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Versions: (draft-xie-bier-6man-encapsulation) 00 01 02 03 04 05 06 08

Network Working Group                                             J. Xie
Internet-Draft                                       Huawei Technologies
Updates: 8296 (if approved)                                      L. Geng
Intended status: Standards Track                            China Mobile
Expires: January 14, 2021                                     M. McBride
                                                               Futurewei
                                                                R. Asati
                                                                   Cisco
                                                             S. Dhanaraj
                                                                  Huawei
                                                                  Y. Zhu
                                                           China Telecom
                                                                  Z. Qin
                                                            China Unicom
                                                                 M. Shin
                                                                LG Uplus
                                                               G. Mishra
                                                            Verizon Inc.
                                                                 X. Geng
                                                                  Huawei
                                                           July 13, 2020


            Encapsulation for BIER in Non-MPLS IPv6 Networks
                  draft-xie-bier-ipv6-encapsulation-08

Abstract

   This document proposes a BIER IPv6 (BIERv6) encapsulation for Non-
   MPLS IPv6 Networks using the IPv6 Destination Option extension
   header.  This document updates RFC 8296.

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] and
   [RFC8174].

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/.



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   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 14, 2021.

Copyright Notice

   Copyright (c) 2020 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
   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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  BIER IPv6 Encapsulation . . . . . . . . . . . . . . . . . . .   4
     3.1.  BIER Option in IPv6 Destination Options Header  . . . . .   4
     3.2.  Destination Address in BIERv6 Encapsulation . . . . . . .   6
     3.3.  BIERv6 Packet Format  . . . . . . . . . . . . . . . . . .   8
   4.  BIERv6 Packet Processing  . . . . . . . . . . . . . . . . . .   9
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
     5.1.  Intra Domain Deployment . . . . . . . . . . . . . . . . .  12
     5.2.  ICMP Error Processing . . . . . . . . . . . . . . . . . .  13
     5.3.  Security caused by BIER option  . . . . . . . . . . . . .  13
     5.4.  Applicability of IPsec  . . . . . . . . . . . . . . . . .  14
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
     6.1.  BIER Option Type  . . . . . . . . . . . . . . . . . . . .  15
     6.2.  End.BIER Function . . . . . . . . . . . . . . . . . . . .  15
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  15
   8.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  16
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  16
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  17
   Appendix A.  Relationship to BIER Core Standards  . . . . . . . .  18
   Appendix B.  Extensions to BIER Control-plane Standards . . . . .  19
   Appendix C.  Considerations of Using Unicast Address  . . . . . .  19
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  20



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1.  Introduction

   Bit Index Explicit Replication (BIER) [RFC8279] is an architecture
   that provides optimal multicast forwarding without requiring
   intermediate routers to maintain any per-flow state by using a
   multicast-specific BIER header.

   [RFC8296] defines a common BIER Header format for MPLS and Non-MPLS
   networks.  It has defined two types of encapsulation methods using
   the common BIER Header, (1) BIER encapsulation in MPLS networks,
   here-in after referred as MPLS BIER Header in this document and (2)
   BIER encapsulation in Non-MPLS networks, here-in after referred as
   Non-MPLS BIER Header in this document.  [RFC8296] also assigned
   Ethertype=0xAB37 for Non-MPLS BIER Header packets to be directly
   carried over the Ethernet links.

   This document proposes a BIER IPv6 encapsulation for Non-MPLS IPv6
   Networks, defining a method to carry the standard Non-MPLS BIER
   header (as defined in [RFC8296]) in the native IPv6 header.  A new
   IPv6 Option type - BIER Option is defined to encode the standard Non-
   MPLS BIER header and this newly defined BIER Option is carried under
   the Destination Options header of the native IPv6 Header [RFC8200].

   The relationship of this document to BIER core standards is listed in
   Appendix A.

   The relevant extensions to BIER Control-plane Standards are listed in
   Appendix B.

2.  Terminology

   Readers of this document are assumed to be familiar with the
   terminology and concepts of the documents listed as Normative
   References.

   The following new terms are used throughout this document:

   o  BIERv6 - Bit indexed explicit replication using IPv6 data plane.

   o  BIERv6 Domain - A limited-domain using BIERv6 encapsulation as
      specified in this document for transporting customer multicast
      packets from one router to multiple destination routers.  It is
      usually managed by a single administrative entity, e.g., a
      service-provider.  It could be a single AS network or a large-
      scale network that includes multiple ASes.  BIER Domain is also
      used for the same meaning as BIERv6 domain in this document.





