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rfc:rfc4611

Network Working Group M. McBride Request for Comments: 4611 J. Meylor BCP: 121 D. Meyer Category: Best Current Practice August 2006

  Multicast Source Discovery Protocol (MSDP) Deployment Scenarios

Status of This Memo

 This document specifies an Internet Best Current Practices for the
 Internet Community, and requests discussion and suggestions for
 improvements.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2006).

Abstract

 This document describes best current practices for intra-domain and
 inter-domain deployment of the Multicast Source Discovery Protocol
 (MSDP) in conjunction with Protocol Independent Multicast Sparse Mode
 (PIM-SM).

Table of Contents

 1. Introduction ....................................................2
    1.1. BCP, Experimental Protocols, and Normative References ......3
 2. Inter-domain MSDP Peering Scenarios .............................4
    2.1. Peering between PIM Border Routers .........................4
    2.2. Peering between Non-Border Routers .........................5
    2.3. MSDP Peering without BGP ...................................7
    2.4. MSDP Peering at a Multicast Exchange .......................7
 3. Intra-domain MSDP Peering Scenarios .............................7
    3.1. Peering between MSDP- and MBGP-Configured Routers ..........8
    3.2. MSDP Peer Is Not BGP Peer (or No BGP Peer) .................8
    3.3. Hierarchical Mesh Groups ...................................9
    3.4. MSDP and Route Reflectors .................................10
    3.5. MSDP and Anycast RPs ......................................11
 4. Security Considerations ........................................11
    4.1. Filtering SA Messages .....................................11
    4.2. SA Message State Limits ...................................12
 5. Acknowledgements ...............................................12
 6. References .....................................................12
    6.1. Normative References ......................................12
    6.2. Informative References ....................................13

McBride, et al. Best Current Practice [Page 1] RFC 4611 MSDP Deployment Scenarios August 2006

1. Introduction

 MSDP [RFC3618] is used primarily in two deployment scenarios:
 o  Between PIM Domains
    MSDP can be used between Protocol Independent Multicast Sparse
    Mode (PIM-SM) [RFC4601] domains to convey information about active
    sources available in other domains.  MSDP peering used in such
    cases is generally one-to-one peering, and utilizes the
    deterministic peer-RPF (Reverse Path Forwarding) rules described
    in the MSDP specification (i.e., it does not use mesh-groups).
    Peerings can be aggregated on a single MSDP peer.  Such a peer can
    typically have from one to hundreds of peerings, which is similar
    in scale to BGP peerings.
 o  Within a PIM Domain
    MSDP is often used between Anycast Rendezvous Points (Anycast-RPs)
    [RFC3446] within a PIM domain to synchronize information about the
    active sources being served by each Anycast-RP peer (by virtue of
    IGP reachability).  MSDP peering used in this scenario is
    typically based on MSDP mesh groups, where anywhere from two to
    tens of peers can comprise a given mesh group, although more than
    ten is not typical.  One or more of these mesh-group peers may
    also have additional one-to-one peerings with MSDP peers outside
    that PIM domain for discovery of external sources.  MSDP for
    anycast-RP without external MSDP peering is a valid deployment
    option and common.
 Current best practice for MSDP deployment utilizes PIM-SM and the
 Border Gateway Protocol with multi-protocol extensions (MBGP)
 [RFC4271, RFC2858].  This document outlines how these protocols work
 together to provide an intra-domain and inter-domain Any Source
 Multicast (ASM) service.
 The PIM-SM specification assumes that SM operates only in one PIM
 domain.  MSDP is used to enable the use of multiple PIM domains by
 distributing the required information about active multicast sources
 to other PIM domains.  Due to breaking the Internet multicast
 infrastructure down to multiple PIM domains, MSDP also enables the
 possibility of setting policy on the visibility of the groups and
 sources.
 Transit IP providers typically deploy MSDP to be part of the global
 multicast infrastructure by connecting to their upstream and peer
 multicast networks using MSDP.

McBride, et al. Best Current Practice [Page 2] RFC 4611 MSDP Deployment Scenarios August 2006

 Edge multicast networks typically have two choices: to use their
 Internet providers' RP, or to have their own RP and connect it to
 their ISP using MSDP.  By deploying their own RP and MSDP, they can
 use internal multicast groups that are not visible to the provider's
 RP.  This helps internal multicast be able to continue to work in the
 event that there is a problem with connectivity to the provider or
 that the provider's RP/MSDP is experiencing difficulties.  In the
 simplest cases, where no internal multicast groups are necessary,
 there is often no need to deploy MSDP.

