Use of BIER IPv6 Encapsulation (BIERv6) for
Multicast VPN in IPv6 networksHuawei Technologiesxiejingrong@huawei.comFutureweimmcbride7@gmail.comHuawei Technologiessenthil.dhanaraj@huawei.comChina Mobilegengliang@chinamobile.comThis draft defines the procedures and messages for using Bit Index
Explicit Replication (BIER) for Multicast VPN Services in IPv6 networks
using the BIER IPv6 encapsulation. It provides a migration path for
Multicast VPN service using BIER MPLS encapsulation in MPLS networks to
multicast VPN service using BIER IPv6 encapsulation (BIERv6) in IPv6
networks.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
and .Bit Index Explicit Replication (BIER) 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. BIERv6 refers to the deployment of BIER
in IPv6 networks using the BIER IPv6 encapsulation format defined in
.This document describes a method to realize MVPN services using BIER
as a P-tunnel in the IPv6 Networks (BIERv6 Networks). It defines a
method to use an IPv6 address, called Src.DTx in this document, as
source address of an IPv6 header, to identify the MVPN instance at the
Egress PE. The Src.DTx address used as source address of a BIERv6 packet
represent both the context and the upstream-assigned VPN Label
in MVPN scenario defined in .The Src.DTx address can be a normal IPv6 address of the BFR, for
example, a loopback address of the BFR. The Src.DTx address can also be an
IPv6 address allocated from an IPv6 address block, for example, an IPv6
address allocated from an SRv6 locator if BIERv6 MVPN is deployed in an
SRv6 network.In particular, MVPN deployment in IPv6 networks relies on L3VPN
deployment on IPv6 networks firstly, thus the c-multicast routing
procedure like UMH Selection can be done. As an example, the L3VPN
deployment in SRv6 networks can be referred to .GTM defined in [RFC7716] is also covered in this document, as GTM
shares the same BGP-MVPN signaling, while providing an approach of
Non-VPN multicast over a service provider core with various P-tunnel
type. For the same reason of UMH selection as a base of GTM, the Global
IPv4/IPv6 over SRv6 networks can be referred to .Readers of this document are assumed to be familiar with the
terminology and concepts of the documents listed as Normative
References. Additionally the following terms are used through out the
document.BIERv6 - BIER in IPv6 networks using the BIERv6 encapsulation
format defined in .SRv6 - Segment Routing instantiated on the IPv6 dataplane as
defined in .SRv6 SID - SRv6 Segment Identifier as defined in .End.DTx - Refers to the functions End.DT6, End.DT4, End.DT46
defined in .Src.DTx - Refers to the functions Src.DT4, Src.DT6, Src.DT46
defind in this document.SRv6 L3 Service - L3VPN/Global-L3 service in SRv6 networks
defined in , or
MVPN/GTM service in BIERv6 networks defined in this document.The BGP-MVPN I-PMSI A-D (Type 1) or S-PMSI A-D (Type 3) route (called
x-PMSI A-D route in this document), advertised by Ingress PE carries the
BIER (Type 11) PTA as specified in . The BIER
PTA carried in the x-PMSI A-D route is used for explicitly tracking the
receiver-site PEs which are interested in a specific multicast flow. It
includes three BIER-specific fields, Sub-domain-id, BFR-id, and
BFR-prefix. For BIER P-tunnel using the BIERv6 encapsulation in IPv6
networks, the BFR-prefix field in the PTA MUST be set to the BFIR IPv6
prefix and the MPLS Label field in the PTA MUST set to 0. For MVPN over
BIERv6, the Src.DTx IPv6 address of the BFIR is used to identify the VRF
instead of an MPLS Label. The Src.DTx IPv6 Address (Src.DT6 or Src.DT4
or Src.DT46) MUST be carried within an SRv6 L3 Service TLV of BGP Prefix-SID attribute in
the x-PMSI A-D route.The Ingress PE encapsulates the c-multicast IP packet with BIERv6
header and the source address in the outer IPv6 header will be set to
the Src.DTx IPv6 address advertised in the BGP-MVPN x-PMSI A-D routes.
