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

Network Working Group                                             J. Xie
Internet-Draft                                       Huawei Technologies
Intended status: Standards Track                                 L. Geng
Expires: June 13, 2020                                      China Mobile
                                                              M. McBride
                                                               Futurewei
                                                                R. Asati
                                                                   Cisco
                                                             S. Dhanaraj
                                                                  Huawei
                                                       December 11, 2019


            Encapsulation for BIER in Non-MPLS IPv6 Networks
                  draft-xie-bier-ipv6-encapsulation-04

Abstract

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

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/.

   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 June 13, 2020.






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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
   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
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  BIER IPv6 Encapsulation . . . . . . . . . . . . . . . . . . .   3
     3.1.  BIER Option in IPv6 Destination Options Header  . . . . .   3
     3.2.  Multicast and Unicast Destination Address . . . . . . . .   6
     3.3.  BIERv6 Packet Format  . . . . . . . . . . . . . . . . . .   8
   4.  BIERv6 Packet Processing  . . . . . . . . . . . . . . . . . .   9
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
     5.1.  Intra Domain Deployment . . . . . . . . . . . . . . . . .  12
     5.2.  Inter Domain Deployment . . . . . . . . . . . . . . . . .  13
     5.3.  ICMP Error Processing . . . . . . . . . . . . . . . . . .  13
     5.4.  Security caused by BIER option  . . . . . . . . . . . . .  14
     5.5.  Applicability of IPsec  . . . . . . . . . . . . . . . . .  14
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
     6.1.  BIER Option Type  . . . . . . . . . . . . . . . . . . . .  15
     6.2.  End.BIER Function . . . . . . . . . . . . . . . . . . . .  15
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  16
   8.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  16
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  16
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

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.





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   [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].

   This document details one of the proposed solutions for transporting
   BIER packets in an IPv6 network.  To better understand the overall
   BIER IPv6 problem space, use cases and proposed solutions, refer to
   [I-D.ietf-bier-ipv6-requirements].

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 - BIER IPv6.

   o  BIER Option - An Option type carried in IPv6 Destination Options
      Header which includes the standard Non-MPLS BIER Header.

   o  BIERv6 Header - An IPv6 Header with BIER Option.

   o  BIERv6 Packet - An IPv6 packet with BIERv6 Header.  Such an IPv6
      packet typically carries the user multicast payload and is
      forwarded by BFRs in the BIERv6 network 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.



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   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.

   Co-existence of Destination Options Header with BIER option TLV and
   other IPv6 extension headers MUST confirm to the general requirements
   defined in [RFC8200].  In addition to the requirements defined in
   [RFC8200], this document requires that the Destination Options Header
   with a BIER Option TLV MUST appear only after the Routing Header if
   the Routing Header is present in the IPv6 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 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       ~          Non-MPLS BIER Header (defined in RFC8296)            ~
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   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.

   Non-MPLS BIER Header  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.




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        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 0 upon transmission, and MUST be ignored
        upon reception.  The function of TTL is replaced by the Hop
        Limit field in IPv6 header.

        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 IPv6 BIER encapsulation,
        uses highest 6-bit of Traffic Class field of IPv6 header to hold
        a Differentiated Services Codepoint [RFC2474].

        Proto: SHOULD be set to 0 upon transmission and MUST be ignored
        upon reception.  In IPv6 BIER encapsulation, the functionality
        of this 6-bit Proto field is replaced by the Next Header field
        in Destination Options header, which is the last IPv6 extension
        header, to indicate the BIER payload, which is also IPv6
        payload.



           For BIER Proto 1, indicating a Downstream-assigned MPLS
           payload, use Next Header value 137.

           For BIER Proto 2, indicating an Upstream-assigned MPLS
           payload, there is no Next Header code currently.  An
           upstream-assigned MPLS label within the context of special
           BFIR router, which in turn is represented by the BFIR-id and
           the Sub-domain indirectly indicated by the BIFT-id in a BIER-
           MPLS or BIER-ETH packet, can be replaced by an IPv6 source
           address in a BIER IPv6 encapsulation packet in a direct



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           manner.  In this case, use Next Header value 4 for IPv4
           payload, or value 41 for IPv6 payload.

           For BIER Proto 3, indicating an Ethernet payload, use Next
           Header value 97.

