Internet DRAFT - draft-wang-lsr-passive-interface-attribute

draft-wang-lsr-passive-interface-attribute







LSR Working Group                                                A. Wang
Internet-Draft                                             China Telecom
Intended status: Standards Track                                   Z. Hu
Expires: July 13, 2020                               Huawei Technologies
                                                        January 10, 2020


                      Passive Interface Attribute
             draft-wang-lsr-passive-interface-attribute-00

Abstract

   This document describes the mechanism that can be used to
   differentiate the passive interfaces from the normal interfaces
   within ISIS domain.

Status of This Memo

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   2
   3.  Scenario Description  . . . . . . . . . . . . . . . . . . . .   3
   4.  Passive Interface Attribute . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   7.  Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .   4
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   Passive interfaces are used commonly within operator or enterprise
   networks, especially at the boundary of different IGP domains.  Using
   passive interface can keep the address that associated with it is
   reachable within the domain it belongs to but no other link
   information is leaked to the other side in another domain.

   For operator which runs different IGP domains that interconnect with
   each other, there is desire that to get the inter-as topology
   information as that described in
   [I-D.ietf-idr-bgpls-inter-as-topology-ext].  If the router that run
   BGP-LS within one IGP domain can distinguish the passive
   interfaces(also the links between two boundary) from the other normal
   interfaces, then it is easy for them to report these link in the
   "Stub Link NLRI" via the BGP-LS.

   OSPF has the mechanism as described in [RFC2328] to label the passive
   interface, but ISIS protocol has no such attribute to label the
   passive interface.

   This document introduces the mechanism that can be used in such
   situation, to label the passive interface via the newly defined
   passive interface attribute.

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] .







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3.  Scenario Description

   Figure1 illustrates the topology scenario when ISIS/OSPF is running
   in different domain.  B1, B3 are border routers within IGP domain A,
   B2, B4 are border routers within domain B.  S1-S4 are the internal
   routers within domain A, T1-T4 are the internal routers within domain
   B.  The two domain are interconnected via the links between B1/B2 and
   B3/B4.

   Passive interfaces are enabled in the links between B1/B2 and B3/B4
   respectively.  For domain B, the T1 router that runs OSPF can extract
   the passives links from the normal links and report it to IP SDN
   controller via the BGP-LS protocol.  But for domain A, the S2 router
   that runs ISIS can only judge the passive interfaces from other
   characteristics, such as no IGP neighbor on this link.  Such
   judgement can extract these passive links but it is not exactly,
   because it covers also the situation when there is some issues to
   establish the ISIS adjacency but not the passive interface.

   The passive interfaces are also often used in the edge router which
   connects the server, for example in the router S1/S4 and T2/T4 in
   Figure 1.  Knowing these interfaces are correctly configured will
   also benefit the management of these interfaces.

   The method to label these passive interface explicitly is necessary
   then.

                             +-----------------+
                        +----+IP SDN Controller+----+
                        |    +-----------------+    |
                        |                           |
                        |BGP-LS                     |BGP-LS
                        |                           |
        +---------------+-----+               +-----+--------------+
        | +--+        +-++   ++-+           +-++   +|-+        +--+|
        | |S1+--------+S2+---+B1+-----------+B2+---+T1+--------+T2||
        | +-++   N1   +-++   ++-+           +-++   ++++   N2   +-++|
        |   |           |     |               |     ||           | |
        |   |           |     |               |     ||           | |
        | +-++        +-++   ++-+           +-++   ++++        +-++|
        | |S4+--------+S3+---+B3+-----------+B4+---+T3+--------+T4||
        | +--+        +--+   ++-+           +-++   ++-+        +--+|
        |                     |               |                    |
        |                     |               |                    |
        |  Domain A(ISIS)     |               |  Domain B(OSPF)    |
        +---------------------+               +--------------------+

                    Figure 1: Inter-AS Domain Scenarios



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4.  Passive Interface Attribute

   [RFC7794] defines the "IPv4/IPv6 Extended Reachability Attribute
   Flags" sub-TLV to advertise the additional flags associated with a
   given prefix advertisement.  Currently, only X(Bit 0),R(Bit 1),N(Bit
   2), E(Bit 3) flags are defined, here we propose another bit(Bit 4 is
   desired) to be assigned by the IANA for the passive interface
   attribute, as illustrated in the following Figure2:

          0 1 2 3 4 5 6 7...
         +-+-+-+-+-+-+-+-+...
         |X|R|N|E|P       ...
         +-+-+-+-+-+-+-+-+...
               Figure 2: Prefix Attribute Flags
P-flag: Passive Flag(Bit 4)
        Set for local interface that is configured as passive interface.

   When the interfaces on one router be configured as the passive
   interface, the P-flag bit will be set in the "IPv4/IPv6 Extended
   Reachability Attribute Flags" sub-TLV.  This sub-TLV will be included
   in the TLV 135, TLV 235, TLV 236 and TLV 237 as necessary and be
   flooded within the ISIS domain.

   The router receives such advertisement can then easily distinguish
   the passive interfaces from the normal interface, and report them to
   the SDN controller if it run the BGP-LS protocol.

5.  Security Considerations

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

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

6.  IANA Considerations

   IANA is requested to allocate the P-bit (bit position 4 is desired)
   from the "Bit Values for Prefix Attribute Flags Sub-TLV" registry.

7.  Acknowledgement

   Thanks Shunwan Zhang, Les Ginsberg and Robert Raszuk for their
   suggestions and comments on this idea.








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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>.

   [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>.

   [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>.

8.2.  Informative References

   [I-D.ietf-idr-bgpls-inter-as-topology-ext]
              Wang, A., Chen, H., Talaulikar, K., Zhuang, S., and S. Ma,
              "BGP-LS Extension for Inter-AS Topology Retrieval", draft-
              ietf-idr-bgpls-inter-as-topology-ext-07 (work in
              progress), September 2019.

Authors' Addresses

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

   Email: wangaj3@chinatelecom.cn







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

   Email: huzhibo@huawei.com












































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