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Network Working Group                                         X. Xu, Ed.
Internet-Draft                                                    Huawei
Intended status: Standards Track                         S. Somasundaram
Expires: March 27, 2017                                   Alcatel-Lucent
                                                       C. Jacquenet, Ed.
                                                          France Telecom
                                                               R. Raszuk
                                                            Bloomberg LP
                                                           Z. Zhang, Ed.
                                                                 Juniper
                                                      September 23, 2016


     A Transport-Independent Bit Index Explicit Replication (BIER)
                          Encapsulation Header
                     draft-xu-bier-encapsulation-06

Abstract

   Bit Index Explicit Replication (BIER) is a new multicast forwarding
   paradigm which doesn't require an explicit tree-building protocol nor
   intermediate routers to maintain any multicast state.  This document
   proposes a transport-independent BIER encapsulation header which is
   applicable regardless of the underlying transport technology.

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 http://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 March 27, 2017.

Copyright Notice

   Copyright (c) 2016 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
   (http://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
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  BIER Header . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  BIER Header Transport . . . . . . . . . . . . . . . . . . . .   5
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Bit Index Explicit Replication (BIER) [I-D.ietf-bier-architecture] is
   a new multicast forwarding paradigm which doesn't require an explicit
   tree-building protocol nor intermediate routers to maintain any
   multicast state.  As described in [I-D.ietf-bier-architecture], BIER
   adds a header to a multicast data packet (e.g., an IP packet or an
   MPLS packet).  The BIER header carries the information needed for
   supporting the BIER forwarding procedures.  This document proposes a
   transport-independent BIER encapsulation header which is applicable
   regardless of the underlying transport technology.

1.1.  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].

2.  Terminology

   This memo makes use of the terms defined in
   [I-D.ietf-bier-architecture].




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3.  BIER Header

   The BIER header is shown in Figure 1.

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Ver  |  BSL  | Resv  |                Entropy                |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |           BFIR-ID             |       DS      |    Protocol   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |         SI        |     Sub-domain    |O| Resv|      TTL      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                BitString  (first 32 bits)                     ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ~                                                               ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ~                BitString  (last 32 bits)                      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                     Figure 1: BIER Header Format.



      Ver(sion): a 4-bit field identifying the version of the BIER
      header.  This document specifies version 0 of the BIER header.

      BSL: Bit String Length.  If k is the length of the BitString, the
      value of this field is log2(k)-5.  However, only the following
      values are supported [I-D.ietf-bier-mpls-encapsulation] :



      *  64 bits

      *  128 bits

      *  256 bits

      *  512 bits

      *  1024 bits

      *  2048 bits

      *  4096 bits






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      The value of the BSL field MUST NOT be set to any value other than
      those listed above.  A received packet containing another value in
      this field SHOULD be discarded, and an error logged.

      Entropy: a 20-bit field containing an "entropy" value that can be
      used for load balancing purposes.

      BFIR-ID: a 2-octet field encoding the BFR-ID of the Bit-Forwarding
      Ingress Router (BFIR), in the BIER sub-domain where the packet is
      forwarded to.

      DS: The usage of this field is no different from that of the
      Differentiated Services (DS) field of IPv4 and IPv6 headers.
      [RFC2474].

      Protocol: a one-octet field indicating the protocol type of the
      BIER payload as per the protocol numbers used in the Protocol
      field [RFC5237] of the IPv4 header and the Next Header field of an
      IPv6 header.  Theoretically, with the use of the IPv4/IPv6
      equivalent Protocol/Next-Header field, the payload of a BIER
      packet could be any type of payload permitted within the IPv4/IPv6
      packet.  However, this document currently only considers the use
      of the BIER encapsulation for "transport" type services where the
      encapsulated packets are either L2.5 (e.g., MPLS) or L3 (e.g., IP)
      packets . The valid BIER payload types include (but are not
      limited to) IPv4, IPv6, MPLS, VXLAN [RFC7348],VXLAN-GPE
      [I-D.ietf-nvo3-vxlan-gpe] and LISP [RFC6830].  The corresponding
      IP Protocol numbers for VXLAN, VXLAN-GPE and LISP are to be
      allocated by IANA.

      SI: a 10-bit field encoding the Set-Identifier (SI) for this
      packet in the case where the O-Flag bit is cleared.

      Sub-domain: a 10-bit field encoding the sub-domain where the
      packet is forwarded to in the case where the O-Flag bit is
      cleared.

      O-flag: If it's set, the leftmost 20 bits (i.e., the combination
      of the SI and Sub-domain fields) should be interpreted as an
      opaque number signaled and used much as the MPLS-BIER label in
      MPLS BIER encapsulation [I-D.ietf-bier-mpls-encapsulation].  A BFR
      signals the mapping between the opaque number and (subdomain-id,
      set-id, BSL) and it derives the (subdomain-id,set-id,BSL) from the
      opqaue number in an incoming BIER header just like in the MPLS
      BIER encapsulation case, except that regular MPLS signaling and
      forwarding infrastructure is not required.





