[Docs] [txt|pdf|xml] [Tracker] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 draft-ietf-bier-mld

Network Working Group                                         P. Pfister
Internet-Draft                                              IJ. Wijnands
Intended status: Standards Track                               S. Venaas
Expires: September 10, 2017                                Cisco Systems
                                                                 C. Wang
                                                                Z. Zhang
                                                         ZTE Corporation
                                                             M. Stenberg
                                                           March 9, 2017


 BIER Ingress Multicast Flow Overlay using Multicast Listener Discovery
                               Protocols
                       draft-pfister-bier-mld-03

Abstract

   This document specifies the ingress part of a multicast flow overlay
   for BIER networks.  Using existing multicast listener discovery
   protocols, it enables multicast membership information sharing from
   egress routers, acting as listeners, toward ingress routers, acting
   as queriers.  Ingress routers keep per-egress-router state, used to
   construct the BIER bit mask associated with IP multicast packets
   entering the BIER domain.

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 10, 2017.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





Pfister, et al.        Expires September 10, 2017               [Page 1]


Internet-Draft        MLD BIER ingress flow overlay           March 2017


   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Applicability Statement . . . . . . . . . . . . . . . . . . .   4
   5.  Querier and Listener Specifications . . . . . . . . . . . . .   4
     5.1.  Configuration Parameters  . . . . . . . . . . . . . . . .   5
     5.2.  MLDv2 instances.  . . . . . . . . . . . . . . . . . . . .   5
       5.2.1.  Sending Queries . . . . . . . . . . . . . . . . . . .   6
       5.2.2.  Sending Reports . . . . . . . . . . . . . . . . . . .   6
       5.2.3.  Receiving Queries . . . . . . . . . . . . . . . . . .   6
       5.2.4.  Receiving Reports . . . . . . . . . . . . . . . . . .   7
     5.3.  Packet Forwarding . . . . . . . . . . . . . . . . . . . .   7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Appendix A.  BIER Use Case in Data Centers  . . . . . . . . . . .   9
     A.1.  Convention and Terminology  . . . . . . . . . . . . . . .  11
     A.2.  BIER in data centers  . . . . . . . . . . . . . . . . . .  11
     A.3.  A BIER MLD solution for Virtual Network information . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   The Bit Index Explicit Replication (BIER -
   [I-D.ietf-bier-architecture]) forwarding technique enables IP
   multicast transport across a BIER domain.  When receiving or
   originating a packet, ingress routers have to construct a bit mask
   indicating which BIER egress routers located within the same BIER
   domain will receive the packet.  A stateless approach would consist
   in forwarding all incoming packets toward all egress routers, which
   would in turn make a forwarding decision based on local information.
   But any more efficient approach would require ingress routers to keep
   some state about egress routers multicast membership information,



Pfister, et al.        Expires September 10, 2017               [Page 2]


Internet-Draft        MLD BIER ingress flow overlay           March 2017


   hence requiring state sharing from egress routers toward ingress
   routers.

   This document specifies how to use the Multicast Listener Discovery
   protocol version 2 [RFC3810] (resp. the Internet Group Management
   protocol version 3 [RFC3376]) as the ingress part of a BIER multicast
   flow overlay (BIER layering is described in
   [I-D.ietf-bier-architecture]) for IPv6 (resp.  IPv4).  It enables
   multicast membership information sharing from egress routers, acting
   as listeners, toward ingress routers, acting as queriers.  Ingress
   routers keep per-egress-router state, used to construct the BIER bit
   mask associated with IP multicast packets entering the BIER domain.

   This specification is applicable to both IP version 4 and version 6.
   It therefore specifies two separate mechanisms operating
   independently.  For the sake of simplicity, the rest of this document
   uses IPv6 terminology.  It can be applied to IPv4 by replacing
   'MLDv2' with 'IGMPv3', and following specific requirements when
   explicitly stated.

