Networking Working Group                                     L. Ginsberg
Internet-Draft                                               A. Bashandy
Intended status: Standards Track                             C. Filsfils
Expires: April 2, September 20, 2018                                Cisco Systems
                                                             B. Decraene
                                                                  Orange
                                                      September 29, 2017
                                                                   Z. Hu
                                                     Huawei Technologies
                                                          March 19, 2018

        IS-IS Extensions to Support Routing over IPv6 Dataplane
               draft-bashandy-isis-srv6-extensions-01.txt
               draft-bashandy-isis-srv6-extensions-02.txt

Abstract

   Segment Routing (SR) allows for a flexible definition of end-to-end
   paths by encoding paths as sequences of topological sub-paths, called
   "segments".  Segment routing architecture can be implemented over an
   MPLS data plane as well as an IPv6 data plane.  This draft describes
   the IS-IS extensions required to support Segment Routing over an IPv6
   data plane.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

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 April 2, September 20, 2018.

Copyright Notice

   Copyright (c) 2017 2018 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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  SRv6-Capabilities sub-TLV . . . . . . . . . . . . . . . . . .   3
     2.1.  Maximum SL sub-sub-TLV  . . . . . . . . . . . . . . . . .   4
     2.2.  Maximum End Pop SRH sub-sub-TLV . . . . . . . . . . . . .   5
     2.3.  Maximum T.Insert SRH sub-sub-TLV  . . . . . . . . . . . .   5
     2.4.  Maximum T.Encap SRH sub-sub-TLV . . . . . . . . . . . . .   5   6
     2.5.  Maximum End D SRH sub-sub-TLV . . . . . . . . . . . . . .   6
   3.  SRv6-function  SRv6 Endpoint function Descriptor . . . . . . . . . . . . . . . . . .   6   7
   4.  SRv6-SID  SRv6 Node SID TLV . . . . . . . . . . . . . . . . . . . . . . . .   9   7
   5.  Function  Endpoint function Code Points . . . . . . . . . . . . . . . . . . . .  11   9
   6.  Advertising SRv6 SIDs associated with a Neighbor  . . . . . .  11   9
     6.1.  P2P Srv6 X-SID  SRv6 Adjacency-SID sub-TLV  . . . . . . . . . . . . . . . . .  11  10
     6.2.  LAN  SRv6 X-SID LAN Adjacency-SID sub-TLV  . . . . . . . . . . . . . . . . .  12  10
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13  11
     7.1.  SRv6 Node SID TLV and sub-TLVs . . . . . . . . . . . . . . . .  14
     7.2.  IS-IS SRv6-functions Codepoints Registry . . . . . . . .  14
     7.3.  12
     7.2.  SRv6 Capabilities sub-TLV . . . . . . . . . . . . . . . .  15
     7.4.  P2P  12
     7.3.  SRv6 X-SID Adjacency-SID and LAN SRv6 X-SID LAN Adjacecncy-SID sub-TLVs . . . . . . .  15
     7.5.  IS-IS SRv6 X-SID sub-sub-TLV Codepoints Registry  . . . .  16  13
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  16  13
   9.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  16  13
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  17  14
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  18  15
     10.2.  Informative References . . . . . . . . . . . . . . . . .  18  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18  16

1.  Introduction

   With Segment Routing (SR)[SRARCH], (SR) [I-D.ietf-spring-segment-routing], a node
   steers a packet through an ordered list of instructions, called
   segments.

   Segments are identified through Segment Identifiers (SIDs).

   Segment Routing can be directly instantiated on the IPv6 data plane
   through the use of the Segment Routing Header defined in [SRH].
   [I-D.ietf-6man-segment-routing-header].  SRv6 refers to this SR
   instantiation on the IPv6 dataplane.

   The network programming paradigm [NP]
   [I-D.filsfils-spring-srv6-network-programming] is central to SRv6.
   It describes how any function can be bound to a SID and how any
   network program can be expressed as a combination of SID's.

