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Versions: 00 01 draft-ietf-bess-evpn-igmp-mld-proxy

BESS Working Group                                           Ali Sajassi
Internet-Draft                                               Keyur Patel
Intended Status: Standards Track                            Samir Thoria
                                                             Derek Yeung
                                                                   Cisco

                                                              John Drake
                                                                 Wen Lin
                                                                 Juniper

Expires: April 17, 2016                                 October 17, 2015


                      IGMP and MLD Proxy for EVPN
               draft-sajassi-bess-evpn-igmp-mld-proxy-00


Abstract

   Ethernet Virtual Private Network (EVPN) solution [RFC 7432] is
   becoming pervasive in data center (DC) applications for Network
   Virtualization Overlay (NVO) services, for DC interconnect (DCI)
   services, and for next generation virtual private LAN services in
   service provider (SP) applications.

   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.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as
   Internet-Drafts.

   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."

   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
   http://www.ietf.org/shadow.html


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
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document. Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



Table of Contents

   1  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1  Terminology . . . . . . . . . . . . . . . . . . . . . . . .  4
   2  IGMP Proxy  . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1  Proxy Reporting . . . . . . . . . . . . . . . . . . . . . .  4
       2.1.1  IGMP Membership Report Advertisement in BGP . . . . . .  4
       2.1.1  IGMP Leave Group Advertisement in BGP . . . . . . . . .  6
     2.2  Proxy Querier . . . . . . . . . . . . . . . . . . . . . . .  7
   3 Operation  . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     3.1 PE with only attached hosts/VMs for a given subnet . . . . .  8
     3.2 PE with mixed of attached hosts/VMs and multicast source . .  9
     3.1 PE with mixed of attached hosts/VMs, multicast source and
         router . . . . . . . . . . . . . . . . . . . . . . . . . . .  9
   5 BGP Encoding . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     5.1 Selective Multicast Ethernet Tag Route . . . . . . . . . . .  9
     5.2 Constructing the Selective Multicast route . . . . . . . . . 11
   6  Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . 12
   7  Security Considerations . . . . . . . . . . . . . . . . . . . . 12
   8  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 12
   9  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     9.1  Normative References  . . . . . . . . . . . . . . . . . . . 12
     9.2  Informative References  . . . . . . . . . . . . . . . . . . 12
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12






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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) services, for DC interconnect (DCI)
   services, and for next generation virtual private LAN services in
   service provider (SP) applications.

   In DC applications, a POD can consist of a collection of servers
   supported by several TOR and Spine routers. This collection of
   servers and routers 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 both of 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 processing. 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 provided 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 between 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 readvertise 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.

   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 readvertising 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-PER 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
   any) attached to the multicast router for that multicast group. It
   also removes the remote PE from the OIF list associated with 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



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   route withdraw for the last version flag.

   4) If the reset version flag is for version-1 or if the EVPN route
   withdraw is for version-1, the PE removes the remote PE from its OIF
   list for that multicast group. 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
   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:



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        - 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
   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



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   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.

3.1 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.


5 BGP Encoding

   This document defines a new BGP EVPN route to carry IGMP membership
   reports. This route type is known as:

           + 6 -  Selective Multicast Ethernet Tag Route

   The detailed encoding and procedures for this route type is described
   in subsequent section.


5.1 Selective Multicast Ethernet Tag Route

   An Selective Multicast Ethernet Tag 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 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:

                      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



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   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.

5.2 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 to zero for VLAN-based service and to a
   valid normalized VID for VLAN-aware bundle service.

   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.

   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 to BGP EVPN 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 Ethernet
   Multicast Source Group Routes are announced with ES-Import Route



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   Target extended communities.



6  Acknowledgement


7  Security Considerations

   Same security considerations as [RFC7432].

8  IANA Considerations

   Allocation of Extended Community Type and Sub-Type for EVPN.

9  References

9.1  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.

9.2  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.

Authors' Addresses


   Ali Sajassi
   Cisco
   Email: sajassi@cisco.com



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   Keyur Patel
   Cisco
   Email: keyupate@cisco.com


   Samir Thoria
   Cisco
   Email: sthoria@cisco.com


   Derek Yeung
   Cisco
   Email: myeung@cisco.com


   John Drake
   Juniper
   Email: jdrake@juniper.net


   Wen Lin
   Juniper
   Email: wlin@juniper.net




























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