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Versions: 00 01 02 draft-ietf-bier-use-cases

Network Working Group                                           N. Kumar
Internet-Draft                                                  R. Asati
Intended status: Informational                                     Cisco
Expires: August 13, 2015                                         M. Chen
                                                                   X. Xu
                                                                  Huawei
                                                             A. Dolganow
                                                          Alcatel-Lucent
                                                           T. Przygienda
                                                                Ericsson
                                                                A. Gulko
                                                         Thomson Reuters
                                                             D. Robinson
                                                       id3as-company Ltd
                                                        February 9, 2015


                             BIER Use Cases
                   draft-kumar-bier-use-cases-02.txt

Abstract

   Bit Index Explicit Replication (BIER) 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.

   This document describes some of the use-cases for BIER.

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/.





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

   This Internet-Draft will expire on August 13, 2015.

Copyright Notice

   Copyright (c) 2015 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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Specification of Requirements . . . . . . . . . . . . . . . .   3
   3.  BIER Use Cases  . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Multicast in L3VPN Networks . . . . . . . . . . . . . . .   3
     3.2.  BUM in EVPN . . . . . . . . . . . . . . . . . . . . . . .   4
     3.3.  IPTV and OTT Services . . . . . . . . . . . . . . . . . .   5
     3.4.  Multi-service, converged L3VPN network  . . . . . . . . .   6
     3.5.  Control-plane simplification and SDN-controlled networks    7
     3.6.  Data center Virtualization/Overlay  . . . . . . . . . . .   7
     3.7.  Financial Services  . . . . . . . . . . . . . . . . . . .   8
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   9
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   Bit Index Explicit Replication (BIER)
   [I-D.wijnands-bier-architecture] is an architecture that provides
   optimal multicast forwarding through a "BIER domain" without
   requiring intermediate routers to maintain any multicast related per-



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   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.

   The obvious advantage of BIER is that there is no per flow multicast
   state in the core of the network and there is no tree building
   protocol that sets up tree on demand based on users joining a
   multicast flow.  In that sense, BIER is potentially applicable to
   many services where Multicast is used and not limited to the examples
   described in this draft.  In this document we are describing a few
   use-cases where BIER could provide benefit over using existing
   mechanisms.

2.  Specification of Requirements

   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 [RFC2119].

3.  BIER Use Cases

3.1.  Multicast in L3VPN Networks

   The Multicast L3VPN architecture [RFC6513] describes many different
   profiles in order to transport L3 Multicast across a providers
   network.  Each profile has its own different tradeoffs (see section
   2.1 [RFC6513]).  When using "Multidirectional Inclusive" "Provider
   Multicast Service Interface" (MI-PMSI) an efficient tree is build per
   VPN, but causes flooding of egress PE's that are part of the VPN, but
   have not joined a particular C-multicast flow.  This problem can be
   solved with the "Selective" PMSI to build a special tree for only
   those PE's that have joined the C-multicast flow for that specific
   VPN.  The more S-PMSI's, the less bandwidth is wasted due to
   flooding, but causes more state to be created in the providers
   network.  This is a typical problem network operators are faced with
   by finding the right balance between the amount of state carried in
   the network and how much flooding (waste of bandwidth) is acceptable.
   Some of the complexity with L3VPN's comes due to providing different
   profiles to accommodate these trade-offs.

   With BIER there is no trade-off between State and Flooding.  Since
   the receiver information is explicitly carried within the packet,



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   there is no need to build S-PMSI's to deliver multicast to a sub-set
   of the VPN egress PE's.  Due to that behaviour, there is no need for
   S-PMSI's.

   Mi-PMSI's and S-PMSI's are also used to provide the VPN context to
   the Egress PE router that receives the multicast packet.  Also, in
   some MVPN profiles it is also required to know which Ingress PE
   forwarded the packet.  Based on the PMSI the packet is received from,
   the target VPN is determined.  This also means there is a requirement
   to have a least a PMSI per VPN or per VPN/Ingress PE.  This means the
   amount of state created in the network is proportional to the VPN and
   ingress PE's.  Creating PMSI state per VPN can be prevented by
   applying the procedures as documented in [RFC5331].  This however has
   not been very much adopted/implemented due to the excessive flooding
   it would cause to Egress PE's since *all* VPN multicast packets are
   forwarded to *all* PE's that have one or more VPN's attached to it.

   With BIER, the destination PE's are identified in the multicast
   packet, so there is no flooding concern when implementing [RFC5331].
   For that reason there is no need to create multiple BIER domain's per
   VPN, the VPN context can be carry in the multicast packet using the
   procedures as defined in [RFC5331].  Also see
   [I-D.rosen-l3vpn-mvpn-bier] for more information.

