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Versions: 00 01                                                         
Network Working Group                                         P. Pfister
Internet-Draft                                              IJ. Wijnands
Intended status: Standards Track                           Cisco Systems
Expires: March 6, 2017                                 September 2, 2016


                  An IPv6 based BIER Routing Underlay
                    draft-pfister-bier-over-ipv6-00

Abstract

   This document specifies a routing underlay which enables transport of
   IPv6 payloads to multiple IPv6 destinations using the Bit Index
   Explicit Replication (BIER).  The BIER bits are stored within the
   low-order bits of the IPv6 destination address while the high-order
   bits are left untouched and used in order to decide whether an IPv6
   packet is a regular IPv6 packet or an IPv6 BIER packet, and if so, to
   identify the BIER set identifier.

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
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   This Internet-Draft will expire on March 6, 2017.

Copyright Notice

   Copyright (c) 2016 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
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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  IPv6 BIER Packet Format . . . . . . . . . . . . . . . . . . .   3
   4.  BIER Layer Operations . . . . . . . . . . . . . . . . . . . .   3
   5.  Routing Underlay Operations . . . . . . . . . . . . . . . . .   4
   6.  Advantages of this Technique  . . . . . . . . . . . . . . . .   4
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   The Bit Index Explicit Replication (BIER -
   [I-D.ietf-bier-architecture]) forwarding technique enables IP
   multicast transport across a BIER domain.  It operates using three
   different elements, a multicast flow overlay, a BIER Layer, and a
   routing underlay.  This document specifies a way to send IPv6
   payloads to multiple destinations using regular IPv6 packets with no
   additional extension header.

   BIER bits are encoded in the low-order bits of the IPv6 destination
   address of each packet.  The high-order bits of the IPv6 destination
   address are left untouched and used by intermediate BIER routers to
   decide whether the packet should be forwarded as a regular IPv6
   packet or an IPv6 BIER packet, and if so, to know the BIER Set
   Identifier.

   Transported payloads can be of many types such as IPv6 or IPv4
   unicast or multicast packets (e.g. using generic packet tunneling
   [RFC2473]), or transported data (e.g. using UDP).  Special care must
   be taken when forwarding some types of payloads.  For example, the
   UDP checksum must be recomputed when the BIER bits are changed.

2.  Terminology

   In this document, the key words "MAY", "MUST", "MUST NOT",
   "RECOMMENDED", and "SHOULD", are to be interpreted as described in
   [RFC2119].




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3.  IPv6 BIER Packet Format

   BIER IPv6 packets are IPv6 unicast packets.  There is no
   specificities to the format of the packet.  The BIER bits are encoded
   in the low-order bits of the IPv6 destination address of the packet
   while the high-order bits are used by intermediate routers to
   identify that the forwarded packet is an IPv6 BIER packet, and which
   BIER Set Identifier to use.

   |     p bits         |  i bits   |          128-p-i bits           |
   +--------------------+-----------+---------------------------------+
   |  BIER IPv6 Prefix  |  SI bits  |         BitString bits          |
   +--------------------+-----------+---------------------------------+

              Figure 1: IPv6 BIER destination address format

   BIER IPv6 Prefix:  This is a prefix used for BIER forwarding within
         the domain.  BIER routers will consider all packets sent to
         this prefix as IPv6 BIER packets.

   SI bits:  These bits are used to encode the Set Identifier.  It is
         used in order to address more BFERs than there are bits in the
         last part of the IPv6 address.

   BitString bits:  Set of bits encoding the set of BFERs the packet
         should be sent to.  Those bits are modified as the packet is
         replicated by intermediate BIER routers.  The length of this
         field is equal to 128-p-i and specifies the value of the
         BitStringLength to be used in the BIER forwarding process.

