IS-IS Extensions to Support Transport Network Slices using Segment Routing
draft-zch-lsr-isis-network-slicing-06

Document Type Active Internet-Draft (individual)
Authors Yongqing Zhu  , Ran Chen  , Shaofu Peng  , Fengwei Qin 
Last updated 2020-09-04
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Networking Working Group                                          Y. Zhu
Internet-Draft                                             China Telecom
Intended status: Standards Track                                 R. Chen
Expires: March 9, 2021                                           S. Peng
                                                         ZTE Corporation
                                                                  F. Qin
                                                            China Mobile
                                                      September 05, 2020

   IS-IS Extensions to Support Transport Network Slices using Segment
                                Routing
                 draft-zch-lsr-isis-network-slicing-06

Abstract

   [I-D.nsdt-teas-ns-framework] provides a framework of transport
   slices.

   This draft describes the IS-IS extensions required to support
   transport slices using Segment Routing.

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 March 9, 2021.

Copyright Notice

   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
   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

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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
   3.  Router Capabilities for TN-slice Identifier . . . . . . . . .   3
   4.  Advertising TN-slice Identifier as a new TE parameter of a
       link  . . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Advertising Dedicated Bandwidth Resouce of a Link for
           Each VN . . . . . . . . . . . . . . . . . . . . . . . . .   5
       4.1.1.  Unidirectional Residual Bandwidth per TN-slice
               Identifier Sub-TLV  . . . . . . . . . . . . . . . . .   6
       4.1.2.  Unidirectional Available Bandwidth per TN-slice
               Identifier Sub-TLV  . . . . . . . . . . . . . . . . .   7
       4.1.3.  Unidirectional Utilized Bandwidth per TN-slice
               Identifier Sub-TLV  . . . . . . . . . . . . . . . . .   8
   5.  Advertising TN-slice Identifier for L2 Bundle Member  . . . .   8
     5.1.  Advertising Bandwidth Information of member Link  . . . .   9
   6.  Advertising prefix-SID per TN-slice Identifier  . . . . . . .   9
   7.  Advertising Adjacency-SID per TN-slice Identifier . . . . . .  11
   8.  Advertising Adjacency-SID per TN-slice Identifier in LANs . .  12
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
     9.1.  Router Capabilities for TN-slice Identifier . . . . . . .  13
     9.2.  TN-slice Identifier list sub-TLV  . . . . . . . . . . . .  13
     9.3.  Unidirectional Residual Bandwidth per TN-slice Identifier
           Sub-TLV . . . . . . . . . . . . . . . . . . . . . . . . .  13
     9.4.  Unidirectional Available Bandwidth per TN-slice
           Identifier Sub-TLV  . . . . . . . . . . . . . . . . . . .  14
     9.5.  Unidirectional Utilized Bandwidth per TN-slice Identifier
           Sub-TLV . . . . . . . . . . . . . . . . . . . . . . . . .  14
     9.6.  L2 Bundle Member TN-slice Identifier sub-TLV  . . . . . .  14
     9.7.  Prefix-SID for TN-slice Identifier sub-TLV  . . . . . . .  14
     9.8.  Adjacency-SID for TN-slice Identifier sub-TLV . . . . . .  14
     9.9.  LAN-Adj-SID for TN-slice Identifier sub-TLV . . . . . . .  14
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  15
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  15
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     12.1.  Normative references . . . . . . . . . . . . . . . . . .  15
     12.2.  Informative references . . . . . . . . . . . . . . . . .  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  16

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1.  Introduction

   [I-D.nsdt-teas-ns-framework] provides a framework for discussing
   transport slices.

   For a Transport Network, transport network slicing requires the
   underlying network to support partitioning of the network resources
   to provide the client with dedicated (private) networking, computing,
   and storage resources drawn from a shared pool.
   [I-D.peng-teas-network-slicing] introduce a unified TN-slice
   identifier (termes as AII) to the underlay transport network
   according to the requirement of network slice.  AII is convenient to
   indicate the topology, computing, storage resources of the dedicated
   virtual network for both intra-domain and inter-domain network
   slicing scenarios, and it is flexible to compute SR-BE or SR-TE path
   according to AII combined with other creteria.