   With BIER only a few MVPN profiles will remain relevant, simplifying
   the operational cost and making it easier to be interoperable among
   different vendors.

3.2.  BUM in EVPN

   The current widespread adoption of L2VPN services [RFC4664],
   especially the upcoming EVPN solution [I-D.ietf-l2vpn-evpn] which
   transgresses many limitations of VPLS, introduces the need for an
   efficient mechanism to replicate broadcast, unknown and multicast
   (BUM) traffic towards the PEs that participate in the same EVPN
   instances (EVIs).  As simplest deployable mechanism, ingress
   replication is used but poses accordingly a high burden on the
   ingress node as well as saturating the underlying links with many
   copies of the same frame headed to different PEs.  Fortunately
   enough, EVPN signals internally P-Multicast Service Interface (PMSI)
   [RFC6513] attribute to establish transport for BUM frames and with
   that allows to deploy a plethora of multicast replication services
   that the underlying network layer can provide.  It is therefore
   relatively simple to deploy BIER P-Tunnels for EVPN and with that
   distribute BUM traffic without building of P-router state in the core
   required by PIM, mLDP or comparable solutions.





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   Specifically, the same I-PMSI attribute suggested for mVPN can be
   used easily in EVPN and given EVPN can multiplex and disassociate BUM
   frames on p2mp and mp2mp trees using upstream assigned labels, BIER
   P-Tunnel will support BUM flooding for any number of EVIs over a
   single sub-domain for maximum scalability but allow at the other
   extreme of the spectrum to use a single BIER sub-domain per EVI if
   such a deployment is necessary.

   Multiplexing EVIs onto the same PMSI forces the PMSI to span more
   than the necessary number of PEs normally, i.e. the union of all PEs
   participating in the EVIs multiplexed on the PMSI.  Given the
   properties of BIER it is however possible to encode in the receiver
   bitmask only the PEs that participate in the EVI the BUM frame
   targets.  In a sense BIER is an inclusive as well as a selective tree
   and can allow to deliver the frame to only the set of receivers
   interested in a frame even though many others participate in the same
   PMSI.

   As another significant advantage, it is imaginable that the same BIER
   tunnel needed for BUM frames can optimize the delivery of the
   multicast frames though the signaling of group memberships for the
   PEs involved has not been specified as of date.

3.3.  IPTV and OTT Services

   IPTV is a service, well known for its characteristics of allowing
   both live and on-demand delivery of media traffic over end-to-end
   Managed IP network.

   Over The Top (OTT) is a similar service, well known for its
   characteristics of allowing live and on-demand delivery of media
   traffic between IP domains, where the source is often on an external
   network relative to the receivers.

   Content Delivery Networks (CDN) operators provide layer 4
   applications, and often some degree of managed layer 3 IP network,
   that enable media to be securely and reliably delivered to many
   receivers.  In some models they may place applications within third
   party networks, or they may place those applications at the edges of
   their own managed network peerings and similar inter-domain
   connections.  CDNs provide capabilities to help publishers scale to
   meet large audience demand.  Their applications are not limited to
   audio and video delivery, but may include static and dynamic web
   content, or optimized delivery for Massive Multiplayer Gaming and
   similar.  Most publishers will use a CDN for public Internet
   delivery, and some publishers will use a CDN internally within their
   IPTV networks to resolve layer 4 complexity.




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   In a typical IPTV environment the egress routers connecting to the
   receivers will build the tree towards the ingress router connecting
   to the IPTV servers.  The egress routers would rely on IGMP/MLD
   (static or dynamic) to learn about the receiver's interest in one or
   more multicast group/channels.  Interestingly, BIER could allows
   provisioning any new multicast group/channel by only modifying the
   channel mapping on ingress routers.  This is deemed beneficial for
   the linear IPTV video broadcasting in which every receivers behind
   every egress PE routers would receive the IPTV video traffic.

   With BIER in IPTV environment, there is no need of tree building from
   egress to ingress.  Further, any addition of new channel or new
   egress routers can be directly controlled from ingress router.  When
   a new channel is included, the multicast group is mapped to Bit
   string that includes all egress routers.  Ingress router would start
   sending the new channel and deliver it to all egress routers.  As it
   can be observed, there is no need for static IGMP provisioning in
   each egress routers whenever a new channel/stream is added.  Instead,
   it can be controlled from ingress router itself by configuring the
   new group to Bit Mask mapping on ingress router.

   With BIER in OTT environment, these edge routers in CDN domain
   terminating the OTT user session connect to the Ingress BIER routers
   connecting content provider domains or a local cache server and
   leverage the scalability benefit that BIER could provide.  This may
   rely on MBGP interoperation (or similar) between the egress of one
   domain and the ingress of the next domain, or some other SDN control
   plane may prove a more effective and simpler way to deploy BIER.  For
   a single CDN operator this could be well managed in the Layer 4
   applications that they provide and it may be that the initial
   receiver in a remote domain is actually an application operated by
   the CDN which in turn acts as a source for the Ingress BIER router in
   that remote domain, and by doing so keeps the BIER more descrete on a
   domain by domain basis.

