Internet DRAFT - draft-zzhang-bess-mcast-in-evpn-signaled-l3vpn
draft-zzhang-bess-mcast-in-evpn-signaled-l3vpn
BESS Z. Zhang
Internet-Draft W. Lin
Intended status: Standards Track Juniper Networks
Expires: April 16, 2021 J. Rabadan
Nokia
October 13, 2020
Multicast in L3VPNs Signaled by EVPN SAFI
draft-zzhang-bess-mcast-in-evpn-signaled-l3vpn-01
Abstract
[ietf-bess-evpn-prefix-advertisement] specifies an EVPN SAFI Type-5
route that can be used to signal L3VPNs. This document specifies
procedures for multicast in such an L3VPN.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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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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 April 16, 2021.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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
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Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Optimized Inter-Subnet Multicast for EVPN . . . . . . . . 3
2.2. Using [RFC6514] Procedures . . . . . . . . . . . . . . . 4
2.3. Using [RFC6037] Procedures . . . . . . . . . . . . . . . 4
2.4. Adapted [RFC6514] Procedures . . . . . . . . . . . . . . 5
3. Specifications . . . . . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Normative References . . . . . . . . . . . . . . . . . . 6
5.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Terminology
It is expected that audience is familiar with EVPN and MVPN concepts
and terminologies. For convenience, the following terms are briefly
explained.
o PMSI: P-Multicast Service Interface - a conceptual interface for a
PE to send customer multicast traffic to all or some PEs in the
same VPN.
o I-PMSI: Inclusive PMSI - to all PEs in the same VPN.
o S-PMSI: Selective PMSI - to some of the PEs in the same VPN.
o Leaf A-D routes: For explicit leaf tracking purpose. Triggered by
S-PMSI A-D routes and targeted at triggering route's originator.
o IMET A-D route: Inclusive Multicast Ethernet Tag A-D route. The
EVPN equivalent of MVPN Intra-AS I-PMSI A-D route.
o SMET A-D route: Selective Multicast Ethernet Tag A-D route. The
EVPN equivalent of MVPN Leaf A-D route but unsolicited and
untargeted.
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2. Introduction
Traditionally, an L3VPN is signaled with BGP "MPLS-labeled VPN
address" SAFI and uses MPLS as provider tunnel as specified in
[RFC4364>]. Multicast support in such an L3VPN is specified in
[RFC6513] and [RFC6514].
[ietf-bess-evpn-prefix-advertisement] specifies another way of
signaling L3VPN via EVPN SAFI Type-5 routes for two reasons:
o VXLAN tunnels can be used, either for deployment scenarios where
MPLS is not desired or for the purpose of better ECMP hashing.
o In an environment where EVPN is already needed for L2VPN, an
operator may prefer just using an additional EVPN route type to
signal L3VPN routes, instead of using another SAFI. This is
especially the case when L3VPN is used to provide inter-DC
connection.
[ietf-bess-evpn-prefix-advertisement] does not define procedures for
multicast. This document provides three options for different
deployment scenarios.
2.1. Optimized Inter-Subnet Multicast for EVPN
If all multicast senders and receivers are in an EVPN domain
(including both intra-DC and inter-DC cases), the Optimized Inter-
Subnet Multicast (OISM) procedures defined in [ietf-bess-evpn-irb-
mcast] is the best and preferred option. The advantages are that no
new procedures are needed and Any Source Multicast (ASM) does not
need PIM Rendezvous Point (RP) procedures.
This does require that, if not all BDs are presented on every PE,
then a Supplemental Bridge Domain (SBD) needs to be configured on
every PE. Since the "Interface-less IP-VRF-to-IP-VRF Model" defined
in Section 4.4.1 of [ietf-bess-evpn-prefix-advertisement] does not
use SBD, for multicast purpose it is better to move away from that
model.
Additionally, in case of inter-DC, the SBD needs be stretched across
DCs even if regular BDs are not stretched. If the number of PEs in
all DCs becomes very large, segmentation procedures defined in [ietf-
bess-evpn-bum-procedures-update] and further enhanced in [zzhang-
bess-mvpn-evpn-cmcast-enhancements] can be used. Alternatively, MVPN
procedures defined in [RFC6514] can be used/adapted for an L3VPN
signaled by EVPN Type-5 routes, as described in the following two
sections.
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2.2. Using [RFC6514] Procedures
If the OISM procedure cannot be used for any of the following
situations that use L3VPN signaled by EVPN Type-5 routes:
o There are senders/receivers not on a BD of an EVPN domain and OISM
cannot extend to connect them.
o Stretching SBD across a DCI is not desired as described in the
previous section.
o It's a pure L3VPN scenario, where EVPN does not add any value.
MVPN procedures defined in [RFC6514] (often referred to as BGP-MVPN)
can be used as is as long as:
o The MVPN procedures treat EVPN Type-5 routes the same as routes
signaled with "MPLS-labeled VPN address" when it comes to UMH
selection.
o The EVPN Type-5 routes to C-RP or C-src carry the VRF Route Import
Extended Community and Source AS Extended Extended Community.
In other words, the only difference is that the routes used for UMH
selection now includes those signaled via EVPN Type-5 routes, and
they MUST carry the two ECs mentioned above. The rest of [RFC6514]
procedures are unchanged.
