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BIER WG                                                      Quan. Xiong
Internet-Draft                                               Fangwei. Hu
Intended status: Standards Track                            Zheng. Zhang
Expires: January 19, 2018                                ZTE Corporation
                                                           July 18, 2017


                         BIER-TE Encapsulation
                draft-xiong-bier-te-encapsulation-00.txt

Abstract

   Traffic Engineering for Bit Index Explicit Replication (BIER-TE)
   shares part of architecture , definition and packet format with Bit
   Index Explicit Replication (BIER) according to the introduce in
   [I-D.eckert-bier-te-arch].  BIER-TE supports the traffic engineering
   by explicit hop-by-hop forwarding and loose hop forwarding of
   packets.[I-D.ietf-bier-mpls-encapsulation] specifies a BIER
   encapsulation that BIER header contains a bitstring in which each bit
   represents exactly one egress router in the domain.

   This document proposes a set of extensions to BIER encapsulation for
   BIER-TE.  The extensions define the BIER-TE header which contains
   serveral bitstrings and each bit in each bitstring represents one or
   more adjacencies in BIER-TE domain.  The encapsulation can be used
   both in an MPLS network and a non-MPLS network.

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 January 19, 2018.








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Copyright Notice

   Copyright (c) 2017 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
   (http://trustee.ietf.org/license-info) in effect on the date 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.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  BIER-TE Encapsulation . . . . . . . . . . . . . . . . . . . .   3
     3.1.  BitString Sub-TLV . . . . . . . . . . . . . . . . . . . .   4
   4.  Processing Rules with the BIER-TE Encapsulation . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Traffic Engineering for Bit Index Explicit Replication (BIER-TE)
   shares part of architecture, definition and packet format with Bit
   Index Explicit Replication (BIER) according to the introductions in
   [I-D.eckert-bier-te-arch].  But BIER-TE supports the traffic
   engineering by explicit hop-by-hop forwarding and loose hop
   forwarding of packets.  The BIER-TE controller host determines and
   assigns the BitPositions to the adjacencies which explicit paths
   passing through.

   [I-D.ietf-bier-mpls-encapsulation] specifies a BIER encapsulation
   that BIER header contains a bitstring in which each bit represents
   exactly one egress router in the domain.  But in BIER-TE every
   BitPosition of the BitString of a BIER-TE packet indicates one or
   more adjacencies instead of an egress router as in BIER.  That MUST
   be a huge number of adjacencies from BFIR to all BFERs and the
   BitString in BIER encapsulation is related to SD,BSL and SI
   combination.  For these distinct SD,BSL and SI combinations, there



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   must be more than one BitStrings and the BFR must make many copies of
   multicast data packet.  Even more, BitPositions of all adjacencies
   passing through BFIR to a BFER MAY be carried in different BitStrings
   and within the different packets.

   Based on the discussion above, this document proposes a set of
   extensions to BIER encapsulation for BIER-TE.  The extensions define
   the BIER-TE header which contains one or more bitstrings and each bit
   in each bitstring represents one or more adjacencies in BIER-TE
   domain.The encapsulation can be used both in an MPLS network and a
   non-MPLS network.

2.  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 [RFC2119].

2.1.  Terminology

   The terminology is defined as [I-D.ietf-bier-architecture],
   [I-D.eckert-bier-te-arch] and [I-D.ietf-bier-mpls-encapsulation].

3.  BIER-TE Encapsulation

   The BIER-TE header is shown in Figure 1.  It extends the BIER
   encapsulation and adds one or more BitString Sub-TLVs.

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |            BIFT-id                    | TC  |S|     TTL       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |Nibble |  Ver  |  BSL  |              Entropy                  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |OAM|B|Rsv|    DSCP   |   Proto   |          BFIR-id            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                BitString  (first 32 bits)                     ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ~                                                               ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ~                BitString  (last 32 bits)                      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |             BitString  Sub-TLVs (variable)                    |
       +-                                                             -+
       |                                                               |
                 Figure 1:BIER-TE Header Format




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   B bit : 1bit, indicates BIER-TE packet when it is set.  As the
   [I-D.eckert-bier-te-arch] mentioned, when a BFR receives a packet, it
   needs to interpret the BitString of a BIER-TE packet differently from
   a BIER packet and it is necessary to distinguish BIER from BIER-TE
   packets.

   BitString Sub-TLV: identifies BitString related information and each
   BitString Sub-TLV corresponds to a particular combination of SD, BSL,
   SI and bitstring.The format details see section 3.1.

   The definition of other fields is the same with
   [I-D.ietf-bier-mpls-encapsulation].

3.1.  BitString Sub-TLV

   This document proposes BitString Sub-TLV for BIER-TE header.  The TLV
   is optional.  The format of the new sub-TLV is shown in Figure 2 and
   3.