3.4.  Multi-service, converged L3VPN network

   Increasingly operators deploy single networks for multiple-services.
   For example a single Metro Core network could be deployed to provide
   Residential IPTV retail service, residential IPTV wholesale service,
   and business L3VPN service with multicast.  It may often be desired
   by an operator to use a single architecture to deliver multicast for
   all of those services.  In some cases, governing regulations may
   additionally require same service capabilities for both wholesale and
   retail multicast services.  To meet those requirements, some
   operators use multicast architecture as defined in [RFC5331].
   However, the need to support many L3VPNs, with some of those L3VPNs
   scaling to hundreds of egress PE's and thousands of C-multicast



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   flows, make scaling/efficiency issues defined in earlier sections of
   this document even more prevalent.  Additionally support for ten's of
   millions of BGP multicast A-D and join routes alone could be required
   in such networks with all consequences such a scale brings.

   With BIER, again there is no need of tree building from egress to
   ingress for each L3VPN or individual or group of c-multicast flows.
   As described earlier on, any addition of a new IPTV channel or new
   egress router can be directly controlled from ingress router and
   there is no flooding concern when implementing [RFC5331].

3.5.  Control-plane simplification and SDN-controlled networks

   With the advent of Software Defined Networking, some operators are
   looking at various ways to reduce the overall cost of providing
   networking services including multicast delivery.  Some of the
   alternatives being consider include minimizing capex cost through
   deployment of network-elements with simplified control plane
   function, minimizing operational cost by reducing control protocols
   required to achieve a particular service, etc.  Segment routing as
   described in [I-D.ietf-spring-segment-routing] provides a solution
   that could be used to provide simplified control-plane architecture
   for unicast traffic.  With Segment routing deployed for unicast, a
   solution that simplifies control-plane for multicast would thus also
   be required, or operational and capex cost reductions will not be
   achieved to their full potential.

   With BIER, there is no longer a need to run control protocols
   required to build a distribution tree.  If L3VPN with multicast, for
   example, is deployed using [RFC5331] with MPLS in P-instance, the
   MPLS control plane would no longer be required.  BIER also allows
   migration of C-multicast flows from non-BIER to BIER-based
   architecture, which makes transition to control-plane simplified
   network simpler to operationalize.  Finally, for operators, who would
   desire centralized, offloaded control plane, multicast overlay as
   well as BIER forwarding could migrate to controller-based
   programming.

3.6.  Data center Virtualization/Overlay

   Virtual eXtensible Local Area Network (VXLAN) [RFC7348] is a kind of
   network virtualization overlay technology which is intended for
   multi-tenancy data center networks.  To emulate a layer2 flooding
   domain across the layer3 underlay, it requires to have a mapping
   between the VXLAN Virtual Network Instance (VNI) and the IP multicast
   group in a ratio of 1:1 or n:1.  In other words, it requires to
   enable the multicast capability in the underlay.  For instance, it
   requires to enable PIM-SM [RFC4601] or PIM-BIDIR [RFC5015] multicast



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   routing protocol in the underlay.  VXLAN is designed to support 16M
   VNIs at maximum.  In the mapping ratio of 1:1, it would require 16M
   multicast groups in the underlay which would become a significant
   challenge to both the control plane and the data plane of the data
   center switches.  In the mapping ratio of n:1, it would result in
   inefficiency bandwidth utilization which is not optimal in data
   center networks.  More importantly, it is recognized by many data
   center operators as a unaffordable burden to run multicast in data
   center networks from network operation and maintenance perspectives.
   As a result, many VXLAN implementations are claimed to support the
   ingress replication capability since ingress replication eliminates
   the burden of running multicast in the underlay.  Ingress replication
   is an acceptable choice in small-sized networks where the average
   number of receivers per multicast flow is not too large.  However, in
   multi-tenant data center networks, especially those in which the NVE
   functionality is enabled on a high amount of physical servers, the
   average number of NVEs per VN instance would be very large.  As a
   result, the ingress replication scheme would result in a serious
   bandwidth waste in the underlay and a significant replication burden
   on ingress NVEs.

   With BIER, there is no need for maintaining that huge amount of
   multicast states in the underlay anymore while the delivery
   efficiency of overlay BUM traffic is the same as if any kind of
   stateful multicast protocols such as PIM-SM or PIM-BIDIR is enabled
   in the underlay.

