PIM Signaling Through BIER Core
draft-ietf-bier-pim-signaling-09
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Expired".
|
|
|---|---|---|---|
| Authors | Hooman Bidgoli , Fengman Xu , Jayant Kotalwar , IJsbrand Wijnands , Mankamana Prasad Mishra , Zhaohui (Jeffrey) Zhang | ||
| Last updated | 2020-07-14 (Latest revision 2020-07-09) | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | In WG Last Call | |
| Document shepherd | Nabeel Cocker | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | Nabeel Cocker <nabeel.cocker@gmail.com> |
draft-ietf-bier-pim-signaling-09
Network Working Group H. Bidgoli, Ed.
Internet-Draft Nokia
Intended status: Informational F. Xu
Expires: January 10, 2021 Verizon
J. Kotalwar
Nokia
I. Wijnands
M. Mishra
Cisco System
Z. Zhang
Juniper Networks
July 09, 2020
PIM Signaling Through BIER Core
draft-ietf-bier-pim-signaling-09
Abstract
Consider large networks deploying traditional PIM multicast service.
Typically, each portion of these large networks have their own
mandates and requirements.
It might be desirable to deploy BIER technology in some part of these
networks to replace traditional PIM services. In such cases
downstream PIM states need to be signaled over BIER Domain toward the
source.
This draft explains the procedure to signal PIM joins and prunes
through a BIER Domain, as such enable provisioning of traditional PIM
services through a BIER Domain.
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 January 10, 2021.
Bidgoli, et al. Expires January 10, 2021 [Page 1]
Internet-Draft PIM Signaling Through BIER Core July 2020
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. Conventions used in this document . . . . . . . . . . . . . . 3
2.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 3
3. PIM Signaling Through BIER domain . . . . . . . . . . . . . . 5
3.1. Ingress BBR procedure . . . . . . . . . . . . . . . . . . 5
3.1.1. Determining EBBR on IBBR . . . . . . . . . . . . . . 6
3.1.2. Considering ECMP in EBBR selection . . . . . . . . . 6
3.1.3. PIM Signaling packet construction at IBBR . . . . . . 7
3.1.3.1. BIER packet construction at IBBR . . . . . . . . 8
3.2. Signaling PIM through the BIER domain procedure . . . . . 8
3.3. EBBR procedure . . . . . . . . . . . . . . . . . . . . . 9
4. Datapath Forwarding . . . . . . . . . . . . . . . . . . . . . 9
4.1. BFIR tracking of (S,G) . . . . . . . . . . . . . . . . . 9
4.2. Datapath traffic flow . . . . . . . . . . . . . . . . . . 9
5. PIM-SM behavior . . . . . . . . . . . . . . . . . . . . . . . 9
6. Applicability to MVPN . . . . . . . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
8. Security Considerations . . . . . . . . . . . . . . . . . . . 11
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
10.1. Normative References . . . . . . . . . . . . . . . . . . 11
10.2. Informative References . . . . . . . . . . . . . . . . . 11
Appendix A. . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
A.1. SPF . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
A.2. Indirect next-hop . . . . . . . . . . . . . . . . . . . . 12
A.2.1. Static Route . . . . . . . . . . . . . . . . . . . . 12
A.2.2. Interior Border Gateway Protocol (iBGP) . . . . . . . 12
A.3. Inter-area support . . . . . . . . . . . . . . . . . . . 13
A.3.1. Inter-area Route summarization . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
Bidgoli, et al. Expires January 10, 2021 [Page 2]
Internet-Draft PIM Signaling Through BIER Core July 2020
1. Introduction
Consider large networks deploying traditional PIM multicast service.
Typically, each portion of these large networks have their own
mandates and requirements.
It might be desirable to deploy BIER technology in some part of these
networks to replace traditional PIM services. In such cases
downstream PIM states need to be signaled over BIER Domain toward the
source.
This draft explains the procedure to signal PIM joins and prunes
through a BIER Domain, as such enable provisioning of traditional PIM
services through a BIER Domain.