2.  Terminology

   In this document, the key words "MAY", "MUST", "MUST NOT",
   "RECOMMENDED", and "SHOULD", are to be interpreted as described in
   [RFC2119].

   The terms "Bit-Forwarding Router" (BFR), "Bit-Forwarding Egress
   Router" (BFER), "Bit-Forwarding Ingress Router" (BFIR), "BFR-id" and
   "BFR-Prefix" are to be interpreted as described in
   [I-D.ietf-bier-architecture].

   Additionally, the following definitions are used:

   BIER Multicast Listener Discovery (BMLD):  The modified version of
      MLD specified in this document.

   BMLD Querier:  A BFR implementing the Querier part of this
      specification.  A BMLD Node MAY be both a Querier and a Listener.

   BMLD Listener:  A BFR implementing the Listener part of this
      specification.  A BMLD Node MAY be both a Querier and a Listener.

3.  Overview

   This document proposes to use the mechanisms described in MLDv2 in
   order to enable multicast membership information sharing from BFERs
   toward BFIRs within a given BIER domain.  BMLD queries (resp.
   reports) are sent over BIER toward all BMLD Nodes (resp.  BMLD



Pfister, et al.        Expires September 10, 2017               [Page 3]


Internet-Draft        MLD BIER ingress flow overlay           March 2017


   Queriers) using modified MLDv2 messages which IP destination is set
   to a configured 'all BMLD Nodes' (resp. 'all BMLD Queriers') IP
   multicast address.

   By running MLDv2 instances with per-listener explicit tracking, BMLD
   Queriers are able to map BMLD Listeners with MLDv2 membership states.
   This state is then used to construct the set of BFERs associated with
   each incoming IP multicast data packet.

4.  Applicability Statement

   BMLD runs on top of a BIER Layer and provides the ingress part of a
   BIER multicast flow overlay, i.e, it specifies how BFIRs construct
   the set of BFERs for each ingress IP multicast data packet.  The BFER
   part of the Multicast Flow Overlay is out of scope of this document.

   The BIER Layer MUST be able to transport BMLD messages toward all
   BMLD Queriers and Listeners.  Such packets are IP multicast packets
   with a BFR-Prefix as source address, a multicast destination address,
   and containing a MLDv2 message.

   BMLD only requires state to be kept by Queriers, and is therefore
   more scalable than PIMv2 [RFC7761] in terms of overall state, but is
   also likely to be less scalable than PIMv2 in terms of the amount of
   control traffic and the size of the state that is kept by individual
   routers.

   This specification is applicable to both IP version 4 and version 6.
   It therefore specifies two separate mechanisms operating
   independently.  For the sake of simplicity, this document uses IPv6
   terminology.  It can be applied to IPv4 by replacing 'MLDv2' with
   'IGMPv3', and following specific requirements when explicitly stated.

5.  Querier and Listener Specifications

   Routers desiring to receive IP multicast traffic (e.g., for their own
   use, or for forwarding) MUST behave as BMLD Listeners.  Routers
   receiving IP multicast traffic from outside the BIER domain, or
   originating multicast traffic, MUST behave as BMLD Queriers.

   BMLD Queriers (resp.  BMLD Listeners) MUST act as MLDv2 Queriers
   (resp.  MLDv2 Listeners) as specified in [RFC3810] unless stated
   otherwise in this section.








Pfister, et al.        Expires September 10, 2017               [Page 4]


Internet-Draft        MLD BIER ingress flow overlay           March 2017


5.1.  Configuration Parameters

   Both Queriers and Listeners MUST operate as BFIRs and BFERs within
   the BIER domain in order to send and receive BMLD messages.  They
   MUST therefore be configured accordingly, as specified in
   [I-D.ietf-bier-architecture].

   All Listeners MUST be configured with a 'all BMLD Queriers' multicast
   address and the BFR-ids of all the BMLD Queriers.  This is used by
   Listeners to send BMLD reports over BIER toward all Queriers.  All
   Queriers MUST be configured to accept BMLD reports sent to this
   address.

