Network Working Group J. Zhang
Internet-Draft Z. Li
Intended status: Standards Track Huawei Technologies
Expires: January 4, 2015 July 3, 2014
Selective Multicast in EVPN
draft-zhang-l2vpn-evpn-selective-mcast-01
Abstract
[I-D.ietf-l2vpn-evpn] describes a solution of carrying multicast
traffic using replication ingress and inclusive trees (P2MP LSPs).
It does not provide the usage of selective trees for carrying
multicast traffic. This document provides protocols and procedures
by which a selective tree can be used to carry traffic belonging only
to a specified set of IP multicast streams from one or more EVPN
instances.
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 RFC 2119 [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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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
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This Internet-Draft will expire on January 4, 2015.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. BGP EVPN NLRI Extensions . . . . . . . . . . . . . . . . . . 3
3.1. Seletive Multicast A-D Route . . . . . . . . . . . . . . 3
3.2. Leaf A-D Route . . . . . . . . . . . . . . . . . . . . . 4
4. Optimizing Multicast Distribution via Selective Trees . . . . 5
4.1. Originating Selective Multicast A-D Routes . . . . . . . 5
4.1.1. Construction of the Selective Multicast A-D Route . . 5
4.1.2. P-Tunnel Identification . . . . . . . . . . . . . . . 5
4.1.2.1. P2MP LSPs . . . . . . . . . . . . . . . . . . . . 6
4.1.2.2. MP2MP LSPs . . . . . . . . . . . . . . . . . . . 7
4.2. Receiving Selective Multicast A-D Route by PE . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. Reference . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
[I-D.ietf-l2vpn-evpn] describes a solution of carrying multicast
traffic using replication ingress and inclusive trees (P2MP LSPs).
It does not provide the usage of selective trees for carrying
multicast traffic. When replication ingress or inclusive tree is
used to carry multicast traffic, it is likely that a PE may receive
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multicast traffic for a multicast stream even if it doesn't have any
receivers that are interested in receiving traffic for that stream.
If a particular stream has a large amount of traffic, it may result
in highly non-optimal bandwidth utilization in the provider network.
To improve bandwidth utilization for IP multicast streams, this
document provides protocols and procedures by which a selective tree
can be used to carry traffic belonging only to a specified set of IP
multicast streams from one or more EVPN instances.
Optimizing multicast distribution needs the binding of particular IP
multicast stream to an selective tree and the explicit tracking of
particular IP multicast stream. The granularity of binding to a
selective tree is <RD, PE, S, G> where S is an IP multicast source
address and G is an IP multicast group address. Wildcard sources and
wildcard groups are supported.
This document assumes that the exchanging of BGP messages is within
the AS.
Section 3 describes the needed extensions of the current defined BGP
EVPN NLRI. Section 4 describes the procedures of binding and
explicit tracking.
2. Terminology
This document uses terminology described in [I-D.ietf-l2vpn-evpn].
3. BGP EVPN NLRI Extensions
The format of BGP EVPN NLRI is defined in [I-D.ietf-l2vpn-evpn].
This section describes the encoding of the BGP EVPN NLRI extensions
required by this document.
This document defines the following two new route types for BGP EVPN
NLRI:
+ 5 - Seletive Multicast Auto-Discovery (A-D) Route
+ 6 - Leaf Auto-Discovery (A-D) Route
The detailed encoding are described in subsequent sections.
3.1. Seletive Multicast A-D Route
A Selective Multicast A-D Route type specific EVPN NLRI consists of
the following:
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+---------------------------------------+
| RD (8 octets) |
+---------------------------------------+
| Ethernet Tag ID (4 octets) |
+---------------------------------------+
| Multicast Source Length (1 octet) |
+---------------------------------------+
| Multicast Source (Variable) |
+---------------------------------------+
| Multicast Group Length (1 octet) |
+---------------------------------------+
| Multicast Group (Variable) |
+---------------------------------------+
| Originating Router's IP Addr |
+---------------------------------------+
The RD and the Ethernet Tag ID are encoded as described in
[I-D.ietf-l2vpn-evpn].
The Multicast Source field contains the C-S address i.e the address
of the multicast source. If the Multicast Source field contains an
IPv4 address, then the value of the Multicast Source Length field is
32. If the Multicast Source field contains an IPv6 address, then the
value of the Multicast Source Length field is 128. The value of the
Multicast Source Length field may be set to 0 to indicate a wildcard.
The Multicast Group field contains the C-G address i.e. the address
of the multicast group. If the Multicast Group field contains an
IPv4 address, then the value of the Multicast Group Length field is
32. If the Multicast Group field contains an IPv6 address, then the
value of the Multicast Group Length field is 128. The Multicast
Group Length field may be set to 0 to indicate a wildcard.
Usage of Selective Multicast A-D Route is described in section 4.