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   o  BIERv6 Option - An Option type carried in IPv6 Destination Options
      Header (DO header, DOH) which includes the standard Non-MPLS BIER
      Header.  It is in type-length-value (TLV) format.  The value
      portion of the BIERv6 Option TLV, or the BIERv6 Option Data, is in
      the format of the standard Non-MPLS BIER header.  BIER option is
      also used for the same meaning as BIERv6 option in this document.

   o  BIERv6 Header - An IPv6 Header with BIER Option.

   o  BIERv6 Packet - An IPv6 packet with BIERv6 Header.  An IP/IPv6/
      Ethernet multicast packet is encapsulated with an outside BIERv6
      header and transformed to a BIERv6 packet on the ingress PE
      (BFIR).  BIERv6 packet is transported by the transit routers
      (BFRs) through a BIERv6 domain towards egress PEs(BFERs).  BIERv6
      packet is decapsulated by the BFERs, with the original IP/IPv6/
      Ethernet multicast packet being obtained and forwarded towards the
      multicast receivers .

3.  BIER IPv6 Encapsulation

3.1.  BIER Option in IPv6 Destination Options Header

   Destination Options Header and the Options that can be carried under
   this extension header is defined in [RFC8200].  This document defines
   a new Option type - BIER Option, to encode the Non-MPLS BIER header.
   As specified in Section 4.2 [RFC8200], the BIER Option follows type-
   length-value (TLV) encoding format and the standard Non-MPLS BIER
   header [RFC8296] is encoded in the value portion of the BIER Option
   TLV.

   This BIER Option MUST be carried only inside the IPv6 Destination
   Options header and MUST NOT be carried under the Hop-by-Hop Options
   header.

   The BIER Option is encoded in type-length-value (TLV) format as
   follows:

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Next Header  |  Hdr Ext Len  |  Option Type  | Option Length |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       ~  BIERv6 Option Data (Non-MPLS BIER Header defined in RFC8296) ~
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+





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   Next Header  8-bit selector.  Identifies the type of header
      immediately following the Destination Options header.

   Hdr Ext Len  8-bit unsigned integer.  Length of the Destination
      Options header in 8-octet units, not including the first 8 octets.

   Option Type  To be allocated by IANA.  See section 6.

   Option Length  8-bit unsigned integer.  Length of the option, in
      octets, excluding the Option Type and Option Length fields.

   BIERv6 Option Data  The BIERv6 Option Data contains the Non-MPLS BIER
      Header defined in RFC8296.  Fields in the Non-MPLS BIER Header
      MUST be encoded as below.

        BIFT-id: The BIFT-id is a domain-wide unique value in Non-MPLS
        IPv6 encapsulation.  See Section 2.2 of RFC 8296.

        TC: SHOULD be set to binary value 000 upon transmission and MUST
        be ignored upon.  See Section 2.2 of RFC 8296.

        S bit: SHOULD be set to 1 upon transmission, and MUST be ignored
        upon reception.  See Section 2.2 of RFC 8296.

        TTL: MUST be set to a value larger than 0 upon encapsulation,
        and SHOULD decrease by 1 by a BFR when forwarding a BIERv6
        packet to a BFR adjacency.  If the incoming TTL is 0, the packet
        is considered to be "expired".  See Section 2.1.1.2 of RFC 8296.

        Nibble: SHOULD be set to 0000 upon transmission, and MUST be
        ignored upon reception.  See Section 2.2 of RFC 8296.

        Ver: MUST be set to 0 upon transmission, and MUST be discarded
        when it is not 0 upon reception.  See Section 2.2 of RFC 8296.

        BSL: See Section 2.1.2 of RFC 8296.

        Entropy: See Section 2.1.2 of RFC 8296.

        OAM: See Section 2.1.2 of RFC 8296.

        Rsv: See Section 2.1.2 of RFC 8296.

        DSCP: SHOULD be set to binary value 000000 upon transmission and
        MUST be ignored upon reception.  In BIERv6 encapsulation, uses
        Traffic Class field of IPv6 header instead.





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        Proto: SHOULD be set to 0 upon transmission and be ignored upon
        reception.  In BIERv6 encapsulation, the functionality of this
        6-bit Proto field is replaced by the Next Header field in
        Destination Options header or the last IPv6 extension header to
        indicate the type of the payload.  This updates section 2.1.2 of
        [RFC8296] about Proto definition.  Next Header value in BIERv6
        encapsulation for common usage includes:

          Value 4 for IPv4 packet as BIERv6 payload.

          Value 41 for IPv6 packet as BIERv6 payload.

          Value 143 for Ethernet packet as BIERv6 payload.

        Multicast VPN (MVPN) service is considered as part of the BIER
        layering mode defined in [RFC8279], and should be supported by
        BIERv6 encapsulation.  [I-D.xie-bier-ipv6-mvpn] illustrates how
        MVPN is supported in BIERv6 encapsulation without using this
        Proto field.