   All Queriers MUST be configured with a 'all BMLD Nodes' multicast
   address and the BFR-ids of all the Queriers and Listeners.  This
   information is used by Queriers to send BMLD queries over BIER toward
   all BMLD Nodes.  All BMLD Nodes MUST be configured to accept BMLD
   queries sent to this address.

   Note that BMLD (unlike MLDv2) makes use of per-instance configured
   multicast group addresses rather than well-known addresses so that
   multiple instances of BMLD (using different group addresses) can be
   run simultaneously within the same BIER domain.  Configured group
   addresses MAY be obtained from allocated IP prefixes using [RFC3306].
   One MAY choose to use the well-known MLDv2 addresses in one instance,
   but different instances MUST use different addresses.

   IP packets coming from outside of the BIER domain and having a
   destination address set to the configured 'all BMLD Queriers' or the
   'all BMLD Nodes' group address MUST be dropped.  It is RECOMMENDED
   that these configured addresses have a limited scope, enforcing this
   behavior by scope-based filtering on BIER domain's egress interfaces.

5.2.  MLDv2 instances.

   BMLD Queriers MUST run a MLDv2 Querier instance with per-host
   tracking, which means they keep track of the MLDv2 state associated
   with each BMLD Listener.  For that purpose, Listeners are identified
   by their respective BFR-Prefix, used as IP source address in all BMLD
   reports.

   BMLD Listeners MUST run a MLDv2 Listener instance expressing their
   interest in the multicast traffic they are supposed to receive for
   local use or forwarding.

   BMLD Listeners and Queriers MUST NOT run the MLDv1 (IGMPv2 and IGMPv1
   for IPv4) backward compatibility procedures.




Pfister, et al.        Expires September 10, 2017               [Page 5]


Internet-Draft        MLD BIER ingress flow overlay           March 2017


5.2.1.  Sending Queries

   BMLD Queries are IP packets sent over BIER by BMLD Queriers:

   o  Toward all BMLD Nodes (i.e., providing to the BIER Layer the BFR-
      ids of all BMLD Nodes).

   o  Without the IPv6 router alert option [RFC2711] in the hop-by-hop
      extension header [RFC2460] (or the IPv4 router alert option
      [RFC2113] for IPv4).

   o  With the IP destination address set to the 'all BMLD Nodes' group
      address.

   o  With the IP source address set to the BFR-Prefix of the sender.

   o  With a TTL value great enough such that the packet can be received
      by all BMLD Nodes, depending on the underlying BIER layer (whether
      it decrements the IP TTL or not) and the size of the network.  The
      default value is 64.

5.2.2.  Sending Reports

   BMLD Reports are IP packets sent over BIER by BMLD Listeners:

   o  Toward all BMLD Queriers (i.e., providing to the BIER layer the
      BFR-ids of all BMLD Queriers).

   o  Without the IPv6 router alert option [RFC2711] in the hop-by-hop
      extension header [RFC2460] (or the IPv4 router alert option
      [RFC2113] for IPv4).

   o  With the IP destination address set to the 'all BMLD Queriers'
      group address.

   o  With the IP source address set to the BFR-Prefix of the sender.

   o  With a TTL value great enough such that the packet can be received
      by all BMLD Queriers, depending on the underlying BIER layer
      (whether it decrements the IP TTL or not) and the size of the
      network.  The default value is 64.

5.2.3.  Receiving Queries

   BMLD Queriers and Listeners MUST check the destination address of all
   the IP packets that are received or forwarded over BIER whenever
   their own BIER bit is set in the packet.  If the destination address




Pfister, et al.        Expires September 10, 2017               [Page 6]


Internet-Draft        MLD BIER ingress flow overlay           March 2017


   is equal to the 'all BMLD Nodes' group address the packet is
   processed as specified in this section.

