Internet DRAFT - draft-geng-bier-sr-multicast-deployment
draft-geng-bier-sr-multicast-deployment
Network Working Group L. Geng
Internet-Draft L. Wang
Intended status: Standards Track China Mobile
Expires: January 3, 2019 J. Xie
M. McBride
G. Yan
Huawei Technologies
July 2, 2018
MVPN using Segment Routing and BIER for High Reachability Multicast
Deployment
draft-geng-bier-sr-multicast-deployment-00
Abstract
Bit Index Explicit Replication (BIER) introduces a stateless
multicast approach for a specific IGP area. Segment Routing
introduces an approach for end-to-end stateless deployment for both
inter-area and inter-as scenarios. This document proposes a MVPN
using Segment Routing and BIER for a high reachability multicast
deployment.
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].
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
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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
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 3, 2019.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Problem Statement and Considerations . . . . . . . . . . . . 3
3.1. Problem Statement and Considerations . . . . . . . . . . 3
4. MVPN Using SR-MPLS and BIER-MPLS Encapsulation . . . . . . . 4
4.1. Anchor information Advertisement and Usage . . . . . . . 4
4.2. MVPN Forwarding State and Forwarding Procedure . . . . . 6
5. MVPN Using SRv6 and BIER-IPv6 Encapsulation . . . . . . . . . 7
5.1. Anchor information Advertisement and Usage . . . . . . . 7
5.2. MVPN Forwarding State and Forwarding Procedure . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
9.1. Normative References . . . . . . . . . . . . . . . . . . 8
9.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
Bit Index Explicit Replication (BIER) [RFC8279] introduces a
stateless multicast approach for a specific IGP area. Segment
Routing [I-D.ietf-spring-segment-routing] introduces an approach for
end-to-end stateless deployment for both inter-area and inter-as
scenario. An end-to-end VPN deployment may benefit from the
combination of this two technology in which the stateless nature can
be maintained. This document proposes an MVPN deployment with high
reachability in such scenario using both Segment Routing and BIER.
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2. Terminology
Readers of this document are assumed to be familiar with the
terminology and concepts of the documents listed as Normative
References.
3. Problem Statement and Considerations
3.1. Problem Statement and Considerations
In a BIER deployment in multi-area or multi-AS network, a segmented
MVPN has to be used. As a result, multicast states are created at
the segment boundary. The per-flow multicast states are maintained
on the routers which are considered beyond of the "MVPN service"
sites. This significant disadvantage for multicast service
deployment is due to the poor reachability of BIER and is hard to
solve solely by BIER itself.
Segment Routing, however, has high reachability for both multi-area
and multi-as deployment. VPN services can use pre-defined Segments
(SIDs) on the area boundary routers (ABR) or AS boundary routers
(ASBR) for end-to-end deployment, without requiring such boundary
routers to include per-vpn or per-flow states, or per-vpn or per-flow
signaling to establish the end-to-end connection.
BIER and Segment Routing can be used for different partition of an
end-to-end MVPN service deployment. A packet with BIER encapsulation
is carried by Segment Routing to a boundary router. When reaching
the boundary router, it is replicated according to the BitString in
the BIER encapsulation to destination routers. Hence, the whole
multicast deployment can be stateless end-to-end.
A typical scenario for this type of deployment is in a service-
provider network for business L3VPN service with multicast as defined
in [I-D.ietf-bier-use-cases]. Service provider network tends to be
very heterogeneous with full-mesh backbone network, ring-shaped metro
networks for sparse area coverage, and sometime a fabric for dense
area coverage. A source router can send multicast packets to each of
the boundary routers of each metro network, with a loose path
selection in the full-mesh core network to avoid overloading by using
Segment Routing. The boundary router or boundary routers replicate
the packets to its own metro network according to the BIER
encapsulation.
To achieve the end-to-end statelessness, the boundary router will not
proxy any per-vpn or per-flow state. Instead, each of the edge
routers, in a specific metro network, directly tell the interest of
some multicast flow to the ingress edge router. This is the same as
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the L3VPN deployed end-to-end on Option-C style or SR style. For
MVPN service, this can be done by the current BGP MVPN signaling.
While for MVPN using Segment Routing and BIER, it is required to
include the information of boundary router(s) of the area the egress
edge router belongs to. The boundary router(s) can be thought as
anchor(s) of the area for BIER replication.
Below is an example of end-to-end MVPN deployment on a simple network
containing one ABR in each of the edge network area.