   This draft describes the IS-IS extensions required to distribute TN-
   slice Identifier information in an AS.

2.  Conventions used in this document

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

3.  Router Capabilities for TN-slice Identifier

   Although a router can deduce which TN-slices it has participated in
   according to the AII(administrative instance identifier)
   configuration of all links, an ISIS instance can explicitly control
   which TN-slices it wants to enable (or join), to explicitly control
   which SPT (shortest path tree) for a specific AII to be created.  It
   is possible for a route process not to join any TN-slices (except the
   default AII 0) in despite of any AII configuration of any links.
   Especially, it is hard to deduce the participated TN-slice according
   to the AII configuration of L2 Bundle Member.

   This section defines AII Participation sub-TLV which is inserted into
   the IS-IS Router Capability TLV-242 that is defined in [RFC7981], to
   explicitly advertise which TN-slice a router wants to take part in.

   The TN-slice identifier Participation sub-TLV has the following
   format:

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        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Type=TBD1    |   Length      |    Number     |               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                    AII for virtual networks 1                 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                       ......                                  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                    AII for virtual networks N                 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                 Figure 1: Node Participation to TN-slice

   where:

   Type: TBD1 (Suggested value to be assigned by IANA)

   Length: variable.

   Number:Number of virtual networks.

   AII for VN: allocate different TN-slice identifier (AII) for
   different virtual networks.  AII is used to distinguish different
   virtual network resources.

4.  Advertising TN-slice Identifier as a new TE parameter of a link

   [RFC5305] describes extensions to the Intermediate System to
   Intermediate System (IS-IS) protocol to support Traffic Engineering
   (TE).

   TN-slice Identifier can be used to color links to partition underlay
   resource.  This document defines a new extension of the existing IGP-
   TE mechanisms [RFC5305] to distribute TN-slice Identifier information
   in an AS as a new TE parameter of a link.

   The TN-slice Identifier list sub-TLV has the following format:

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         0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Type=TBD2    |   Length      |    Reserved   |    Number     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                   AII for virtual networks 1                  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                       ......                                  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                   AII for virtual networks N                  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                 Figure 2: Link Participation to TN-slice

   Type: TBD2 (Suggested value to be assigned by IANA)

   Length: variable.

   Number:Number of virtual networks.

   AII for VN: allocate different TN-slice identifier (AII) for
   different virtual networks.  AII is used to distinguish different
   virtual network resources.

   This sub-TLV MAY be present in any of the following TLVs:

   TLV-22 (Extended IS reachability) [RFC5305].

   TLV-222 (Multitopology IS) [RFC5120].

   TLV-23 (IS Neighbor Attribute) [RFC5311].

   TLV-223 (Multitopology IS Neighbor Attribute) [RFC5311].

   TLV-141 (inter-AS reachability information) [RFC5316].

   This sub-TLV SHOULD appear once at most in each TLV.  Indicates that
   a link MAY belong to multiple virtual networks.

   Note that AII 0 does not require notification, and all links are
   always in AII 0 at the same time.

4.1.  Advertising Dedicated Bandwidth Resouce of a Link for Each VN

   [RFC8570] provide ways to distribute network-performance information,
   and it defines Unidirectional Residual Bandwidth Sub-TLV (URB Sub-
   TLV), Unidirectional Available Bandwidth Sub-TLV (UAB Sub-TLV),
   Unidirectional Utilized Bandwidth Sub-TLV (UUB Sub-TLV) for each

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   directly connected IS-IS neighbors.  As described above, a link can
   belong to multiple VNs, as traditional ways that these VNs can share
   the total bandwidth resouce of the link with preemption mode based on
   packet priority, this is what we know as soft slices.  However, In
   some other scenarios, a hard slicing scheme can be used to establish
   a hardened pipe to meet the slicing business requirements, at this
   time each VN need dedicated bandwidth resouce reserved from the same
   link, and in each node the packet rate limit and QoS policy per slice
   may be used to ensure that the traffic between different slices is
   isolated and does not affect each other.  For this purpose, this
   section continues to introduce and register new bandwidth related IS-
   IS TE sub-TLVs in the "Sub-TLVs for TLVs 22, 23, 141, 222, and 223"
   registry.