1.1. BCP, Experimental Protocols, and Normative References

 This document describes the best current practice for a widely
 deployed Experimental protocol, MSDP.  There is no plan to advance
 the MSDP's status (for example, to Proposed Standard).  The reasons
 for this include:
 o  MSDP was originally envisioned as a temporary protocol to be
    supplanted by whatever the IDMR working group produced as an
    inter-domain protocol.  However, the IDMR WG (or subsequently, the
    BGMP WG) never produced a protocol that could be deployed to
    replace MSDP.
 o  One of the primary reasons given for MSDP to be classified as
    Experimental was that the MSDP Working Group came up with
    modifications to the protocol that the WG thought made it better
    but that implementors didn't see any reasons to deploy.  Without
    these modifications (e.g., UDP or GRE encapsulation), MSDP can
    have negative consequences to initial packets in datagram streams.
 o  Scalability: Although we don't know what the hard limits might be,
    readvertising everything you know every 60 seconds clearly limits
    the amount of state you can advertise.
 o  MSDP reached nearly ubiquitous deployment as the de facto standard
    inter-domain multicast protocol in the IPv4 Internet.
 o  No consensus could be reached regarding the reworking of MSDP to
    address the many concerns of various constituencies within the
    IETF.  As a result, a decision was taken to document what is
    (ubiquitously) deployed and to move that document to Experimental.
    While advancement of MSDP to Proposed Standard was considered, for
    the reasons mentioned above, it was immediately discarded.
 o  The advent of protocols such as source-specific multicast and bi-
    directional PIM, as well as embedded RP techniques for IPv6, have
    further reduced consensus that a replacement protocol for MSDP for
    the IPv4 Internet is required.

McBride, et al. Best Current Practice [Page 3] RFC 4611 MSDP Deployment Scenarios August 2006

 The RFC Editor's policy regarding references is that they be split
 into two categories known as "normative" and "informative".
 Normative references specify those documents that must be read for
 one to understand or implement the technology in an RFC (or whose
 technology must be present for the technology in the new RFC to work)
 [RFCED].  In order to understand this document, one must also
 understand both the PIM and MSDP documents.  As a result, references
 to these documents are normative.
 The IETF has adopted the policy that BCPs must not have normative
 references to Experimental protocols.  However, this document is a
 special case in that the underlying Experimental document (MSDP) is
 not planned to be advanced to Proposed Standard.
 The MBONED Working Group has requested approval under the Variance
 Procedure as documented in RFC 2026 [RFC2026].  The IESG followed the
 Variance Procedure and, after an additional 4 week IETF Last Call,
 evaluated the comments and status, and has approved this document.
 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in RFC 2119 [RFC2119].

2. Inter-domain MSDP Peering Scenarios

 The following sections describe the most common inter-domain MSDP
 peering possibilities and their deployment options.

2.1. Peering between PIM Border Routers

 In this case, the MSDP peers within the domain have their own RP
 located within a bounded PIM domain.  In addition, the domain will
 typically have its own Autonomous System (AS) number and one or more
 MBGP speakers.  The domain may also have multiple MSDP speakers.
 Each border router has an MSDP and MBGP peering with its peer
 routers.  These external MSDP peering deployments typically configure
 the MBGP peering and MSDP peering using the same directly connected
 next hop peer IP address or other IP address from the same router.
 Typical deployments of this type are providers who have a direct
 peering with other providers, providers peering at an exchange, or
 providers who use their edge router to MSDP/MBGP peer with customers.
 For a direct peering inter-domain environment to be successful, the
 first AS in the MBGP best path to the originating RP should be the
 same as the AS of the MSDP peer.  As an example, consider the
 following topology:

McBride, et al. Best Current Practice [Page 4] RFC 4611 MSDP Deployment Scenarios August 2006

