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Network Working Group                                         M. McBrideRequest for Comments: 4611                                     J. MeylorBCP: 121                                                        D. MeyerCategory: Best Current Practice                              August 2006Multicast Source Discovery Protocol (MSDP) Deployment ScenariosStatus 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 Contents1. Introduction ....................................................21.1. BCP, Experimental Protocols, and Normative References ......32. Inter-domain MSDP Peering Scenarios .............................42.1. Peering between PIM Border Routers .........................42.2. Peering between Non-Border Routers .........................52.3. MSDP Peering without BGP ...................................72.4. MSDP Peering at a Multicast Exchange .......................73. Intra-domain MSDP Peering Scenarios .............................73.1. Peering between MSDP- and MBGP-Configured Routers ..........83.2. MSDP Peer Is Not BGP Peer (or No BGP Peer) .................83.3. Hierarchical Mesh Groups ...................................93.4. MSDP and Route Reflectors .................................103.5. MSDP and Anycast RPs ......................................114. Security Considerations ........................................114.1. Filtering SA Messages .....................................114.2. SA Message State Limits ...................................125. Acknowledgements ...............................................126. References .....................................................126.1. Normative References ......................................126.2. Informative References ....................................13McBride, et al.          Best Current Practice                  [Page 1]

RFC 4611               MSDP Deployment Scenarios             August 20061.  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 inRFC 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 inRFC 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 20062.3.  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 20063.1.  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 useRFC 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.  References6.1.  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.htmlAuthors' Addresses   Mike McBride   Cisco Systems   EMail: mcbride@cisco.com   John Meylor   Cisco Systems   EMail: jmeylor@cisco.com   David Meyer   EMail: dmm@1-4-5.netMcBride, et al.          Best Current Practice                 [Page 13]

RFC 4611               MSDP Deployment Scenarios             August 2006Full Copyright Statement   Copyright (C) The Internet Society (2006).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.Acknowledgement   Funding for the RFC Editor function is provided by the IETF   Administrative Support Activity (IASA).McBride, et al.          Best Current Practice                 [Page 14]