BESS Working Group Ali Sajassi
Internet-Draft Samir Thoria
Intended Status: Standards Track Cisco
Keyur Patel
Derek Yeung
Arrcus
John Drake
Wen Lin
Juniper
Expires: April 28, 2017 October 28, 2016
IGMP and MLD Proxy for EVPN
draft-sajassi-bess-evpn-igmp-mld-proxy-01
Abstract
Ethernet Virtual Private Network (EVPN) solution [RFC 7432] is
becoming pervasive in data center (DC) applications for Network
Virtualization Overlay (NVO) and DC interconnect (DCI) services, and
in service provider (SP) applications for next generation virtual
private LAN services.
This draft describes how to support efficiently endpoints running
IGMP for the above services over an EVPN network by incorporating
IGMP proxy procedures on EVPN PEs.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
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The list of current Internet-Drafts can be accessed at
http://www.ietf.org/1id-abstracts.html
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The list of Internet-Draft Shadow Directories can be accessed at
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Copyright and License Notice
Copyright (c) 2013 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
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 5
2 IGMP Proxy . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1 Proxy Reporting . . . . . . . . . . . . . . . . . . . . . . 5
2.1.1 IGMP Membership Report Advertisement in BGP . . . . . . 5
2.1.1 IGMP Leave Group Advertisement in BGP . . . . . . . . . 7
2.2 Proxy Querier . . . . . . . . . . . . . . . . . . . . . . . 8
3 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.1 PE with only attached hosts/VMs for a given subnet . . . . . 9
3.2 PE with mixed of attached hosts/VMs and multicast source . . 10
3.3 PE with mixed of attached hosts/VMs, multicast source and
router . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4 All-Active Multi-Homing . . . . . . . . . . . . . . . . . . . . 10
4.1 Local IGMP Join Synchronization . . . . . . . . . . . . . . 11
4.2 Local IGMP Leave Group Synchronization . . . . . . . . . . . 11
4.2.1 Remote Leave Group Synchronization . . . . . . . . . . . 12
4.2.2 Common Leave Group Synchronization . . . . . . . . . . . 13
5 Single-Active Multi-Homing . . . . . . . . . . . . . . . . . . . 13
6 Discovery of Selective P-Tunnel Types . . . . . . . . . . . . . 13
7 BGP Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 15
7.1 Selective Multicast Ethernet Tag Route . . . . . . . . . . . 15
7.1.1 Constructing the Selective Multicast route . . . . . . . 16
7.2 IGMP Join Synch Route . . . . . . . . . . . . . . . . . . . 17
7.2.1 Constructing the IGMP Join Synch Route . . . . . . . . 19
7.3 IGMP Leave Synch Route . . . . . . . . . . . . . . . . . . . 20
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7.3.1 Constructing the IGMP Leave Synch Route . . . . . . . . 21
7.4 Multicast Flags Extended Community . . . . . . . . . . . . . 22
7.5 EVI-RT Extended Community . . . . . . . . . . . . . . . . . 23
8 Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . 24
9 Security Considerations . . . . . . . . . . . . . . . . . . . . 24
10 IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
11 References . . . . . . . . . . . . . . . . . . . . . . . . . . 24
11.1 Normative References . . . . . . . . . . . . . . . . . . . 24
11.2 Informative References . . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25
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1 Introduction
Ethernet Virtual Private Network (EVPN) solution [RFC 7432] is
becoming pervasive in data center (DC) applications for Network
Virtualization Overlay (NVO) and DC interconnect (DCI) services, and
in service provider (SP) applications for next generation virtual
private LAN services.
In DC applications, a POD can consist of a collection of servers
supported by several TOR and Spine switches. This collection of
servers and switches are self contained and may have their own
control protocol for intra-POD communication and orchestration.
However, EVPN is used as way of standard inter-POD communication for
both intra-DC and inter-DC. A subnet can span across multiple PODs
and DCs. EVPN provides robust multi-tenant solution with extensive
multi-homing capabilities to stretch a subnet (e.g., VLAN) across
multiple PODs and DCs. There can be many hosts/VMs (e.g., several
hundreds) attached to a subnet that is stretched across several PODs
and DCs.
These hosts/VMs express their interests in multicast groups on a
given subnet/VLAN by sending IGMP membership reports (Joins) for
their interested multicast group(s). Furthermore, an IGMP router
(e.g., IGMPv1) periodically sends membership queries to find out if
there are hosts on that subnet still interested in receiving
multicast traffic for that group. The IGMP/MLD Proxy solution
described in this draft has three objectives to accomplish:
1) Just like ARP/ND suppression mechanism in EVPN to reduce the
flooding of ARP messages over EVPN, it is also desired to have a
mechanism to reduce the flood of IGMP messages (both Queries and
Reports) in EVPN.
2) If there is no physical/virtual multicast router attached to the
EVPN network for a given (*,G) or (S,G), it is desired for the EVPN
network to act as a distributed anycast multicast router for all the
hosts attached to that subnet.
3) To forward multicast traffic efficiently over EVPN network such
that it only gets forwarded to the PEs that have interest in the
multicast group(s) - i.e., multicast traffic will not be forwarded to
the PEs that have no receivers attached to them for that multicast
group. This draft shows how the above objectives are achieved.