3.2. Leaf A-D Route
A Leaf A-D Route type specific EVPN NLRI consists of the following:
+---------------------------------------+
| Route Key (variable) |
+---------------------------------------+
| Originating Router's IP Addr |
+---------------------------------------+
Leaf A-D routes may be originated as a result of processing a
received Selective Multicast A-D route. A Leaf A-D route is
originated in these situations only if the received route has a PMSI
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Tunnel attribute whose "Leaf Information Required" bit is set to 1,
and the Route Key of the Leaf A-D route is set to the NLRI of the
received route.
Usage of Leaf A-D routes is described in Section 4.
4. Optimizing Multicast Distribution via Selective Trees
This section describes the binding (C-S, C-G) to a Selective Tree
using Selective Multicast A-D Route and the explicit tracking of the
IP multicast stream using Leaf A-D Route.
4.1. Originating Selective Multicast A-D Routes
The ingress PE informs all the PEs those are on the path to receivers
of the (C-S, C-G) of the binding of the Selective tree to the (C-S,
C-G), using Selective Multicast A-D routes. The format of the NLRI
of this route is described in section 3. The following describes
procedures for originating Selective Multicast A-D Route by a PE.
4.1.1. Construction of the Selective Multicast A-D Route
The settings of the RD, Ethernet Tag ID, Originating Router's IP
address, Next Hop field of the MP_REACH_NLRI, RT attributes of the
Selective Multicast A-D Route are the same as the Inclusive Multicast
Ethernet Tag Route described in [I-D.ietf-l2vpn-evpn].
The Multicast Source field MUST contain the source address associated
with the C-multicast stream, and the Multicast Source Length field is
set appropriately to reflect this. If the source address is a
wildcard the source address is set to 0.
The Multicast Group field MUST contain the group address associated
with the C-multicast stream, and the Multicast Group Length field is
set appropriately to reflect this. If the group address is a
wildcard the group address is set to 0.
4.1.2. P-Tunnel Identification
The selective multicast A-D route MUST carry a "PMSI Tunnel
Attribute" as specified in [RFC6514]. Depending on the technology
used for the selective tree for the EVPN instance on the PE, the PMSI
Tunnel attribute of the selective multicast A-D Route is constructed
differently.
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4.1.2.1. P2MP LSPs
The P-Tunnel attribute MUST contain the identity of the tree (note
that the PE could create the identity of the tree prior to the actual
instantiation of the tree).
If in order to establish the P-Multicast tree the PE needs to know
the leaves of the tree, then the PE obtains this information from the
leaf A-D routes received from other PEs (as other PEs originate leaf
A-D routes in response to receiving the selective multicast A-D
route) by setting the Leaf Information Required flag in the PMSI
Tunnel attribute to 1. This enables explicit tracking for the
multicast stream(s) advertised by the selective multicast A-D route.
If a PE originates Selective Multicast A-D routes with the Leaf
Information Required flag in the PMSI Tunnel attribute set to 1, then
the PE MUST be (auto)configured with an import Route Target, which
controls acceptance of leaf A-D routes by the PE. This Route Target
is IP address specific. The Global Administrator field of this Route
Target MUST be set to the IP address carried in the Next Hop of all
the selective multicast A-D routes advertised by this PE (if the PE
uses different Next Hops, then the PE MUST be (auto)configured with
multiple import RTs, one per each such Next Hop). The Local
Administrator field of this Route Target MUST be set to 0.
A PE MAY aggregate two or more selective trees originated by the PE
onto the same P-Multicast tree. If the PE already advertises
selective multicast A-D routes for these selective trees, then
aggregation requires the PE to re-advertise these routes. The re-
advertised routes MUST be the same as the original ones, except for
the PMSI tunnel attribute. If the PE has not previously advertised
selective multicast A-D routes for these selective trees, then the
aggregation requires the PE to advertise (new) selective multicast
A-D routes for these selective trees. The PMSI Tunnel attribute in
the newly advertised/re-advertised routes MUST carry the identity of
the P-Multicast tree that aggregates the selective trees. If at
least some of the selective trees aggregated onto the same
P-Multicast tree belong to different EVPN instances, then all these
routes MUST carry an MPLS upstream assigned label [RFC5331]. If all
these aggregated selective trees belong to the same EVPN, then the
routes MAY carry an MPLS upstream assigned label [RFC5331]. The
labels can be assigned per EVPN instance or per selective multicast
A-D route.
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4.1.2.2. MP2MP LSPs
Construction of MP2MP LSPs P-Tunnel identification is the same as
specified in section 4.1.2.1 except the upstream assigned label
demultiplexing the EVPN multicast traffic received over the selective
tree. The allocation of this label will be described in future
version.