           For BIER Proto 4, indicating an IPv4 payload, use Next Header
           value 4.

           For BIER Proto 5, indicating a BIER-OAM payload, use Next
           Header value 58.  How the BIER-PING is supported with BIER
           IPv6 encapsulation is outside the scope of this document.

           For BIER Proto 6, indicating an IPv6 payload, use Next Header
           value 41.

        BFIR-id: See Section 2.1.2 of RFC 8296.

        BitString: See Section 2.1.2 of RFC 8296.

3.2.  Multicast and Unicast Destination 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.  Tunneling 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.

   4.  Connecting BIER domains, for example Data Center domains, in an
       overlay manner.

   Some of the above functions are assumed very basic requirements and
   part of BIER architecture as described in [RFC8279].  This document
   uses unicast address for both one-hop replication and multi-hop
   replication.

   The unicast address used in BIERv6 packet targeting a BFR SHOULD be
   the IPv6 BFR-Prefix advertised from this BFR.  When a BFR advertises
   the BIER information with BIERv6 encapsulation capability, the IPv6
   BFR-prefix of this BFR MUST be selected specifically for BIERv6



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   packet forwarding.  Locally this "BIER Specific" IPv6 address is
   initialized in FIB with a flag of "BIER specific handling",
   represented as End.BIER function.  For convenience, the indication in
   FIB share the same space as SRv6 Endpoints Behaviors defined in
   [I-D.ietf-spring-srv6-network-programming].  Apart from this sharing
   of code space, there is nothing dependent on SRv6.  The co-existance
   of BIERv6 and SRv6 is outside the scope of this document.

   BFR Prefix is used only in control plane in BIER MPLS encapsulation
   but not used in data plane.  While in BIERv6, BFR prefix is used in
   both control plane and data plane.  For the convinence of migration
   to BIERv6, it is RECOMMENDED to use an "exclusive" IPv6 address as
   BFR prefix when deploying BIER-MPLS in IPv6 networks.  The
   "exclusive" IPv6 address should not be used for general purpose like
   BGP session establishment, but for "BIER specific" function.  For
   Non-BIER IPv6 routers, the IPv6 address is a regular IPv6 prefix
   reachable through IPv6 unicast routing.

   The following is an example of configuring a BIER specific IPv6
   address and using this address as BFR prefix:

    # Config a BIER specific IPv6 address with 128-bit mask on loopback0.
    interface loopback0
      ipv6 address 2001:DB8::AB37 128 End.BIER

    # Config the BIER-specific IPv6 address on loopback0 as BFR Prefix.
    bier sub-domain 6 ipv6-underlay
      bfr-prefix interface loopback0

   The address used as "BIER specific" IPv6 address can be from inside
   the scope of an SRv6 Locator or outside the scope of the SRv6
   Locator(s) since it is a host prefix (128-bit prefix-length prefix).

   Each "BIER specific" address can be used in one or many sub-domains
   as BFR-prefix, such that it can be associated with one or many Multi-
   Topologies (MTs) or algorithms.

   More than one "BIER specific" address are also allowed as different
   BFR-prefix of more than one sub-domain, as described in section 2 of
   [RFC8279].

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









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     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.

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.

   Typically a BIERv6 header would contain the Destination Options
   Header as the only Extensions Header besides IPv6 Header.  However,
   it is allowed and possible for other extension headers to appear
   along with the Destination Options Header as long as the requirements
   listed in section 3.1 of this document is met.

   Format of the multicast packet with BIERv6 encapsulation carrying
   only the Destination Options header is depicted in the below figure.

      +---------------+--------------+------------
      | IPv6 header   | Dest Options | X type of
      |               | Header with  | multicast
      |               | BIER Option  | packet
      |               |              |
      | Next Hdr = 60 |  Nxt Hdr = X |
      +---------------+--------------+------------

   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



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   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 Non-MPLS BIER 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 bit-string field
   in the Non-MPLS BIER header 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 Non-MPLS BIER
   header.  The source address in the IPv6 header MUST NOT be modified
   by the BFRs.

4.  BIERv6 Packet Processing

   There is no BIER-specific processing, and all the 8 steps in section
   6.5 of RFC8279 apply to BIERv6 packet processing.  However, there are
   some IPv6-specific processing procedures due to the base and general
   procedures of IPv6.