The first two objectives are achieved by using IGMP/MLD proxy on the
PE and the third objective is achieved by setting up a multicast
tunnel (ingress replication or P2MP) only among the PEs that have
interest in that multicast group(s) based on the trigger from
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IGMP/MLD proxy processes. The proposed solutions for each of these
objectives are discussed in the following sections.
1.1 Terminology
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 [KEYWORDS].
2 IGMP Proxy
IGMP Proxy mechanism is used to reduce the flooding of IGMP messages
over EVPN network similar to ARP proxy used in reducing the flooding
of ARP messages over EVPN. It also provides triggering mechanism for
the PEs to setup their underlay multicast tunnels. IGMP Proxy
mechanism consist of two components: a) Proxy for IGMP Reports and b)
Proxy for IGMP Queries.
2.1 Proxy Reporting
When IGMP protocol is used between host/VMs and its first hop EVPN
router (EVPN PE), Proxy-reporting is used by the EVPN PE to summarize
(when possible) reports received from downstream hosts and propagate
it in BGP to other PEs that are interested in the info. This is done
by terminating IGMP Reports in the first hop PE, translating and
exchanging the relevant information among EVPN BGP speakers. The
information is again translated back to IGMP message at the recipient
EVPN speaker. Thus it helps create an IGMP overlay subnet using BGP.
In order to facilitate such an overlay, this document also defines a
new EVPN route type NLRI (EVPN Selective Multicast Ethernet Tag
route) along with its procedures to help exchange and register IGMP
multicast groups [section 5].
2.1.1 IGMP Membership Report Advertisement in BGP
When a PE wants to advertise an IGMP membership report (Join) using
the BGP EVPN route, it follows the following rules:
1) When the first hop PE receives several IGMP membership reports
(Joins) , belonging to the same IGMP version, from different attached
hosts/VMs for the same (*,G) or (S,G), it only sends a single BGP
message corresponding to the very first IGMP Join. This is because
BGP is a statefull protocol and no further transmission of the same
report is needed. If the IGMP Join is for (*,G), then multicast group
address along with the corresponding version flag (v1, v2, or v3) are
set. In case of IGMPv3, exclude flag also needs to be set to indicate
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that no source IP address to be excluded (e.g., include all sources
"*"). If the IGMP Join is for (S,G), then besides setting multicast
group address along with the version flag v3, the source IP address
and the include/exclude flag must be set. It should be noted that
when advertising the EVPN route for (S,G), the only valid version
flag is v3 (i.e., v1 and v2 flags must be set to zero).
2) When the first hop PE receives an IGMPv3 Join for (S,G), then the
PE checks to see if the source (S) is attached to self. If so, it
does not send the corresponding BGP EVPN route advertisement.
3) When the first hop PE receives an IGMP version-X Join first for
(*,G) and then later it receives an IGMP version-Y Join for the same
(*,G), then it will readvertise the same EVPN Selective Multicast
route with flag for version-Y set in addition to any previously-set
version flag(s). In other words, the first hop PE does not withdraw
the EVPN route before sending the new route because the flag field is
not part of BGP route key processing.
4) When the first hop PE receives an IGMP version-X Join first for
(*,G) and then later it receives an IGMPv3 Join for the same
multicast group address but for a specific source address S, then the
PE will advertise a new EVPN Selective Multicast route with v3 flag
set (and v1 and v2 reset). Include/exclude flag also need to be set
accordingly. Since source IP address is used as part of BGP route key
processing, it is considered as a new BGP route advertisement.
5) When a PE receives an EVPN Selective Multicast route with more
than one version flag set, it will generate the corresponding IGMP
report for (*,G) for each version specified in the flag field. With
multiple version flags set, there should be no source IP address in
the receive EVPN route. If there is, then an error should be logged.
If v3 flag is set (in addition to v1 or v2), then the include/exclude
flag needs to indicate "exclude". If not, then an error should be
logged. The PE MUST generate an IGMP membership report (Join) for
that (*,G) and each IGMP version in the version flag.
6) When a PE receives a list of EVPN Selective Multicast NLRIs in its
BGP update message, each with a different source IP address and the
multicast group address, and the version flag is set to v3, then the
PE generates an IGMPv3 membership report with a record corresponding
to the list of source IP addresses and the group address along with
the proper indication of inclusion/exclusion.
7) Upon receiving EVPN Selective Multicast route(s) and before
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generating the corresponding IGMP Join(s), the PE checks to see
whether it has any multicast router's AC(s) (Attachment Circuits
connected to multicast routers). If it has router's ACs, then the
generated IGMP Join(s) are sent to those ACs. If it doesn't have any
router's AC, then no IGMP Join(s) needs to be generated because
sending IGMP Joins to other hosts can result in unintentionally
preventing a host from joining a specific multicast group for IGMPv1
and IGMPv2 - i.e., if the PE does not receive a join from the host it
will not forward multicast data to it. Per [RFC4541], when an IGMPv1
or IGMPv2 host receives a membership report for a group address that
it intends to join, the host will suppress its own membership report
for the same group. This message suppression is a requirement for
IGMPv1 and IGMPv2 hosts. This is not a problem for hosts running
IGMPv3 because there is no suppression of IGMP Membership reports.