   It defines several well-known functions such as End, End.X, T.Insert,
   T.Encaps, etc.

   This document specifies IS-IS extensions that allow IS-IS protocol to
   encode some of these functions.

   Familiarity with the network programming paradigm [NP]
   [I-D.filsfils-spring-srv6-network-programming] is necessary to
   understand the extensions specified in this document.

   This document defines one new top level IS-IS_TLV IS-IS TLV and three several new IS-
   IS sub-TLVs.

   The SRv6 Capabilities sub-TLV announces the ability to support SRv6
   and some Endpoint functions defined listed in [NP] Section 5 as well as
   advertising limitations when applying such Endpoint functions.

   The SRv6 Node SID top level TLV, the P2P SRv6 X-SID Adjacency-SID sub-TLV, and
   the LAN SRv6 X-SID LAN Adjacency-SID sub-TLV are used to advertise which SIDs
   are instantiated at a node and what Endpoint function is bound to
   each instantiated SID.

   Only ISIS-related functions such as End and its variants D and X [NP]
   are defined in this document.

2.  SRv6-Capabilities sub-TLV

   As described in [SRH] and [NP], the list of Segments is stored in the
   segment routing header referred hereafter as "SRH".

   A router node indicates that supports it has support for SRv6 MUST be able to process the segment
   routing header as described in [SRH] and [NP] up to the limitations
   set by the advertised SRv6-capabilities sub-TLV.

   To announce this ability, advertising a router uses the newly defined new
   SRv6- capabilities sub-TLV of the router capabilities TLV [RFC7981].
   The SRv6- capabilities sub-TLV may contain optional sub-sub-TLVs.

   The SRv6 Capabilities sub-TLV has the following format:

      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              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   optional sub-sub-TLVs...

        Type: Suggested value 22, 25, to be assigned by IANA

        Length: 2 + length of sub-sub-TLVs

        Flags: 2 octets  The following flags are defined:

         0                   1
          0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         |E|
         |E|O|                           |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         where:
           E-flag: If set, then router is able to apply "T.Encap"
           operation
           operation. Further limitations as regards T.encap are
           indicated by the advertisement of the Maximum T.Insert
           sub-sub-TLV described below.

           O-flag: If set, the router supports use of the O-bit
           in the Segment Routing Header(SRH) as defined in
           [draft-ietf-6man-segment-routing-header].

   The following sections define the supported sub-sub-TLVs.

2.1.  Maximum SL sub-sub-TLV

   The Maximum Segments Left sub-sub-TLV specifies the maximum value of
   the "SL" field [SRH] [I-D.ietf-6man-segment-routing-header] in the SRH of a
   received packet before applying the Endpoint function associated with
   a SID.

     0                   1                   2
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Type        |     Length    |  Max SL       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type: 1
      Length: 1
      SL Value: 1 octet
      An 8 bit unsigned integer.

      If the sub-sub-TLV is NOT advertised the value is assumed to be 0.

2.2.  Maximum End Pop SRH sub-sub-TLV

   The Maximum End Pop SRH sub-sub-TLV specifies the maximum number of
   SIDs in the top SRH in an SRH stack to which the router can apply
   "PSP" or USP" [NP] [I-D.filsfils-spring-srv6-network-programming] flavors.

    0                   1                   2
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Type        |     Length    |Max-End-Pop-SRH|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Type: 2
     Length: 1
     Max-End-Pop-SRH Value: 1 octet
     An 8 bit unsigned integer.

     If the value is zero or the sub-sub-TLV is NOT advertised,
     then it is assumed that the router cannot apply PSP or USP flavors.

2.3.  Maximum T.Insert SRH sub-sub-TLV

   The Maximum T.Insert SRH sub-sub-TLV specifies the maximum number of
   SIDs that can be inserted as part of the "T.insert" behavior [NP].
   [I-D.filsfils-spring-srv6-network-programming].

     0                   1                   2
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Type        |     Length    | Max-T.Insert  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type: 3
      Length: 1
      Max-T.Insert Value: 1 octet
      An 8 bit unsigned integer.