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
2.1. Definitions
Some of the terminology specified in [I-D. rfc8279] is replicated
here and extended by necessary definitions:
BIER:
Bit Index Explicit Replication (The overall architecture of
forwarding multicast using a Bit Position).
BFR:
Bit Forwarding Router (A router that participates in Bit Index
Multipoint Forwarding).A BFR is identified by a unique BFR-prefix in
a BIER domain.
BFIR:
Bit Forwarding Ingress Router (The ingress border router that
performs BIER encapsulation). Each BFIR must have a valid BFR-id
assigned. In this draft BIER will be used for forwarding and
tunneling of control plane packet (i.e. PIM) and forwarding
dataplane packets. BFIR is term used for dataplane packet
forwarding.
BFER:
Bidgoli, et al. Expires January 10, 2021 [Page 3]
Internet-Draft PIM Signaling Through BIER Core July 2020
Bit Forwarding Egress Router. A router that participates in Bit
Index Forwarding as leaf. Each BFER must have a valid BFR-id
assigned. In this draft BIER will be used for forwarding and
tunneling of control plane packet (i.e. PIM) and forwarding
dataplane packets. BFIR is term used for dataplane packet
forwarding.
BBR:
BIER Boundary router. A router between the PIM domain and BIER
domain. Maintains PIM adjacency for all routers attached to it on
the PIM domain and terminates the PIM adjacency toward the BIER
domain.
IBBR:
Ingress BIER Boundary Router. An ingress router from signaling point
of view. It maintains PIM adjacency toward the PIM domain and
determines if PIM joins and prunes arriving from PIM domain need to
be signaled across the BIER domain. If so it terminates the PIM
adjacency toward the BIER domain and signals the PIM joins/prunes
through the BIER core.
EBBR:
Egress BIER Boundary Router. An egress router in BIER domain from
signaling point of view. It terminates the BIER packet and forwards
the signaled joins and prunes into PIM Domain.
BFT:
Bit Forwarding Tree used to reach all BFERs in a domain.
BIFT:
Bit Index Forwarding Table.
BIER sub-domain:
A further distinction within a BIER domain identified by its unique
sub-domain identifier. A BIER sub-domain can support multiple
BitString Lengths.
BFR-id:
An optional, unique identifier for a BFR within a BIER sub-domain.
Bidgoli, et al. Expires January 10, 2021 [Page 4]
Internet-Draft PIM Signaling Through BIER Core July 2020
3. PIM Signaling Through BIER domain
BBR BBR
|--PIM Domain--|-----BIER domain-----|--PIM domain--|
S--( A )----------( B ) ---- ( C ) ---- ( D )----------( E )--h
EBBR IBBR
Sig <-----PIM-----|<--BIER Tunneling----|<----PIM------
(new)
BFIR BFER
------------->|--------BIER-------->|-------------> Datapath
(no change)
Figure 1: BIER boundry router
As per figure 1, the procedures of PIM signaling is done at the BIER
boundary router. The BIER boundary routers (BBR) are connected to
PIM capable routers toward the PIM domain and BIER routers toward the
BIER domain. PIM routers in PIM domain continue to send PIM state
messages to the BBR. The BBR will create PIM adjacency between all
the PIM routers attached to it on the PIM domain. That said the BBR
does not propagate all PIM packets natively into the BIER domain.
Instead when it determines that the PIM join or prune messages needs
to be signaled through the BIER domain it will tunnel the PIM packet
through the BIER network. This tunneling is only done for signaling
purposes and not for creating a PIM adjacency between the two
disjoint PIM domains through the BIER domain.
The terminology ingress BBR (IBBR) and egress BBR (EBBR) are relative
from signaling point of view.
The ingress BBR will determine if an arriving PIM join or prune needs
to be signaled across the BIER domain. While the egress BBR will
determine if the arriving BIER packet is a signaling packet and if so
it will generate a PIM signaling packet toward its attached PIM
domain.