       AS1----AS2----AS4
       |    /
       |   /
       |  /
       AS3
 In this case, AS4 receives a Source Active (SA) message, originated
 by AS1, from AS2.  AS2 also has an MBGP peering with AS4.  The MBGP
 first hop AS from AS4, in the best path to the originating RP, is
 AS2.  The AS of the sending MSDP peer is also AS2.  In this case, the
 peer-Reverse Path Forwarding check (peer-RPF check) passes, and the
 SA message is forwarded.
 A peer-RPF failure would occur in this topology when the MBGP first
 hop AS, in the best path to the originating RP, is AS2 and the origin
 AS of the sending MSDP peer is AS3.  This reliance upon BGP AS PATH
 information prevents endless looping of SA packets.
 Router code, which has adopted the latest rules in the MSDP document,
 will relax the rules between AS's a bit.  In the following topology,
 we have an MSDP peering between AS1<->AS3 and AS3<->AS4:
                             RP
       AS1----AS2----AS3----AS4
 If the first AS in best path to the RP does not equal the MSDP peer,
 MSDP peer-RPF fails.  So AS1 cannot MSDP peer with AS3, since AS2 is
 the first AS in the MBGP best path to AS4 RP.  With the latest MSDP
 document compliant code, AS1 will choose the peer in the closest AS
 along best AS path to the RP.  AS1 will then accept SA's coming from
 AS3.  If there are multiple MSDP peers to routers within the same AS,
 the peer with the highest IP address is chosen as the RPF peer.

2.2. Peering between Non-Border Routers

 For MSDP peering between border routers, intra-domain MSDP
 scalability is restricted because it is necessary to also maintain
 MBGP and MSDP peerings internally towards their border routers.
 Within the intra-domain, the border router becomes the announcer of
 the next hop towards the originating RP.  This requires that all
 intra-domain MSDP peerings mirror the MBGP path back towards the
 border router.  External MSDP (eMSDP) peerings rely upon AS path for
 peer RPF checking, while internal MSDP (iMSDP) peerings rely upon the
 announcer of the next hop.

McBride, et al. Best Current Practice [Page 5] RFC 4611 MSDP Deployment Scenarios August 2006

 While the eMBGP peer is typically directly connected between border
 routers, it is common for the eMSDP peer to be located deeper into
 the transit provider's AS.  Providers, which desire more flexibility
 in MSDP peering placement, commonly choose a few dedicated routers
 within their core networks for the inter-domain MSDP peerings to
 their customers.  These core MSDP routers will also typically be in
 the provider's intra-domain MSDP mesh group and be configured for
 Anycast RP.  All multicast routers in the provider's AS should
 statically point to the Anycast RP address.  Static RP assignment is
 the most commonly used method for group-to-RP mapping due to its
 deterministic nature.  Auto-RP [RFC4601] and/or the Bootstrap Router
 (BSR) [BSR] dynamic RP mapping mechanisms could also be used to
 disseminate RP information within the provider's network
 For an SA message to be accepted in this (multi-hop peering)
 environment, we rely upon the next (or closest, with latest MSDP
 spec) AS in the best path towards the originating RP for the RPF
 check.  The MSDP peer address should be in the same AS as the AS of
 the border router's MBGP peer.  The MSDP peer address should be
 advertised via MBGP.
 For example, in the diagram below, if customer R1 router is MBGP
 peering with the R2 router and if R1 is MSDP peering with the R3
 router, then R2 and R3 must be in the same AS (or must appear, to
 AS1, to be from the same AS in the event that private AS numbers are
 deployed).  The MSDP peer with the highest IP address will be chosen
 as the MSDP RPF peer.  R1 must also have the MSDP peer address of R3
 in its MBGP table.
       +--+    +--+    +--+
       |R1|----|R2|----|R3|
       +--+    +--+    +--+
       AS1     AS2     AS2
 From R3's perspective, AS1 (R1) is the MBGP next AS in the best path
 towards the originating RP.  As long as AS1 is the next AS (or
 closest) in the best path towards the originating RP, RPF will
 succeed on SAs arriving from R1.
 In contrast, with the single hop scenario, with R2 (instead of R3)
 border MSDP peering with R1 border, R2's MBGP address becomes the
 announcer of the next hop for R3, towards the originating RP, and R3
 must peer with that R2 address.  Moreover, all AS2 intra-domain MSDP
 peers need to follow iMBGP (or other IGP) peerings towards R2 since
 iMSDP has a dependence upon peering with the address of the MBGP (or
 other IGP) announcer of the next hop.