        BIER-PING [I-D.ietf-bier-ping] is considered a useful function
        of the BIER architecture, and should be supported by BIERv6
        encapsulation.  How BIER-PING is supported in BIERv6
        encapsulation without using this Proto field is outside the
        scope of this document.

        BFIR-id: See Section 2.1.2 of RFC 8296.

        BitString: See Section 2.1.2 of RFC 8296.

3.2.  Destination Address in BIERv6 Encapsulation

   When a BIERv6 packet is replicated to a next hop BFR, an unicast
   address of the next hop BFR is used as the destination address of the
   BIERv6 packet.  Considerations of using unicast (or multicast)
   address is listed in Appendix C.

   The unicast address used in BIERv6 packet targeting a BFR SHOULD be
   advertised as part of the BIER IPv6 Encapsulation.  When a BFR
   advertises the BIER information with BIERv6 encapsulation capability,
   an IPv6 unicast address of this BFR MUST be selected specifically for
   BIERv6 packet forwarding.  Locally this "BIER Specific" IPv6 address
   is initialized in FIB with a flag of "BIER specific handling",
   represented as End.BIER function.

   If a BFR belongs to more than one sub-domain, it may (though it need
   not) have a different End.BIER in each sub-domain.  If different
   End.BIER is used for each sub-domain, implementation SHOULD support



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   verifying the DA of a BIERv6 packet is the End.BIER address bound by
   the sub-domain of the packet.

   For security deployment of BIERv6, the End.BIER address(es) is
   required to be allocated from an IPv6 address block, and the IPv6
   address block is used for domain boundary security policy.  See
   section 5.1 of this document for such security policy.  Such kind of
   security policy using IPv6 address block follows the paradigm settled
   by the [RFC8754] section 5.

   Deployment of BIERv6 in SRv6 network is allowed.  In this case, the
   BIERv6 domain is the same as SRv6 domain, and the End.BIER address is
   allocated from the locator of SRv6.

   To better understand the configuration mode of End.BIER address in
   BIERv6, [I-D.geng-bier-bierv6-yang] could be referenced.

   For the convenience of such co-existence of BIERv6 and SRv6, the
   indication of End.BIER or "BIER specific handling" in FIB shares the
   same space as SRv6 Endpoints Behaviors defined in
   [I-D.ietf-spring-srv6-network-programming].

   The following is an example pseudo-code of the End.BIER function:

     1. IF NH = 60 and HopLimit > 0                               ;;Ref1
     2.   IF (OptType1 = BIER) and (OptLength1 = HdrExtLen*8 + 4) ;;Ref2
     3.     Lookup the BIER Header inside the BIER option TLV.
     4.     Forward via the matched entry.
     5.   ELSE                                                    ;;Ref3
     6.     Drop the packet and end the process.
     7. ELSE IF NH=ICMPv6 or (NH=60 and Dest_NH=ICMPv6)           ;;Ref4
     8.   Send to CPU.
     9. ELSE                                                      ;;Ref5
    10.   Drop the packet.

   Ref1: Destination options header follows the IPv6 header directly and
   HopLimit is bigger than zero.

   Ref2: The first TLV is BIER type and is the only TLV present in
   Destination options header.

   Ref3/Ref5: Undesired packet is droped because the destination address
   is the BIER specific IPv6 address (End.BIER function).

   Ref4: An ICMPv6 packet using End.BIER as destination address.






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3.3.  BIERv6 Packet Format

   As a multicast packet enters the BIER domain in a Non-MPLS IPv6
   network, the multicast packet will be encapsulated with BIERv6 Header
   by the Ingress BFR (BFIR).

   Typically a BIERv6 header would contain the Destination Options
   Header as the only Extensions Header besides IPv6 Header, as depicted
   in the below figure.

      +---------------+------------------+----------------------+
      |  IPv6 header  |  IPv6 DO Header  |      X type of       |
      |               | with BIER Option |  C-multicast packet  |
      |               |                  |                      |
      | Next Hdr = 60 |   Nxt Hdr = X    | (IPv4/IPv6/Ethernet) |
      +---------------+------------------+----------------------+
      |                                  |                      |
      |<----------BIERv6 header--------->|<---BIERv6 payload--->|

   Format of the multicast packet with BIERv6 encapsulation carrying
   other extension headers along with Destination Options extension
   header is required to follow general recommendations of [RFC8200] and
   examples in other RFCs.  [RFC6275] introduces how the order should be
   when other extension headers carries along with Home address option
   in a destination options header.  Similar to this example, this
   document requires the Destination Options Header carrying the BIER
   option MUST be placed as follows:

   o  After the routing header, if that header is present

   o  Before the Fragment Header, if that header is present

   o  Before the AH Header or ESP Header, if either one of those headers
      is present

   Source Address field in the IPv6 header MUST be a routable IPv6
   unicast address of the BFIR in any case.

