\
LSR Working Group                                                A. Wang
Internet-Draft                                             China Telecom
Intended status: Standards Track                                   Z. Hu
Expires: November 17, 2022                           Huawei Technologies
                                                               A. Lindem
                                                           Cisco Systems
                                                               G. Mishra
                                                            Verizon Inc.
                                                                  J. Sun
                                                         ZTE Corporation
                                                            May 16, 2022


                 Advertisement of Stub Link Attributes
                 draft-wang-lsr-stub-link-attributes-04

Abstract

   This document describes the mechanism that can be used to advertise
   the stub link attributes within the ISIS or OSPF domain.

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
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on November 17, 2022.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect



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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
   3.  Consideration for Identifying Stub Link . . . . . . . . . . .   3
   4.  Protocol Extension for Stub Link Attributes . . . . . . . . .   3
     4.1.  OSPF Stub-Link TLV  . . . . . . . . . . . . . . . . . . .   4
     4.2.  ISIS Stub-link TLV  . . . . . . . . . . . . . . . . . . .   5
     4.3.  IPv4 Prefix Sub-TLV . . . . . . . . . . . . . . . . . . .   6
     4.4.  IPv6 Prefix Sub-TLV . . . . . . . . . . . . . . . . . . .   6
   5.  Application of the Stub Link attributes . . . . . . . . . . .   7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   8.  Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .   8
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   Stub links are used commonly within enterprise or service provider
   networks.  One common use case is the inter-AS routing scenario where
   there are no IGP adjacencies between the adjacent BGP domains.  Using
   stub link on the inter-AS connections can ensure that prefixes
   contained within a domain are only reachable within the domain itself
   and are not advertised between domains which could result in
   undesirable consequences.

   For operators that have multiple ASes interconnect with each other
   via the stub links, there is a requirement to obtain the inter-AS
   topology information as described in
   [I-D.ietf-idr-bgpls-inter-as-topology-ext].  If the router that uses
   BGP-LS within one IGP domain can distinguish stub links from other
   normal interfaces, it is then easy for the router to report these
   stub links using BGP-LS to a centralized PCE controller.  The
   controller can then pair the two endpoints of the stub link together
   via the prefixes information (for numbered stub link) or other
   attributes (for unnumbered stub link) associated with the stub link.

   Stub links are also normally the boundary of one IGP domain, knowing
   them can facilitate the operators to apply various policies on such




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   interfaces, for example, to secure their networks, or filtering the
   incoming traffic with scrutiny.

   But OSPF and ISIS have no capability to identify such stub links and
   their associated attributes now.

   This document defines the protocol extension for OSPFv2/v3 and ISIS
   to indicate the stub links and their associated attributes.

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.  Consideration for Identifying Stub Link

   OSPF[RFC5392] defines the Inter-AS-TE-v2 LSA and Inter-AS-TE-v3 LSA
   to carry the TE information about inter-AS links.  ISIS[RFC5316]
   defines the Inter-AS Reachability TLV to carry the TE information
   about inter-AS links.  These LSAs and TLVs can be used to transfer
   the information about the stub link which are located at the boundary
   of one AS, but to accomplish the scenario that described in
   [I-D.ietf-idr-bgpls-inter-as-topology-ext], every inter-AS link
   should be configured with the Remote AS Number and IPv4/IPv6 Remote
   ASBR ID.

   And, if the inter-AS stub link is LAN type, every inter-AS link must
   be configured with several Remote AS Numbers and IPv4/IPv6 Remote
   ASBR ID pairs to achieve the accurate description of the inter-AS
   connection.  Although the peers on the LAN share the same prefixes,
   existing solutions doesn't utilize such information to form the
   connection topology.

   To solve the problems that raised by the solutions based on [RFC5392]
   and [RFC5316], this document defines the Stub-Link TLV to identify
   the stub link and transmit the associated attributes for OSPF and
   ISIS respectively.

4.  Protocol Extension for Stub Link Attributes

   The following sections define the protocol extension to indicate the
   stub link and its associated attributes in OSPFv2/v3 and ISIS.








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4.1.  OSPF Stub-Link TLV

   This document defines the OSPF Stub-Link TLV to describe stub link of
   a single router.  This Stub-Link TLV is only applicable to the Inter-
   AS-TE-v2 LSA and Inter-AS-TE-v3 LSA.  Inclusion in other LSAs MUST be
   ignored.