The EVPN Type-2 signaled IP routes may be used as well, though from
MVPN point of view, they're no different from "local" routes
associated with IRB interfaces.
2.3. Using [RFC6037] Procedures
The historic RFC 6037 describes the legacy PIM-based MVPN (often
referred to as Rosen/PIM-MVPN). While the BGP-MVPN specified in
[RFC6514] is widely used and deemed more scalable and more versatile,
the legacy PIM/Rosen-MVPN is still used by some operators, and in
case of EVPN-signaled L3VPN, it can also be used, perhaps with little
implementation change, especially if PIM-ASM based Multicast
Distribution Tree (MDT, or provider tunnel) is appropriate or
desired.
It must be pointed out that, if PIM-SSM or other types of MDTs are
desired, or if Inter-AS MDTs are needed, [RFC6037] requires a MDT
SAFI to be used. In that case, the BGP-MVPN approach as discussed in
the previous section is recommended (since a new SAFI is needed
anyway even with PIM-MVPN in this case).
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2.4. Adapted [RFC6514] Procedures
Notice that, an operator may have chosen to use EVPN Type-5 routes to
signal L3VPN because they wanted to avoid signaling another BGP SAFI.
Using [RFC6514] procedures as described in the previous section
defeats that purpose because a new MCAST-VPN SAFI has to be used.
That can be resolved by adapting the [RFC6514] procedures with EVPN
SAFI, as described below.
RFC6514 uses 7 route types and only the Source Active route does not
already have a corresponding EVPN route type:
MVPN EVPN
Type Name Type Name
---- ---- ---- ----
1 Intra-AS I-PMSI 3 IMET
2 Inter-AS I-PMSI 9 Per-Region I-PMSI
3 S-PMSI 10 S-PMSI
4 Leaf 11 Leaf
5 Source Active TBD Source Active (added in this spec)
6 (*,G) C-Multicast 6 SMET
7 (S,G) C-Multicast 7 SMET
As pointed out in [zzhang-bess-mvpn-evpn-cmcast-enhancements], the
MVPN Type-6/7 C-multicast routes don't have leaf tracking semantics
while EVPN SMET route has built-in leaf tracking semantics. Both
have pros and cons depending on the situation. This document will
specify when SMET routes used for MVPN do or do not need leaf
tracking semantics and the corresponding procedures.
Also as pointed out in [zzhang-bess-mvpn-evpn-cmcast-enhancements],
the MVPN Type-6/7 C-multicast routes are targeted while EVPN SMET
routes are not. This document specifies that the EVPN SMET routes
used for MVPN purpose will be targeted, except in a special case as
mentioned in [zzhang-bess-mvpn-evpn-cmcast-enhancements].
With this, the MEG (MVPN/EVPN Gateway) [ietf-bess-evpn-irb-mcast]
follows the adapted MVPN procedures as specified in this document
instead of the [RFC6514] procedures on MVPN side.
Detailed procedures are specified in the following section.
3. Specifications
Details to be added.
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4. Security Considerations
This document does not introduce new security risks. Whatever
security aspects that are applicable to [RFC7432], [RFC6513],
[RFC6514] and [ietf-bess-evpn-prefix-advertisement] apply here.
5. References
5.1. Normative References
[I-D.ietf-bess-evpn-irb-mcast]
Lin, W., Zhang, Z., Drake, J., Rosen, E., Rabadan, J., and
A. Sajassi, "EVPN Optimized Inter-Subnet Multicast (OISM)
Forwarding", draft-ietf-bess-evpn-irb-mcast-04 (work in
progress), October 2019.
[I-D.ietf-bess-evpn-prefix-advertisement]
Rabadan, J., Henderickx, W., Drake, J., Lin, W., and A.
Sajassi, "IP Prefix Advertisement in EVPN", draft-ietf-
bess-evpn-prefix-advertisement-11 (work in progress), May
2018.
[I-D.zzhang-bess-mvpn-evpn-cmcast-enhancements]
Zhang, Z., Kebler, R., Lin, W., and E. Rosen, "MVPN/EVPN
C-Multicast Routes Enhancements", draft-zzhang-bess-mvpn-
evpn-cmcast-enhancements-01 (work in progress), March
2019.
[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>.
[RFC6037] Rosen, E., Ed., Cai, Y., Ed., and IJ. Wijnands, "Cisco
Systems' Solution for Multicast in BGP/MPLS IP VPNs",
RFC 6037, DOI 10.17487/RFC6037, October 2010,
<https://www.rfc-editor.org/info/rfc6037>.
[RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
Encodings and Procedures for Multicast in MPLS/BGP IP
VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012,
<https://www.rfc-editor.org/info/rfc6514>.
[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>.
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5.2. Informative References
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
2006, <https://www.rfc-editor.org/info/rfc4364>.
[RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/
BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February
2012, <https://www.rfc-editor.org/info/rfc6513>.
[RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
2015, <https://www.rfc-editor.org/info/rfc7432>.
Authors' Addresses
Zhaohui Zhang
Juniper Networks
EMail: zzhang@juniper.net
Wen Lin
Juniper Networks
EMail: wlin@juniper.net
Jorge Rabadan
Nokia
EMail: jorge.rabadan@nokia.com
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