   BFIR encodes the BIERv6 header in the above mentioned encapsulation
   format and forwards the BIERv6 packet to the nexthop BFR following
   the local BIFT table.

   BFRs in the IPv6 network, processes and replicates the packets
   towards the BFERs using the local BIFT table.  The BitString field in
   the BIERv6 Option Data may be changed by the BFRs as they replicate
   the packet.  BFRs MUST follow the procedures defined in section 3.1
   as they modify the other fields in the BIERv6 Option Data.  The
   source address in the IPv6 header MUST NOT be modified by the BFRs.



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4.  BIERv6 Packet Processing

   When a multicast packet enters the BIER domain, the Ingress BFR
   (BFIR) encapsulates the multicast packet with a BIERv6 Header,
   transforming it to a BIERv6 packet.  The BIERv6 header includes an
   IPv6 header and a BIERv6 Option in IPv6 Destination Options Header.
   Source Address field in the IPv6 header MUST be set to a routable
   IPv6 unicast address of the BFIR.  Destination Address field in the
   IPv6 header is set to the End.BIER address of the next-hop BFR the
   BIERv6 packet replicating to, no matter next-hop BFR is directly
   connected (one-hop) or not directly connected (multi-hop).

   Upon receiving an BIERv6 packet, the BFR processes the IPv6 header
   first.  This is the general procedure of IPv6.

   If the IPv6 Destination address is an End.BIER IPv6 unicast address
   of this BFR, a 'BIER Specific Handling' indication will be obtained
   by the preceding Unicast DA lookup (FIB lookup).  The BIER option, if
   exists, will be checked to decide which neighbor(s) to replicate the
   BIERv6 packet to.

   It is a local behavior to handle the combination of extension
   headers, options and the BIER option(s) in destination options header
   when a 'BIER Specific Handling' indication is got by the preceding
   FIB lookup.  Early deployment of BIERv6 may require there is only one
   BIER option TLV in the destination options header followed the IPv6
   header.  How other extension headers or more BIER option TLVs in a
   BIERv6 packet is handled is outside the scope of this document.

   A packet having a 'BIER Specific Handling' indication but not having
   a BIER option is supposed to be a wrong packet or an ICMPv6 packet,
   and the process can be referred to the example in section 3.2.

   A packet not having a 'BIER Specific Handling' indication but having
   a BIER option SHOULD be processed normally as unicast forwarding
   procedures, which may be a behavior of drop, or send to CPU, or other
   behaviors in existing implementations.

   The Destination Address field in the IPv6 Header MUST change to the
   nexthop BFR's End.BIER Unicast address in BIERv6.

   The Hop Limit field of IPv6 header MUST decrease by 1 when sending
   packets to a BFR neighbor, while the TTL in the BIER header MUST be
   unchanged on a Non-BIER router, or decrease by 1 on a BFR.

   The BitString in the BIER header in the Destination Options Header
   may change when sending packets to a neighbor.  Such change of
   BitString MUST be aligned with the procedure defined in RFC8279.



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   Because of the requirement to change the content of the option when
   forwarding BIERv6 packet, the BIER option type should have chg flag 1
   per section 4.2 of RFC8200.

   The procedures applies normally if a bit corresponding to the self
   bfr-id is set in the BitString field of the BIERv6 Option Data of the
   BIERv6 packet.  The node is considered to be an Egress BFR (BFER) in
   this case.  The BFER removes the BIERv6 header, including the IPv6
   header and the Destination Options header, and copies the packet to
   the multicast flow overlay.  The egress VRF of a packet may be
   determined by a further lookup on the IPv6 source address instead of
   the upstream-assigned MPLS Label as described in [RFC8556].

   The Fragment Header, AH Header or ESP Header, if exists after the
   BIER options header, can be processed on BFER only as part of the
   multicast flow overlay process.

   The following diagram shows the whole progression of the multicast
   packet as it enters the BIERv6 domain on PE1, and leaves the BIERv6
   domain on PE2 and PE3.


                   +-------------+    +-------------+
                   |{S=PE1,D=P2} |    |{S=PE1,D=PE2}|
                   +-------------+    +-------------+
                   |[BitStr=0110]|    |[BitStr=0010]|
   +==========+    +=============+    +=============+    +==========+
   |(C-MC Pkt)| >> | (C-MC Pkt)  | >> | (C-MC Pkt)  | >> |(C-MC Pkt)|
   +==========+    +=============+    +=============+    +==========+
  CE1-----------PE1------[P1]------P2----------------PE2------------CE2
               (BFIR)             /(BFR)        (BFER, BFR-id=2)
                                 /
                                /     +-------------+
                               |      |{S=PE1,D=PE3}|
                               |      +-------------+
                               |      |[BitStr=0100]|
                                \     +=============+    +==========+
                                 \ >> | (C-MC Pkt)  | >> |(C-MC Pkt)|
                                  \   +=============+    +==========+
                                   +------[P3]-------PE3------------CE3
                                                (BFER, BFR-id=3)

   {S=PE1,D=PE2}: Source address and Destination address in IPv6 header.
   [BitStr=0110]: BitString value in IPv6 DO Header.
      (C-MC Pkt): Customer MultiCast packet.

   o  PE1 is Provider Edge router, acting as BFIR.