The BFER and BFIR are BBR from datapath point of view. It should be
noted the new procedures in this draft are only applicable to
signaling and there are no changes from datapath point of view.
3.1. Ingress BBR procedure
IBBR will create PIM adjacency to all PIM routers attached to it
toward the PIM domain.
Bidgoli, et al. Expires January 10, 2021 [Page 5]
Internet-Draft PIM Signaling Through BIER Core July 2020
When a PIM join or prune for certain (S,G) arrives, the IBBR first
determines whether the join or prune is meant for a source that is
reachable through the BIER domain. As an example, this source is
located in a disjoint PIM domain that is reachable through the BIER
domain. If so the IBBR will try to resolve the source via an EBBR
closest to the source.
The procedure to find the EBBR (BFIR from datapath point of view) can
be via many mechanisms explained in more detail in upcoming section.
After discovering the EBBR and its BFR-ID, the IBBR will include a
new PIM Join Attribute in the Join/prune message as per [RFC5384].
Two new "BIER IBBR" attributes are defined and explained in upcoming
section. The PIM Join Attribute is used on EBBR to obtain necessary
BIER information to build its multicast states. In addition the IBBR
will change the PIM signaling packet source IP address to its BIER
prefix address (standard PIM procedure). It will also keep the
destination address as the well known multicast IP address. It then
will construct the BIER header. The signaling packet, in this case
the PIM join/prune packet, is encapsulated in the BIER header and
transported through BIER domain to EBBR.
The IBBR will track all the PIM interfaces on the attached PIM domain
which are interested in a certain (S,G). It creates multicast states
for arriving (S,G)s from PIM domain, with incoming interface as BIER
"tunnel" interface and outgoing interface as the PIM domain
interface(s) on which PIM Join(s) were received on.
3.1.1. Determining EBBR on IBBR
As it was explained in previous section, IBBR needs to determine the
EBBR closest to the source. This is needed to encode the BIER header
BitString field to forward the signaling packet through the BIER
domain.
It should be noted, the PIM domains can be either part of the same
IGP area as BIER domain(single area) or are stitched to the BIER
domain via an ABR or ASBR routers. As such on IBBR, there can be
many different procedures to determine the EBBR. Some examples of
these procedures have been provided in Appendix A.
3.1.2. Considering ECMP in EBBR selection
If the lookup for source results into multiple EBBRs, then the EBBR
selection algorithm should ensure that all signaling for a particular
(C-S, C-G) is forward to a single EBBR. How the this selection is
done is vendor specific and beyond this draft. As an example it can
Bidgoli, et al. Expires January 10, 2021 [Page 6]
Internet-Draft PIM Signaling Through BIER Core July 2020
be round robin per (C-S, C-G) or smallest EBBR IP for all (C-S,
C-G)s.
3.1.3. PIM Signaling packet construction at IBBR
To ensure all necessary BIER information needed by EBBR is present in
the BIER signaling message, a new PIM Join Attribute [RFC5384] is
used. EBBR can use this attribute to build its multicast states, as
described in EBBR procedure section. This new PIM join Attribute is
added to PIM signaling message on the IBBR. Its format is as follow:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|F|E| Type=tbd | Length | Addr Family | BIER info
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...
Figure 2: PIM Join Attribute
F bit: The Transitive bit. Specifies whether this attribute is
transitive or non-transitive. MUST be set to zero. This attribute
is ALWAYS non-transitive.
E bit: End-of-Attributes bit. Specifies whether this attribute is
the last. Set to zero if there are more attributes. Set to 1 if
this is the last attribute.
