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Versions: (draft-ginsberg-isis-prefix-attributes) 00 01 02 03 04 RFC 7794

Networking Working Group                                     L. Ginsberg
Internet-Draft                                             Cisco Systems
Intended status: Standards Track                             B. Decraene
Expires: December 22, 2015                                        Orange
                                                             C. Filsfils
                                                           Cisco Systems
                                                            S. Litkowski
                                                 Orange Business Service
                                                              S. Previdi
                                                           Cisco Systems
                                                                   X. Xu
                                                                  Huawei
                                                             U. Chunduri
                                                                Ericsson
                                                           June 20, 2015


     IS-IS Prefix Attributes for Extended IP and IPv6 Reachability
                draft-ietf-isis-prefix-attributes-01.txt

Abstract

   This document introduces new sub-TLVs to support advertisement of
   prefix attribute flags and the source router ID of the router which
   originated a prefix advertisement.

Requirements Language

   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 RFC 2119 [RFC2119].

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 http://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 December 22, 2015.



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Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   than English.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  New sub-TLVs for Extended Reachability TLVs . . . . . . . . .   3
     2.1.  IPv4/IPv6 Extended Reachability Attribute Flags . . . . .   3
     2.2.  IPv4/IPv6 Source Router ID  . . . . . . . . . . . . . . .   5
     2.3.  Advertising Router IDs  . . . . . . . . . . . . . . . . .   5
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     6.2.  Informational References  . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   There are existing use cases in which knowing additional attributes
   of a prefix is useful.  For example, it is useful to know whether an
   advertised prefix is directly connected to the advertising router or
   not.  In the case of [SR] knowing whether a prefix is directly



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   connected or not determines what action should be taken as regards
   processing of labels associated with an incoming packet.  Current
   formats of the Extended Reachability TLVs for both IP and IPv6 are
   fixed and do not allow the introduction of additional flags without
   backwards compatibility issues.  Therefore a new sub-TLV is
   introduced which allows for the advertisement of attribute flags
   associated with prefix advertisements.

   It is also useful to know the source of a prefix advertisement when
   the advertisement has been leaked to another level.  Therefore a new
   sub-TLV is introduced to advertise the router-id of the originator of
   a prefix advertisement.

2.  New sub-TLVs for Extended Reachability TLVs

   The following new sub-TLVs are introduced:

   o  IPv4/IPv6 Extended Reachability Attributes

   o  IPv4 Source Router ID

   o  IPv6 Source Router ID

   All sub-TLVs are applicable to TLVs 135, 235, 236, and/or 237.

2.1.  IPv4/IPv6 Extended Reachability Attribute Flags

   This sub-TLV supports the advertisement of additional flags
   associated with a given prefix advertisement.  The behavior of each
   flag when a prefix advertisement is leaked from one level to another
   (upwards or downwards) is explicitly defined below.

   All flags are applicable to TLVs 135, 235, 236, 237 unless otherwise
   stated.

















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   Prefix Attribute Flags
   Type:   4 (suggested - to be assigned by IANA)
   Length: Number of octets to follow
   Value

        (Length * 8) bits.

     0 1 2 3 4 5 6 7...
    +-+-+-+-+-+-+-+-+...
    |X|R|N|          ...
    +-+-+-+-+-+-+-+-+...

   Bits are defined/sent starting with Bit #0 defined below. Additional
   bit definitions which may be defined in the future SHOULD be assigned
   in ascending bit order so as to minimize the number of bits which
   will need to be transmitted.

   Undefined bits SHOULD be transmitted as 0 and MUST be
   ignored on receipt.

   Bits which are NOT transmitted MUST be treated as if they are
   set to 0 on receipt.

   X-Flag: External Prefix Flag (Bit 0)
       Set if the prefix has been redistributed from another protocol.
       This includes the case where multiple virtual routers are
       supported and the source of the redistributed prefix is another
       IS-IS instance.
       The flag MUST be preserved when leaked between levels.
       In TLVs 236 and 237 this flag SHOULD always be sent as 0 and
       MUST be ignored on receipt. This is because there is an existing
       X flag defined in the fixed format of these TLVs as specified in
       [RFC5308] and [RFC5120].

   R-Flag: Re-advertisement Flag (Bit 1)
       Set when the prefix has been leaked from one level to another
       (upwards or downwards).