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   o  P2 is Provider Core router, acting as BFR.

   o  P1 and P3 are IPv6 routers, acting as Non-BFR.

   o  PE2 and PE3 are Provider Edge routers, acting as BFER.

   o  CE1 and CE2 are Customer Edge routers.

5.  Security Considerations

   BIER IPv6 encapsulation provides a new encapsulation based on IPv6
   and BIER to transport multicast data packet in a BIER domain.  The
   BIER domain can be a single IGP area, an anonymous system (AS) with
   multiple IGP areas, or multiple anonymous systems (ASes) operated by
   a network operator.  A single BIER Sub-domain may be deployed through
   the whole BIER Domain, as illustrated in
   [I-D.geng-bier-ipv6-inter-domain].

   This section reviews security considerations related to the BIER IPv6
   encapsulation, based on security considerations of [RFC8279],
   [RFC8296], and other documents related to IPv6 extension.

   It is expected that all nodes in a BIER IPv6 domain are managed by
   the same administrative entity.  BIER-encapsulated packets should
   generally not be accepted from untrusted interfaces or tunnels.  For
   example, an operator may wish to have a policy of accepting BIER-
   encapsulated packets only from interfaces to trusted routers, and not
   from customer-facing interfaces.  See section 5.1 for normal Intra
   domain deployment.

   For applications that require a BFR to accept a BIER-encapsulated
   packet from an interface to a system that is not controlled by the
   network operator, the security considerations of [RFC8296] apply.

   BIER IPv6 encapsulation may cause ICMP packet sent to BFIR and cause
   security problems.  See section 5.2 for ICMP related problems.

   This document introduces a new option used in IPv6 Destination
   Options Header, together with the special-use IPv6 address called
   End.BIER in IPv6 destination address for BIER IPv6 forwarding.
   However the option newly introduced may be wrongly used with normal
   IPv6 destination address.  See section 5.3 for problems introduced by
   the new IPv6 option with normal IPv6 destination address.

   If the multicast data packet of a BIERv6 packet is altered by an
   intermediate router, contents of the multicast data packet will be
   damaged.  BIER IPv6 encapsulation provides the ability of IPsec to




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   ensure the confidentiality or integrity for multicast data packet.
   See section 5.4 for this security problem.

   If the BIERv6 encapsulation of a particular packet specifies a
   BitString (together with SI) other than the one intended by the BFIR,
   the packet is likely to be misdelivered.  Some modifications of the
   BIER encapsulation, e.g., setting every bit in the BitString, may
   result in denial-of-service (DoS) attacks.  This kind of DoS attack
   is a challenge not only in BIERv6 but also in BIER as specified in
   [RFC8279] and [RFC8296], as the BitString is required to change on
   BFR per the BIER forwarding procedures.  This document does not
   provide new mechanisms to improve this kind of weakness.

   A BIER router accepts and uses the End.BIER IPv6 address to construct
   BIFT only when the IPv6 address is configured explicitly, or received
   from a router via control-plane protocols.  The received information
   is validated using existing authentication and security mechanisms of
   the control-plane protocols.  BIER IPv6 encapsulation does not define
   any additional security mechanism in existing control-plane
   protocols, and it inherits any security considerations that apply to
   the control-plane protocols.

5.1.  Intra Domain Deployment

   Generally nodes outside the BIER Domain are not trusted: they cannot
   directly use the End.BIER of the domain.  This is enforced by two
   levels of access control lists:

   1.  Any packet entering the BIER Domain and destined to an End.BIER
   IPv6 Address within the BIER Domain is dropped.  This may be realized
   with the following logic.  Other methods with equivalent outcome are
   considered compliant:

   * allocate all the End.BIER IPv6 Address from a block S/s

   * configure each external interface of each edge node of the domain
   with an inbound infrastructure access list (IACL) which drops any
   incoming packet with a destination address in S/s

   * Failure to implement this method of ingress filtering exposes the
   BIER Domain to BIER attacks as described and referenced in [RFC8296].

   2.  The distributed protection in #1 is complemented with per node
   protection, dropping packets to End.BIER IPv6 Address from source
   addresses outside the BIER Domain.  This may be realized with the
   following logic.  Other methods with equivalent outcome are
   considered compliant:




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   * assign all interface addresses from prefix A/a

   * assign all the IPv6 addresses used as source address of BIER IPv6
   packets from a block B/b

   * at node k, all End.BIER IPv6 addresses local to k are assigned from
   prefix Sk/sk

   * configure each internal interface of each BIER node k in the BIER
   Domain with an inbound IACL which drops any incoming packet with a
   destination address in Sk/sk if the source address is not in A/a or
   B/b.

