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SPRING Working Group                                           A. Alston
Internet-Draft                                              D. Henriques
Intended status: Standards Track                          Liquid Telecom
Expires: January 9, 2020                                       R. Bonica
                                                        Juniper Networks
                                                            July 8, 2019


        BGP Extensions for IPv6 Compressed Routing Header (CRH)
               draft-alston-spring-crh-bgp-signalling-00

Abstract

   This document describes a new BGP extension for signalling the
   mapping between Segment Identifiers (SID's), as used by a SRv6+
   Compressed Routing Header (CRH) and the IPv6 Addresses they
   represent.  The extension defines both a new optional BGP attribute
   to signal the Maximum SID Value (MSV) and a new Sub-Address Family
   (SAFI) of the IPv6 Address family.

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 January 9, 2020.

Copyright Notice

   Copyright (c) 2019 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
   to this document.  Code Components extracted from this document must



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   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.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
   3.  SID Signalling  . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  BGP Attribute . . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  MP Reach Attribute  . . . . . . . . . . . . . . . . . . .   3
     3.3.  NLRI Format . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  BGP Path Attributes . . . . . . . . . . . . . . . . . . .   5
     4.2.  Subsequent Address Family Identifiers (SAFI) Parameters .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Overview

   The SRv6+ Compressed Routing Header uses an ordered sequence of
   segment identifiers (SID) to specify the end to end path a packet
   should follow through the network.  This allows for much smaller
   header sizes than found in the SRH (Segment Routing Header), which
   utilizes an ordered sequence of 128 bit IPv6 address to achieve the
   same goal.  In addition, this method prevents the overloading of the
   IPv6 address space.

   This results in the need to signal the mapping between the SIDs used
   in the CRH and the IPv6 addresses they represent.  While such
   signalling can be achieved through IGP extensions
   [I-D.bonica-lsr-crh-isis-extensions] in a single network domain,
   circumstances may dictate that the SID to address mapping be signaled
   both to systems that do not partake in the IGP used within that
   network domain, and between autonomous systems.

   It is envisaged that such signalling will be required to signal,
   among other things, deep packet inspection systems and flow analysis
   systems that need the ability to see the full path a packet is
   traversing, while at the same time not necessarily partaking in the
   IGP which would normally be used for such signalling.  This also
   allows signalling of SID to Address mapping in environments that do
   not run an IGP capable of such signalling.




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2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  SID Signalling

3.1.  BGP Attribute

   This document describes a new BGP extension for signalling the
   mapping between Segment Identifiers (SIDs) as used by an SRv6+
   Compressed Routing Header (CRH) and the IPv6 Addresses they
   represent.

   The extension defines both a new optional transitive attribute to
   signal the SID size in Octets and a new Subsequent Address Family
   Identifier (SAFI) of the IPv6 Address family.

   The document defines a new BGP attribute which signals the maximum
   size in octets of a CRH Segment Identifier (SID).  The attribute MUST
   be included in any BGP session carrying the CRH signalling SAFI.
   Additionally a new attribute BGP Path Attribute code will need to be
   assigned by IANA.

   The attribute is comprised of a single octet, which signals the
   maximum length in octets of the SIDs found in the Network Layer
   Reachability Information (NLRI) section of the relevant MP-BGP
   Attribute.

   Since SIDs in the context of a compressed routing header can be
   either 16bit of 32bit, the attribute value MUST be either 2 or 4 and
   the attribute MUST be ignored if this is not the case.  In the event
   of the CRH signalling attribute not being present in a BGP Update
   Message, any BGP Updates containing the CRH SAFI MUST be considered
   malformed and should be ignored.

3.2.  MP Reach Attribute

   The format of the MP Reach Attribute utilized by the CRH SAFI is as
   per [RFC4760].  The AFI MUST be set to 2, and the SAFI is currently
   TBD (see Section 4.2).

   The Nexthop field of the attribute contains no significance and is
   maintained purely for compatibility.  For standardization purposes we
   maintain a next-hop length field of 16 which contains an arbitrary



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   value.  Implementations MAY at their discretion use the originating
   router ID, or 128 bit mapped equivalent, in this field for simple
   identification of mapping source

3.3.  NLRI Format

   The format of the NLRI contained within the MP Reach Attribute is
   comprised of a 16bit Length (2 octets) field, followed by a series of
   repeating tuples.  The length in octets of the first element of each
   tuple is determined by the SID Length specified in the CRH signalling
   attribute (Section 3.1).  The second element of the tuple is an IPv6
   address and MUST be 16 octets in length.  The length of the NLRI can
   be calculated as (SID Length+16)*N where N is the number of tuples
   contained within the NLRI.