See section 3 of for
the detailed packet format.Egress PE (BFER) receiving the x-PMSI A-D routes with BIER PTA and
SRv6 L3 Service TLV learns the Src.DTx IPv6 address and uses it to
identify the VRF of the c-multicast packet.When Egress PE receives a BIERv6 packet and the self bfr-id is set in
the bit-string field of the BIERv6 header, it retrieves the Src.DTx IPv6
address from the source address of the IPv6 header to determine the VRF
and the Address Family (AF) of the c-multicast data packet, and performs
the MFIB lookup in the corresponding table. specifies the protocol and procedures to be
followed by the Ingress and Egress PEs to use BIER as a P-tunnel for
MVPN in MPLS networks. This section specifies the required changes and
procedures in addition to support BIER as a P-tunnel in IPv6 networks
using BIERv6.In a IPv6 service provider network, many of the IP address fields
used in the BGP-MVPN routes are IPv6 address as specified in . These are listed below."Originating Router's IP Address" in the NLRI of Type 1 or Type 3
BGP-MVPN route is an IPv6 address."Network Address of Next Hop" field in the MP_REACH_NLRI
attribute is an IPv6 address.Route Targets Extended Community (EC) used in C-multicast join
(Type 6 or 7) route or Leaf A-D (Type 5) route is an IPv6 Address
Specific Extended Community, where the Global Administrator field
will be an IPv6 address identifies the Upstream PE or the UMH."VRF Route Import Extended Community (EC)" carried by unicast
VPN-IPv4 or VPN-IPv6 routes as [RFC6515] specifies, or SAFI 1, 2, or
4 unicast routes, or MVPN (SAFI 5) Source-Active routes as [RFC7716]
specifies.On the Ingress PE (BFIR), the BGP-MVPN x-PMSI A-D route is
constructed as per the procedures specified in
and with the following specifications.MPLS Label field in the BIER PTA MUST be set to Zero.BFR-prefix field in the BIER PTA MUST be set to the Ingress PEs
(BFIR) IPv6 BFR-Prefix Address. It does not need to be the same as
the other IPv6 address of the x-PMSI AD route.Route MUST also carry an BGP Prefix SID attribute with an SRv6 L3
Service TLV carrying an Src.DTx IPv6 address uniquely identifying
the MVPN instance.If the MVPN is IPv4 MVPN, the Src.DTx can be either Src.DT4 or
Src.DT46. If the MVPN is IPv6 MVPN, the Src.DTx can be either Src.DT6 or
Src.DT46. The distribution of the x-PMSI A-D routes uses the Src.DTx
according to the local configuration, and is independent to the use of
End.DTx in VPN-IP unicast routes of this VPN. For example, one can use
End.DT46 for VPNv4 and VPNv6 unicast routes, but use Src.DT4 for the
MVPN routes for the same VPN. Another example, one can use End.DX for
VPNv4 unicast routes, but use Src.DT46 for the MVPN routes for the same
VPN.BFIR MAY carry the BGP Prefix-SID attribute only in I-PMSI A-D route
when I-PMSI A-D route is used, while other S-PMSI A-D routes do not
carry the BGP Prefix-SID attribute.BFIR MAY carry the BGP Prefix-SID attribute only in wildcard S-PMSI
A-D routes when the "S-PMSI Only" mode as described in is used, while other S-PMSI A-D routes do not carry
the BGP Prefix-SID attribute.On the Egress PE (BFER), the BGP-MVPN x-PMSI A-D route is processed
as per the procedures specified in and with the
following specifications:The MPLS Label field in the BIER PTA of the BGP-MVPN x-PMSI A-D
route MUST be ignored and MUST not be used for the identification of
the VRF.The BGP-MVPN x-PMSI A-D route MUST be dropped if the BFR-prefix
field in the BIER PTA is not an IPv6 address.The BGP-MVPN x-PMSI A-D route MUST be dropped if it does not
carry a Src.DTx IPv6 address in the SRv6 L3 Service TLV in BGP
Prefix SID attribute.Leaf A-D route originated by the Egress PE (BFER) MUST carry the
BIER PTA with the BFR-prefix field set to the BFER IPv6
BFR-prefix.Valid BGP-MVPN x-PMSI A-D route received by an Egress PE (BFER)
is stored locally, and the Src.DTx IPv6 Address carried in the SRv6 L3
service TLV is used to identify the VRF of a c-multicast data packet.