        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   SubDomainId |      SI         |   BSL   |      Rsv        |N|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                     BitString  (variable)                     |
       +-                                                             -+
       |                                                               |
                         Figure 2: BitString Sub-TLV Format 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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |               BIFT-id                 |       Rsv           |N|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                 BitString  (variable)                         |
       +-                                                             -+
       |                                                               |
                         Figure 3: BitString Sub-TLV Format 2


   The fields in the format are:

   SD : 8bits, indicates the Sub-DomainId of the BitString in the range
   [0,255].





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   SI : 10bits,indicates the Set Identification ofthe BitString in the
   range [0,1023].

   BSL : 4bits,indicates the length in bits of the BitString.  If k is
   the length of the BitString, the value of this field is log2(k)-5.
   The values are supported as follows:

   1: 64 bits

   2: 128 bits

   3: 256 bits

   4: 512 bits

   5: 1024 bits

   6: 2048 bits

   7: 4096 bits

   N : 1bit, indicates that there are one or more BitString Sub-TLVs
   immediately preceding the TLV when it is set.

   BitString: variable, identifies the collection of the adjacencies
   from BFIR to all BFERs and each BitString is related to SD,BSL and SI
   combination or BIFT-id of the packet.

   BIFT-id: 22bits,The BIFT-id represents a particular Bit Index
   Forwarding Table (BIFT); see Section 6.4 of
   [I-D.ietf-bier-architecture].  Each BIFT corresponds to a particular
   combination of SD,BSL and SI.

4.  Processing Rules with the BIER-TE Encapsulation

   As defined in [I-D.eckert-bier-te-arch], the BIER-TE operations
   consists of four layers: the "Multicast Flow Overlay", the "BIER-TE
   Controller Host", the "Routing Underlay" and the "BIER-TE forwarding
   layer".The BIER-TE Multicast flow processing with BIER-TE
   encapsulation is as follows:

   1.  The BIER-TE Controller assigns the BitPositions for adjacencies
   based on the operator policy and populates the BitPositions to the
   BIFT of each BFR as mentioned in [I-D.eckert-bier-te-arch].

   2.  The Multicast Flow Overlay determines the BFIR and a set of BFERs
   and sends this information to the BIER-TE controller.




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   3.  The BIER-TE controller calculates the explicit paths based on
   algorithms from BFIR to all BFERs.

   4.  The BIER-TE controller gets all adjacencies which the paths
   passing through and determines the list of bitstrings based on the
   SD,BSL and SI combination and BitPositions/adjacencies assignments.
   Each bit/BitPosition in each bitstring represents one or more
   adjacencies in BIER-TE domain.  The BitPositions of the adjacencies
   that have the same SD,BSL and SI combination can be encoded into the
   same BitString.  It then pushes the BitStrings into the BFIR.

   5.  When a BFIR receives a multicast packet from outside the BIER-TE
   domain, the BFIR carries out the following procedure:

   a.  The BFIR makes a copy of the multicast data packet and
   encapsulates the copy in a BIER-TE header as this document
   proposes(see Section 3).  The BitStrings which received from the
   BIER-TE controller are mapped to the field of BitString Sub-TLVs.

   b.  The BFIR checks the BIER-TE header and get the BitString Sub-TLVs
   infomation.  Then traverses the Sub-TLVs and related local BIFT which
   has the same SD,BSL and SI combination.  The packet may then be
   transmitted to adjacencies/neighboring BFRs and applies to that copy
   with the forwarding procedure of [I-D.eckert-bier-te-arch].

5.  Security Considerations

   TBD.

6.  IANA Considerations

   TBD.

7.  Acknowledgements

   TBD.

8.  Normative References

   [I-D.eckert-bier-te-arch]
              Eckert, T., Cauchie, G., Braun, W., and M. Menth, "Traffic
              Engineering for Bit Index Explicit Replication BIER-TE",
              draft-eckert-bier-te-arch-05 (work in progress), June
              2017.







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   [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-07 (work in
              progress), June 2017.

   [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 and non-MPLS Networks",
              draft-ietf-bier-mpls-encapsulation-07 (work in progress),
              June 2017.

   [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>.

Authors' Addresses

   Quan Xiong
   ZTE Corporation
   No.6 Huashi Park Rd
   Wuhan, Hubei  430223
   China

   Phone: +86 27 83531060
   Email: xiong.quan@zte.com.cn


   Fangwei Hu
   ZTE Corporation
   No.889 Bibo Rd
   Shanghai  201203
   China

   Phone: +86 21 68896273
   Email: hu.fangwei@zte.com.cn


   Zheng Zhang
   ZTE Corporation
   No.50 Software Avenue,Yuhuatai District
   Nanjing, Jiangsu Province  210012
   China

   Phone: +86 025 88016576
   Email: zhang.zheng@zte.com.cn



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