McBride, et al. Best Current Practice [Page 6] RFC 4611 MSDP Deployment Scenarios August 2006

2.3. MSDP Peering without BGP

 In this case, an enterprise maintains its own RP and has an MSDP
 peering with its service provider but does not BGP peer with them.
 MSDP relies upon BGP path information to learn the MSDP topology for
 the SA peer-RPF check.  MSDP can be deployed without BGP, however,
 and as a result, there are some special cases where the requirement
 to perform a peer-RPF check on the BGP path information is suspended.
 These cases are:
 o  There is only a single MSDP peer connection.
 o  A default peer (default MSDP route) is configured.
 o  The originating RP is directly connected.
 o  A mesh group is used.
 o  An implementation is used that allows for an MSDP peer-RPF check
    using an IGP.
 An enterprise will typically configure a unicast default route from
 its border router to the provider's border router and then MSDP peer
 with the provider's MSDP router.  If internal MSDP peerings are also
 used within the enterprise, then an MSDP default peer will need to be
 configured on the border router that points to the provider.  In this
 way, all external multicast sources will be learned, and internal
 sources can be advertised.  If only a single MSDP peering was used
 (no internal MSDP peerings) towards the provider, then this stub site
 will MSDP default peer towards the provider and skip the peer-RPF
 check.

2.4. MSDP Peering at a Multicast Exchange

 Multicast exchanges allow multicast providers to peer at a common IP
 subnet (or by using point-to-point virtual LANs) and share MSDP SA
 updates.  Each provider will MSDP and MBGP peer with each others
 directly connected exchange IP address.  Each exchange router will
 send/receive SAs to/from their MSDP peers.  They will then be able to
 forward SAs throughout their domain to their customers and any direct
 provider peerings.

3. Intra-domain MSDP Peering Scenarios

 The following sections describe the different intra-domain MSDP
 peering possibilities and their deployment options.

McBride, et al. Best Current Practice [Page 7] RFC 4611 MSDP Deployment Scenarios August 2006

3.1. Peering between MSDP- and MBGP-Configured Routers

 The next hop IP address of the iBGP peer is typically used for the
 MSDP peer-RPF check (IGP can also be used).  This is different from
 the inter-domain BGP/MSDP case, where AS path information is used for
 the peer-RPF check.  For this reason, it is necessary for the IP
 address of the MSDP peer connection to be the same as the internal
 MBGP peer connection whether or not the MSDP/MBGP peers are directly
 connected.  A successful deployment would be similar to the
 following:
                               +----+
                               | Rb | 3.3.3.3
                             / +----+
        AS1          AS2    /     |
       +---+         +--+  /      |
       |RP1|---------|Ra|         |
       +---+         +--+         |
       1.1.1.1     2.2.2.2        |
                           \      |
                            \     |
                             \ +-----+
                               | RP2 |
                               +-----+
 where RP2 MSDP and MBGP peers with Ra (using 2.2.2.2) and with Rb
 (using 3.3.3.3).  When the MSDP SA update arrives on RP2 from Ra, the
 MSDP RPF check for 1.1.1.1 passes because RP2 receives the SA update
 from MSDP peer 2.2.2.2, which is also the correct MBGP next hop for
 1.1.1.1.
 When RP2 receives the same SA update from MSDP peer 3.3.3.3, the MBGP
 lookup for 1.1.1.1 shows a next hop of 2.2.2.2, so RPF correctly
 fails, preventing a loop.
 This deployment could also fail on an update from Ra to RP2 if RP2
 was MBGP peering to an address other than 2.2.2.2 on Ra.  Intra-
 domain deployments must have MSDP and MBGP (or other IGP) peering
 addresses that match, unless a method to skip the peer-RPF check is
 deployed.

3.2. MSDP Peer Is Not BGP Peer (or No BGP Peer)

 This is a common MSDP intra-domain deployment in environments where
 few routers are running MBGP or where the domain is not running MBGP.
 The problem here is that the MSDP peer address needs to be the same
 as the MBGP peer address.  To get around this requirement, the intra-
 domain MSDP RPF rules have been relaxed in the following topologies:

McBride, et al. Best Current Practice [Page 8] RFC 4611 MSDP Deployment Scenarios August 2006

 o  By configuring the MSDP peer as a mesh group peer.
 o  By having the MSDP peer be the only MSDP peer.
 o  By configuring a default MSDP peer.
 o  By peering with the originating RP.
 o  By relying upon an IGP for MSDP peer-RPF.
 The common choice around the intra-domain BGP peering requirement,
 when more than one MSDP peer is configured, is to deploy MSDP mesh
 groups.  When an MSDP mesh group is deployed, there is no RPF check
 on arriving SA messages when they are received from a mesh group
 peer.  Subsequently, SA messages are always accepted from mesh group
 peers.  MSDP mesh groups were developed to reduce the amount of SA
 traffic in the network since SAs, which arrive from a mesh group
 peer, are not flooded to peers within that same mesh group.  Mesh
 groups must be fully meshed.
 If recent (but not currently widely deployed) router code is running
 that is fully compliant with the latest MSDP document, another
 option, to work around not having BGP to MSDP RPF peer, is to RPF
 using an IGP like OSPF, IS-IS, RIP, etc.  This new capability will
 allow for enterprise customers, who are not running BGP and who don't
 want to run mesh groups, to use their existing IGP to satisfy the
 MSDP peer-RPF rules.