Type: TBD assign by IANA
Length: The length in octets of the attribute value. MUST be set to
the length in octets of the BIER info +1 octet to account for the
Address Family field. For IPv4 AF Length = 7+1 For IPv6 AF Length =
19+1
Addr Family: Signaled PIM Join/Prune address family as defined in
[RFC7761]
BIER Info: IBBR Prefix (IPv4 or IPv6), SD, bfr-id as per below figure
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ IBBR Prefix IPv4 or IPv6 ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| subdomain-id | BFR-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: PIM Join Attribute detail
Bidgoli, et al. Expires January 10, 2021 [Page 7]
Internet-Draft PIM Signaling Through BIER Core July 2020
3.1.3.1. BIER packet construction at IBBR
The BIER header will be encoded with the BFR-id of the IBBR(with
appropriate bit set in the bitstring) and the PIM signaling packet is
then encapsulated in the packet.
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BIFT-id | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Nibble | Ver | BSL | Entropy |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|OAM|Rsv| DSCP | Proto | BFIR-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BitString (first 32 bits) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ BitString (last 32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: BIER header
BIERHeader.Proto = IPv4 or IPv6
BIERHeader.BitString= Bit corresponding to the BFR-ID of the EBBR
BIERHeader.BFIR-id = BFR-Id of the BER originating the encapsulated
PIM packet, i.e. the IBBR.
Rest of the values in the BIER header are determined based on the
network (MPLS/non-MPLS), capabilities (BSL), and network
configuration.
3.2. Signaling PIM through the BIER domain procedure
Throughout the BIER domain the BIER forwarding procedure is on par
with RFC 8279. No BIER router will examine the BIER packet
encapsulating the PIM signaling packet. As such there is no
multicast state built in the BIER domain.
The packet will be forwarded through the BIER domain until it reaches
the BER with matching BFR-ID as in the BIERHeader.Bitstring. EBBR
will remove the BIER header and examine the PIM IPv4 or IPv6
signaling packet farther as per EBBR Procedure section.
Bidgoli, et al. Expires January 10, 2021 [Page 8]
Internet-Draft PIM Signaling Through BIER Core July 2020
3.3. EBBR procedure
EBBR will remove the BIER header and determine this is a signaling
packet. The Received PIM join/prune Signaling packet is processed as
if it were received from neighbors on a virtual interface, (i.e. as
if the pim adjacency was presents, regardless of the fact there is no
adjacency)
The EBBR will build a forwarding table for the arriving (S,G) using
the obtained BFIR-id and the Sub-Domain information from BIER Header
and/or the PIM join Attributes added to the PIM Signaling packet. In
short it tracks all IBBRs interested in this (S,G). This is
explained in section 4.1.
The multicast state on EBBR will contain PIM domain incoming
interfaces, according to PIM specification and outgoing interfaces
based on the above build forwarding table.
It should be noted EBBR will maintain PIM adjacency toward the PIM
domain and all PIM routers which are connected to it. At this point
the end-to-end multicast traffic flow setup is complete.
4. Datapath Forwarding
4.1. BFIR tracking of (S,G)
For a specific Source and Group, BFIR (EBBR)should track all the
interested BFERs (IBBRs) via arriving PIM signaling from BIER Domain.
BFIR builds its (s,g)forwarding state with incoming interface (IIF)
as the RPF interface (in PIM domain) towards the source and one of
the outgoing interfaces as for sending to tracked BFERs in the SD.
4.2. Datapath traffic flow
When the multicast data traffic arrives on the BFIR (EBBR) the router
will find all the interested BFERs for that specific (S,G). The
router then constructs the BIERHeader.BitString with all the BFER
interested in the group and will forward the packet to the BIER
domain. The BFER(s) will accept the packets and remove the BIER
header and forward the multicast packet as per pre-build multicast
state for (S,G) and its outgoing interfaces.
5. PIM-SM behavior
The procedures described in this document can work with ASM as long
as static RP or embedded RP for IPv6 is used. Future drafts would
cover BSR and more complicated SM discovery mechanisms.
Bidgoli, et al. Expires January 10, 2021 [Page 9]
Internet-Draft PIM Signaling Through BIER Core July 2020
It should be noted that this draft only signals PIM Joins and Prunes
through the BIER domain and not any other PIM message types including
PIM Hellos or Asserts. As such functionality related to these other
type of massages will not be possible through a BIER domain with this
draft and future drafts might cover these scenarios. As an example
DR selection should be done in the PIM domain or if the PIM routers
attached to IBBRs are performing DR selection there needs to be a
dedicated PIM interface between these routers.