   If the IPv6 (resp.  IPv4) packet contains an ICMPv6 (resp.  IGMP)
   message of type 'Multicast Listener Query' (resp. of type 'Membership
   Query'), it is processed by the MLDv2 (resp.  IGMPv3) instance run by
   the BMLD Querier.  It MUST be dropped otherwise.

   During the MLDv2 processing, the packet MUST NOT be checked against
   the MLDv2 consistency conditions (i.e., the presence of the router
   alert option, the TTL equaling 1 and, for IPv6 only, the source
   address being link-local).

5.2.4.  Receiving Reports

   BMLD Queriers MUST check the destination address of all the IP
   packets that are received or forwarded over BIER whenever their own
   BIER bit is set.  If the destination address is equal to the 'all
   BMLD Queriers' the packet is processed as specified in this section.

   If the IPv6 (resp.  IPv4) packet contains an ICMPv6 (resp.  IGMP)
   message of type 'Multicast Listener Report Message v2' (resp.
   'Version 3 Membership Report'), it is processed by the MLDv2 (resp.
   IGMPv3) instance run by the BMLD Querier.  It MUST be dropped
   otherwise.

   During the MLDv2 processing, the packet MUST NOT be checked against
   the MLDv2 consistency conditions (i.e., the presence of the router
   alert option, the TTL equaling 1 and, for IPv6 only, the source
   address being link-local).

5.3.  Packet Forwarding

   BMLD Queriers configure the BIER Layer using the information obtained
   using BMLD, which associates BMLD Listeners (identified by their BFR-
   Prefixes) with their respective MLDv2 membership state.

   More specifically, the MLDv2 state associated with each BMLD Listener
   is provided to the BIER layer such that whenever a multicast packet
   enters the BIER domain, if that packet matches the membership
   information from a BMLD Listener, its BFR-id is added to the set of
   BFR-ids the packet should be forwarded to by the BIER-Layer.

6.  Security Considerations

   BMLD makes use of IP MLDv2 messages transported over BIER in order to
   configure the BIER Layer of BFIRs.  BMLD messages MUST be secured,
   either by relying on physical or link-layer security, by securing the



Pfister, et al.        Expires September 10, 2017               [Page 7]


Internet-Draft        MLD BIER ingress flow overlay           March 2017


   IP packets (e.g., using IPSec [RFC4301]), or by relying on security
   features provided by the BIER Layer.

   Whenever an attacker would be able to spoof the identity of a router,
   it could:

   o  Redirect undesired traffic toward the spoofed router by
      subscribing to undesired multicast traffic.

   o  Prevent desired multicast traffic from reaching the spoofed router
      by unsubscribing to some desired multicast traffic.

7.  IANA Considerations

   This specification does not require any action from IANA.

8.  Acknowledgements

   Comments concerning this document are very welcome.

9.  References

9.1.  Normative References

   [RFC2113]  Katz, D., "IP Router Alert Option", RFC 2113,
              DOI 10.17487/RFC2113, February 1997,
              <http://www.rfc-editor.org/info/rfc2113>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC3376]  Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
              Thyagarajan, "Internet Group Management Protocol, Version
              3", RFC 3376, DOI 10.17487/RFC3376, October 2002,
              <http://www.rfc-editor.org/info/rfc3376>.

   [RFC3810]  Vida, R., Ed. and L. Costa, Ed., "Multicast Listener
              Discovery Version 2 (MLDv2) for IPv6", RFC 3810,
              DOI 10.17487/RFC3810, June 2004,
              <http://www.rfc-editor.org/info/rfc3810>.

   [I-D.ietf-bier-architecture]
              Wijnands, I., Rosen, E., Dolganow, A., Przygienda, T., and
              S. Aldrin, "Multicast using Bit Index Explicit
              Replication", draft-ietf-bier-architecture-05 (work in
              progress), October 2016.



Pfister, et al.        Expires September 10, 2017               [Page 8]


Internet-Draft        MLD BIER ingress flow overlay           March 2017


9.2.  Informative References

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
              December 1998, <http://www.rfc-editor.org/info/rfc2460>.