This may be populated into forwarding table only when there is
c-multicast flow state with UMH of the specific BFIR this Src.DTx
located in.If more than one x-PMSI A-D routes belonging to the same VRF has
different Src.DTx value, the processing is determined by the local
policy of the BFER.If more than one x-PMSI A-D routes belonging to different VRF has the
same Src.DTx value, the BFER must log an error, and a BIERv6 packet with
this Src.DTx as the IPv6 source address MUST be dropped.The BGP Prefix-SID attribute (which may include the Src.DTx in SRv6
L3 Service TLV) MUST NOT be carried in Leaf A-D route upon sending, and
MUST be ignored upon reception.As specified in [RFC7716], Global Table Multicast (GTM) uses the same
Subsequent Address Family Identifier (SAFI) value, the same Network
Layer Reachability Information (NLRI) format, and the same procedures of
MVPN with only a few adaptions. It support for both IPv4 and IPv6
multicast flows over either an IPv4 or IPv6 SP infrastructure. GTM over
BIERv6 core is obviously a case of IPv4/IPv6 multicast over an IPv6 SP
infrastructure with BIERv6 data-plane.The BIER (Type 11) PTA attribute and the BGP Prefix-SID attribute are
carried in the x-PMSI A-D route in GTM cases. When the a BGP-MVPN x-PMSI
A-D route is received by Egress PE, it is stored locally, and the
Src.DTx IPv6 Address of the Ingress PE in the route is used to determine
the VRF of a packet, which is the 'public' VRF in the case of GTM.There are some other attributes listed below for GTM over a BIERv6
core:Route Distinguishers - the RD field of a BGP-MVPN route's NLRI
MUST be set to zero (i.e., to 64 bits of zero) to represent a
Non-VPN GTM. See section 2.2 of [RFC7716].Route Targets Extended Community (EC) - The RT EC carried by the
BGP-MVPN C-multicast (Type 6 or 7) route or Leaf A-D (Type 4) route
MUST be an IPv6-address-specific Extended Community (EC). The Global
Administrator field identifies the Upstream PE or the UMH, and the
Local Administrator field MUST always be set to zero in GTM
case.VRF Route Import Extended Community (EC) - The VRF Route Import
EC used in BIERv6 core MUST be an IPv6-address-specific EC if used,
either used in UMH-eligible unicast routes having a SAFI of 1, 2, or
4, or used in the MVPN (SAFI of 5) Source Active A-D route.GTM IPv4 multicast over an BIERv6 core may be considered an
alternative to support IPv4 IPTV content delivery during transition to
IPv6 period comparing to [RFC8114]. They both use IPv4-in-IPv6
encapsulation, while BIERv6 uses an additional BIER header within an
IPv6 Extension header to support stateless core.BIER IPv6 encapsulation (BIERv6) is used for forwarding the
c-multicast traffic through an IPv6 core. The following diagram shows
the progression of an MVPN c-multicast packet as it enters and leaves
the intra-AS service-provider network.In case of inter-AS scenario, BIERv6 packets may travel through
unicast to a Boarder Router (BR), and then replicate in a single
intra-AS BIERv6 domain. How such non-segmented BIERv6 scenario can be
supported is outside the scope of this document.How segmented MVPN, for example, between BIERv6 and BIERv6, or
between BIERv6 and Ingress Replication(IR) in Non-MPLS IPv6 networks,
is outside the scope of this document.The Src.DTx SHOULD support as destination address of an ICMPv6
packet. If a loopback address of the BFR is used as Src.DTx address,
this is supported. If an address from an SRv6 locator is used as
Src.DTx address, the following pseudo-code describes how a packet
with Src.DTx as destination address is handled: Ref1: ICMPv6 packet using Src.DT4, Src.DT6 or Src.DT46 as
destination address.Each BFIR is expected to know the Maximum Transmission Unit (MTU)
of the BIER domain. This may be known by provisioning, or by method
specified in [draft-ietf-bier-mtud]. The section 3 of [RFC8296]
applies.The ingress PE (BFIR) should not copy the Time to Live (TTL) field
from the payload IP header received from a CE router to the delivery
IP header. Setting the TTL of the delivery IP header is determined by
the local policy of the ingress PE (BFIR) router per section 3 of
[RFC8296].The security considerations SEC-1, SEC-2, SEC-3 defined in apply equally to
this document.Allocation is expected from IANA for the following Src.DTx functions
codepoints from the "SRv6 Endpoint Behaviors" sub-registry.Values 68, 69, 70 is suggested for Src.DT6, Src.DT4, Src.DT46
respectively.TBD.