2.1.1 IGMP Leave Group Advertisement in BGP
When a PE wants to withdraw an EVPN Selective Multicast route
corresponding to an IGMPv2 Leave Group (Leave) or IGMPv3 "Leave"
equivalent message, it follows the following rules:
1) For IGMPv1, there is no explicit membership leave; therefore, the
PE needs to periodically send out an IGMP membership query to
determine whether there is any host left who is interested in
receiving traffic directed to this multicast group (this proxy query
function will be described in more details in section 2.2). If there
is no host left, then the PE re-advertises EVPN Selective Multicast
route with the v1 version flag reset. If this is the last version
flag to be reset, then instead of re-advertising the EVPN route with
all version flags reset, the PE withdraws the EVPN route for that
(*,G).
2) When a PE receives an IGMPv2 Leave Group or its "Leave" equivalent
message for IGMPv3 from its attached host, it checks to see if this
host is the last host who is interested in this multicast group by
sending a query for the multicast group. If the host was indeed the
last one, then the PE re-advertises EVPN Selective Multicast route
with the corresponding version flag reset. If this is the last
version flag to be reset, then instead of re-advertising the EVPN
route with all version flags reset, the PE withdraws the EVPN route
for that (*,G).
3) When a PE receives an EVPN Selective Multicast route for a given
(*,G), it compares the received version flags from the route with its
per-PE stored version flags. If the PE finds that a version flag
associated with the (*,G) for the remote PE is reset, then the PE
generates IGMP Leave for that (*,G) toward its local interface (if
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any) attached to the multicast router for that multicast group. It
should be noted that the received EVPN route should at least have one
version flag set. If all version flags are reset, it is an error
because the PE should have received an EVPN route withdraw for the
last version flag. If the PE receives an EVPN Selective Multicast
route withdraw, then it must remove the remote PE from the OIF list
associated with that multicast group.
4) When a PE receives an EVPN Selective Multicast route withdraw, it
removes the remote PE from its OIF list for that multicast group and
if there are no more OIF entries for that multicast group (either
locally or remotely), then the PE MUST stop responding to queries
from the locally attached router (if any). If there is a source for
that multicast group, the PE stops sending multicast traffic for that
source.
2.2 Proxy Querier
As mentioned in the previous sections, each PE need to have proxy
querier functionality for the following reasons:
1) To enable the collection of EVPN PEs providing L2VPN service to
act as distributed multicast router with Anycast IP address for all
attached hosts/VMs in that subnet.
2) To enable suppression of IGMP membership reports and queries over
MPLS/IP core.
3) To enable generation of query messages locally to their attached
host. In case of IGMPv1, the PE needs to send out an IGMP membership
query to verify that at least one host on the subnet is still
interested in receiving traffic directed to that group. When there is
no reply to three consecutive IGMP membership queries, the PE times
out the group, stops forwarding multicast traffic to the attached
hosts for that (*,G), and sends a EVPN Selective Multicast route
associated with that (*,G) with the version-1 flag reset or withdraws
that route.
3 Operation
Consider the EVPN network of figure-1, where there is an EVPN
instance configured across the PEs shown in this figure (namely PE1,
PE2, and PE3). Lets consider that this EVPN instance consist of a
single bridge domain (single subnet) with all the hosts, sources and
the multicast router shown in this figure connected to this subnet.
PE1 only has hosts connected to it. PE2 has a mix of hosts and
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multicast source. PE3 has a mix of hosts, multicast source, and
multicast router. Further more, lets consider that for (S1,G1), R1 is
used as the multicast router but for (S2, G2), distributed multicast
router with Anycast IP address is used. The following subsections
describe the IGMP proxy operation in different PEs with regard to
whether the locally attached devices for that subnet are:
- only hosts/VMs
- mix of hosts/VMs and multicast source
- mix of hosts/VMs, multicast source, and multicast router
+--------------+
| |
| |
+----+ | | +----+
H1:(*,G1)v1 ---| | | | | |---- H6(*,G1)v2
H2:(*,G1)v1 ---| PE1| | IP/MPLS | | PE2|---- H7(S2,G2)v3
H3:(*,G1)v2 ---| | | Network | | |---- S2
H4:(S2,G2)v3 --| | | | | |
+----+ | | +----+
| |
+----+ | |
H5:(S1,G1)v3 --| | | |
S1 ---| PE3| | |
R1 ---| | | |
+----+ | |
| |
+--------------+
Figure 1:
3.1 PE with only attached hosts/VMs for a given subnet
When PE1 receives an IGMPv1 Join Report from H1, it does not forward
this join to any of its other ports (for this subnet) because all
these local ports are associated with the hosts/VMs. PE1 sends an
EVPN Multicast Group route corresponding to this join for (*,G1) and
setting v1 flag. This EVPN route is received by PE2 and PE3 that are
the member of the same EVI. PE3 reconstructs IGMPv1 Join Report from
this EVPN BGP route and only sends it to the port(s) with multicast
routers attached to it (for that subnet). In this example, PE3 sends
the reconstructed IGMPv1 Join Report for (*,G1) to only R1.
Furthermore, PE2 although receives the EVPN BGP route, it does not
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send it to any of its port for that subnet - namely ports associated
with H6 and H7.
When PE1 receives the second IGMPv1 Join from H2 for the same
multicast group (*,G1), it only adds that port to its OIF list but it
doesn't send any EVPN BGP route because there is no change in
information. However, when it receives the IGMPv2 Join from H3 for
the same (*,G1), besides adding the corresponding port to its OIF
list, it re-advertises the previously sent EVPN Selective Multicast
route with the version-2 flag set.