      If the value is zero or the sub-sub-TLV is omitted,
      then the router is assumed not to support any variation
      of the "T.insert" behavior.

2.4.  Maximum T.Encap SRH sub-sub-TLV

   The Maximum T.Encap SRH sub-sub-TLV specifies the maximum number of
   SIDs that can be included as part of the "T.Encap" behavior [NP].
   [I-D.filsfils-spring-srv6-network-programming].

     0                   1                   2
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Type        |     Length    | Max-T.Encap  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type: 4
      Length: 1
      Max-T.Encap Value: 1 octet
      An 8 bit unsigned integer.

      If this value is zero or the sub-sub-TLV is omitted and
      the "E" flag is set in the associated SRv6 Capabilities
      sub-TLV, then it is assumed that the router can apply T.Encap
      by encapsulating the incoming packet in another IPv6 header
      without SRH the same way IPinIP encapsulation is performed.
      If the "E" flag is clear, then this sub-sub-TLV SHOULD NOT
      be transmitted and MUST be ignored on receipt.

2.5.  Maximum End D SRH sub-sub-TLV

   The Maximum End D SRH sub-sub-TLV specifies the maximum number of
   SIDs in an SRH when applying "End.DX6" and "End.DT6" Endpoint
   functions.

     0                   1                   2
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Type        |     Length    | Max End D     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type: 5
      Length: 1
      Max End D Value: 1 octet
      An 8 bit unsigned integer.

      If this value is zero or the sub-sub-TLV is omitted,
      then it is assumed that the router cannot apply
      "End.DX6" or "End.DT6" Endpoint functions if the extension
      header right underneath the outer IPv6 header is an SRH.

3.  SRv6-function  SRv6 Endpoint function Descriptor

   The SRv6 SID TLV defined in Section 4, P2P SRv6 X-SID sub-TLV
   specified in Section 6.1, and LAN SRv6 X-SID sub-TLV specified in
   section 6.2 MUST include have one (and only one) SRv6 Endpoint function
   Descriptor.

   When included in the SRv6 SID TLV, the descriptor is encoded as a
   sub-TLV.  When included in a P2P/LAN SRv6 X-SID sub-TLV, the
   descriptor is encoded as a sub-sub-TLV.

   The SRv6-function Descriptor encodes the function (and its flavors)
   bound to the SRv6 SID advertised in the SRv6 SID TLV [NP].

   The SRv6 SID Endpoint function Descriptor has the following format:

      0                   1
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
      +-+-+-+-+-+-+-+-+
      |   Type        |
    +-+-+-+-+-+-+-+-+
    |   Length      |
    +-+-+-+-+-+-+-+-+
    |   Flags       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Function Endpoint function (2 octets)  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Type: See IANA considerations in Section 7.

       Length: 3

       Flags:

           0 1 2 3 4 5 6 7
          +-+-+-+-+-+-+-+-+
          |P|U| Reserved  |
          +-+-+-+-+-+-+-+-+

      This document defines two

        No flags to specify the
      flavor(s) [NP] associated with the SRv6 function
      specified in the "Function" field:

         P bit: If set, then the PSP flavor [NP] is associated with the
         function encoded in the "function" field

         U bit: If set, then the USP flavor [NP] is associated with the
         function encoded in the "function" field

         Reserved Bits SHOULD be transmitted as 0 and MUST be ignored on
         receipt. are currently defined.

        The second two octets encode the Endpoint function. Function code points
      are defined in Section 5.

      For a given

4.  SRv6 Node SID function encoded in the "Function" field,
      the "P" and "U" bits are set/cleared according to the rules of
      enabling/disabling the PSP and USP flavors, respectively, for
      that function as specified in [NP].

4.  SRv6-SID TLV

   A new top level

   The SRv6 Node SID TLV is introduced to advertise SRv6 Segment
   Identifiers (SID) and their attributes.