                              0 1 2 3 4 5 6 7
                             +-+-+-+-+-+-+-+-+
                             |  NLRI Length  |
                             |   2 octets    |
                             +-+-+-+-+-+-+-+-+
                             |               |
                             |     SID 1     |
                             |  (M octets)   |
                             |               |
                             +-+-+-+-+-+-+-+-+
                             |               |
                             | IPv6 Address 1|
                             |  (16 octets)  |
                             |               |
                             +-+-+-+-+-+-+-+-+
                             |               |
                             |     SID N     |
                             |   (N octets)  |
                             |               |
                             +-+-+-+-+-+-+-+-+
                             |               |
                             | IPv6 Address N|
                             |  (16 octets)  |
                             |               |
                             +-+-+-+-+-+-+-+-+


   The CRH SAFI uses a new NLRI defined as follows: where M MUST be the
   size in octets of the MSV signalled via BGP upon session
   establishment and N specifies a given number of SID/IPv6 Address
   pairings.




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4.  IANA Considerations

   This document defines new Sub-TLVs in the following existing
   registries:

   o  BGP Path Attributes

   o  Subsequent Address Family Identifiers (SAFI) Parameters

4.1.  BGP Path Attributes

   A new SAFI in the IANA registry for "Subsequent Address Family
   Identifiers (SAFI) Parameters" will be required:

              Codepoint    Description          Reference
              -----------------------------------------------
                 TBD        SRv6+ CRH       This document

4.2.  Subsequent Address Family Identifiers (SAFI) Parameters

   A new SAFI in the IANA registry for "Subsequent Address Family
   Identifiers (SAFI) Parameters" will be required:

        Codepoint    Description          Reference
        -----------------------------------------------
           TBD        SRv6+ CRH Signalling SAFI       This document

5.  Security Considerations

   SRv6+ CRH BGP Signalling is envisioned to be run within a trusted
   domain.

   Further aspects of security are TBD.

6.  Acknowledgements

   The authors wish to acknowledge Ben Roberts for his support.

7.  References

7.1.  Normative References

   [I-D.bonica-6man-comp-rtg-hdr]
              Bonica, R., Kamite, Y., Niwa, T., Alston, A., Henriques,
              D., So, N., Xu, F., Chen, G., Zhu, Y., Yang, G., and Y.
              Zhou, "The IPv6 Compressed Routing Header (CRH)", draft-
              bonica-6man-comp-rtg-hdr-04 (work in progress), May 2019.




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   [I-D.bonica-lsr-crh-isis-extensions]
              Kaneriya, P., Shetty, R., Hegde, S., and R. Bonica, "IS-IS
              Extensions To Support The IPv6 Compressed Routing Header
              (CRH)", draft-bonica-lsr-crh-isis-extensions-00 (work in
              progress), May 2019.

   [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>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <https://www.rfc-editor.org/info/rfc4271>.

   [RFC4760]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
              "Multiprotocol Extensions for BGP-4", RFC 4760,
              DOI 10.17487/RFC4760, January 2007,
              <https://www.rfc-editor.org/info/rfc4760>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", STD 86, RFC 8200,
              DOI 10.17487/RFC8200, July 2017,
              <https://www.rfc-editor.org/info/rfc8200>.

7.2.  Informative References

   [I-D.ietf-6man-segment-routing-header]
              Filsfils, C., Dukes, D., Previdi, S., Leddy, J.,
              Matsushima, S., and d. daniel.voyer@bell.ca, "IPv6 Segment
              Routing Header (SRH)", draft-ietf-6man-segment-routing-
              header-21 (work in progress), June 2019.

   [I-D.ietf-spring-segment-routing-mpls]
              Bashandy, A., Filsfils, C., Previdi, S., Decraene, B.,
              Litkowski, S., and R. Shakir, "Segment Routing with MPLS
              data plane", draft-ietf-spring-segment-routing-mpls-22
              (work in progress), May 2019.








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   [I-D.ietf-spring-srv6-network-programming]
              Filsfils, C., Camarillo, P., Leddy, J.,
              daniel.voyer@bell.ca, d., Matsushima, S., and Z. Li, "SRv6
              Network Programming", draft-ietf-spring-srv6-network-
              programming-00 (work in progress), April 2019.

   [RFC3031]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
              Label Switching Architecture", RFC 3031,
              DOI 10.17487/RFC3031, January 2001,
              <https://www.rfc-editor.org/info/rfc3031>.

Authors' Addresses

   Andrew Alston
   Liquid Telecom
   Nairobi
   Kenya

   Email: Andrew.Alston@liquidtelecom.com


   Daniam Henriques
   Liquid Telecom
   Johannesburg
   South Africa

   Email: daniam.henriques@liquidtelecom.com


   Ron Bonica
   Juniper Networks
   Herndon, Virginia  20171
   USA

   Email: rbonica@juniper.net
















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