LSR Working Group                                                A. Wang
Internet-Draft                                             China Telecom
Intended status: Standards Track                                   Z. Hu
Expires: 1 February 2022                             Huawei Technologies
                                                               G. Mishra
                                                            Verizon Inc.
                                                                  J. Sun
                                                         ZTE Corporation
                                                            31 July 2021


                 Advertisement of Stub Link Attributes
                 draft-wang-lsr-stub-link-attributes-00

Abstract

   This document describes the mechanism that can be used to
   differentiate the stub links from the normal interfaces within 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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   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 1 February 2022.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.










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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include 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 flagging passive interface  . . . . . . . .   3
   4.  Passive Interface Attribute . . . . . . . . . . . . . . . . .   4
     4.1.  OSPFv2 Extended Stub-Link TLV . . . . . . . . . . . . . .   4
     4.2.  OSPFv3 Router-Stub-Link TLV . . . . . . . . . . . . . . .   5
     4.3.  ISIS Stub-link TLV  . . . . . . . . . . . . . . . . . . .   6
     4.4.  Stub-Link Prefix Sub-TLV  . . . . . . . . . . . . . . . .   7
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   7.  Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .   9
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   Stub links are used commonly within an operators enterprise or
   service provider networks.  One of the most common use cases for stub
   links is in a data center Layer 2 and Layer 3 Top of Rack(TOR) switch
   where the inter connected links between the TOR switches and uplinks
   to the core switch are only a few links and a majority of the links
   are Layer 3 VLAN switched virtual interface trunked between the TOR
   switches serving Layer 2 broadcast domains.  In this scenario all the
   VLANs are made as stub links as it is recommended to limit the number
   of network LSAs between routers and switches to avoid unnecessary
   hello processing overhead.

   Another common use case is an inter-as routing scenario where the
   same routing protocol but different IGP instance is running 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 not allow the link state
   database to be merged between domain which could result in
   undesirable consequences.




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   For operator which runs different IGP domains that interconnect with
   each other via the stub links, there is desire to obtain the inter-as
   topology information as described in
   [I-D.ietf-idr-bgpls-inter-as-topology-ext].  If the router that runs
   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.

   Draft [I-D.dunbar-lsr-5g-edge-compute-ospf-ext] describes the case
   that edge compute server attach the network and needs to flood some
   performance index information to the network to facilitate the
   network select the optimized application resource.  The edge compute
   server will also not run IGP protocol.

   And, stub links are normally the boundary of one IGP domain, knowing
   them can facilitate the operators to apply various policies on such
   interfaces, for example, to secure their networks, or filtering the
   incoming traffic with scrutiny.

   But OSPF and ISIS have no position to flag such stub links and their
   associated attributes now.

   This document defines the protocol extension for OSPF 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 flagging passive interface

   ISIS[RFC5029] defines the Link-Attributes Sub-TLV to carry the link
   attribute information, but this Sub-TLV can only be carried within
   the TLV 22, which is used to described the attached neighbor.  For
   stub link, there is no ISIS neighbor, then it is not appropriate to
   use this Sub-TLV to indicate the attribute of such link.

   OSPFv2[RFC2328] defines link type field within Router LSA, the type 3
   for connections to a stub network can be used to identified the stub
   link.  But in OSPFv3[RFC5340], type 3 within the Router-LSA has been
   reserved.  The information that associated with stub network has been
   put in the Intra-Area-Prefix-LSAs.

   It is necessary to define one general solution for ISIS and OSPF to
   flag the stub link and transfer the associated attributes then.




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4.  Passive Interface Attribute

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

4.1.  OSPFv2 Extended Stub-Link TLV

   [RFC7684] defines the OSPFv2 Extended Link Opaque LSA to contain the
   additional link attribute TLV.  Currently, only OSPFv2 Extended Link
   TLV is defined to contain the link related sub-TLV.  Because stub
   link is not the normal link that participate in the OSPFv2 process,
   we select to define one new top TLV within the OSPFv2 Extended Link
   Opaque LSA to contain the stub link related attribute information.

   The OSPFv2 Extended 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   |              Metric             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                            Link ID                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           Link Data                           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      Sub-TLVs (variable)                      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                Figure 1: OSPFv2 Extended Stub-Link TLV

   Type: The TLV type.  The value is 2(TBD) for this stub-link type

   Length: Variable, dependent on sub-TLVs

   Link Type: Define the type of the stub-link.  This document defines
   the followings type:

   *  0: Reserved

   *  1: AS boundary link

   *  2: Loopback link

   *  3: Vlan interface link

   *  4-255: For future extension




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   Metric: Link metric used for inter-AS traffic engineering.