+------+ +------+ +------+ +------+
SRC---| PE11 | | ABR1 | | ABR2 | | PE21 |---RCV
+------+ +------+ +------+ +------+
|<--- Area 1--->|<--- Area 0--->|<--- Area 2--->|
| | | |
|---------- BIER in SR -------->|----- BIER --->|
| | |
|<------------ MVPN E2E Deployment ------------>|
Figure 1: MVPN using BIER and SR for E2E deployment
A more realistic network may contain two ABRs in each metro network
area for realibility.
+------+ +------+
| ABR1a| | ABR2a|
+------+ +------+ +------+ +------+
SRC---| PE11 | | PE21 |---RCV
+------+ +------+ +------+ +------+
| | ABR1b| | ABR2b| |
| +------+ +------+ |
| | | |
|<--- Area 1--->|<--- Area 0--->|<--- Area 2 --->|
| (Metro) | (CORE) | (Metro) |
| | | |
|---------- BIER in SR -------->|----- BIER ---->|
| | |
|<------------ MVPN E2E Deployment ------------->|
Figure 2: MVPN using BIER and SR for E2E deployment and protection
4. MVPN Using SR-MPLS and BIER-MPLS Encapsulation
4.1. Anchor information Advertisement and Usage
In an area of the receiver side, the anchor router or routers
advertise the BIER Label, the router IP, and the associated Sub-
domain, BSL and SI. The egress edge routers receive this information
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accordingly. When an egress edge router advertiseing MVPN Leaf A-D
routes to the ingress edge router at the sender side, it includes the
anchor router IP, the anchor router BIER Label, together with the
egress edge router's Sub-domain, BFR-prefix and BFR-id, just as the
PTA defined in [I-D.ietf-bier-mvpn].
For a deployment where more than one (typically two) anchor routers
exist in the area, it is expected to use only one BIER sub-domain for
the ease of configuration, while supporting the anchor routers with
different BIER labels or with same BIER label (anycast label). The
BIER label of an anchor is selected from SRGB and called a BIER SRGB-
label. Each of the routers in the area do not have to allocate a
local label (from SRLB) for a specific (Sub-domain, BSL, SI) tuple
when building the BIER forwarding table. Instead, it uses the BIER
SRGB-label for building the BIER forwarding table of the BIER label
itself. More than one BIER SRGB labels for the same (Sub-domain,
BSL, SI) tuple are allowed, each forming a forwarding table, and the
local-allocated (from SRLB) BIER label forwarding table of the same
(Sub-domain, BSL, SI) tuple can coexist as well.
Procedures of building the BIER SRGB label forwarding table are
outside the scope of this document.
For many areas, it is not required to have a universe-unique sub-
domain number or same sub-domain with universe-unique SI number from
0 to 255. For example, it is allowed for area 2 having a sub-domain
0 and SI from 0 to 10, while area 3 having a sub-domain 0 and SI from
0 to 10 too, only if their anchor routers are not the same.
The anchor information of Hybird SR and BIER MPLS is carried in a
specific PTA as below.
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+------------------------------------+
| Flags (1 octet) |
+------------------------------------+
| Tunnel Type = TBD (1 octet) |
+------------------------------------+
| MPLS Label (3 octets) |
+------------------------------------+ ------+
| Sub-domain-id (1 octet) | |
+------------------------------------+ |
| BFR-id (2 octets) | |
+------------------------------------+ |
| BFR-prefix (4 or 16 octets) | Tunnel Identifier
+------------------------------------+ |
| Anchor BIER Label ( 3 octets) | |
+------------------------------------+ |
| Anchor Node IP ( 4 or 16 octets) | |
+------------------------------------+ ------+
Figure 3: PTA for Hybird SR and BIER MPLS Tunnel
4.2. MVPN Forwarding State and Forwarding Procedure
Ingress edge router has a per-flow forwarding state, indicating
forwarding to every anchor router(s) of an egress area, and a
BitString representing the final egress edge routers.
o (VRF, S, G, Anchor Node SID, Anchor BIER Label of a <SD,BSL,SI>,
SD, BSL, SI, BitString of a <SD,BSL,SI>).
Ingress edge router can have its own policy about how to reach some
anchor router.
Each of the anchor router(s) has a per-SRGB-label BIER forwarding
state, but don't have any per-VPN or per-flow state. When an anchor
router receives a BIER packet encapsulated in the Segment Routing
label, it pops the Segment Routing label, sees the BIER SRGB-label,
and performs hop-by-hop BIER replication with BIER SRGB-label MPLS
encapsulation. The hop-by-hop BIER forwarding can further change to
on-hop replications directly to the egress edge routers over Segment
Routing tunnels, by building BIER forwarding table over Segment
Routing on anchar router(s) and egress edge routers only.