4.1.1.  Unidirectional Residual Bandwidth per TN-slice Identifier Sub-
        TLV

   This sub-TLV (URBPTSI Sub-TLV) advertises the residual bandwidth for
   a specific slice between two directly connected IS-IS neighbors.  The
   residual bandwidth advertised by this sub-TLV MUST be the residual
   bandwidth from the system originating the Link State Advertisement
   (LSA) to its neighbor.  This sub-TLV may appear more than once.

        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=TBD3    |     Length    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                              AII                              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                          Residual Bandwidth                   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         Figure 3: Unidirectional Residual Bandwidth per TN-slice

   Type: TBD3 (Suggested value to be assigned by IANA)

   Length: 8

   AII: Identifies the TN-slice information.

   Residual Bandwidth: This field carries the residual bandwidth for
   specific TN-slice on a link or bundled link in IEEE floating-point
   format with units of bytes per second.

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   When AII is 0, the URBPTSI Sub-TLV has the same function with the URB
   Sub-TLV defined in [RFC8570].  Note that the sum of URBPTSI Sub-TLV
   for all slices MUST not be larger than the result of Maximum Link
   Bandwidth [RFC5305] minus RSVP-TE tunnel reservations.

   For the system originating the URBPTSI Sub-TLV, the residual
   bandwidth for each specific slice could be configured explicitly.
   For example, for a link with 10G bandwidth without any RSVP-TE tunnel
   reservations, the configuration could be: 4G is allocated for AII 1,
   4G is allocated for AII 2, then the rest 2G is allocated for AII 0.
   Thus, an URBPTSI Sub-TLV for AII 0 or traditional URB Sub-TLV with
   Residual Bandwidth field set to 2G can be advertised, and two URBPTSI
   Sub-TLVs each for AII 1 or 2 with Residual Bandwidth field set to 4G
   can be advertised respectively.

4.1.2.  Unidirectional Available Bandwidth per TN-slice Identifier Sub-
        TLV

   This sub-TLV (UABPTSI Sub-TLV) advertises the available bandwidth for
   a specific slice between two directly connected IS-IS neighbors.  The
   available bandwidth advertised by this sub-TLV MUST be the available
   bandwidth from the system originating this sub-TLV.  This sub-TLV may
   appear more than once.  The format of this sub-TLV is shown in the
   following diagram:

        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=TBD4    |     Length    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                              AII                              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Available Bandwidth                   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         Figure 4: Unidirectional Available Bandwidth per TN-slice

   Type: TBD4 (Suggested value to be assigned by IANA)

   Length: 8

   AII: Identifies the TN-slice information.

   Available Bandwidth: This field carries the available bandwidth for
   specific TN-slice on a link or bundled link in IEEE floating-point
   format with units of bytes per second.  It is defined to be residual

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   bandwidth per TN-slice minus the measured bandwidth (the UUBPTSI
   introduced in next section) used for the actual forwarding of packets
   within that slice.

4.1.3.  Unidirectional Utilized Bandwidth per TN-slice Identifier Sub-
        TLV

   This sub-TLV (UUBPTSI Sub-TLV) advertises the bandwidth utilization
   for a specific slice between two directly connected IS-IS neighbors.
   The bandwidth utilization advertised by this sub-TLV MUST be the
   bandwidth from the system originating this sub-TLV.  This sub-TLV may
   appear more than once.  The format of this sub-TLV is shown in the
   following diagram:

        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=TBD5    |     Length    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                              AII                              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Utilized Bandwidth                    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         Figure 5: Unidirectional Utilized Bandwidth per TN-slice

   Type: TBD5 (Suggested value to be assigned by IANA)

   Length: 8

   AII: Identifies the TN-slice information.

   Utilized Bandwidth: This field carries the bandwidth utilization for
   specific TN-slice on a link or bundled link in IEEE floating-point
   format with units of bytes per second.  It represents the actual
   utilization of the link (i.e., as measured by the advertising node)
   for that slice.