   Link ID: Link ID is defined in Section A.4.2 of [RFC2328]

   Link Data: Link Data is defined in Section A.4.2 of [RFC2328]

   Sub-TLVs: Existing sub-TLV that defined within "OSPFv2 Extended Link
   TLV Sub-TLV" can be included if necessary, the definition of new sub-
   TLV can refer to Section 4.4


   If this TLV is advertised multiple times in the same OSPFv2 Extended
   Link Opaque LSA, only the first instance of the TLV is used by
   receiving OSPFv2 routers.  This situation SHOULD be logged as an
   error.

   If this TLV is advertised multiple times for the same link in
   different OSPFv2 Extended Link Opaque LSAs originated by the same
   OSPFv2 router, the OSPFv2 Extended Stub-Link TLV in the OSPFv2
   Extended Link Opaque LSA with the smallest Opaque ID is used by
   receiving OSPFv2 routers.  This situation may be logged as a warning.

   It is RECOMMENDED that OSPFv2 routers advertising OSPFv2 Extended
   Stub-Link TLVs in different OSPFv2 Extended Link Opaque LSAs re-
   originate these LSAs in ascending order of Opaque ID to minimize the
   disruption.


   This document creates a registry for Stub-Link attribute in
   Section 6.

4.2.  OSPFv3 Router-Stub-Link TLV

   [RFC8362] extend the LSA format by encoding the existing OSPFv3 LSA
   [RFC5340] in TLV tuples and allowing advertisement of additional
   information with additional TLV.

   This document defines the Router-Stub-Link TLV to describes stub link
   of a single router.  The Router-Stub-Link TLV is only applicable to
   the E-Router-LSA.  Inclusion in other Extended LSA MUST be ignored.











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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(Router-Stub-Link)   |            Length               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Link Type |    Reserved   |              Metric             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      Interface ID                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Sub-TLVs(Variable)                           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                Figure 2: OSPFv3 Router-Stub-Link TLV

   Type: OSPFv3 Extended-LSA TLV Type.  Value is 10(TBD) for Router-
   Stub-Link TLV.

   Length: Variable, dependent on sub-TLVs

   Link Type: Define the type of the stub-link.  This document defines
   the followings type:

   *  0: Reserved

   *  1: AS boundary link

   *  2: Loopback link

   *  3: Vlan interface link

   *  4-255: For future extension

   Metric: Link metric used for inter-AS traffic engineering.

   Interface ID: 32-bit number uniquely identifying this interface among
   the collection of this router's interfaces.  For example, in some
   implementations it may be possible to use the MIB-II IfIndex
   [RFC2863].

   Sub-TLVs: Existing sub-TLV that defined within "OSPFv3 Extended-LSA
   Sub-TLV" can be included if necessary.  The definition of new sub-TLV
   can refer to Section 4.4.

4.3.  ISIS Stub-link TLV

   This document defines one new top TLV to contain the stub link
   attributes, which is shown in Figure 4:





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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(Stub-Link)          |             Length              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Link Type |    Reserved   |              Metric             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      Interface ID                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                   Sub-TLVs(Variable)                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                 Figure 3: ISIS Stub-Link TLV

   Type: ISIS TLV Codepoint.  Value is 28(TBD) for stub-link TLV.

   Length: Variable, dependent on sub-TLVs

   Link Type: Define the type of the stub-link.  This document defines
   the followings type:

   *  0: Reserved

   *  1: AS boundary link

   *  2: Loopback link

   *  3: Vlan interface link

   *  4-255: For future extension

   Metric: Link metric used for inter-AS traffic engineering.

   Interface ID: 32-bit number uniquely identifying this interface among
   the collection of this router's interfaces.  For example, in some
   implementations it may be possible to use the MIB-II IfIndex
   [RFC2863].

   Sub-TLVs: Existing sub-TLV that defined within "Sub-TLVs for TLVs 22,
   23, 25, 141, 222, and 223" can be included if necessary.  The
   definition of new sub-TLV can refer to Section 4.4.

4.4.  Stub-Link Prefix Sub-TLV

   This document defines one new sub-TLV that can be contained within
   the OSPFv2 Extended Stub-Link TLV , OSPFv3 Router-Stub-Link TLV or
   ISIS Stub-Link TLV, to describe the prefix information associated
   with the stub link.