In case of PIM ASM Static RP or embedded RP for IPv6 the procedure
for leaves joining RP is same as above. It should be noted that for
ASM, the EBBRs are determined with respect to the RP instead of the
source.
6. Applicability to MVPN
With just minor changes, the above procedures apply to MVPN as well,
with BFIR/BFER/EBBR/IBBR being VPN PEs. All the PIM related
procedures, and the determination of EBBR happens in the context of a
VRF, following procedures for PIM-MVPN.
When a PIM packet arrives from PIM domain attached to the VRF (IBBR),
and it is determined that the source is reachable via the VRF through
the BIER domain, a PIM signaling message is sent via BIER to the
EBBR. In this case usually the PE terminating the PIM-MVPN is the
EBBR. A label is imposed before the BIER header is imposed, and the
"proto" field in the BIER header is set to 1 (for "MPLS packet with
downstream-assigned label at top of stack"). The label is advertised
by the EBBR/BFIR to associate incoming packets to its correct VRF.
In many scenarios a label is already bound to the VRF loopback
address on the EBBR/BFIR and it can be used.
When a multicast data packet is sent via BIER by an EBBR/BFIR, a
label is imposed before the BIER packet is imposed, and the "proto"
field in the BIER header is set to 1 (for "MPLS packet with
downstream-assigned label at top of stack"). The label is assigned
to the VPN consistently on all VRFs [draft-zzhang-bess-mvpn-evpn-
aggregation-label].
If the more complicated label allocation scheme is needed for the
data packets as specified in [draft-zzhang-bess-mvpn-evpn-
aggregation-label], then additional PMSI signaling is needed as
specified in [RFC6513].
To support per-area subdomain in this case, the ABRs would need to
become VPN PEs and maintain per-VPN state so it is unlikely
practical.
Bidgoli, et al. Expires January 10, 2021 [Page 10]
Internet-Draft PIM Signaling Through BIER Core July 2020
7. IANA Considerations
This document contains no actions for IANA.
8. Security Considerations
The procedures of this document do not, in themselves, provide
privacy, integrity, or authentication for the control plane or the
data plane. For a discussion of the security considerations
regarding the use of BIER, please see RFC8279 and RFC8296. Security
considerations regarding PIM protocol is based on RFC 7761.
9. Acknowledgments
The authors would like to thank Eric Rosen, Stig Venaas for thier
reviews and comments.
10. References
10.1. Normative References
[RFC8279] "Wijnands, IJ., Rosen, E., Dolganow, A., Przygienda, T.
and S. Aldrin, "Multicast using Bit Index Explicit
Replication"", October 2016.
10.2. Informative References
[BIER-MVPN]
"Rosen, E., Ed., Sivakumar, M., Wijnands, IJ., Aldrin,
S.,Dolganow, A., and T. Przygienda, "Multicast VPN Using
BIER", internet-draft draft-ietf-bier-mvpn-11", March
2018.
[RFC8401] "Ginsberg, L., Przygienda, T., Aldrin, S., and Z. Zhang,
"BIER Support via ISIS"", June 2018.
[RFC8444] "Psenak, P., Kumar, N., Wijnands, IJ., Dolganow, A.,
Przygienda, T., Zhang, Z., and S. Aldrin, "OSPF Extensions
for Bit Index Explicit Replication"", June 2018.
Appendix A.
This appendix provides some examples and routing procedures that can
be used to determine the EBBR on IBBR. It should be noted, the PIM
domains can be either part of the same IGP area as BIER domain(single
area) or are stitched to the BIER domain via an ABR or ASBR routers.
As such on IBBR, there can be many different procedures to determine
the EBBR. Not all procedures are listed below.