   [RFC2711]  Partridge, C. and A. Jackson, "IPv6 Router Alert Option",
              RFC 2711, DOI 10.17487/RFC2711, October 1999,
              <http://www.rfc-editor.org/info/rfc2711>.

   [RFC3306]  Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6
              Multicast Addresses", RFC 3306, DOI 10.17487/RFC3306,
              August 2002, <http://www.rfc-editor.org/info/rfc3306>.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005, <http://www.rfc-editor.org/info/rfc4301>.

   [RFC5015]  Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano,
              "Bidirectional Protocol Independent Multicast (BIDIR-
              PIM)", RFC 5015, DOI 10.17487/RFC5015, October 2007,
              <http://www.rfc-editor.org/info/rfc5015>.

   [RFC7348]  Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
              L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
              eXtensible Local Area Network (VXLAN): A Framework for
              Overlaying Virtualized Layer 2 Networks over Layer 3
              Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014,
              <http://www.rfc-editor.org/info/rfc7348>.

   [RFC7365]  Lasserre, M., Balus, F., Morin, T., Bitar, N., and Y.
              Rekhter, "Framework for Data Center (DC) Network
              Virtualization", RFC 7365, DOI 10.17487/RFC7365, October
              2014, <http://www.rfc-editor.org/info/rfc7365>.

   [RFC7761]  Fenner, B., Handley, M., Holbrook, H., Kouvelas, I.,
              Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent
              Multicast - Sparse Mode (PIM-SM): Protocol Specification
              (Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March
              2016, <http://www.rfc-editor.org/info/rfc7761>.

Appendix A.  BIER Use Case in Data Centers

   In current data center virtualization, virtual eXtensible Local Area
   Network (VXLAN) [RFC7348] is a kind of network virtualization overlay
   technology which is overlaid between NVEs and is intended for multi-
   tenancy data center networks, whose reference architecture is
   illustrated as per Figure 1.



Pfister, et al.        Expires September 10, 2017               [Page 9]


Internet-Draft        MLD BIER ingress flow overlay           March 2017


       +--------+                                             +--------+
       | Tenant +--+                                     +----| Tenant |
       | System |  |                                    (')   | System |
       +--------+  |          ................         (   )  +--------+
                   |  +-+--+  .              .  +--+-+  (_)
                   |  | NVE|--.              .--| NVE|   |
                   +--|    |  .              .  |    |---+
                      +-+--+  .              .  +--+-+
                      /       .              .
                     /        .  L3 Overlay  .  +--+-++--------+
       +--------+   /         .    Network   .  | NVE|| Tenant |
       | Tenant +--+          .              .--|    || System |
       | System |             .              .  +--+-++--------+
       +--------+             ................

                        Figure 1: NVO3 Architecture

   And there are two kinds of most common methods about how to forward
   BUM packets in this virtualization overlay network.  One is using PIM
   as underlay multicast routing protocol to build explicit multicast
   distribution tree, such as PIM-SM [RFC7761] or PIM-BIDIR [RFC5015]
   multicast routing protocol.  Then, when BUM packets arrive at NVE, it
   requires NVE to have a mapping between the VXLAN Network Identifier
   and the IP multicast group.  According to the mapping, NVE can
   encapsulate BUM packets in a multicast packet which group address is
   the mapping IP multicast group address and steer them through
   explicit multicast distribution tree to the destination NVEs.  This
   method has two serious drawbacks.  It need the underlay network
   supports complicated multicast routing protocol and maintains
   multicast related per-flow state in every transit nodes.  What is
   more, how to configure the ratio of the mapping between VNI and IP
   multicast group is also an issue.  If the ratio is 1:1, there should
   be 16M multicast groups in the underlay network at maximum to map to
   the 16M VNIs, which is really a significant challenge for the data
   center devices.  If the ratio is n:1, it would result in inefficiency
   bandwidth utilization which is not optimal in data center networks.