Finally when PE1 receives the IMGMPv3 Join from H4 for (S2,G2), it
advertises a new EVPN Selective Multicast route corresponding to it.
3.2 PE with mixed of attached hosts/VMs and multicast source
The main difference in here is that when PE2 receives IGMPv3 Join
from H7 for (S2,G2), it does not advertises it in BGP because PE2
knows that S2 is attached to its local AC. PE2 adds the port
associated with H7 to its OIF list for (S2,G2). The processing for
IGMPv2 received from H6 is the same as the v2 Join described in
previous section.
3.3 PE with mixed of attached hosts/VMs, multicast source and router
The main difference in here relative to the previous two sections is
that Join messages received locally needs to be sent to the port
associated with router R1. Furthermore, the Joins received via BGP
need to be passed to the R1 port but filtered for all other ports.
4 All-Active Multi-Homing
Because a CE's LAG flow hashing algorithm is unknown, in an All-
Active redundancy mode it must be assumed that the CE can send a
given IGMP message to any one of the multi-homed PEs, either DF or
non-DF - i.e., different IGMP Join messages can arrive at different
PEs in the redundancy group and furthermore their corresponding Leave
messages can arrive at PEs that are different from the ones received
the Join messages. Therefore, all PEs attached to a given ES must
coordinate IGMP Join and Leave Group (x, G) state, where x may be
either '*' or a particular source S, for each [EVI, broadcast domain
(BD)] on that ES. This allows the DF for that [ES, EVI, BD] to
correctly advertise or withdraw a Selective Multicast Ethernet Tag
(SMET) route for that (x, G) group in that [EVI, BD] when needed.
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All-Active multihoming PEs for a given ES MUST support IGMP synch
procedures described in this section if they want to perform IGMP
proxy for hosts connects to that ES.
4.1 Local IGMP Join Synchronization
When a PE, either DF or non-DF, receives, on a given multihomed ES
operating in All-Active redundancy mode, an IGMP Membership Report
for (x, G), it determines the [EVI, BD] to which the IGMP Membership
Report belongs. If the PE doesn't already have local IGMP Join (x, G)
state for that [EVI, BD] on that ES, it instantiates local IGMP Join
(x, G) state and advertises a BGP IGMP Join Synch route for that [ES,
EVI, BD]. Local IGMP Join (x, G) state refers to IGMP Join (x, G)
state that is created as the result of processing an IGMP Membership
Report for (x, G).
The IGMP Join Synch route carries the ES-Import RT for the ES on
which the IGMP Membership Report was received. Thus it may only go
to the PEs attached to that ES (and not any other PEs).
When a PE, either DF or non-DF, receives an IGMP Join Synch route it
installs that route and if it doesn't already have IGMP Join (x, G)
state for that [ES, EVI, BD], it instantiates that IGMP Join (x,G)
state - i.e., IGMP Join (x, G) state is the union of local IGMP Join
(x, G) state and installed IGMP Join Synch route. If the DF is not
currently advertising (originating) a SMET route for that (x, G)
group in that [EVI, BD], it does so now.
When a PE, either DF or non-DF, deletes its local IGMP Join (x, G)
state for that [ES, EVI, BD], it withdraws its BGP IGMP Join Synch
route for that [ES, EVI, BD].
When a PE, either DF or non-DF, receives the withdrawal of an IGMP
Join Synch route from another PE it removes that route. When a PE
has no local IGMP Join (x, G) state and it has no installed IGMP Join
Synch routes, it removes IGMP Join (x, G) state for that [ES, EVI,
BD]. If the DF no longer has IGMP Join (x, G) state for that [EVI,
BD] on any ES for which it is DF, it withdraws its SMET route for
that (x, G) group in that [EVI, BD].
I.e., A PE advertises an SMET route for that (x, G) group in that
[EVI, BD] when it has IGMP Join (x, G) state in that [EVI, BD] on at
least one ES for which it is DF and it withdraws that SMET route when
it does not have IGMP Join (x, G) state in that [EVI, BD] on any ES
for which it is DF.
4.2 Local IGMP Leave Group Synchronization
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When a PE, either DF or non-DF, receives, on a given multihomed ES
operating in All-Active redundancy mode, an IGMP Leave Group message
for (x, G) from the attached CE, it determines the [EVI, BD] to which
the IGMPv2 Leave Group belongs. Regardless of whether it has IGMP
Join (x, G) state for that [ES, EVI, BD], it initiates the (x, G)
leave group synchronization procedure, which consists of the
following steps:
1) It computes the Maximum Response Time, which is the duration of
(x, G) leave group synchronization procedure. This is the product of
two locally configured values, Last Member Query Count and Last
Member Query Interval (described in Section 3 of [RFC2236]), plus
delta, the time it takes for a BGP advertisement to propagate between
the PEs attached to the multihomed ES (delta is a consistently
configured value on all PEs attached to the multihomed ES).
2) It starts the Maximum Response Time timer. Note that the receipt
of subsequent IGMP Leave Group messages or BGP Leave Synch routes for
(x, G) do not change the value of a currently running Maximum
Response Time timer and are ignored by the PE.
3) It initiates the Last Member Query procedure described in Section
3 of [RFC2236]; viz, it sends a number of Group-Specific Query (x, G)
messages (Last Member Query Count) at a fixed interval (Last Member
Query Interval) to the attached CE.