Each egress edge router has a per-flow forwarding state, indicating
forwarding a packet to its interfaces connected to CE or receivers.
Egress edge router can use the upstream-assigned vpnlabel to
differentiate the local VRF.
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5. MVPN Using SRv6 and BIER-IPv6 Encapsulation
MVPN service using SRv6 and BIER IPv6 Encapsulation is also possible
by using the [I-D.xie-bier-6man-encapsulation], which allows BIER
packets to run on a SRv6 tunnel.
Procedures of building the BIER IPv6 BIFT-ID forwarding table are
outside the scope of this document.
5.1. Anchor information Advertisement and Usage
The anchor information of Hybird SPv6 and BIER IPv6 is carried in a
specific PTA as below.
+------------------------------------+
| Flags (1 octet) |
+------------------------------------+
| Tunnel Type = TBD (1 octet) |
+------------------------------------+
| MPLS Label (3 octets) |
+------------------------------------+ ------+
| Sub-domain-id (1 octet) | |
+------------------------------------+ |
| BFR-id (2 octets) | |
+------------------------------------+ |
| BFR-prefix (16 octets) | Tunnel Identifier
+------------------------------------+ |
| Anchor BIER BIFT-ID ( 3 octets) | |
+------------------------------------+ |
| Anchor Node BIER SID ( 16 octets) | |
+------------------------------------+ ------+
Figure 4: PTA for Hybird SRv6 and BIER IPv6 Tunnel
5.2. MVPN Forwarding State and Forwarding Procedure
Ingress edge router has a per-flow forwarding state, indicating
forwarding to every anchor router(s) of an egress area.
o (VRF, S, G, Anchor Node BIER SID, Anchor BIER BIFT-ID of a
<SD,BSL,SI>, SD, BSL, SI, BitString of a <SD,BSL,SI>).
Ingress edge router can have its own policy about how to reach some
anchor router.
Each of the anchor router(s) has a per-BIFT-ID BIER forwarding state,
but doesn't have any per-VPN or per-flow state. When an anchor
router receives a BIER packet encapsulated in the SRv6 SRH header, it
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first pops the SRH, and then sees the BIER specific Multicast
address, and then performs the hop-by-hop BIER replication by using
the BIFT-ID and other BIER header fields as described in [I-D.xie-
bier-6man-encapsulation].
Egress edge router has a per-flow forwarding state, indicating
forwarding a packet to its interfaces connected to CE or receivers.
Egress edge router can use the upstream-assigned vpnlabel to
differentating the local VRF.
6. Security Considerations
The procedures of this document do not, in themselves, provide
privacy, integrity, or authentication for the control plane or the
data plane.
7. IANA Considerations
Allocation is expected from IANA for two new tunnel type codepoints
for "Hybird SR-MPLS and BIER MPLS Tunnel" and "Hybird SRv6 and BIER
IPv6 Tunnel" from the "P-Multicast Service Interface Tunnel (PMSI
Tunnel) Tunnel Types" registry.
8. Acknowledgements
TBD.
9. References
9.1. Normative References
[I-D.ietf-bier-mvpn]
Rosen, E., Sivakumar, M., Aldrin, S., Dolganow, A., and T.
Przygienda, "Multicast VPN Using BIER", draft-ietf-bier-
mvpn-11 (work in progress), March 2018.
[I-D.ietf-bier-use-cases]
Kumar, N., Asati, R., Chen, M., Xu, X., Dolganow, A.,
Przygienda, T., Gulko, A., Robinson, D., Arya, V., and C.
Bestler, "BIER Use Cases", draft-ietf-bier-use-cases-06
(work in progress), January 2018.
[I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing
Architecture", draft-ietf-spring-segment-routing-15 (work
in progress), January 2018.
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[I-D.xie-bier-6man-encapsulation]
Xie, J., Yan, G., McBride, M., and Y. Xia, "Encapsulation
for BIER in Non-MPLS IPv6 Networks", draft-xie-bier-6man-
encapsulation-00 (work in progress), April 2018.
[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>.
9.2. Informative 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>.
Authors' Addresses
Liang Geng
China Mobile
Beijing 10053
Email: gengliang@chinamobile.com
Lei Wang
China Mobile
Beijing 10053
Email: wangleiyjy@chinamobile.com
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Jingrong Xie
Huawei Technologies
Email: xiejingrong@huawei.com
Mike McBride
Huawei Technologies
Email: mmcbride7@gmail.com
Gang Yan
Huawei Technologies
Email: yangang@huawei.com
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