   The new TLV is used to advertise SRv6 SIDs with any of the Endpoint functions
   defined in [NP] whose code point is defined in this document except
   those SIDs
   which must be associated with do not require a particular neighbor in order to be correctly
   applied [NP]. [I-D.filsfils-spring-srv6-network-programming].  SRv6 SIDs
   associated with a neighbor are advertised in using the sub-TLVs defined
   in Section 6.

   This new TLV shares the sub-TLV space defined for TLVs 135, 235, 236
   and 237.  The SRv6 Node SID TLV has the following format:

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   SID-size   Flags       | Func-flags    |    Endpoint function Value    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | SID size      | SID (variable) . . .                                   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | sub-tlv-len  Sub-tlv-len  |         Sub-TLVs (variable) . . .             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type: 27 (Suggested value to be assigned by IANA)

      Length: variable.

      One or more SID entries, each of which has the following format:

      Flags: 1 octet. The following flags are defined

        0
        0 1 2 3 4 5 6 7
       +-+-+-+-+-+-+-+-+
       |D| Reserved    |
       +-+-+-+-+-+-+-+-+

       where:
         D bit: When the SID is leaked from level-2 to level-1, the D
         bit MUST be set.  Otherwise, this bit MUST be clear.  SIDs with
         the D bit set MUST NOT be leaked from level-1 to level-2.  This
         is to prevent looping.

         The remaining bits are reserved for future use. They SHOULD be
         set to zero on transmission and MUST be ignored on receipt.

      Func-flags: 1 octet. As defined in Section 3

      Endpoint function Value: 2 octets. As defined in Section 3

      SID-Size: 1 octet. Number of bits in the SID field.

      SID: 1-16 octets. This field encodes the advertised SRv6 SID. The
      "SID-size" field can have the values 1-128 and indicates the
      number of bits in the SID.  The SRv6 SID is encoded in the
      minimal number of octets for the given number of bits. The owning
       router may associate one or more functions as specified in [NP],
       in other documents, or as locally configured.

      Sub-TLV-length: 1 octet. Number of octets used by sub-TLVs

      The function associated with the advertised SID is specified by
      the SRv6-Function Descriptor sub-TLV specified in Section 3.

5.  Function  Endpoint function Code Points

   This section defines the

   Endpoint function code points for supported functions
   associated with SRv6 SIDs.  Functions are defined in [NP].
   [I-D.filsfils-spring-srv6-network-programming].  The numerical values
   are defined in the "Endpoint Types" registry defined in
   [I-D.filsfils-spring-srv6-network-programming].  This section lists
   the Endpoint function types which may be advertised by IS-IS.

   o  0: Reserved  End (no PSP, no USP)

   o  1:  End Function with PSP

   o  End with USP

   o  End with PSP&USP

   o  2:  End.X Function (no PSP, no USP)

   o  End.X with PSP

   o  End.X with USP

   o  End.X with PSP&USP

   o  3:  End.DX6 Function

   o  4:  End.DT6 Function

   o  End.OTP

6.  Advertising SRv6 SIDs associated with a Neighbor

   Certain SRv6 Endpoint functions [NP]
   [I-D.filsfils-spring-srv6-network-programming] must be associated
   with a particular neighbor, and in case of multiple layer 3 links to
   the same neighbor, with a particular link in order to be correctly
   applied.

   This document specifies how to advertise two such functions in IS-
   IS, namely End.X and End.DX6 [NP].

   SIDs associated with the End.X and End.DX6 functions are advertised
   within neighbor reachability TLVs.
   variants as described in Section 5.

   This document defines two new sub-TLVs of TLV 22, 23, 222, 223, and
   141 - namely "P2P SRv6 X-SID" "SRv6 Adjacency-SID" and "LAN SRv6 X- SID". "SRv6 LAN Adjacency-SID".

6.1.  P2P Srv6 X-SID  SRv6 Adjacency-SID sub-TLV

   This sub-TLV is used to advertise one or more SRv6 SIDs associated
   with End.X and End.DX6 [NP] functions over a point to point adjacency.