4.2. Receiving Selective Multicast A-D Route by PE
When a PE receives a BGP Update message that carries an Selective
Multicast A-D route such that (a) at least one of the Route Targets
of the route matches one of the import Route Targets configured for a
particular EVI on the local PE, (b) the BGP route selection
determines that this is the best route with respect to the NLRI
carried by the route, and (c) the multicast state snooped on the PE-
CE interfaces match the Selective Multicast A-D route. (The
procedures of determining the multicast snooped state will be
described in a future version.), the PE performs the following:
+ If the Tunnel Type in the PMSI Tunnel attribute is set to P2MP
LSP, the PE SHOULD join the P-Multicast tree whose identity is
carried in the PMSI Tunnel attribute. (The procedures of building
P2MP LSP are described in [RFC6388].). If the PMSI Tunnel
attribute does not carry a label, then all packets that are
received on the P-Multicast tree, as identified by the PMSI Tunnel
attribute, are forwarded using the EVI that has at least one of
its import Route Targets that matches one of the Route Targets of
the received Selective Multicast A-D route. If the PMSI Tunnel
attribute carries an MPLS label, then the egress PE MUST treat
this as an upstream-assigned label, and all packets that are
received on the P-Multicast tree, as identified by the PMSI Tunnel
attribute, with that upstream label are forwarded using the EVI
that has at least one of its import Route Target that matches one
of the Route Targets of the received Selective Multicast A-D
route.
+ The process in case of Tunnel Type set to mLDP MP2MP LSP will be
described in future version.
If the received Selective Multicast A-D route has a PMSI Tunnel
attribute with the Leaf Information Required flag set to 1, then the
PE originates a Leaf A-D route constructed as follows (The format of
the NLRI of the Leaf A-D route is described in section 3.).
+ The route carries a single EVPN NLRI with the Route Key field set
to the EVPN NLRI of the Selective Multicast A-D route received
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from that neighbor and the Originating Router's IP address set to
the IP address of the PE (this MUST be a routable IP address).
+ The PE constructs an IP-based Route Target Extended Community by
placing the IP address carried in the Next Hop of the received
Selective Multicast A-D route in the Global Administrator field of
the Community, with the Local Administrator field of this
Community set to 0 and setting the Extended Communities attribute
of the Leaf A-D route to that Community.
+ The Next Hop field of the MP_REACH_NLRI attribute of the route
MUST be set to the same IP address as the one carried in the
Originating Router's IP Address field of the route.
+ To constrain the distribution scope of this route, the route MUST
carry the NO_ADVERTISE BGP Community [RFC1997].
+ Once the Leaf A-D route is constructed, the PE advertises this
route into IBGP.
In addition to the procedures specified above, the PE MUST set up its
forwarding path to receive traffic, for each multicast stream in the
matching snooped state, from the tunnel advertised by the Selective
Multicast A-D route.
When a new snooped state is created by a PE then the PE MUST first
determine if there is a Selective Multicast route that matches the
snooped state. If such a Selective Multicast A-D route is found,
then the PE MUST follow the procedures described in this section, for
that particular Selective Multicast A-D route. If later on the
snooped state ages out and is deleted from the PE, the PE SHOULD
withdraw the leaf A-D route that it had originated in response to the
Selective Multicast A-D route, and SHOULD prune itself off the
associated selective tree.
The snooped state is said to "match" the Selective Multicast A-D
route if any of the following is true:
+ The Selective Multicast A-D route carries (C-S, C-G) and the
snooped state is for (C-S, C-G) or for (C-*, C-G), OR
+ The Selective Multicast A-D route carries (C-*, C-G) and (a) the
snooped state is for (C-*, C-G) OR (b) the snooped state is for at
least one multicast join with the multicast group address equal to
C-G and there doesn't exist another Selective Multicast A-D route
that carries (CS, C-G) where C-S is the source address of the
snooped state.
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+ The Selective Multicast A-D route carries (C-S, C-*) and (a) the
snooped state is for at least one multicast join with the
multicast source address equal to C-S, and (b) there doesn't exist
another Selective Multicast A-D route that carries (C-S, C-G)
where C-G is the group address of the snooped state.
+ The Selective Multicast A-D route carries (C-*, C-*) and there is
no other Selective Multicast A-D route that matches the snooped
state as per the above conditions.
5. IANA Considerations
This document requires IANA to assign two new route type values for
EVPN NLRI.
6. Security Considerations
There are no additional security aspects beyond those of EVPN.
7. Reference
[I-D.ietf-l2vpn-evpn]
Sajassi, A., Aggarwal, R., Bitar, N., Isaac, A., and J.
Uttaro, "BGP MPLS Based Ethernet VPN", draft-ietf-l2vpn-
evpn-07 (work in progress), May 2014.
[RFC1997] Chandrasekeran, R., Traina, P., and T. Li, "BGP
Communities Attribute", RFC 1997, August 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC6388] Wijnands, IJ., Minei, I., Kompella, K., and B. Thomas,
"Label Distribution Protocol Extensions for Point-to-
Multipoint and Multipoint-to-Multipoint Label Switched
Paths", RFC 6388, November 2011.
[RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
Encodings and Procedures for Multicast in MPLS/BGP IP
VPNs", RFC 6514, February 2012.
Authors' Addresses
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Junlin Zhang
Huawei Technologies
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: jackey.zhang@huawei.com
Zhenbin Li
Huawei Technologies
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: lizhenbin@huawei.com
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