   The other method is using ingress replication to require each NVE to
   create a mapping between the VXLAN Network Identifier and the remote
   addresses of NVEs which belong to the same virtual network.  When NVE
   receives BUM traffic from the attached tenant, NVE can encapsulate
   these BUM packets in unicast packets and replicate them and tunnel
   them to different remote NVEs respectively.  Although this method can
   eliminate the burden of running multicast protocol in the underlay
   network, it has a significant disadvantage: large waste of bandwidth,
   especially in big-sized data center where there are many receivers.





Pfister, et al.        Expires September 10, 2017              [Page 10]


Internet-Draft        MLD BIER ingress flow overlay           March 2017


   BIER [I-D.ietf-bier-architecture] is an architecture that provides
   optimal multicast forwarding through a "BIER domain" without
   requiring intermediate routers to maintain any multicast related per-
   flow state.  BIER also does not require any explicit tree-building
   protocol for its operation.  A multicast data packet enters a BIER
   domain at a "Bit-Forwarding Ingress Router" (BFIR), and leaves the
   BIER domain at one or more "Bit-Forwarding Egress Routers" (BFERs).
   The BFIR router adds a BIER header to the packet.  The BIER header
   contains a bit-string in which each bit represents exactly one BFER
   to forward the packet to.  The set of BFERs to which the multicast
   packet needs to be forwarded is expressed by setting the bits that
   correspond to those routers in the BIER header.  Specifically, for
   BIER-TE, the BIER header may also contain a bit-string in which each
   bit indicates the link the flow passes through.

   The following sub-sections try to propose how to take full advantage
   of overlay multicast protocol to carry virtual network information,
   and create a mapping between the virtual network information and the
   bit-string to implement BUM services in data centers.

A.1.  Convention and Terminology

   The terms about NVO3 are defined in [RFC7365].  The most common
   terminology used in this appendix is listed below.

   NVE:  Network Virtualization Edge, which is the entity that
      implements the overlay functionality.  An NVE resides at the
      boundary between a Tenant System and the overlay network.

   VXLAN:  Virtual eXtensible Local Area Network

   VNI:  VXLAN Network Identifier

   Virtal Network Context Identifier:  Field in an overlay encapsulation
      header that identifies the specific VN the packet belongs to.

A.2.  BIER in data centers

   This section tries to describe how to use BIER as an optimal scheme
   to forward the broadcast, unknown and multicast (BUM) packets when
   they arrive at the ingress NVE in data centers.

   The principle of using BIER to forward BUM traffic is that: firstly,
   it requires each ingress NVE to have a mapping between the Virtual
   Network Context Identifier and the bit-string in which each bit
   represents exactly one egress NVE to forward the packet to.  And
   then, when receiving the BUM traffic, the BFIR/Ingree NVE maps the
   receiving BUM traffic to the mapping bit-string, encapsulates the



Pfister, et al.        Expires September 10, 2017              [Page 11]


Internet-Draft        MLD BIER ingress flow overlay           March 2017


   BIER header, and forwards the encapsulated BUM traffic into the BIER
   domain to the other BFERs/Egress NVEs indicated by the bit-string.

   Furthermore, as for how each ingress NVE knows the other egress NVEs
   that belong to the same virtual network and creates the mapping is
   the main issue discussed below.  Basically, BIER Multicast Listener
   Discovery is an overlay solution to support ingress routers to keep
   per-egress-router state to construct the BIER bit-string associated
   with IP multicast packets entering the BIER domain.  The following
   section tries to extend BIER MLD to carry virtual network
   information(such as Virtual Network Context identifier), and
   advertise them between NVEs.  When each NVE receive these
   information, they create the mapping between the virtual network
   information and the bit-string representing the other NVEs belonged
   to the same virtual network.

A.3.  A BIER MLD solution for Virtual Network information

   The BIER MLD solution allows having multiple MLD instances by having
   unique pairs of BMLD Nodes and BMLD Querier addresses for each
   instance.  Assume for now that we have a unique instance per VNI and
   that all BMLD routers are using the same mapping between VNIs and
   BMLD address pairs.  Also for each VNI there is a multicast group
   used for encapsulation of BUM traffic over BIER.  This group may
   potentially be shared by some or all of the VNIs.