   For simplicity of deployment, a configuration of IACL effective for
   all interfaces can be provided by a router.  Such IACL can be
   referred to as global IACL(GIACL) .Each BIER node k then simply
   configs a GIACL which drops any incoming packet with a destination
   address in Sk/sk if the source address is not in A/a or B/b for the
   intra-domain deployment mode.

5.2.  ICMP Error Processing

   The BIERv6 BFR does not send ICMP error messages to the source
   address of a BIERv6 packet, there is still chance that Non-BFR
   routers send ICMP error messages to source nodes within the BIER
   Domain.

   A large number of ICMP may be elicited and sent to a BFIR router, in
   case when a BIERv6 packet is filled with wrong Hop Limit, either
   error or malfeasance.  A rate-limiting of ICMP packet should be
   implemented on each BFR.

   The ingress node can take note of the fact that it is getting, in
   response to BIER IPv6 packet, one or more ICMP error packets.  By
   default, the reception of such a packets MUST be countered and
   logged.  However, it is possible for such log entries to be "false
   positives" that generate a lot of "noise" in the log; therefore,
   implementations SHOULD have a knob to disable this logging.

5.3.  Security caused by BIER option

   This document introduces a new option used in IPv6 Destination
   Options Header.  An IPv6 packet with a normal IPv6 address of a
   router (e.g. loopback IPv6 address of the router) as destination
   address will possibly carry a BIER option.

   For a router incapable of BIERv6, such BIERv6 packet will not be
   processed by the procedure described in this document, but be



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   processed as normal IPv6 packet with unknown option, and the existing
   security considerations for handling IPv6 options apply.  Possible
   way of handling IPv6 packets with BIER option may be send to CPU for
   slow path processing, with rate-limiting, or be discarded according
   to the local policy.

   For a router capable of BIERv6, such BIERv6 packet MUST NOT be
   forwarded, but should be processed as a normal IPv6 packet with
   unknown option, or additionally and optionally be countered and
   logged if the router is capable of doing so.

5.4.  Applicability of IPsec

   IPsec [RFC4301] uses two protocols to provide traffic security
   services -- Authentication Header (AH) [RFC4302] and Encapsulating
   Security Payload (ESP) [RFC4303].  Each protocol supports two modes
   of use: transport mode and tunnel mode.  IPsec support both unicast
   and multicast.  IPsec implementations MUST support ESP and MAY
   support AH.

   This document assume IPsec working in tunnel mode with inner IPv4 or
   IPv6 multicast packet encapsulated in outer BIERv6 header and IPsec
   header(s).

   IPsec used with BIER IPv6 encapsulation to ensure that a BIER payload
   is not altered while in transit between BFIR and BFERs.  If a BFR in
   between BFIR and BFERs is compromised, there is no way to prevent the
   compromised BFR from making illegitimate modifications to the BIER
   payload or to prevent it from misforwarding or misdelivering the
   BIER-encapsulated packet, but the BFERs will detect the illegitimate
   modifications to the BIER Payload (or the inner multicast data
   packet).  This could provide cryptographic integrity protection for
   multicast data transport.  This capability of IPsec comes from the
   design that, the destination options header carrying the BIER header
   is located before the AH or ESP and the BFR routers in between BFIR
   and BFERs can process the BIER header without aware of AH or ESP.

   For ESP, the Integrity Check Value (ICV) is computed over the ESP
   header, Payload, and ESP trailer fields.  It doesn't require the IP
   or extension header for ICV calculating, and thus the change of DA
   and BIER option data does not affect the function of ESP.

   For AH, the Integrity Check Value (ICV) is computed over the IP or
   extension header fields before the AH header, the AH header, and the
   Payload.  The IPv6 DA is immutable for unicast traffic in AH, and the
   change of DA in BIER IPv6 forwarding for multicast traffic is
   incompatible to this rule.  How AH is extended to support multicast




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   traffic transporting through BIER IPv6 encapsulation is outside the
   scope of this document.

   The detailed control-plane for BIER IPv6 encapsulation IPsec function
   is outside the scope of the document.  Internet Key Exchange Protocol
   Version 2 (IKEv2) [RFC7296] and Group Security Association (GSA)
   [RFC5374] can be referred to for further studying.

6.  IANA Considerations

6.1.  BIER Option Type

   Allocation is expected from IANA for a BIER Option Type codepoint
   from the "Destination Options and Hop-by-Hop Options" sub-registry of
   the "Internet Protocol Version 6 (IPv6) Parameters" registry.  The
   value 0x70 is suggested.