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      TTL: The usage of this field is no different from that of the Time
      To Live (TTL) field in the IPv4 header.

      BitString: a variable-length BitString field that, together with
      the SI and Sub-domain fields, identifies all the destination BFERs
      for this packet.

4.  BIER Header Transport

   Since the BIER header format as specified in Section 3 is transport-
   independent by design, it can be carried with any type of transport
   encapsulation headers, such as an Ethernet header, a PPP header, an
   IP header, an MPLS header, a GRE header, an UDP header, etc.  Any
   possible transport encapsulation header must be able to indicate the
   payload is an BIER header.  For instance, in the BIER-in-MAC
   encapsulation case, the EtherType [ETYPES] field of the Ethernet
   header is used for that purpose.  In the BIER-in-IP encapsulation
   case, the Protocol field of the IPv4 header or the Next-Header field
   of the IPv6 header are used.  In the MPLS transport case, the MPLS-
   BIER encapsulation [I-D.ietf-bier-mpls-encapsulation] SHOULD be used
   instead.  Note that more details about BIER-in-UDP encapsualtion
   (e.g., UDP checksum and congestion control) will be specified in
   future versions of this document.

5.  Acknowledgements

   Thanks Antoni Przygienda, IJsbrand Wijnands, Eric Rosen and Toerless
   Eckert for their valuable comments and suggestions on this document.

6.  IANA Considerations

   This document includes a request to IANA to allocate an EtherType
   code,a PPP protocol code, an IPv4 protocol code/an IPv6 Next-Header
   code, a UDP destination port to indicate that BIER-encapsulated data
   follows.  Furthermore, this document includes a request to IANA to
   allocate IP Protocol numbers for VXLAN, VXLAN-GPE and LISP
   respectively.

7.  Security Considerations

   As mentioned in [I-D.ietf-bier-architecture], when BIER is paired
   with any transport underlay, it inherits the security considerations
   of the corresponding transport layer.  Also, SI and BFIR-ID fields of
   the BIER header may carry values other than those intended by the
   BFIR at the risk of misdelivering the packet.  Means to protect BFR
   routers against Man-in-the-Middle and Denial of Service attacks must
   be provided.




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8.  References

8.1.  Normative References

   [ETYPES]   The IEEE Registration Authority, "IEEE 802 Numbers", 2012.

   [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-04 (work in
              progress), July 2016.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

8.2.  Informative References

   [I-D.ietf-bier-mpls-encapsulation]
              Wijnands, I., Rosen, E., Dolganow, A., Tantsura, J.,
              Aldrin, S., and I. Meilik, "Encapsulation for Bit Index
              Explicit Replication in MPLS Networks", draft-ietf-bier-
              mpls-encapsulation-05 (work in progress), July 2016.

   [I-D.ietf-nvo3-vxlan-gpe]
              Kreeger, L. and U. Elzur, "Generic Protocol Extension for
              VXLAN", draft-ietf-nvo3-vxlan-gpe-02 (work in progress),
              April 2016.

   [RFC2474]  Nichols, K., Blake, S., Baker, F., and D. Black,
              "Definition of the Differentiated Services Field (DS
              Field) in the IPv4 and IPv6 Headers", RFC 2474,
              DOI 10.17487/RFC2474, December 1998,
              <http://www.rfc-editor.org/info/rfc2474>.

   [RFC5237]  Arkko, J. and S. Bradner, "IANA Allocation Guidelines for
              the Protocol Field", BCP 37, RFC 5237,
              DOI 10.17487/RFC5237, February 2008,
              <http://www.rfc-editor.org/info/rfc5237>.

   [RFC6830]  Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The
              Locator/ID Separation Protocol (LISP)", RFC 6830,
              DOI 10.17487/RFC6830, January 2013,
              <http://www.rfc-editor.org/info/rfc6830>.






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   [RFC7348]  Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
              L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
              eXtensible Local Area Network (VXLAN): A Framework for
              Overlaying Virtualized Layer 2 Networks over Layer 3
              Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014,
              <http://www.rfc-editor.org/info/rfc7348>.

Authors' Addresses

   Xiaohu Xu (editor)
   Huawei

   Email: xuxiaohu@huawei.com


   S Somasundaram
   Alcatel-Lucent

   Email: somasundaram.s@alcatel-lucent.com


   Christian Jacquenet (editor)
   France Telecom

   Email: christian.jacquenet@orange.com


   Robert Raszuk
   Bloomberg LP

   Email: robert@raszuk.net


   Zhaohui Zhang (editor)
   Juniper

   Email: zzhang@juniper.net














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