--- 1/draft-ietf-mboned-routingarch-05.txt 2006-08-15 22:12:20.000000000 +0200 +++ 2/draft-ietf-mboned-routingarch-06.txt 2006-08-15 22:12:20.000000000 +0200 @@ -1,22 +1,22 @@ Internet Engineering Task Force P. Savola Internet-Draft CSC/FUNET -Obsoletes: July 11, 2006 -3913,2189,2201,1584,1585 (if -approved) +Obsoletes: August 15, 2006 +3913,2189,2201,1584,1585 +(if approved) Intended status: Best Current Practice -Expires: January 12, 2007 +Expires: February 16, 2007 Overview of the Internet Multicast Routing Architecture - draft-ietf-mboned-routingarch-05.txt + draft-ietf-mboned-routingarch-06.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that @@ -27,21 +27,21 @@ and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. - This Internet-Draft will expire on January 12, 2007. + This Internet-Draft will expire on February 16, 2007. Copyright Notice Copyright (C) The Internet Society (2006). Abstract The lack of up-to-date documentation on IP multicast routing protocols and procedures has caused a great deal of confusion. To clarify the situation, this memo describes the routing protocols and @@ -65,43 +65,43 @@ 2.2.1. Multi-protocol BGP . . . . . . . . . . . . . . . . . . 9 2.2.2. OSPF/IS-IS Multi-topology Extensions . . . . . . . . . 9 2.2.3. Issue: Overlapping Unicast/multicast Topology . . . . 9 2.2.4. Summary . . . . . . . . . . . . . . . . . . . . . . . 10 2.3. Learning (Active) Sources . . . . . . . . . . . . . . . . 10 2.3.1. SSM . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.3.2. MSDP . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.3.3. Embedded-RP . . . . . . . . . . . . . . . . . . . . . 11 2.3.4. Summary . . . . . . . . . . . . . . . . . . . . . . . 12 2.4. Configuring and Distributing PIM RP Information . . . . . 12 - 2.4.1. Manual Configuration with an Anycast Address . . . . . 12 + 2.4.1. Manual RP Configuration . . . . . . . . . . . . . . . 12 2.4.2. Embedded-RP . . . . . . . . . . . . . . . . . . . . . 13 2.4.3. BSR and Auto-RP . . . . . . . . . . . . . . . . . . . 13 - 2.4.4. Summary . . . . . . . . . . . . . . . . . . . . . . . 13 + 2.4.4. Summary . . . . . . . . . . . . . . . . . . . . . . . 14 2.5. Mechanisms for Enhanced Redundancy . . . . . . . . . . . . 14 2.5.1. Anycast RP . . . . . . . . . . . . . . . . . . . . . . 14 2.5.2. Stateless RP Failover . . . . . . . . . . . . . . . . 14 - 2.5.3. Bi-directional PIM . . . . . . . . . . . . . . . . . . 14 + 2.5.3. Bi-directional PIM . . . . . . . . . . . . . . . . . . 15 2.5.4. Summary . . . . . . . . . . . . . . . . . . . . . . . 15 2.6. Interactions with Hosts . . . . . . . . . . . . . . . . . 15 2.6.1. Hosts Sending Multicast . . . . . . . . . . . . . . . 15 2.6.2. Hosts Receiving Multicast . . . . . . . . . . . . . . 15 2.6.3. Summary . . . . . . . . . . . . . . . . . . . . . . . 16 2.7. Restricting Multicast Flooding in the Link Layer . . . . . 16 2.7.1. Router-to-Router Flooding Reduction . . . . . . . . . 16 2.7.2. Host/Router Flooding Reduction . . . . . . . . . . . . 16 2.7.3. Summary . . . . . . . . . . . . . . . . . . . . . . . 17 - 3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17 + 3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 5. Security Considerations . . . . . . . . . . . . . . . . . . . 18 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 6.1. Normative References . . . . . . . . . . . . . . . . . . . 18 - 6.2. Informative References . . . . . . . . . . . . . . . . . . 19 + 6.2. Informative References . . . . . . . . . . . . . . . . . . 20 Appendix A. Multicast Payload Transport Extensions . . . . . . . 22 A.1. Reliable Multicast . . . . . . . . . . . . . . . . . . . . 22 A.2. Multicast Group Security . . . . . . . . . . . . . . . . . 23 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 23 Intellectual Property and Copyright Statements . . . . . . . . . . 