Bidgoli, et al. Expires January 10, 2021 [Page 11]
Internet-Draft PIM Signaling Through BIER Core July 2020
A.1. SPF
On IBBR SPF procedures can be used to find the EBBR closest to the
source.
Assuming the BIER domain consists of all BIER forwarding routers, SPF
calculation can identify the router advertising the prefix for the
source. A post process can find the EBBR by walking from the
advertising router back to the IBBR in the reverse direction of
shortest path tree branch until the first BFR is encountered.
A.2. Indirect next-hop
Alternatively, the route to the source could have an indirect next-
hop that identifies the EBBR. These methods are explained in the
following sections.
A.2.1. Static Route
On IBBR there can be a static route configured for the source, with
source next-hop set as EBBR BIER prefix.
A.2.2. Interior Border Gateway Protocol (iBGP)
Consider the following topology:
BBR BBR
EBBR IBBR
|--PIM Domain--|-----BIER domain-----|--PIM domain--|
S--( A )----------( B ) ---- ( C ) ---- ( D )----------( E )--h
Figure 2
Figure 5: Static Route
Suppose BGP is enable between EBBR (B) and IBBR (D) and the PIM
Domain routes are redistributed to the BIER domain via BGP. This
would include the Multicast Source IP address (S), which resides in
the PIM Domain. In such case BGP should use the same loopback
interface as its next-hop as the BBR prefix. This will ensure that
all PIM domain routes, including the Multicast Source IP address (S)
are resolve via BBR's BIER prefix id as their next-hop. When the
host (h) triggers a PIM join message to IBBR (D), IBBR tries to
resolve (S). It resolves (S) via BGP installed route and realizes
its next-hop is EBBR (B). IBBR will use this next-hop (B) to find
its corresponding BIER bit index.
This procedure is inline with RFC6826 mLDP in-band signaling section
Bidgoli, et al. Expires January 10, 2021 [Page 12]
Internet-Draft PIM Signaling Through BIER Core July 2020
A.3. Inter-area support
If each area has its own BIER sub-domain, the above procedure for
post-SPF could identify one of the ABRs and the EBBR. If a sub-
domain spans multiple areas, then additional procedures as described
in A.2 is needed.
A.3.1. Inter-area Route summarization
In a multi-area topology, a BIER sub-domain can span a single area.
Suppose this single area is constructed entirely of BIER capable
routers and the ABRs are the BIER Boundary Routers attaching the BIER
sub-domain in this area to PIM domains in adjacent areas. These BBRs
can summarize the PIM domain routes via summary routes, as an example
for OSPF, a type 3 summary LSAs can be used to advertise summary
routes from a PIM domain area to the BIER area. In such scenarios
the IBBR can be configured to look up the Source via IGP database and
use the summary routes and its Advertising Router field to resolve
the EBBR. The IBBR needs to ensure that the IGP summary route is
generated by a BFR. This can be achieved by ensuring that BIER Sub-
TLV exists for this route. If multiple BBRs (ABRs) have generated
the same summary route the lowest Advertising Router IP can be
selected or a vendor specific hashing algorithm can select the
summary route from one of the BBRs.
Authors' Addresses
Hooman Bidgoli (editor)
Nokia
Ottawa
Canada
Email: hooman.bidgoli@nokia.com
Fengman Xu
Verizon
Richardson
US
Email: fengman.xu@verizon.com
Bidgoli, et al. Expires January 10, 2021 [Page 13]
Internet-Draft PIM Signaling Through BIER Core July 2020
Jayant Kotalwar
Nokia
Montain View
US
Email: jayant.kotalwar@nokia.com
IJsbrand Wijnands
Cisco System
Diegem
Belgium
Email: ice@cisco.com
Mankamana Mishra
Cisco System
Milpitas
USA
Email: mankamis@cisco.com
Zhaohui Zhang
Juniper Networks
Boston
USA
Email: zzhang@juniper.com
Bidgoli, et al. Expires January 10, 2021 [Page 14]