3.7.  Financial Services

   Financial services extensively rely on IP Multicast to deliver stock
   market data and its derivatives, and critically require optimal
   latency path (from publisher to subscribers), deterministic
   convergence (so as to deliver market data derivatives fairly to each
   client) and secured delivery.

   Current multicast solutions e.g.  PIM, mLDP etc., however, don't
   sufficiently address the above requirements.  The reason is that the
   current solutions are primarily subscriber driven i.e. multicast tree
   is setup using reverse path forwarding techniques, and as a result,
   the chosen path for market data may not be latency optimal from
   publisher to the (market data) subscribers.

   As the number of multicast flows grows, the convergence time might
   increase and make it somewhat nondeterministic from the first to the
   last flow depending on platforms/implementations.  Also, by having
   more protocols in the network, the variability to ensure secured
   delivery of multicast data increases, thereby undermining the overall
   security aspect.



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   BIER enables setting up the most optimal path from publisher to
   subscribers by leveraging unicast routing relevant for the
   subscribers.  With BIER, the multicast convergence is as fast as
   unicast, uniform and deterministic regardless of number of multicast
   flows.  This makes BIER a perfect multicast technology to achieve
   fairness for market derivatives per each subscriber.

4.  Security Considerations

   There are no security issues introduced by this draft.

5.  IANA Considerations

   There are no IANA consideration introduced by this draft.

6.  Acknowledgments

   The authors would like to thank IJsbrand Wijnands, Greg Shepherd and
   Christian Martin for their contribution.

7.  References

7.1.  Normative References

   [I-D.rosen-l3vpn-mvpn-bier]
              Rosen, E., Sivakumar, M., Wijnands, I., Aldrin, S.,
              Dolganow, A., and T. Przygienda, "Multicast VPN Using
              BIER", draft-rosen-l3vpn-mvpn-bier-02 (work in progress),
              December 2014.

   [I-D.wijnands-bier-architecture]
              Wijnands, I., Rosen, E., Dolganow, A., Przygienda, T., and
              S. Aldrin, "Multicast using Bit Index Explicit
              Replication", draft-wijnands-bier-architecture-04 (work in
              progress), February 2015.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

7.2.  Informative References

   [I-D.ietf-l2vpn-evpn]
              Sajassi, A., Aggarwal, R., Bitar, N., Isaac, A., and J.
              Uttaro, "BGP MPLS Based Ethernet VPN", draft-ietf-l2vpn-
              evpn-11 (work in progress), October 2014.






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   [I-D.ietf-spring-segment-routing]
              Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
              Litkowski, S., Horneffer, M., Shakir, R., Tantsura, J.,
              and E. Crabbe, "Segment Routing Architecture", draft-ietf-
              spring-segment-routing-01 (work in progress), February
              2015.

   [RFC4601]  Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
              "Protocol Independent Multicast - Sparse Mode (PIM-SM):
              Protocol Specification (Revised)", RFC 4601, August 2006.

   [RFC4664]  Andersson, L. and E. Rosen, "Framework for Layer 2 Virtual
              Private Networks (L2VPNs)", RFC 4664, September 2006.

   [RFC5015]  Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano,
              "Bidirectional Protocol Independent Multicast (BIDIR-
              PIM)", RFC 5015, October 2007.

   [RFC5331]  Aggarwal, R., Rekhter, Y., and E. Rosen, "MPLS Upstream
              Label Assignment and Context-Specific Label Space", RFC
              5331, August 2008.

   [RFC6513]  Rosen, E. and R. Aggarwal, "Multicast in MPLS/BGP IP
              VPNs", RFC 6513, February 2012.

   [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, August 2014.

Authors' Addresses

   Nagendra Kumar
   Cisco
   7200 Kit Creek Road
   Research Triangle Park, NC  27709
   US

   Email: naikumar@cisco.com











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   Rajiv Asati
   Cisco
   7200 Kit Creek Road
   Research Triangle Park, NC  27709
   US

   Email: rajiva@cisco.com


   Mach(Guoyi) Chen
   Huawei

   Email: mach.chen@huawei.com


   Xiaohu Xu
   Huawei

   Email: xuxiaohu@huawei.com


   Andrew Dolganow
   Alcatel-Lucent
   600 March Road
   Ottawa, ON  K2K2E6
   Canada

   Email: andrew.dolganow@alcatel-lucent.com


   Tony Przygienda
   Ericsson
   300 Holger Way
   San Jose, CA  95134
   USA

   Email: antoni.przygienda@ericsson.com


   Arkadiy Gulko
   Thomson Reuters
   195 Broadway
   New York  NY 10007
   USA

   Email: arkadiy.gulko@thomsonreuters.com





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   Dom Robinson
   id3as-company Ltd
   UK

   Email: Dom@id3as.co.uk














































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