5.  Advertising TN-slice Identifier for L2 Bundle Member

   [RFC8668] defines a sub-TLV of L2 Bundle Attribute Descriptors, and
   the sub-TLV may define an attribute common to all of the bundle
   members listed or a sub-TLV may define an attribute unique to each
   bundle member.  For a bundled link, there are two ways to use TN-
   slice Identifier to partition its resource.  The first one is to set
   the parent interface with one or more expected TN-slice Identifier,

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   that is we have seen in Section 4.  The second one is to set each
   member interface with specific TN-slice Identifier, for example,
   member 1 set to AII 0, member 2 set to AII 1, member 3 set to AII 2,
   etc.  For simple deployment and according to actual needs, each
   member is set to a single TN-slice Identifier.  For the second case,
   this section defines a new sub-TLV: L2 Bundle Member TN-slice
   Identifier sub-TLV, to advertise TN-slice Identifier for each L2
   Bundle Member associated with a parent L3 adjacency which is Point-
   to-Point.  The following format is defined for this sub-TLV:

   Type: TBD6.

   Length: variable

   L2 Bundle Member TN-slice Identifier.  There MUST be one TN-slice
   Identifier(AII) for each of the L2 Bundle Members advertised under
   the preceding L2 Bundle Member Attribute Descriptor.

   This sub-TLV MAY be present in the following TLVs:

   TLV-25 (L2 Bundle Member Attributes) [RFC8668].

   This sub-TLV SHOULD appear once at most in the TLV.  Indicates that
   the TN-slice Identifier for L2 Bundle Member.

5.1.  Advertising Bandwidth Information of member Link

   [RFC8668] allows notification of bandwidth information of member
   links using the sub-TLVs defined in [RFC8570].  Because each member
   link belongs to single TN-slice, it is not necessary to advertise the
   bandwidth information of member links for specific slice using the
   sub-TLVs defined in Section 4.1.

6.  Advertising prefix-SID per TN-slice Identifier

   [RFC8667] defines a new IS-IS sub-TLV: the Prefix Segment Identifier
   sub-TLV (Prefix-SID sub-TLV).  The Prefix-SID sub-TLV carries the
   Segment Routing IGP-Prefix-SID as defined in [RFC8402], and is
   associated to a prefix advertised by a node.

   To distinguish forwarding behavior of different virtual networks,
   Prefix-SID need to be allocated per TN-slice Identifier and
   advertised in the IGP domain.  This document defines a new extension
   of the existing Prefix-SID sub-TLV.

   The Prefix-SID for TN-slice Identifier sub-TLV has the following
   format:

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         0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   Type=TBD7   |    Length     |     Flag      |   Algorithm   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                            AII                                |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                      SID/Index/Label(Variable)                |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 6: Prefix-SID per TN-slice

   where:

   Type: TBD7 (Suggested value to be assigned by IANA)

   Length: Variable.  Depending on the size of the SID.

   The "Flags" and "SID/Index/Label" fields are the same as the Prefix-
   SID sub-TLV [RFC8667] .

   Algorithm: Accoridng to section "3.2.  SR-Algorithm Sub-TLV" of
   [RFC8667] , two values can be set in this field.

   o  0: Shortest Path First (SPF) algorithm based on link metric.

   o  1: Strict Shortest Path First (SPF) algorithm based on link
      metric.

   Note that[I-D.ietf-lsr-flex-algo].also allows user to define other
   algorithm values, i.e., FA-id within [128, 255], for the purpose of
   constraint based path computation.  However, an FA-id algorithm value
   MUST not be set in this field, the reason is that FA-id has not
   semantic local within AII.

   AII: Identifies the TN-slice (AII) information corresponding to the
   Prefix-SID.

   This sub-TLV MAY be present in any of the following TLVs:

   TLV-135 (Extended IPv4 reachability) defined in [RFC5305].

   TLV-235 (Multitopology IPv4 Reachability) defined in [RFC5120].

   TLV-236 (IPv6 IP Reachability) defined in [RFC5308].

   TLV-237 (Multitopology IPv6 IP Reachability) defined in [RFC5120].

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   This sub-TLV MAY appear multiple times in each TLV.

7.  Advertising Adjacency-SID per TN-slice Identifier

   [RFC8667] defines the IS-IS sub-TLV: the Adjacency Segment Identifier
   sub-TLV (Adj-SID sub-TLV).The Adj-SID sub-TLV is an optional sub-TLV
   carrying the Segment Routing IGP-Adjacency-SID as defined in
   [RFC8402].