3.3. Hierarchical Mesh Groups

 Hierarchical mesh groups are occasionally deployed in intra-domain
 environments where there are a large number of MSDP peers.  Allowing
 multiple mesh groups to forward to one another can reduce the number
 of MSDP peerings per router (due to the full mesh requirement) and
 hence reduce router load.  A good hierarchical mesh group
 implementation (one that prevents looping) contains a core mesh group
 in the backbone, and these core routers serve as mesh group
 aggregation routers:
                    [R2]{A,2}
                    /  \
                   /    \
                  /      \
                 /        \
                /          \
               /            \
              /              \
       {A,1}[R1]-------------[R3]{A,3}

McBride, et al. Best Current Practice [Page 9] RFC 4611 MSDP Deployment Scenarios August 2006

 In this example, R1, R2, and R3 are in MSDP mesh group A (the core
 mesh group), and each serves as MSDP aggregation routers for their
 leaf (or second tier) mesh groups 1, 2, and 3.  Since SA messages
 received from a mesh group peer are not forwarded to peers within
 that same mesh group, SA messages will not loop.  Do not create
 topologies that connect mesh groups in a loop.  In the above example,
 for instance, second-tier mesh groups 1, 2, and 3 must not directly
 exchange SA messages with each other or an endless SA loop will
 occur.
 Redundancy between mesh groups will also cause a loop and is
 subsequently not available with hierarchical mesh groups.  For
 instance, assume that R3 had two routers connecting its leaf mesh
 group 3 with the core mesh group A.  A loop would be created between
 mesh group 3 and mesh group A because each mesh group must be fully
 meshed between peers.

3.4. MSDP and Route Reflectors

 BGP requires all iBGP speakers that are not route-reflector clients
 or confederation members be fully meshed to prevent loops.  In the
 route reflector environment, MSDP requires that the route reflector
 clients peer with the route reflector since the router reflector (RR)
 is the BGP announcer of the next hop towards the originating RP.  The
 RR is not the BGP next hop, but is the announcer of the BGP next hop.
 The announcer of the next hop is the address typically used for MSDP
 peer-RPF checks.  For example, consider the following case:
             Ra--------RR
                       /|\
                      / | \
                     A  B  C
 Ra is forwarding MSDP SAs to the route reflector RR.  Routers A, B,
 and C also MSDP peer with RR.  When RR forwards the SA to A, B, and
 C, these RR clients will accept the SA because RR is the announcer of
 the next hop to the originating RP address.
 An SA will peer-RPF fail if Ra MSDP peers directly with Routers A, B,
 or C because the announcer of the next hop is RR but the SA update
 came from Ra.  Proper deployment is to have RR clients MSDP peer with
 the RR.  MSDP mesh groups may be used to work around this
 requirement.  External MSDP peerings will also prevent this
 requirement since the next AS is compared between MBGP and MSDP
 peerings, rather than the IP address of the announcer of the next
 hop.

McBride, et al. Best Current Practice [Page 10] RFC 4611 MSDP Deployment Scenarios August 2006

 Some recent MSDP implementations conform to the latest MSDP document,
 which relaxes the requirement of peering with the Advertiser of the
 next hop (the Route Reflector).  This new rule allows for peering
 with the next hop, in addition to the Advertiser of the next hop.  In
 the example above, for instance, if Ra is the next hop (perhaps due
 to using BGP's next hop self attribute), and if routers A, B, and C
 are peering with Ra, the SA's received from Ra will now succeed.