   The OSPF Stub-Link TLV which is under the IANA codepoint "Top Level
   Types in TE LSAs" 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(Stub-Link)            |      Length                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Link Type   |                Reserved                       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      Link Prefix Sub-TLVs                     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Existing Sub-TLVs (variable)                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                 Figure 1: OSPF Stub-Link TLV

   Type: The TLV type.  The value is 7(TBD) for OSPF Stub-Link

   Length: Variable, dependent on sub-TLVs

   Link Type: Define the type of the stub-link:

   o  0: Reserved

   o  1: Numbered Stub Link

   o  2: Unnumbered Stub Link

   o  3-255: For future extension

   Link Prefix Sub-TLV: The prefix of the stub-link.  It's format is
   defined in Section 4.3 and Section 4.4.

   Existing Sub-TLVs: Sub-TLV that defined within "Open Shortest Path
   First (OSPF) Traffic Engineering TLVs" for TE Link TLV(Value 2) can
   be included if necessary.

   If the stub-link is "Unnumbered Stub Link" type, then the "Remote AS
   number" , "IPv4 Remote ASBR ID", "IPv6 Remote ASBR ID" sub-TLV MUST
   be included to facilitate the pairing of inter-AS link.




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   If this TLV is advertised multiple times in the same Inter-AS-TE-v2/
   v3 LSA, only the first instance of the TLV is used by receiving
   OSPFv2/v3 routers.  This situation SHOULD be logged as an error.

   If this TLV is advertised multiple times for the same link in
   different Inter-AS-TE-v2/v3 LSA originated by the same OSPFrouter,
   the OSPFStub-Link TLV in these LSAs with the smallest Opaque ID is
   used by receiving OSPFrouters.  This situation may be logged as a
   warning.

   It is RECOMMENDED that OSPF routers advertising OSPF Stub-Link TLVs
   in different OSPF Inter-AS-TE v2/v3 LSAs re-originate these LSAs in
   ascending order of Opaque ID to minimize the disruption.

   This document creates a registry for Stub-Link attributes in
   Section 7.

4.2.  ISIS Stub-link TLV

   This document defines the ISIS Stub-Link TLV to describes stub link
   of a single router.

   The ISIS Stub-Link 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(Stub-Link)            |           Length              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Link Type   |                Reserved                       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Link Prefix Sub-TLV                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |               Existing Sub-TLVs(Variable)                     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                 Figure 2: ISIS Stub-Link TLV

   Type: ISIS TLV codepoint.  Value is 151 (TBD) for stub-link TLV.

   Length: Variable, dependent on sub-TLVs

   Link Type: Define the type of the stub-link:

   o  0: Reserved

   o  1: Numbered Stub Link

   o  2: Unnumbered Stub Link



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   o  3-255: For future extension

   Link Prefix Sub-TLV: The prefix of the stub-link.  It's format is
   defined in Section 4.3 and Section 4.4.

   Existing Sub-TLVs: Sub-TLVs that defined within "IS-IS Sub-TLVs for
   TLVs Advertising Neighbor Information " can be included if necessary.

   If the stub-link is "Unnumbered Stub Link" type, then the "Remote AS
   number" , "IPv4 Remote ASBR ID", "IPv6 Remote ASBR ID" sub-TLV MUST
   be included to facilitate the pairing of inter-AS link.

4.3.  IPv4 Prefix Sub-TLV

   The IPv4 Prefix 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              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      IPv4 Prefix                              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                 Figure 3: IPv4 Prefix Sub-TLV

   Type: IPv4 Prefix Sub-TLV codepoint.  Value is 25(TBD) for OSPFv2
   (under "OSPFv2 Extended Link Sub-TLVs" )

   30(TBD) for OSPFv3(under OSPFv3 Extended-LSA Sub-TLVs)

   45(TBD) for IS-IS(under "IS-IS Sub-TLVs for TLVs Advertising Neighbor
   Information")

   Length: Netmask length value of the IPv4 Prefix.  Value should be in
   2-32.

   IPv4 Prefix: The value of 4-octet IPv4 Prefix address, the host part
   should be zero.

4.4.  IPv6 Prefix Sub-TLV

   The IPv6 Prefix 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                       |           Length              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      IPv6 Prefix                              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      IPv6 Prefix                              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      IPv6 Prefix                              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      IPv6 Prefix                              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                 Figure 4: IPv6 Prefix Sub-TLV

   Type: IPv6 Prefix Sub-TLV codepoint.  Value is 31(TBD) for
   OSPFv3.(under OSPFv3 Extended-LSA Sub-TLVs)

   46(TBD) for IS-IS(under "IS-IS Sub-TLVs for TLVs Advertising Neighbor
   Information")

   Length: Netmask length value of the IPv6 Prefix.  Value should be in
   2-128.