   For example, a BIER domain assigns the prefix 2001:db8::/56 as a BIER
   IPv6 Prefix, and sets i to 8.  Every BIER router within the domain is
   configured with such values and is therefore able to identify all
   BIER packets and treat them accordingly.  As the SI bits length is 8,
   the lowest-weight 64 bits are used as a BIER bit field.  A single
   packet can be sent to at most 64 different BFERs, while the entire
   domain can include up to 64 * 2^8 = 16384 BFERs.

4.  BIER Layer Operations

   When a multicast packet enters the BIER domain, the BFIR first
   consults the multicast flow overlay and obtains the set of BFERs the
   packet must be sent to.  This set is used in order to compute the set
   of bit indexes representing the set of destination BFERs.  All
   indexes that have the same SI are grouped in order to create a set of
   BitString associated with their respective SI.  For each SI, the
   multicast packet is encapsulated within an IPv6 BIER packet, as
   specified in Section 3.



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   The same process is used when a given IPv6 payload should be sent to
   a set of destinations.  But instead of encapsulating the packet, the
   payload is attached to the BIER IPv6 header and the IPv6 protocol
   number is set to the type of the payload.

5.  Routing Underlay Operations

   A BIER router is configured with at least one, and possibly more,
   rules.  Each rule includes a BIER IPv6 Prefix (value and prefix
   length), the value of 'i', and the set of mappings used by BIER in
   order to associate BIER bits with IPv6 destinations.

   For each packet forwarded by a BFR, the router first performs a
   longest prefix match operation over the destination address.  If the
   found entry corresponds to a BIER rule, the packet is treated as a
   BIER packet.  Otherwise, it is treated as a regular IPv6 packet.

   When an IPv6 BIER packet is forwarded, the BFR retrieves the SI value
   and BitString and performs the BIER forwarding algorithm.  For each
   replicated packet, the BitString is possibly modified and the packet
   is sent on the outgoing interface.

6.  Advantages of this Technique

   The technique described in this document offers different advantages:

      BIER IPv6 packets are regular IPv6 packets.  If the BIER IPv6
      Prefix is a globally unique IPv6 prefix, reachable from outside
      the BIER domain, it is possible to send a packet from outside the
      BIER domain to multiple destination within the BIER domain.

      It may be used for transporting IP multicast packets, but also for
      sending IP payloads directly to multiple destinations.

      It does not rely on a new IPv6 extension header, which simplifies
      deployment and is likely to improve performances.

      It makes use of a typical IP longest match in order to decide
      whether a packet is a BIER packet or not, which means hardware and
      software existing solutions may be used for that purpose.

      It is possible to configure a host with an address which
      corresponds to a BIER address with a single bit set.  From the
      host perspective, such address is not different from a regular
      IPv6 address.  Which means a BIER-unaware host may receive BIER
      packets transparently (With possible additional duplication by the
      last BFR when multiple hosts are located on the same link).




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7.  Security Considerations

   This technique allows IPv6 BIER packets to be sent across the
   internet toward multiple destination located in a given BIER domain.
   If this is considered a threat, a firewall at the entrance of the
   BIER domain in order to avoid BIER packets from being injected and
   replicated within the network.

8.  IANA Considerations

   This specification does not require any action from IANA.

9.  References

9.1.  Normative References

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

   [RFC2473]  Conta, A. and S. Deering, "Generic Packet Tunneling in
              IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473,
              December 1998, <http://www.rfc-editor.org/info/rfc2473>.

9.2.  Informative References

   [I-D.ietf-bier-architecture]
              Wijnands, I., Rosen, E., Dolganow, A., Przygienda, T., and
              S. Aldrin, "Multicast using Bit Index Explicit
              Replication", draft-ietf-bier-architecture-01 (work in
              progress), June 2015.

Appendix A.  Acknowledgements

   Comments concerning this document are very welcome.

Authors' Addresses

   Pierre Pfister
   Cisco Systems
   Paris
   France

   Email: pierre.pfister@darou.fr








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   IJsbrand Wijnands
   Cisco Systems
   De Kleetlaan 6a
   Diegem  1831
   Belgium

   Email: ice@cisco.com












































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