4) It advertises an IGMP Leave Synch route for that that [ES, EVI,
BD]. This route notifies the other multihomed PEs attached to the
given multihomed ES that it has initiated an (x, G) leave group
synchronization procedure; i.e., it carries the ES-Import RT for the
ES on which the IGMP Leave Group was received. It also contains the
Maximum Response Time and the Leave Group Synchronization Procedure
Sequence number. The latter identifies the specific (x, G) leave
group synchronization procedure initiated by the advertising PE,
which increments the value whenever it initiates a procedure.
5) When the Maximum Response Timer expires, the PE that has
advertised the IGMP Leave Synch route withdraws it.
4.2.1 Remote Leave Group Synchronization
When a PE, either DF or non-DF, receives an IGMP Leave Synch route it
installs that route and it starts a timer for (x, G) on the specified
[ES, EVI, BD] whose value is set to the Maximum Response Time in the
received IGMP Leave Synch route. Note that the receipt of subsequent
IGMPv2 Leave Group messages or BGP Leave Synch routes for (x, G) do
not change the value of a currently running Maximum Response Time
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timer and are ignored by the PE.
4.2.2 Common Leave Group Synchronization
If a PE attached to the multihomed ES receives an IGMP Membership
Report for (x, G) before the Maximum Response Time timer expires, it
advertises a BGP IGMP Join Synch route for that [ES, EVI, BD]. If it
doesn't already have local IGMP Join (x, G) state for that [ES, EVI,
BD], it instantiates local IGMP Join (x, G) state. If the DF is not
currently advertising (originating) a SMET route for that (x, G)
group in that [EVI, BD], it does so now.
If a PE attached to the multihomed ES receives an IGMP Join Synch
route for (x, G) before the Maximum Response Time timer expires, it
installs that route and if it doesn't already have IGMP Join (x, G)
state for that [EVI, BD] on that ES, it instantiates that IGMP Join
(x,G) state. If the DF is not currently advertising (originating) a
SMET route for that (x, G) group in that [EVI, BD], it does so now.
When the Maximum Response Timer expires a PE that has advertised an
IGMP Leave Synch route, withdraws it. Any PE attached to the
multihomed ES, that started the Maximum Response Time and has no
local IGMP Join (x, G) state and no installed IGMP Join Synch routes,
it removes IGMP Join (x, G) state for that [ES, EVI, BD]. If the DF
no longer has IGMP Join (x, G) state for that [EVI, BD] on any ES for
which it is DF, it withdraws its SMET route for that (x, G) group in
that [EVI, BD].
5 Single-Active Multi-Homing
Note that to facilitate state synchronization after failover, the PEs
attached to a multihomed ES operating in Single-Active redundancy
mode should also coordinate IGMP Join (x, G) state. In this case all
IGMP Join messages are received by the DF and distributed to the non-
DF PEs using the procedures described above.
6 Discovery of Selective P-Tunnel Types
To allow an ingress PE that supports IGMP proxy procedures and SMET
route to properly assign a selective P-tunnel supported by the
receiving PEs, the ingress PE needs to discovery the types of
selective P-tunnels supported by the receiving PEs and select the
preferred tunnel type among the ones that it has in common with the
receiving PEs.
In order to support such discovery mechanism, the Multicast Flags
extended community defined in section 7.2 is used. Each PE that
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supports different types of P-tunnels, marks the corresponding bits
and advertise this extended community along with its IMET route.
Therefore, the ingress PE can discover types of P-tunnels supported
by the receiving PEs. If the ingress PE does not receive this
extended community along with an IMET route for a given EVI, it
assumes the only P-tunnel type supported by the egress PE, is ingress
replication.
If besides ingress-replication P-tunnel type, there is no other P-
tunnel types in common among the participant PEs for an EVI, then the
ingress PE MUST use ingress-replication P-tunnel type.
If besides ingress-replication P-tunnel type, there is one ore more
P-tunnel types in common among the participant PEs for an EVI, then
the ingress PE can choose the P-tunnel type that it prefers.
If besides ingress-replication P-tunnel type, there is no other P-
tunnel types in common among the participant PEs for an EVI, then the
ingress PE MAY choose several different P-tunnel types where the
union of them covers the tunnel types supported by the participant
PEs for that EVI. This implies that the ingress PE replicates the
multicast traffic into different P-tunnels - i.e., to replicate the
multicast traffic onto P2MP mLDP P-tunnel and ingress-replication P-
tunnel.
If an ingress PE uses ingress replication, then for a given (x, G)
group in a given [EVI, BD]:
1) It sends (x, G) traffic to the set of PEs not supporting IGMP
Proxy. This set consists of any PE that has advertised an Inclusive
Multicast Tag route for the [EVI, BD] without the "IGMP Proxy
Support" flag.
2) It sends (x, G) traffic to the set of PEs supporting IGMP Proxy
and having listeners for that (x, G) group in that [EVI, BD]. This
set consists of any PE that has advertised an Inclusive Multicast Tag
route for the [EVI, BD] with the "IGMP Proxy Support" flag and that
has advertised an SMET route for that (x, G) group in that [EVI, BD].
If an ingress PE's Selective P-Tunnel for a given [EVI, BD] uses P2MP
and all of the PEs in the [EVI, BD] support that tunnel type and
IGMP, then for a given (x, G) group in a given [EVI, BD] it sends (x,
G) traffic using the Selective P-Tunnel for that (x, G) group in that
[EVI, BD]. This tunnel will include those PEs that have advertised
an SMET route for that (x, G) group on that [EVI, BD] (for Selective
P-tunnel) but it may include other PEs as well (for Aggregate
Selective P-tunnel).