   To distinguish forwarding behavior of different virtual networks,
   Adjacency-SID need to be allocated per TN-slice Identifier and
   advertised in the IGP domain.  This document defines a new extension
   of the existing Adjacency-SID sub-TLV.

   The Adjacency-SID for TN-slice Identifier 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=TBD8   |    Length     |     Flag      |   Algorithm   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                            AII                                |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                      SID/Index/Label(Variable)                |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 7: Adjacency-SID per TN-slice

   where:

   Type: TBD8 (Suggested value to be assigned by IANA)

   Length: Variable.  Depending on the size of the SID.

   The "Flags" and "SID/Index/Label" fields are the same as the
   Adjacency-SID sub-TLV [RFC8667].

   AII: Identifies the TN-slice (AII) information corresponding to the
   Adjacency-SID.

   This sub-TLV MAY be present in any of the following TLVs:

   TLV-22 (Extended IS reachability) [RFC5305].

   TLV-222 (Multitopology IS)[RFC5120].

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   TLV-23 (IS Neighbor Attribute)[RFC5311].

   TLV-223 (Multitopology IS Neighbor Attribute)[RFC5311].

   TLV-141 (inter-AS reachability information)[RFC5316].

   Multiple Adj-SID sub-TLVs MAY be associated with a single IS-
   neighbor.  This sub-TLV MAY appear multiple times in each TLV.

8.  Advertising Adjacency-SID per TN-slice Identifier in LANs

   In LAN subnetworks,[RFC8667] defines the LAN-Adj-SID sub-TLV for a
   router to advertise the Adj-SID of each of its neighbors.

   To distinguish forwarding behavior of different virtual networks,
   Adjacency-SID need to be allocated per TN-slice Identifier and
   advertised in the IGP domain.  This document defines a new extension
   of the existing Adjacency-SID sub-TLV.

   The LAN-Adj-SID for TN-slice Identifier 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=TBD9   |     Length    |      Flags    |    Weight     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Neighbor System-ID (ID length octets)        |
     +                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                              AII                              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                   SID/Label/Index (variable)                  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 8: Adjacency-SID per TN-slice in LANs

   where:

   Type: TBD9 (Suggested value to be assigned by IANA)

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   Length: Variable.  Depending on the size of the SID.

   The "Flags" and "SID/Index/Label" fields are the same as the
   Adjacency-SID sub-TLV [RFC8667].

   AII: Identifies the TN-slice (AII) information corresponding to the
   Adjacency-SID.

   This sub-TLV MAY be present in any of the following TLVs:

   TLV-22 (Extended IS reachability) [RFC5305].

   TLV-222 (Multitopology IS)[RFC5120].

   TLV-23 (IS Neighbor Attribute)[RFC5311].

   TLV-223 (Multitopology IS Neighbor Attribute)[RFC5311].

   Multiple Adj-SID sub-TLVs MAY be associated with a single IS-
   neighbor.  This sub-TLV MAY appear multiple times in each TLV.

9.  IANA Considerations

   This document requests allocation for the following Sub-TLVs.

9.1.  Router Capabilities for TN-slice Identifier

   This document requests IANA to assign a new code point in the "sub-
   TLV for TLV 242" registry.

   Type: TBD1

9.2.  TN-slice Identifier list sub-TLV

   This TLV shares sub-TLV space with existing "Sub-TLVs for TLVs 22,
   222, 23, 223 and 141 registry".

   Type:TBD2(to be assigned by IANA).

9.3.  Unidirectional Residual Bandwidth per TN-slice Identifier Sub-TLV

   This TLV shares sub-TLV space with existing "Sub-TLVs for TLVs 22,
   222, 23, 223 and 141 registry".

   Type:TBD3(to be assigned by IANA).

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9.4.  Unidirectional Available Bandwidth per TN-slice Identifier Sub-TLV

   This TLV shares sub-TLV space with existing "Sub-TLVs for TLVs 22,
   222, 23, 223 and 141 registry".

   Type:TBD4(to be assigned by IANA).

9.5.  Unidirectional Utilized Bandwidth per TN-slice Identifier Sub-TLV

   This TLV shares sub-TLV space with existing "Sub-TLVs for TLVs 22,
   222, 23, 223 and 141 registry".

   Type:TBD5(to be assigned by IANA).