   The "P2P SRv6 X-SID" Adjacency-SID sub-TLV has the following format:

    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       |   SID-size Func-flags    |    Endpoint function Value    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | SID size      | SID (variable) . . .                                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |sub-sub-tlv-len|
   |Sub-sub-tlv-len|         Sub-sub-TLVs (variable) . . .         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Type: 40 (Suggested value to be assigned by IANA)

       Length: variable.

       One or more SIDs each of which has the following format:

       Flags: 1 octet. No flags defined in this document

       Func-flags: 1 octet. As defined in Section 3

       Endpoint function Value: 2 octets. As defined in Section 3.
       Legal values are the End.X and End.DX6 variants.

       SID-Size: 1 octet. Number of bits in the SID field.

       SID: 1-16 octets. This field encodes the advertised SRv6 SID. The
       "SID-size" field can have the values 1-128 and indicates the
       number of bits in the SID.  The SRv6 SID is encoded in the
       minimal number of octets for the given number of bits. The owning
       router may associate one or more functions as specified in [NP],
       in other documents, or as locally configured.

       Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub-
       TLVs

   The function associated with the advertised SID is specified by the
   SRv6-Function Descriptor sub-sub-TLV specified in Section 3.  If the
   SRv6-Function Descriptor is encoded in the P2P SRv6 X-SID sub-TLV,
   then the encoded SRv6 SID function MUST include only the code points
   of SRv6 SID functions that require the specification of a neighbor to
   be correctly applied.  This document specifies the code points of two
   such functions, namely End.X and End.DX6 [NP].

6.2.  LAN  SRv6 X-SID LAN Adjacency-SID sub-TLV

   This sub-TLV is used to advertise one or more SRv6 SIDs associated
   with End.X and End.DX6 [NP] functions over a LAN adjacency.

   The "LAN SRv6 X-SID" LAN Adjacency-SID sub-TLV has the following format:

     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    |    System ID (6 octets)       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Flags       |  Func-flags   | Endpoint function Value       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   SID-size    |    SID (variable) . . .                       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |sub-sub-tlv-len|
    |Sub-sub-tlv-len|      sub-sub-TLVs (variable) . . .            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Type: 41 (Suggested value to be assigned by IANA)
       Length: variable.

       System-ID: 6 octets of IS-IS System-ID of length "ID Length" as
       defined in [ISO10589].

       One or more SIDs each of which has the following format:

       Flags 1 Octet. No flags are defined in this document

       Func-flags: 1 octet. As defined in Section 3

       Endpoint function Value: 2 octets. As defined in Section 3.
       Legal values are the End.X and End.DX6 variants.

       SID-Size: 1 octet. Number of bits in the SID field.

       SID: 1-16 octets. This field encodes the advertised SRv6 SID. The
       "SID-size" field can have the values 1-128 and indicates the
       number of bits in the SID.  The SRv6 SID is encoded in the
       minimal number of octets for the given number of bits. The owning
       router may associate one or more functions as specified in [NP],
       in other documents, or as locally configured.

       Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub-
       TLVs.

   The function associated with the advertised SID is specified by the
   SRv6-Function Descriptor sub-sub-TLV specified in Section 3.  If the
   SRv6-Function Descriptor is encoded in the P2P SRv6 X-SID sub-TLV,
   then the encoded SRv6 SID function MUST include only the code points
   of SRv6 SID functions that require the specification of a neighbor to
   be correctly applied.  This document specifies the code points of two
   such functions, namely End.X and End.DX6 [NP].

7.  IANA Considerations

   This documents request allocation for the following TLVs, sub- TLVs,
   and sub-sub-TLVs as well updating the ISIS TLV registry and defining
   a new registry.

7.1.  SRv6 Node SID TLV and sub-TLVs

   This document adds the following new TLV to the IS-IS TLV Codepoints
   registry.

   Value: 27 (suggested - to be assigned by IANA)

   Name: SRv6 Node SID

   The name of the "Sub-TLVs for TLVs 135, 235, 236 and 237 registry"
   needs to be changed to "Sub-TLVs for TLVs 27, 135, 235, 236 and 237
   registry".