           +-----------+-----+-----+-------+-------------+------------+
           | Hex Value | act | chg |  rest | Description | Reference  |
           +-----------+-----+-----+-------+-------------+------------+
           |    0x70   |  01 |  1  | 10000 | BIER Option | This draft |
           +-----------+-----+-----+-------+-------------+------------+

6.2.  End.BIER Function

   Allocation is expected from IANA for an End.BIER function codepoint
   from the "SRv6 Endpoint Behaviors" sub-registry.  The value 60 is
   suggested.

           +-------+--------+--------------------------+------------+
           | Value |  Hex   |    Endpoint function     | Reference  |
           +-------+--------+--------------------------+------------+
           | TBD   |  TBD   |    End.BIER              | This draft |
           +-------+--------+--------------------------+------------+

7.  Acknowledgements

   The authors would like to thank Stig Venaas for his valuable
   comments.  Thanks IJsbrand Wijnands, Greg Shepherd, Tony Przygienda,
   Toerless Eckert, Jeffrey Zhang, Pascal Thubert for the helpful
   comments to improve this document.

   Thanks Aijun Wang for comments about BIER OAM function in BIER IPv6
   encapsulation.

   Thanks Mach Chen for review and suggestions about BIER-PING function
   in BIER IPv6 encapsulation.




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8.  Contributors

   Gang Yan

   Huawei Technologies

   China

   Email: yangang@huawei.com

   Yang(Yolanda) Xia

   Huawei Technologies

   China

   Email: yolanda.xia@huawei.com

9.  References

9.1.  Normative References

   [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>.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005, <https://www.rfc-editor.org/info/rfc4301>.

   [RFC4302]  Kent, S., "IP Authentication Header", RFC 4302,
              DOI 10.17487/RFC4302, December 2005,
              <https://www.rfc-editor.org/info/rfc4302>.

   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, DOI 10.17487/RFC4303, December 2005,
              <https://www.rfc-editor.org/info/rfc4303>.

   [RFC5374]  Weis, B., Gross, G., and D. Ignjatic, "Multicast
              Extensions to the Security Architecture for the Internet
              Protocol", RFC 5374, DOI 10.17487/RFC5374, November 2008,
              <https://www.rfc-editor.org/info/rfc5374>.

   [RFC6275]  Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
              Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July
              2011, <https://www.rfc-editor.org/info/rfc6275>.




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   [RFC7296]  Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
              Kivinen, "Internet Key Exchange Protocol Version 2
              (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
              2014, <https://www.rfc-editor.org/info/rfc7296>.

   [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>.

   [RFC8279]  Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
              Przygienda, T., and S. Aldrin, "Multicast Using Bit Index
              Explicit Replication (BIER)", RFC 8279,
              DOI 10.17487/RFC8279, November 2017,
              <https://www.rfc-editor.org/info/rfc8279>.

   [RFC8296]  Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
              Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation
              for Bit Index Explicit Replication (BIER) in MPLS and Non-
              MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January
              2018, <https://www.rfc-editor.org/info/rfc8296>.

   [RFC8401]  Ginsberg, L., Ed., Przygienda, T., Aldrin, S., and Z.
              Zhang, "Bit Index Explicit Replication (BIER) Support via
              IS-IS", RFC 8401, DOI 10.17487/RFC8401, June 2018,
              <https://www.rfc-editor.org/info/rfc8401>.

   [RFC8556]  Rosen, E., Ed., Sivakumar, M., Przygienda, T., Aldrin, S.,
              and A. Dolganow, "Multicast VPN Using Bit Index Explicit
              Replication (BIER)", RFC 8556, DOI 10.17487/RFC8556, April
              2019, <https://www.rfc-editor.org/info/rfc8556>.

   [RFC8754]  Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
              Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
              (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
              <https://www.rfc-editor.org/info/rfc8754>.

9.2.  Informative References

   [I-D.geng-bier-bierv6-yang]
              Geng, X., Qin, Z., and F. Zheng, "YANG Data Model for
              Bierv6", draft-geng-bier-bierv6-yang-00 (work in
              progress), June 2020.




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   [I-D.geng-bier-ipv6-inter-domain]
              Geng, L., Xie, J., McBride, M., and G. Yan, "Inter-Domain
              Multicast Deployment using BIERv6", draft-geng-bier-ipv6-
              inter-domain-01 (work in progress), January 2020.

   [I-D.ietf-bier-ipv6-requirements]
              McBride, M., Xie, J., Dhanaraj, S., Asati, R., Zhu, Y.,
              and G. Mishra, "BIER IPv6 Requirements", draft-ietf-bier-
              ipv6-requirements-05 (work in progress), July 2020.