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7 BGP Encoding
This document defines three new BGP EVPN routes to carry IGMP
membership reports. This route type is known as:
+ 6 - Selective Multicast Ethernet Tag Route
+ 7 - IGMP Join Synch Route
+ 8 - IGMP Leave Synch Route
The detailed encoding and procedures for this route type is described
in subsequent section.
7.1 Selective Multicast Ethernet Tag Route
An Selective Multicast Ethernet Tag route type specific EVPN NLRI
consists of the following:
+---------------------------------------+
| RD (8 octets) |
+---------------------------------------+
| Ethernet Tag ID (4 octets) |
+---------------------------------------+
| Multicast Source Length (1 octet) |
+---------------------------------------+
| Multicast Source Address (variable) |
+---------------------------------------+
| Multicast Group Length (1 octet) |
+---------------------------------------+
| Multicast Group Address (Variable) |
+---------------------------------------+
| Originator Router Length (1 octet) |
+---------------------------------------+
| Originator Router Address (variable) |
+---------------------------------------+
| Flags (1 octets) (optional) |
+---------------------------------------+
For the purpose of BGP route key processing, all the fields are
considered to be part of the prefix in the NLRI except for the one-
octet optional flag field (if included). The Flags fields are defined
as follows:
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0 1 2 3 4 5 6 7
+--+--+--+--+--+--+--+--+
| reserved |IE|v3|v2|v1|
+--+--+--+--+--+--+--+--+
The least significant bit, bit 7 indicates support for IGMP version
1.
The second least significant bit, bit 6 indicates support for IGMP
version 2.
The third least significant bit, bit 5 indicates support for IGMP
version 3.
The forth least significant bit, bit 4 indicates whether the (S, G)
information carried within the route-type is of Include Group type
(bit value 0) or an Exclude Group type (bit value 1). The Exclude
Group type bit MUST be ignored if bit 5 is not set.
This EVPN route type is used to carry tenant IGMP multicast group
information. The flag field assists in distributing IGMP membership
interest of a given host/VM for a given multicast route. The version
bits help associate IGMP version of receivers participating within
the EVPN domain.
The include/exclude bit helps in creating filters for a given
multicast route.
7.1.1 Constructing the Selective Multicast route
This section describes the procedures used to construct the Selective
Multicast route. Support for this route type is optional.
The Route Distinguisher (RD) SHOULD be a Type 1 RD [RFC4364]. The
value field comprises an IP address of the PE (typically, the
loopback address) followed by a number unique to the PE.
The Ethernet Tag ID MUST be set as follows:
EVI is VLAN-Based or VLAN Bundle service - set to 0
EVI is VLAN-Aware Bundle service without translation - set to
the customer VID for the [EVI, BD]
EVI is VLAN-Aware Bundle service with translation - set to the
normalized Ethernet Tag ID for the [EVI, BD]
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The Multicast Source length MUST be set to length of multicast source
address in bits. In case of a (*, G) Join, the Multicast Source
Length is set to 0.
The Multicast Source is the Source IP address of the IGMP membership
report. In case of a (*, G) Join, this field does not exist.
The Multicast Group length MUST be set to length of multicast group
address in bits.
The Multicast Group is the Group address of the IGMP membership
report.
The Originator Router Length is the length of the Originator Router
address in bits.
The Originator Router Address is the IP address of Router Originating
the prefix. It should be noted that using the "Originating Router's
IP address" field to get the PE IP address, needed for building
multicast underlay tunnels, allows for inter-AS operations where BGP
next hop can get over written.
The Flags field indicates the version of IGMP protocol from which the
membership report was received. It also indicates whether the
multicast group had INCLUDE or EXCLUDE bit set.
IGMP protocol is used to receive group membership information from
hosts/VMs by TORs. Upon receiving the hosts/VMs expression of
interest of a particular group membership, this information is then
forwarded using Ethernet Multicast Source Group Route NLRI. The NLRI
also keeps track of receiver's IGMP protocol version and any "source
filtering" for a given group membership. All EVPN Selective Multicast
Group routes are announced with per-EVI Route Target extended
communities.
7.2 IGMP Join Synch Route
This EVPN route type is used to coordinate IGMP Join (x,G) state for
a given [EVI, BD] between the PEs attached to a given ES operating in
All-Active (or Single-Active) redundancy mode and it consists of
following:
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+--------------------------------------------------+
| RD (8 octets) |
+--------------------------------------------------+
| Ethernet Segment Identifier (10 octets) |
+--------------------------------------------------+
| Ethernet Tag ID (4 octets) |
+--------------------------------------------------+
| Multicast Source Length (1 octet) |
+--------------------------------------------------+
| Multicast Source Address (variable) |
+--------------------------------------------------+
| Multicast Group Length (1 octet) |
+--------------------------------------------------+
| Multicast Group Address (Variable) |
+--------------------------------------------------+
| Originator Router Length (1 octet) |
+--------------------------------------------------+
| Originator Router Address (variable) |
+--------------------------------------------------+
| Flags (1 octet) |
+--------------------------------------------------+
For the purpose of BGP route key processing, all the fields are
considered to be part of the prefix in the NLRI except for the one-
octet Flags field, whose fields are defined as follows:
0 1 2 3 4 5 6 7
+--+--+--+--+--+--+--+--+
| reserved |IE|v3|v2|v1|
+--+--+--+--+--+--+--+--+
The least significant bit, bit 7 indicates support for IGMP version
1. The second least significant bit, bit 6 indicates support for
IGMP version 2. The third least significant bit, bit 5 indicates
support for IGMP version 3. The fourth least significant bit, bit 4
indicates whether the (S, G) information carried within the route-
type is of Include Group type (bit value 0) or an Exclude Group type
(bit value 1). The Exclude Group type bit MUST be ignored if bit 5 is
not set.