3.5. MSDP and Anycast RPs

 A network with multiple RPs can achieve RP load sharing and
 redundancy by using the Anycast RP mechanism in conjunction with MSDP
 mesh groups [RFC3446].  This mechanism is a common deployment
 technique used within a domain by service providers and enterprises
 that deploy several RPs within their domains.  These RPs will each
 have the same IP address configured on a Loopback interface (making
 this the Anycast address).  These RPs will MSDP peer with each other
 using a separate loopback interface and are part of the same fully
 meshed MSDP mesh group.  This loopback interface, used for MSDP
 peering, will typically also be used for the MBGP peering.  All
 routers within the provider's domain will learn of the Anycast RP
 address through Auto-RP, BSR, or a static RP assignment.  Each
 designated router in the domain will send source registers and group
 joins to the Anycast RP address.  Unicast routing will direct those
 registers and joins to the nearest Anycast RP.  If a particular
 Anycast RP router fails, unicast routing will direct subsequent
 registers and joins to the nearest Anycast RP.  That RP will then
 forward an MSDP update to all peers within the Anycast MSDP mesh
 group.  Each RP will then forward (or receive) the SAs to (from)
 external customers and providers.

4. Security Considerations

 An MSDP service should be secured by explicitly controlling the state
 that is created by, and passed within, the MSDP service.  As with
 unicast routing state, MSDP state should be controlled locally, at
 the edge origination points.  Selective filtering at the multicast
 service edge helps ensure that only intended sources result in SA
 message creation, and this control helps to reduce the likelihood of
 state-aggregation related problems in the core.  There are a variety
 of points where local policy should be applied to the MSDP service.

4.1. Filtering SA Messages

 The process of originating SA messages should be filtered to ensure
 that only intended local sources are resulting in SA message
 origination.  In addition, MSDP speakers should filter which SA
 messages get received and forwarded.

McBride, et al. Best Current Practice [Page 11] RFC 4611 MSDP Deployment Scenarios August 2006

 Typically, there is a fair amount of (S,G) state in a PIM-SM domain
 that is local to the domain.  However, without proper filtering, SA
 messages containing these local (S,G) announcements may be advertised
 to the global MSDP infrastructure.  Examples of this include domain-
 local applications that use global IP multicast addresses and sources
 that use RFC 1918 addresses [RFC1918].  To improve on the scalability
 of MSDP and to avoid global visibility of domain local (S,G)
 information, an external SA filter list is recommended to help
 prevent unnecessary creation, forwarding, and caching of well-known
 domain local sources.

4.2. SA Message State Limits

 Proper filtering on SA message origination, receipt, and forwarding
 will significantly reduce the likelihood of unintended and unexpected
 spikes in MSDP state.  However, an SA-cache state limit SHOULD be
 configured as a final safeguard to state spikes.  When an MSDP
 peering has reached a stable state (i.e., when the peering has been
 established and the initial SA state has been transferred), it may
 also be desirable to configure a rate limiter for the creation of new
 SA state entries.

5. Acknowledgements

 The authors would like to thank Pekka Savola, John Zwiebel, Swapna
 Yelamanchi, Greg Shepherd, and Jay Ford for their feedback on earlier
 versions of this document.

6. References

6.1. Normative References

 [RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
           "Protocol Independent Multicast - Sparse Mode (PIM-SM):
           Protocol Specification (Revised)", RFC 4601, August 2006.
 [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
           Protocol 4 (BGP-4)", RFC 4271, January 2006.
 [RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
           and E. Lear, "Address Allocation for Private Internets",
           BCP 5, RFC 1918, February 1996.
 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
           Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2858] Bates, T., Rekhter, Y., Chandra, R., and D. Katz,
           "Multiprotocol Extensions for BGP-4", RFC 2858, June 2000.

McBride, et al. Best Current Practice [Page 12] RFC 4611 MSDP Deployment Scenarios August 2006

 [RFC3446] Kim, D., Meyer, D., Kilmer, H., and D. Farinacci, "Anycast
           Rendevous Point (RP) mechanism using Protocol Independent
           Multicast (PIM) and Multicast Source Discovery Protocol
           (MSDP)", RFC 3446, January 2003.
 [RFC3618] Fenner, B. and D. Meyer, "Multicast Source Discovery
           Protocol (MSDP)", RFC 3618, October 2003.

6.2. Informative References

 [BSR]     Fenner, W., et. al., "Bootstrap Router (BSR) Mechanism for
           PIM Sparse Mode", Work in Progress, February 2003.
 [RFCED]   http://www.rfc-editor.org/policy.html

Authors' Addresses

 Mike McBride
 Cisco Systems
 EMail: mcbride@cisco.com
 John Meylor
 Cisco Systems
 EMail: jmeylor@cisco.com
 David Meyer
 EMail: dmm@1-4-5.net

McBride, et al. Best Current Practice [Page 13] RFC 4611 MSDP Deployment Scenarios August 2006

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 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
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McBride, et al. Best Current Practice [Page 14]

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