9.6.  L2 Bundle Member TN-slice Identifier sub-TLV

   This TLV shares sub-TLV space with existing "Sub-TLVs for TLVs 22,
   222, 23, 25, 223 and 141 registry.

   Type:TBD6(to be assigned by IANA).

   This sub-TLV is allowed in the following TLVs:

          22 23 25 141 222 223
          n  n  y  n   n   n

9.7.  Prefix-SID for TN-slice Identifier sub-TLV

   This TLV shares sub-TLV space with existing "Sub-TLVs for TLVs
   135,235,226 and 237 registry".

   Type:TBD7(to be assigned by IANA).

9.8.  Adjacency-SID for TN-slice Identifier sub-TLV

   This TLV shares sub-TLV space with existing "Sub-TLVs for TLVs 22,
   222, 23, 223 and 141 registry".

   Type:TBD8(to be assigned by IANA).

9.9.  LAN-Adj-SID for TN-slice Identifier sub-TLV

   This TLV shares sub-TLV space with existing "Sub-TLVs for TLVs 22,
   222, 23, and 223 registry".

   Type:TBD9(to be assigned by IANA).

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10.  Security Considerations

   TBD.

11.  Acknowledgements

   TBD.

12.  References

12.1.  Normative references

   [I-D.ietf-lsr-flex-algo]
              Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and
              A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex-
              algo-10 (work in progress), August 2020.

   [I-D.nsdt-teas-ns-framework]
              Gray, E. and J. Drake, "Framework for Transport Network
              Slices", draft-nsdt-teas-ns-framework-04 (work in
              progress), July 2020.

   [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>.

   [RFC5120]  Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
              Topology (MT) Routing in Intermediate System to
              Intermediate Systems (IS-ISs)", RFC 5120,
              DOI 10.17487/RFC5120, February 2008,
              <https://www.rfc-editor.org/info/rfc5120>.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, DOI 10.17487/RFC5305, October
              2008, <https://www.rfc-editor.org/info/rfc5305>.

   [RFC5308]  Hopps, C., "Routing IPv6 with IS-IS", RFC 5308,
              DOI 10.17487/RFC5308, October 2008,
              <https://www.rfc-editor.org/info/rfc5308>.

   [RFC5311]  McPherson, D., Ed., Ginsberg, L., Previdi, S., and M.
              Shand, "Simplified Extension of Link State PDU (LSP) Space
              for IS-IS", RFC 5311, DOI 10.17487/RFC5311, February 2009,
              <https://www.rfc-editor.org/info/rfc5311>.

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   [RFC5316]  Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in
              Support of Inter-Autonomous System (AS) MPLS and GMPLS
              Traffic Engineering", RFC 5316, DOI 10.17487/RFC5316,
              December 2008, <https://www.rfc-editor.org/info/rfc5316>.

   [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>.

   [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>.

   [RFC8570]  Ginsberg, L., Ed., Previdi, S., Ed., Giacalone, S., Ward,
              D., Drake, J., and Q. Wu, "IS-IS Traffic Engineering (TE)
              Metric Extensions", RFC 8570, DOI 10.17487/RFC8570, March
              2019, <https://www.rfc-editor.org/info/rfc8570>.

   [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>.

   [RFC8668]  Ginsberg, L., Ed., Bashandy, A., Filsfils, C., Nanduri,
              M., and E. Aries, "Advertising Layer 2 Bundle Member Link
              Attributes in IS-IS", RFC 8668, DOI 10.17487/RFC8668,
              December 2019, <https://www.rfc-editor.org/info/rfc8668>.

12.2.  Informative references

   [I-D.peng-teas-network-slicing]
              Peng, S., Chen, R., Mirsky, G., and F. Qin, "Packet
              Network Slicing using Segment Routing", draft-peng-teas-
              network-slicing-03 (work in progress), February 2020.

Authors' Addresses

   Yongqing Zhu
   China Telecom

   Email: zhuyq.gd@chinatelecom.cn

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   Ran Chen
   ZTE Corporation

   Email: chen.ran@zte.com.cn

   Shaofu Peng
   ZTE Corporation

   Email: peng.shaofu@zte.com.cn

   Fengwei Qin
   China Mobile

   Email: qinfengwei@chinamobile.com

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