The Flags field assists in distributing IGMP membership interest of a
given host/VM for a given multicast route. The version bits help
associate IGMP version of receivers participating within the EVPN
domain. The include/exclude bit helps in creating filters for a
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given multicast route.
7.2.1 Constructing the IGMP Join Synch Route
This section describes the procedures used to construct the IGMP Join
Synch route. Support for this route type is optional. If a PE does
not support this route, then it MUST not indicate that it supports
'IGMP proxy' in Multicast Flag extended community for the EVIs
corresponding to its multi-homed Ethernet Segments. An IGMP Join
Synch route is advertised with an ES-Import Route Target extended
community whose value is set to the ESI for the ES on which the IGMP
Join was received.
The Route Distinguisher (RD) SHOULD be a Type 1 RD [RFC4364]. The
value field comprises an IP address of the PE (typically, the
loopback address) followed by a number unique to the PE.
The Ethernet Segment Identifier (ESI) MUST be set to the 10-octet
value defined for the ES.
The Ethernet Tag ID MUST be set as follows:
EVI is VLAN-Based or VLAN Bundle service - set to 0
EVI is VLAN-Aware Bundle service without translation - set to
the customer VID for the [EVI, BD]
EVI is VLAN-Aware Bundle service with translation - set to the
normalized Ethernet Tag ID for the [EVI, BD]
The Multicast Source length MUST be set to length of multicast source
address in bits. In case of a (*, G) Join, the Multicast Source
Length is set to 0.
The Multicast Source is the Source IP address of the IGMP membership
report. In case of a (*, G) Join, this field does not exist.
The Multicast Group length MUST be set to length of multicast group
address in bits.
The Multicast Group is the Group address of the IGMP membership
report.
The Originator Router Length is the length of the Originator Router
address in bits.
The Originator Router Address is the IP address of Router Originating
the prefix.
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The Flags field indicates the version of IGMP protocol from which the
membership report was received. It also indicates whether the
multicast group had INCLUDE or EXCLUDE bit set.
7.3 IGMP Leave Synch Route This EVPN route type is used to coordinate
IGMP Leave Group (x,G) state for a given [EVI, BD] between the PEs
attached to a given ES operating in All-Active (or Single-Active)
redundancy mode and it consists of following:
+--------------------------------------------------+
| RD (8 octets) |
+--------------------------------------------------+
| Ethernet Segment Identifier (10 octets) |
+--------------------------------------------------+
| Ethernet Tag ID (4 octets) |
+--------------------------------------------------+
| Multicast Source Length (1 octet) |
+--------------------------------------------------+
| Multicast Source Address (variable) |
+--------------------------------------------------+
| Multicast Group Length (1 octet) |
+--------------------------------------------------+
| Multicast Group Address (Variable) |
+--------------------------------------------------+
| Originator Router Length (1 octet) |
+--------------------------------------------------+
| Originator Router Address (variable) |
+--------------------------------------------------+
| Leave Group Synchronization # (4 octets) |
+--------------------------------------------------+
| Maximum Response Time (1 octet) |
+--------------------------------------------------+
| Flags (1 octet) |
+--------------------------------------------------+
For the purpose of BGP route key processing, all the fields are
considered to be part of the prefix in the NLRI except for the
Maximum Response Time and the one-octet Flags field, whose fields are
defined as follows:
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0 1 2 3 4 5 6 7
+--+--+--+--+--+--+--+--+
| reserved |IE|v3|v2|v1|
+--+--+--+--+--+--+--+--+
The least significant bit, bit 7 indicates support for IGMP version
1. The second least significant bit, bit 6 indicates support for
IGMP version 2. The third least significant bit, bit 5 indicates
support for IGMP version 3. The fourth least significant bit, bit 4
indicates whether the (S, G) information carried within the route-
type is of Include Group type (bit value 0) or an Exclude Group type
(bit value 1). The Exclude Group type bit MUST be ignored if bit 5 is
not set.
The Flags field assists in distributing IGMP membership interest of a
given host/VM for a given multicast route. The version bits help
associate IGMP version of receivers participating within the EVPN
domain. The include/exclude bit helps in creating filters for a
given multicast route.
7.3.1 Constructing the IGMP Leave Synch Route
This section describes the procedures used to construct the IGMP Join
Synch route. Support for this route type is optional. If a PE does
not support this route, then it MUST not indicate that it supports
'IGMP proxy' in Multicast Flag extended community for the EVIs
corresponding to its multi-homed Ethernet Segments. An IGMP Join
Synch route is advertised with an ES-Import Route Target extended
community whose value is set to the ESI for the ES on which the IGMP
Join was received.
The Route Distinguisher (RD) SHOULD be a Type 1 RD [RFC4364]. The
value field comprises an IP address of the PE (typically, the
loopback address) followed by a number unique to the PE.