   Each NVE acquires the Virtual Network information, and advertises
   this Virtual Network information to other NVEs through the MLD
   messages.  For a given VNI it sends BMLD reports to the BMLD nodes
   address used for that VNI, for the group used for delivering BUM
   traffic for that VNI.  This allows all NVE routers to know which
   other NVE routers have interest in BUM traffic for a particular VNI.
   If one attached virtual network is migrated, the NVE will withdraw
   the Virtual Network information by sending an unsolicited BMLD
   report.  Note that NVEs also respond to periodic queries to BMLD
   Nodes addresses corresponding to VNIs for which they have interest.

   When ingress NVE receives the Virtual Network information
   advertisement message, it builds a mapping between the receiving
   Virtual Network Context Identifier in this message and the bit-string
   in which each bit represents one egress NVE who sends the same
   Virtual Network information.  Subsequently, once this ingress NVE
   receives some other MLD advertisements which include the same Virtual
   Network information from some other NVEs , it updates the bit-string
   in the mapping and adds the corresponding sending NVE to the updated
   bit-string.  Once the ingress NVE removes one virtual network, it
   will delete the mapping corresponding to this virtual network as well
   as send withdraw message to other NVEs.



Pfister, et al.        Expires September 10, 2017              [Page 12]


Internet-Draft        MLD BIER ingress flow overlay           March 2017


   After finishing the above interaction of MLD messages, each ingress
   NVE knows where the other egress NVEs are in the same virtual
   network.  When receiving BUM traffic from the attached virtual
   network, each ingress NVE knows exactly how to encapsulate this
   traffic and where to forward them to.

   This can be used in both IPv4 network and IPv6 network.  In IPv4,
   IGMP protocol does the similar extension for carrying Virtual Network
   information TLV in Version 2 membership report message.

   Note that it is possible to have multiple VNIs map to the same pair
   of BMLD addresses.  Provided VNIs that map to the same BMLD address
   uses different multicast groups for encapsulation, this is not a
   problem, because each instance is tracking interest for each
   multicast group separately.  If multiple VNIs map to the same pair
   and the multicast group used is not unique, some NVEs may receive BUM
   traffic for which they are not interested.  An NVE would drop packets
   for an unknown VNI, but it means wasting some bandwidth and
   processing.  This is similar to the non-BIER case where there is not
   a unique multicast group for encapsulation.  The improvement offered
   by using BMLD is by using multiple instance, hence reducing the
   problems caused by using the same transport group for multiple VNIs.

Authors' Addresses

   Pierre Pfister
   Cisco Systems
   Paris
   France

   Email: pierre.pfister@darou.fr


   IJsbrand Wijnands
   Cisco Systems
   De Kleetlaan 6a
   Diegem  1831
   Belgium

   Email: ice@cisco.com











Pfister, et al.        Expires September 10, 2017              [Page 13]


Internet-Draft        MLD BIER ingress flow overlay           March 2017


   Stig Venaas
   Cisco Systems
   Tasman Drive
   San Jose, CA  95134
   USA

   Email: stig@cisco.com


   Cui(Linda) Wang
   ZTE Corporation
   No.50 Software Avenue, Yuhuatai District
   Nanjing, CA
   China

   Email: wang.cui1@zte.com.cn


   Zheng(Sandy) Zhang
   ZTE Corporation
   No.50 Software Avenue, Yuhuatai District
   Nanjing, CA
   China

   Email: zhang.zheng@zte.com.cn


   Markus Stenberg
   Helsinki  00930
   Finland

   Email: markus.stenberg@iki.fi



















Pfister, et al.        Expires September 10, 2017              [Page 14]


Html markup produced by rfcmarkup 1.124, available from https://tools.ietf.org/tools/rfcmarkup/