path to RT4 that does not pass through RT3.  In
   this case, outgoing interface to RT7 with label stack 7004, satisfies
   this requirement.

   c.  So the packet leaves RT2 out the interface to RT7 with label
   stack {7004, 40045}. RT4 forwards it to RT4, where the original path
   is rejoined.

   d.  RT2 forwards packets to RT7.  RT7 queries the local routing table
   to forward the packet to RT4.

5.2.  Next Segment is a Node Segment

   As shown in Figure 1, Label Stack 2 {1003, 3004, 4005} represents SR-
   TE loose path RT1->RT3->RT4->RT5, where 1003 is the node SID of RT3.

   When the node RT3 fails, the proxy forwarding TLV advertised by the
   RT2 is preferred to direct the traffic of the RT1 to the PLR node
   RT2.  Node RT2 acts as a PLR node and queries the proxy forwarding
   table locally built for RT3.  The path returned is the label
   forwarding path to RT3's next hop node RT4, which bypasses RT3.  The
   specific steps are as follows:

   a.  RT1 swaps label 1003 to out-label 2003 to RT3.






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   b.  RT2 receives the label forwarding packet whose top label of label
   stack is 2003, and searches for the local Routing Table, the behavior
   found is to lookup Proxy Forwarding table due to RT3 failure.

   c.  RT2 uses 2003 as the in-label to lookup Proxy Forwarding table,
   and the query result is forwarding the packet to RT4.

   d.  Then RT2 queries the Routing Table to RT4, using the primary or
   backup path to RT4.  The next hop is RT7.

   e.  RT2 forwards the packet to RT7.  RT7 queries the local routing
   table to forward the packet to RT4.

   f.  After RT1 convergences, node SID 1003 is preferred to the proxy
   SID implied/advertised by RT2.

5.3.  Next Segment is a Binding Segment

   As shown in Figure 1, Label Stack 3 {1003, 100} represents SR-TE
   loose path RT1->RT3->RT4->RT5, where 100 is a Binding-SID, which
   represents segment list {30034, 40045}.

   When the node RT3 fails, the proxy forwarding SID implied or
   advertised by the RT2 is preferred to forward the traffic of the RT1
   to the PLR node RT2.  Node RT2 acts as a PLR node and uses Binding-
   SID to query the proxy forwarding table locally built for RT3.  The
   path returned is the label forwarding path to RT3's next hop node
   (RT4), which bypasses RT3.  The specific steps are as follows:

   a.  RT1 swaps label 1003 to out-label 2003 to RT3.

   b.  RT2 receives the label forwarding packet whose top label of label
   stack is 2003, and searches for the local Routing Table, the behavior
   found is to lookup Proxy Forwarding table due to RT3 failure.

   c.  RT2 uses Binding-SID:100 (label 2003 has pop) as the in-label to
   lookup the Next Label record of the Proxy Forwarding Table, the
   behavior found is to swap to Segment list {30034, 40045}.

   d.  RT2 swaps Binding-SID:100 to Segment list {30034, 40045}, and
   uses the 3034 to lookup the Next Label record of the Proxy Forwarding
   table again.  The behavior found is to forward the packet to RT4.

   e.  RT2 queries the Routing Table to RT4, using primary or backup
   path to RT4.  The next hop is RT7.

   f.  RT2 forwards packets to RT7.  RT7 queries the local routing table
   to forward the packet to RT4.



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6.  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.

7.  IANA Considerations

7.1.  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:

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




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   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

7.2.  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

7.3.  IS-IS

   Under Registration "Segment Routing Capability" in the "sub-TLVs for
   TLV 242" registry [I-D.ietf-isis-segment-routing-extensions], IANA is
   requested to assign one bit flag for Proxy Forwarding Capability as
   follows:






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

   Under Registration "Segment Identifier/Label Binding TLV 149"
   [I-D.ietf-isis-segment-routing-extensions], 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 |
     +--------+----------------------+---------------+

8.  Acknowledgements

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

9.  References

9.1.  Normative References

   [I-D.ietf-isis-segment-routing-extensions]
              Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A.,
              Gredler, H., and B. Decraene, "IS-IS Extensions for
              Segment Routing", draft-ietf-isis-segment-routing-
              extensions-25 (work in progress), May 2019.

   [I-D.ietf-ospf-segment-routing-extensions]
              Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
              Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
              Extensions for Segment Routing", draft-ietf-ospf-segment-
              routing-extensions-27 (work in progress), December 2018.





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   [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>.

   [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>.

9.2.  Informative References

   [I-D.ietf-rtgwg-segment-routing-ti-lfa]
              Litkowski, S., Bashandy, A., Filsfils, C., Decraene, B.,
              Francois, P., Voyer, D., Clad, F., and P. Camarillo,
              "Topology Independent Fast Reroute using Segment Routing",
              draft-ietf-rtgwg-segment-routing-ti-lfa-04 (work in
              progress), August 2020.

   [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", draft-ietf-spring-
              segment-protection-sr-te-paths-00 (work in progress),
              September 2020.








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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", draft-
              ietf-spring-segment-routing-policy-08 (work in progress),
              July 2020.

   [I-D.sivabalan-pce-binding-label-sid]
              Sivabalan, S., Filsfils, C., Tantsura, J., Hardwick, J.,
              Previdi, S., and C. Li, "Carrying Binding Label/Segment-ID
              in PCE-based Networks.", draft-sivabalan-pce-binding-
              label-sid-07 (work in progress), July 2019.

   [RFC5462]  Andersson, L. and R. Asati, "Multiprotocol Label Switching
              (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic
              Class" Field", RFC 5462, DOI 10.17487/RFC5462, February
              2009, <https://www.rfc-editor.org/info/rfc5462>.

Authors' Addresses

   Zhibo Hu
   Huawei Technologies
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: huzhibo@huawei.com


   Huaimo Chen
   Futurewei
   Boston, MA
   USA

   Email: Huaimo.chen@futurewei.com


   Junda Yao
   Huawei Technologies
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: yaojunda@huawei.com








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   Chris Bowers
   Juniper Networks
   1194 N. Mathilda Ave.
   Sunnyvale, CA  94089
   USA

   Email: cbowers@juniper.net


   Yongqing
   China Telecom
   109, West Zhongshan Road, Tianhe District
   Guangzhou  510000
   China

   Email: zhuyq8@chinatelecom.cn



































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