   On the overlay layer, when a multicast packet enters the BIER domain
   in a Non-MPLS IPv6 network, 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 IPv6
   Destination Options Header within a standard Non-MPLS BIER 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 BFR prefix 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).

   On the BIER layer, upon receiving an BIERv6 packet, the BFR processes
   the IPv6 header first.  This is the general procedure of IPv6.



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   If the IPv6 Destination address is an IPv6 BFR-Prefix 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 refered 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 BFR Prefix if Unicast address is used 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.

   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.
   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 bit-string field of the Non-MPLS BIER header 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].






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   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.

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.  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.

   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.

   There may be 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.  See section 5.2 for inter domain
   deployment.

   BIER IPv6 encapsulation may cause ICMP packet sent to BFIR and cause
   security problems.  See section 5.3 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 5.4 for problems introduced by
   the new IPv6 option with normal IPv6 destination address.

   If a BIER packet is altered, either the BIER header, or the multicast
   data packet, by an intermediate router, packets may be lost, stolen,
   or otherwise misdelivered.  BIER IPv6 encapsulation provides the
   ability of IPsec to ensure the confidentiality or integrity.  See
   section 5.5 for this security problem.

   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



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   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:

   * 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
   inter-domain deployment mode.



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5.2.  Inter Domain Deployment

   There may be 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.  For instance, there may be an
   application in which a virtual machine in a data center submits BIER-
   encapsulated packets to a router.  In such a case, it is desirable to
   verify that the packet is from a legitimate source and that its
   BitString denotes only systems to which that source is allowed to
   send.  Using BIER IPv6 encapsulation, IACL can be configured on each
   internal interface of each BIER node k to allow packet with a
   destination address in Sk/sk and the source address is in an allowed
   list of IPv6 address.  However, the BIER IPv6 encapsulation itself
   does not provide a way to verify that the source is legitimate or the
   source is allowed to set any particular set of bits in the BitString.

   The IACL allowing specific IPv6 address outside the domain of a
   network operator can be more strict by the following method:

   * configure one sub-domain using only one bit string length, and a
   seperate End.BIER for this sub-domain as a service opened to agreed
   source(s) outside the domain of the operator's network.

   * configure on BIER node to check if the End.BIER address of a packet
   is the correct one bound to the sub-domain of a packet.

   * configure IACL on each interface of each BIER node k (or simply
   configure GIACL on each BIER node k) to allow packet with an End.BIER
   as destination address and the allowed source(s) as source address.

   This provides a way to ensure that the inter-domain source is allowed
   to access only the BIER IPv6 transport service bound to a sub-domain
   with a specific bit string length.

5.3.  ICMP Error Processing

   ICMP error packets generated within the BIER Domain are sent 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 BIER IPv6 packet is filled with wrong TTL, 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



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   positives" that generate a lot of "noise" in the log; therefore,
   implementations SHOULD have a knob to disable this logging.

   OAM functions of PING and TRACE for BIER IPv6 encapsulation may also
   need ICMP based on BIER IPv6 encapsulation and cause ICMP response
   message containing BIER option.  The ability of seperating such OAM
   ICMP packets from error ICMP packets caused by error is necessary for
   the availability of OAM, otherwise the OAM function may fail due to
   the rate-limiting of ICMP error packets.

5.4.  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
   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.

5.5.  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



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   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
   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) [RFC5996] 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.





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           +-------+--------+--------------------------+------------+
           | 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 for the helpful comments to improve
   this document.

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

   [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>.





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   [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>.

   [RFC5996]  Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
              "Internet Key Exchange Protocol Version 2 (IKEv2)",
              RFC 5996, DOI 10.17487/RFC5996, September 2010,
              <https://www.rfc-editor.org/info/rfc5996>.

   [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>.

   [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>.

   [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>.

9.2.  Informative References

   [I-D.ietf-bier-ipv6-requirements]
              McBride, M., Xie, J., Dhanaraj, S., and R. Asati, "BIER
              IPv6 Requirements", draft-ietf-bier-ipv6-requirements-03
              (work in progress), November 2019.

   [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-05 (work in
              progress), October 2019.



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   [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>.

   [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>.

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











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