The Ethernet Segment Identifier (ESI) MUST be set to the 10-octet
value defined for the ES.
The Ethernet Tag ID MUST be set as follows:
EVI is VLAN-Based or VLAN Bundle service - set to 0
EVI is VLAN-Aware Bundle service without translation - set to
the customer VID for the [EVI, BD]
EVI is VLAN-Aware Bundle service with translation - set to the
normalized Ethernet Tag ID for the [EVI, BD]
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The Multicast Source length MUST be set to length of multicast source
address in bits. In case of a (*, G) Join, the Multicast Source
Length is set to 0.
The Multicast Source is the Source IP address of the IGMP membership
report. In case of a (*, G) Join, this field does not exist.
The Multicast Group length MUST be set to length of multicast group
address in bits.
The Multicast Group is the Group address of the IGMP membership
report.
The Originator Router Length is the length of the Originator Router
address in bits.
The Originator Router Address is the IP address of Router Originating
the prefix.
The Flags field indicates the version of IGMP protocol from which the
membership report was received. It also indicates whether the
multicast group had INCLUDE or EXCLUDE bit set.
7.4 Multicast Flags Extended Community
The 'Multicast Flags' extended community is a new EVPN extended
community. EVPN extended communities are transitive extended
communities with a Type field value of 6. IANA will assign a Sub-
Type from the 'EVPN Extended Community Sub-Types' registry.
A PE that supports IGMP proxy on a given [EVI, BD] MUST attach this
extended community to the Inclusive Multicast Ethernet Tag (IMET)
route it advertises for that [EVI, BD] and it Must set the IGMP Proxy
Support flag to 1. Note that an [RFC7432] compliant PE will not
advertise this extended community so its absence indicates that the
advertising PE does not support IGMP Proxy.
The advertisement of this extended community enables more efficient
multicast tunnel setup from the source PE specially for ingress
replication - i.e., if an egress PE supports IGMP proxy but doesn't
have any interest in a given (x, G), it advertises its IGMP proxy
capability using this extended community but it does not advertise
any SMET route for that (x, G). When the source PE (ingress PE)
receives such advertisements from the egress PE, it doesn't not
replicate the multicast traffic to that egress PE; however, it does
replicate the multicast traffic to the egress PEs that don't
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advertise such capability even if they don't have any interests in
that (x, G).
A Multicast Flags extended community is encoded as an 8-octet value,
as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=0x06 | Sub-Type=TBD | Flags (2 Octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved=0 | Tunnel Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The low-order bit of the Flags is defined as the "IGMP Proxy Support"
bit. A value of 1 means that the PE supports IGMP Proxy as defined
in this document, and a value of 0 means that the PE does not support
IGMP proxy. The absence of this extended community also means that
the PE doesn not support IGMP proxy.
Tunnel type field is a 2-octet field with the bits set according to
the following:
LSB = 1, indicates the support for RSVP-TE P2MP LSP
2nd LSB = 1, indicates the support for P2MP LSP
3rd LSB = 1, indicates the support for PIM-SSM
4th LSB = 1, indicates the support for PIM-SM
5th LSB = 1, indicates the support for BIDIR-PIM
6th LSB = 1, indicates the support for mLDP MP2MP LSP
7.5 EVI-RT Extended Community
The 'EVI-RT' extended community is a new EVPN extended community.
EVPN extended communities are transitive extended communities with a
Type field value of 6. IANA will assign a Sub-Type from the 'EVPN
Extended Community Sub-Types' registry.
A PE that supports IGMP synch procedures for All-Active (or Single-
Active) multi-homed ES, MUST attach this extended community to either
IGMP Join Synch route (sec 7.2) or IGMP Leave Synch route (sec 7.3).
This extended community carries the RT associated with the EVI so
that the receiving PE can identify the EVI properly. The reason
standard format RT is not used, is to avoid distribution of these
routes beyond the group of multihoming PEs for that ES.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=0x06 | Sub-Type=TBD | RT associated with EVI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RT associated with the EVI (cont.) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
8 Acknowledgement
9 Security Considerations
Same security considerations as [RFC7432].
10 IANA Considerations
Allocation of Extended Community Type and Sub-Type for EVPN.
11 References
11.1 Normative References
[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4360] S. Sangli et al, ""BGP Extended Communities Attribute",
February, 2006.
[RFC7432] Sajassi et al., "BGP MPLS Based Ethernet VPN", February,
2015.
11.2 Informative References
[ETREE-FMWK] Key et al., "A Framework for E-Tree Service over MPLS
Network", draft-ietf-l2vpn-etree-frwk-03, work in progress, September
2013.
[PBB-EVPN] Sajassi et al., "PBB-EVPN", draft-ietf-l2vpn-pbb-evpn-
05.txt, work in progress, October, 2013.
[RFC4541] Christensen, M., Kimball, K., and F. Solensky,
"Considerations for IGMP and MLD snooping PEs", RFC 4541, 2006.
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Authors' Addresses
Ali Sajassi
Cisco
Email: sajassi@cisco.com
Samir Thoria
Cisco
Email: sthoria@cisco.com
Keyur Patel
Cisco
Email: keyur@arrcus.com
Derek Yeung
Cisco
Email: Yeung@arrcus.com
John Drake
Juniper
Email: jdrake@juniper.net
Wen Lin
Juniper
Email: wlin@juniper.net
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