   [I-D.ietf-bier-ping]
              Nainar, N., Pignataro, C., Akiya, N., Zheng, L., Chen, M.,
              and G. Mirsky, "BIER Ping and Trace", draft-ietf-bier-
              ping-07 (work in progress), May 2020.

   [I-D.ietf-spring-srv6-network-programming]
              Filsfils, C., Camarillo, P., Leddy, J., Voyer, D.,
              Matsushima, S., and Z. Li, "SRv6 Network Programming",
              draft-ietf-spring-srv6-network-programming-16 (work in
              progress), June 2020.

   [I-D.xie-bier-ipv6-isis-extension]
              Xie, J., Wang, A., Yan, G., and S. Dhanaraj, "BIER IPv6
              Encapsulation (BIERv6) Support via IS-IS", draft-xie-bier-
              ipv6-isis-extension-01 (work in progress), January 2020.

   [I-D.xie-bier-ipv6-mvpn]
              Xie, J., McBride, M., Dhanaraj, S., and L. Geng, "Use of
              BIER IPv6 Encapsulation (BIERv6) for Multicast VPN in IPv6
              networks", draft-xie-bier-ipv6-mvpn-02 (work in progress),
              January 2020.

Appendix A.  Relationship to BIER Core Standards

   The BIER architecture [RFC8279] is inherited in this BIERv6 proposal,
   and the layering mode of BIER architecture is fully supported with
   some necessary extension to the data plane as well as the control
   plane standards.

   The focus of this document is BIERv6 data plane, including the BIERv6
   encapsulation and packet forwarding procedures.  The common BIER
   header encoding [RFC8296] is maximum reused in this BIERv6 proposal.

   To better understand the overall BIER IPv6 problem space and
   requirements, refer to [I-D.ietf-bier-ipv6-requirements].






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Appendix B.  Extensions to BIER Control-plane Standards

   The relevant control-plane documents that have done or still to be
   done are listed below.

   o  Based on [RFC8401], IS-IS extension is defined in
      [I-D.xie-bier-ipv6-isis-extension] for intra-AS BIERv6 information
      advertisement and BIRT/BIFT building.

   o  OSPFv3 extension for intra-AS BIERv6 information advertisement and
      BIRT/BIFT building is to be defined.

   o  Based on this BIERv6 encapsulation,
      [I-D.geng-bier-ipv6-inter-domain] illustrates how inter-AS BIRT/
      BIFT are built and how inter-AS multicast deployment is supported.

   o  BGP extension for inter-AS BIERv6 information advertisement and
      BIRT/BIFT building is to be defined.

   o  Based on [RFC8556], BGP-MVPN using BIERv6 encapsulation is defined
      in [I-D.xie-bier-ipv6-mvpn] for multicast service deployment.

Appendix C.  Considerations of Using Unicast Address

   BIER is generally a hop-by-hop and one-to-many architecture, and thus
   the IPv6 Destination Address (DA) being a Multicast Address is a way
   one may think of as an approach for both the two paradigms in BIERv6
   encapsulation.

   However using a unicast address has the following benefits:

   1.  Replicating a BIERv6 packet over a non-BIER capable router.

   2.  Fast rerouting a BIERv6 packet using a unicast by-pass tunnel.

   3.  Forwarding a BIERv6 packet to one of the many BFR neighbors
       connected on a LAN without imposing new requirements of snooping
       on switches.

   4.  Replicating a BIERv6 packet through an anonymous system(AS) to
       BFERs in other ASes, as illustrated in
       [I-D.geng-bier-ipv6-inter-domain].

   Some of the above scenarios are assumed part of BIER architecture as
   described in [RFC8279], and some of them are the scalability aspects
   for inter-AS stateless multicast this document intends to support.
   This document intends to fulfil all these requirements (categorized




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   as multi-hop replication), and proposes to use unicast address for
   both one-hop replication and multi-hop replication.

Authors' Addresses

   Jingrong Xie
   Huawei Technologies

   Email: xiejingrong@huawei.com


   Liang Geng
   China Mobile
   Beijing 10053

   Email: gengliang@chinamobile.com


   Mike McBride
   Futurewei

   Email: mmcbride7@gmail.com


   Rajiv Asati
   Cisco

   Email: rajiva@cisco.com


   Senthil Dhanaraj
   Huawei

   Email: senthil.dhanaraj@huawei.com


   Yongqing Zhu
   China Telecom

   Email: zhuyq8@chinatelecom.cn


   Zhuangzhuang Qin
   China Unicom

   Email: qinzhuangzhuang@chinaunicom.cn





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   MooChang Shin
   LG Uplus

   Email: himzzang@lguplus.co.kr


   Gyan Mishra
   Verizon Inc.

   Email: gyan.s.mishra@verizon.com


   Xuesong Geng
   Huawei

   Email: gengxuesong@huawei.com



































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