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   The format of the sub-TLV is the followings:

     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 or IPv6 Prefix Subobject           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                Figure 4: Stub-Link Prefix Sub-TLV

   Type: The TLV type.  The value is 01(TBD) for this Stub-Link Prefix
   type

   Length: Variable, dependent on associated subobjects

   Subobject: IPv4 prefix subobject or IPv6 prefix subobject, as that
   defined in [RFC3209]

   If the stub link has multiple address, then multiple subobjects will
   be included within this sub-TLV.

5.  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.

6.  IANA Considerations

   IANA is requested to the allocation in following registries:

    +=========================+===========+======================+
    | Registry                | Type      | Meaning              |
    +=========================+===========+======================+
    |OSPFv2 Extended Link     | 2         |Stub-Link TLV         |
    |Opaque LSA TLV           |           |                      |
    +-------------------------+-----------+----------------------+
    |OSPFv3 Extended-LSA TLV  | 10        |Router-Stub-Link TLV  |
    +-------------------------+-----------+----------------------+
    |IS-IS TLV Codepoint      | 28        |Stub-Link TLV         |
    +-------------------------+-----------+----------------------+
        Figure 5: Newly defined TLV in existing IETF registry





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   IANA is requested to allocate one new registry that can be referred
   by OSPFv2, OSPFv3 and ISIS respectively.

   +=========================+==================================+
   |   New Registry          |            Meaning               |
   +=========================+==================================+
   |Stub-Link Attribute      | Attributes for stub-link         |
   +-------------------------+----------------------------------+
      Figure 6: Newly defined Registry for stub-link attributes

   One new sub-TLV is defined in this document under this registry
   codepoint:

 +=========================+===========+===============================+
 | Registry                | Type      | Meaning                       |
 +=========================+===========+===============================+
 |Stub-Link Attribute      | 0         | Reserved
 +=========================+===========+===============================+
 |                         | 1         |Stub-Link Prefix sub-TLV       |
 +-------------------------+-----------+-------------------------------+
 |                         | 2-65535   |Reserved                       |
 +-------------------------+-----------+-------------------------------+
     Figure 7: Stub-Link Prefix Sub-TLV

7.  Acknowledgement

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

8.  References

8.1.  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>.

   [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328,
              DOI 10.17487/RFC2328, April 1998,
              <https://www.rfc-editor.org/info/rfc2328>.

   [RFC2863]  McCloghrie, K. and F. Kastenholz, "The Interfaces Group
              MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000,
              <https://www.rfc-editor.org/info/rfc2863>.





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   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
              <https://www.rfc-editor.org/info/rfc3209>.

   [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>.

   [RFC5029]  Vasseur, JP. and S. Previdi, "Definition of an IS-IS Link
              Attribute Sub-TLV", RFC 5029, DOI 10.17487/RFC5029,
              September 2007, <https://www.rfc-editor.org/info/rfc5029>.

   [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>.

   [RFC5340]  Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
              for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
              <https://www.rfc-editor.org/info/rfc5340>.

   [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>.

   [RFC7794]  Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and
              U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4
              and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794,
              March 2016, <https://www.rfc-editor.org/info/rfc7794>.

   [RFC8362]  Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and
              F. Baker, "OSPFv3 Link State Advertisement (LSA)
              Extensibility", RFC 8362, DOI 10.17487/RFC8362, April
              2018, <https://www.rfc-editor.org/info/rfc8362>.

8.2.  Informative References









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   [I-D.dunbar-lsr-5g-edge-compute-ospf-ext]
              Dunbar, L., Chen, H., and A. Wang, "OSPF extension for 5G
              Edge Computing Service", Work in Progress, Internet-Draft,
              draft-dunbar-lsr-5g-edge-compute-ospf-ext-04, 10 March
              2021, <https://www.ietf.org/archive/id/draft-dunbar-lsr-
              5g-edge-compute-ospf-ext-04.txt>.

   [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", Work in
              Progress, Internet-Draft, draft-ietf-idr-bgpls-inter-as-
              topology-ext-09, 28 September 2020,
              <https://www.ietf.org/archive/id/draft-ietf-idr-bgpls-
              inter-as-topology-ext-09.txt>.

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


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

   Email: gyan.s.mishra@verizon.com







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

   Email: sun.jinsong@zte.com.cn











































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