   IPv6 Prefix: The value of 16-octet IPv6 Prefix address, the host part
   should be zero.

5.  Application of the Stub Link attributes

   For scenario that descried in
   [I-D.ietf-idr-bgpls-inter-as-topology-ext], the prefixes information
   associated with the stub link can be used to pair the two endpoints
   of the stub link by the controller.  Such solution can apply in P2P,
   Broadcast, P2MP, NBMA numbered stub link type.  For unnumbered Stub
   link, the controller can use the associated Remote-AS, IPv4/IPv6
   Remote Router ID to pair the two endpoints of the stub link.

6.  Security Considerations

   Security concerns for ISIS are addressed in [RFC5304] and[RFC5310]

   Security concern for OSPFv3 is addressed in [RFC4552]

   Advertisement of the additional information defined in this document
   introduces no new security concerns.






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7.  IANA Considerations

   IANA is requested to the allocation in following registries:

  +=================================+======+===========================+
  | Registry                        | Type |       Meaning             |
  +=================================+======+===========================+
  |Top Level Types in TE LSAs       | 7    |OSPF Stub-Link TLV         |
  +---------------------------------+------+---------------------------+
  |ISIS Top-Level TLV               | 151  |IS-IS Stub-Link TLV        |
  +---------------------------------+------+---------------------------+
  |OSPFv2 Extended Link TLV         |  25  | IPv4 Prefix Sub-TLV       |
  +---------------------------------+------+---------------------------+
  |OSPFv3 Extended-LSA Sub-TLVs     |  30  | IPv4 Prefix Sub-TLV       |
  +---------------------------------+------+---------------------------+
  |OSPFv3 Extended-LSA Sub-TLVs     |  31  | IPv6 Prefix Sub-TLV       |
  +---------------------------------+------+---------------------------+
  |IS-IS Sub-TLVs for TLVs          |      |                           |
  |Advertising Neighbor Information |  45  | IPv4 Prefix Sub-TLV       |
  +---------------------------------+------+---------------------------+
  |IS-IS Sub-TLVs for TLVs          |      |                           |
  |Advertising Neighbor Information |  46  | IPv6 Prefix Sub-TLV       |
  +---------------------------------+------+---------------------------+
     Figure 5: IANA Allocation for newly defined TLVs and Sub-TLVs

8.  Acknowledgement

   Thanks Shunwan Zhang, Peter Psenak, Tony Li, Les Ginsberg, Dhruv
   Dhody, Jeff Tantsura and Robert Raszuk for their suggestions and
   comments on this idea.

9.  References

9.1.  Normative References

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

   [RFC4552]  Gupta, M. and N. Melam, "Authentication/Confidentiality
              for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006,
              <https://www.rfc-editor.org/info/rfc4552>.

   [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>.




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   [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>.

   [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>.

   [RFC5392]  Chen, M., Zhang, R., and X. Duan, "OSPF Extensions in
              Support of Inter-Autonomous System (AS) MPLS and GMPLS
              Traffic Engineering", RFC 5392, DOI 10.17487/RFC5392,
              January 2009, <https://www.rfc-editor.org/info/rfc5392>.

9.2.  Informative References

   [I-D.ietf-idr-bgpls-inter-as-topology-ext]
              Wang, A., Chen, H., Talaulikar, K., and S. Zhuang, "BGP-LS
              Extension for Inter-AS Topology Retrieval", draft-ietf-
              idr-bgpls-inter-as-topology-ext-11 (work in progress), May
              2022.

Authors' Addresses

   Aijun Wang
   China Telecom
   Beiqijia Town, Changping District
   Beijing  102209
   China

   Email: wangaj3@chinatelecom.cn


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

   Email: huzhibo@huawei.com










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   Acee Lindem
   Cisco Systems
   No. 301 Midenhall Way
   Cary  NC 27513
   United States of America

   Email: acee@cisco.com


   Gyan S. Mishra
   Verizon Inc.
   13101 Columbia Pike
   Silver Spring  MD 20904
   United States of America

   Email: gyan.s.mishra@verizon.com


   Jinsong Sun
   ZTE Corporation
   No. 68, Ziijnhua Road
   Nan Jing  210012
   China

   Email: sun.jinsong@zte.com.cn


























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