   This document adds a new sub-TLV to the (renamed) "Sub-TLVs for TLVs
   27, 135, 235, 236 and 237 registry".

   Value: 5 (Suggested - to be assigned by IANA)

   Name: SRv6-function Descriptor

   The revised table of sub-TLVs in the registry should be:

      Type  27 135 235 236 237

      1     n   y   y   y   y
      2     n   y   y   y   y
      3     y   y   y   y   y
      4     y   y   y   y   y
      5(new)y   n   n   n   n
      11    y   y   y   y   y
      12    y   y   y   y   y

7.2.  IS-IS SRv6-functions Codepoints Registry

   This document requests the creation of a new IANA managed registry to
   identify SRv6 SID functions.  The registration procedure is "Expert
   Review" as defined in [RFC7370].  Suggested registry name is "SRv6
   SID Function Types".  A function identifier is an unsigned 8 bit
   value.  The following values are defined by this document:

   0 Reserved

   1 End function.

   2 End.X function

   3 End.DX6 function.

   4 End.DT6 function.

7.3.  SRv6 Capabilities sub-TLV

   This document adds the definition of a new sub-TLV in the "Sub- TLVs
   for TLV 242 registry".

   Type: 22 25 (Suggested - to be assigned by IANA)

   Description: SRv6 Capabilities

   Thuis document requests the creation of a new IANA managed registry
   for sub-sub-TLVs of the SRv6 Capability sub-TLV.  The registration
   procedure is "Expert Review" as defined in [RFC7370].  Suggested
   registry name is "sub-sub-TLVs for SRv6 Capability sub-TLV".  The
   following sub-TLVs are defined by this document:

   0: Reserved

   1: Max-SL

   2: Max-End-Pop-SRH

   3: Max-T-Ins-SRH
   4: Max-T-Encap-SRH

   5: Max-End-D-SR

7.4.  P2P

7.3.  SRv6 X-SID Adjacency-SID and LAN SRv6 X-SID LAN Adjacecncy-SID sub-TLVs

   This document adds the definition of two new sub-TLVs in the "sub-
   TLVs for TLV 22, 23, 141, 222 and 223 registry".

   Type: 40 (suggested - to be assigned by IANA)

   Description: Point-to-Point SRv6 X-SID Adjacency-SID

   Type: 41 (suggested - to be assigned by IANA)

   Description: LAN SRv6 X-SID LAN Adjacency-SID

      Type  22 23 141 222 223

      40     y  y  y   y   y
      41     y  y  y   y   y

7.5.  IS-IS SRv6 X-SID sub-sub-TLV Codepoints Registry

   This document requests the creation of a new IANA managed registry to
   identify SRv6 SID functions encoded in P2P/LAN X-SID sub-TLVs.  The
   registration procedure is "Expert Review" as defined in [RFC7370].
   Suggested registry name is "SRv6 X-SID sub-sub-TLV Codepoints
   Registry".  The following values are defined by this document:

   Value: 5 (Suggested - to be assigned by IANA)

   Name: SRv6-function

   Descriptor This sub-sub-TLV MAY appear in either the Point-to-Point
   SRv6 X-SID or the LAN SRv6 X-SID sub-TLVs described in Section 7.4.

8.  Security Considerations

   Security concerns for IS-IS are addressed in [ISO10589, [ISO10589], [RFC5304],
   and [RFC5310].