   N-flag: Node Flag (Bit 2)
       Set when the prefix identifies the advertising router i.e., the
       prefix is a host prefix advertising a globally reachable address
       typically associated with a loopback address.
       The advertising router MAY choose to NOT set this flag even when
       the above conditions are met.
       If the flag is set and the prefix length is NOT a host prefix
       (/32 for IPV4, /128 for IPv6) then the flag MUST be ignored.
       The flag MUST be preserved when leaked between levels.




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2.2.  IPv4/IPv6 Source Router ID

   When a reachability advertisement is leaked from one level to
   another, the source of the original advertisement is unknown.  In
   cases where the advertisement is an identifier for the advertising
   router (e.g., N-flag set in the Extended Reachability Attribute sub-
   TLV as described in the previous section) it may be useful for other
   routers to know the source of the advertisement.  The sub-TLVs
   defined below provide this information.

     IPv4 Source Router ID
     Type:   11 (suggested - to be assigned by IANA)
     Length: 4
     Value: IPv4 Router ID of the source of the advertisement

     Inclusion of this TLV is optional and MAY occur in TLVs
     135, 235, 236, or 237. When included the value MUST be
     identical to the value advertised in Traffic Engineering
     router ID (TLV 134) defined in [RFC5305].

     If present the sub-TLV MUST be included when the prefix
     advertisement is leaked to another level.

     IPv6 Source Router ID
     Type:   12 (suggested - to be assigned by IANA)
     Length: 16
     Value: IPv6 Router ID of the source of the advertisement

     Inclusion of this TLV is optional and MAY occur in TLVs
     135, 235, 236, or 237. When included the value MUST be
     identical to the value advertised in IPv6 TE Router ID
     (TLV 140) defined in [RFC6119].

     If present the sub-TLV MUST be included when the prefix
     advertisement is leaked to another level.


2.3.  Advertising Router IDs

   [RFC5305] and [RFC6119] define the advertisement of router IDs for
   IPv4 and IPv6 respectively.  Although both drafts discuss the use of
   router ID in the context of Traffic Engineering (TE), the
   advertisement of router IDs is explicitly allowed for purposes other
   than TE.  The use of router IDs to identify the source of a prefix
   advertisement as defined in the previous section is one such use
   case.  Therefore, whenever the source router ID sub-TLVs defined in
   the previous section are used, the originating router SHOULD also
   advertise the corresponding address-family specific router ID TLV(s).



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3.  IANA Considerations

   This document adds the following new sub-TLVs to the registry of sub-
   TLVs for TLVs 135, 235, 236, 237.

   Value: 4 (suggested - to be assigned by IANA)

   Name: Prefix Attribute Flags

   Value: 11 (suggested - to be assigned by IANA)

   Name: IPv4 Source Router ID

   Value: 12 (suggested - to be assigned by IANA)

   Name: IPv6 Source Router ID

   This document also introduces a new registry for bit values in the
   Prefix Attribute Flags sub-TLV.  Registration policy is Expert Review
   as defined in [RFC5226].  Defined values are:

        Bit #   Name
        -----   ------------------------
        0       External Prefix Flag
        1       Re-advertisement Flag
        2       Node Flag


4.  Security Considerations

   None.

5.  Acknowledgements

   TBD

6.  References

6.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC5120]  Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
              Topology (MT) Routing in Intermediate System to
              Intermediate Systems (IS-ISs)", RFC 5120, February 2008.





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   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, October 2008.

   [RFC5308]  Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, October
              2008.

   [RFC6119]  Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic
              Engineering in IS-IS", RFC 6119, February 2011.

6.2.  Informational References

   [SR]       "IS-IS Extensions for Segment Routing, draft-ietf-isis-
              segment-routing-extensions-04(work in progress)", May
              2015.

Authors' Addresses

   Les Ginsberg
   Cisco Systems
   510 McCarthy Blvd.
   Milpitas, CA  95035
   USA

   Email: ginsberg@cisco.com


   Bruno Decraene
   Orange
   38 rue du General Leclerc
   MIssy Moulineaux cedex 9  92794
   France

   Email: bruno.decraene@orange.com


   Clarence Filsfils
   Cisco Systems

   Email: cf@cisco.com








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   Stephane Litkowski
   Orange Business Service

   Email: stephane.litkowski@orange.com


   Stefano Previdi
   Cisco Systems
   Via Del Serafico 200
   Rome  0144
   Italy

   Email: sprevidi@cisco.com


   Xiaohu Xu
   Huawei

   Email: xuxiaohu@huawei.com


   Uma Chunduri
   Ericsson

   Email: uma.chunduri@ericsson.com


























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