9.  Contributors

   The following people gave a substantial contribution to the content
   of this document and should be considered as co-authors:

     Stefano Previdi
     Cisco Systems, Inc.
     Email: stefano@previdi.net

     Peter Psenak
     Cisco Systems
     Apollo Business Center Mlynske nivy 43
     Bratislava  821 09
     Slovakia
     Email: ppsenak@cisco.com

     Paul Wells
     Cisco Systems
     Saint Paul,
     Minnesota
     United States
     Email: pauwells@cisco.com

     Daniel Voyer
     Email:  daniel.voyer@bell.ca

     Satoru Matsushima
     Email: satoru.matsushima@g.softbank.co.jp

     Bart Peirens
     Email: bart.peirens@proximus.com

     Hani Elmalky
     Email: hani.elmalky@ericsson.com

     Prem Jonnalagadda
     Email: prem@barefootnetworks.com

     Milad Sharif
     Email: msharif@barefootnetworks.com>

     Robert Hanzl
     Cisco Systems
     Millenium Plaza Building, V Celnici 10, Prague 1,
     Prague, Czech Republic
     Email rhanzl@cisco.com

10.  References
10.1.  Normative References

   [I-D.filsfils-spring-srv6-network-programming]
              Filsfils, C., Li, Z., Leddy, J., daniel.voyer@bell.ca, d.,
              daniel.bernier@bell.ca, d., Steinberg, D., Raszuk, R.,
              Matsushima, S., Lebrun, D., Decraene, B., Peirens, B.,
              Salsano, S., Naik, G., Elmalky, H., Jonnalagadda, P., and
              M. Sharif, "SRv6 Network Programming", draft-filsfils-
              spring-srv6-network-programming-04 (work in progress),
              March 2018.

   [I-D.ietf-6man-segment-routing-header]
              Previdi, S., Filsfils, C., Leddy, J., Matsushima, S., and
              d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header
              (SRH)", draft-ietf-6man-segment-routing-header-10 (work in
              progress), March 2018.

   [ISO10589]
              "Intermediate system to Intermediate system intra-domain
              routeing information exchange protocol for use in
              conjunction with the protocol for providing the
              connectionless-mode Network Service (ISO 8473), ISO/IEC
              10589:2002, Second Edition.", Nov 2002.

   [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>.

   [RFC5304]  Li, T. and R. Atkinson, "IS-IS Cryptographic
              Authentication", RFC 5304, DOI 10.17487/RFC5304, October
              2008, <https://www.rfc-editor.org/info/rfc5304>.

   [RFC5310]  Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
              and M. Fanto, "IS-IS Generic Cryptographic
              Authentication", RFC 5310, DOI 10.17487/RFC5310, February
              2009, <https://www.rfc-editor.org/info/rfc5310>.

   [RFC7370]  Ginsberg, L., "Updates to the IS-IS TLV Codepoints
              Registry", RFC 7370, DOI 10.17487/RFC7370, September 2014,
              <https://www.rfc-editor.org/info/rfc7370>.

   [RFC7981]  Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions
              for Advertising Router Information", RFC 7981,
              DOI 10.17487/RFC7981, October 2016,
              <https://www.rfc-editor.org/info/rfc7981>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

10.2.  Informative References

   [NP]       "SRv6 Network Programming, draft-filsfils-spring-srv6-
              network-programming-01 (work in progress)", June 2017.

   [SRARCH]

   [I-D.ietf-spring-segment-routing]
              Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B.,
              Litkowski, S., and R. Shakir, "Segment Routing Architecture, draft-ietf-spring-segment-
              routing-12(work in progress)", June 2017.

   [SRH]      "IPv6 SegmentRouting Header (SRH), draft-ietf-6man-
              segment-routing-header-07
              Architecture", draft-ietf-spring-segment-routing-15 (work
              in progress)", July 2017. progress), January 2018.

Authors' Addresses

   Les Ginsberg
   Cisco Systems
   821 Alder Drive
   Milpitas, CA  95035
   USA

   Email: ginsberg@cisco.com

   Ahmed Bashandy
   Cisco Systems
   170 West Tasman Dr
   San Jose, CA  95134
   USA

   Email: bashandy@cisco.com

   Clarence Filsfils
   Cisco Systems
   Brussels
   Belgium

   Email: cfilsfil@cisco.com

   Bruno Decraene
   Orange
   Issy-les-Moulineaux
   France

   Email: bruno.decraene@orange.com
   Zhibo Hu
   Huawei Technologies

   Email: huzhibo@huawei.com