24 1. Introduction Good, up-to-date documentation of IP multicast is close to non- existent. This issue is severely felt with multicast routing @@ -150,20 +150,21 @@ BSR Bootstrap Router CBT Core Based Trees CGMP Cisco Group Management Protocol DR Designated Router DVMRP Distance Vector Multicast Routing Protocol GARP (IEEE 802.1D-2004) Generic Attribute Reg. Protocol GMRP GARP Multicast Registration Protocol IGMP Internet Group Management Protocol MBGP Multi-protocol BGP (*not* "Multicast BGP") MLD Multicast Listener Discovery + MMRP (IEEE 802.1ak) Multicast Multiple Registration Protocol MOSPF Multicast OSPF MSDP Multicast Source Discovery Protocol PGM Pragmatic General Multicast PIM Protocol Independent Multicast PIM-DM PIM - Dense Mode PIM-SM PIM - Sparse Mode PIM-SSM PIM - Source-Specific Multicast RGMP (Cisco's) Router Group Management Protocol RP Rendezvous Point SSM Source-specific Multicast @@ -336,28 +337,28 @@ reachability information. The topology information is needed to perform efficient distribution of multicast transmissions and to prevent transmission loops by applying it to the Reverse Path Forwarding (RPF) check. This subsection introduces these protocols. 2.2.1. Multi-protocol BGP - Multiprotocol Extensions for BGP-4 [RFC2858] (often referred to as - "MBGP"; however, it is worth noting that "MBGP" does *not* stand for - "Multicast BGP") specifies a mechanism by which BGP can be used to - distribute different reachability information for unicast and - multicast traffic (using SAFI=2 for multicast). Multiprotocol BGP + Multiprotocol Extensions for BGP-4 [I-D.ietf-idr-rfc2858bis] (often + referred to as "MBGP"; however, it is worth noting that "MBGP" does + *not* stand for "Multicast BGP") specifies a mechanism by which BGP + can be used to distribute different reachability information for + unicast (SAFI=1) and multicast traffic (SAFI=2). Multiprotocol BGP has been widely deployed for years, and is also needed to route IPv6. Note that SAFI=3 was originally specified for "both unicast and - multicast" but has been deprecated [I-D.ietf-idr-rfc2858bis]. + multicast" but has since then been deprecated. These extensions are in widespread use wherever BGP is used to distribute unicast topology information. Multicast-enabled networks that use BGP should use Multiprotocol BGP to distribute multicast reachability information explicitly even if the topologies are congruent to make an explicit statement about multicast reachability. A number of significant multicast transit providers even require this, by doing the RPF lookups solely based on explicitly advertised multicast address family. @@ -403,28 +404,30 @@ Another implemented approach is to just look up the information in the unicast routing table, and provide the user capabilities to change that as appropriate, using for example copying functions discussed above. 2.2.4. Summary The following table summarizes the topology distribution approaches described in this Section. In particular, it is recommended that if interdomain routing uses BGP, multicast-enabled sites should use MP- - BGP SAFI=1+2 even if the topology were congruent. + BGP SAFI=2 for multicast and SAFI=1 for unicast even if the topology + was congruent. +-------------+---------------+ | Interdomain | Intradomain | +--------------------- +--------------+--------------+ | Congruent topology | Yes | Yes | | BGP without SAFI | Not recomm. | Yes | - | MP-BGP SAFI=1+2 | Recommended | Yes | + | MP-BGP SAFI=1 only | Not recomm. | Not recomm. | + | MP-BGP SAFI=2 | Recommended | Yes | | MP-BGP SAFI=3 | Doesn't work | Doesn't work | | IS-IS multi-topology | No | Yes | | OSPF multi-topology | No | Few implem. | +----------------------+--------------+--------------+ 2.3. Learning (Active) Sources Typically, multicast routing protocols must either assume that the receivers know the IP addresses of the (active) sources for a group in advance, possibly using an out-of-band mechanism (SSM), or the @@ -496,21 +499,21 @@ | PIM-SM w/ Embedded-RP| No | Yes | Best inter-domain ASM option | | SSM | Yes | Yes | No major uptake yet | +----------------------+------+------+------------------------------+ 2.4. Configuring and Distributing PIM RP Information PIM-SM and Bi-dir PIM configuration mechanisms exist which are used to configure the RP addresses and which groups are to use those RPs in the routers. This section outlines the approaches. -2.4.1. Manual Configuration with an Anycast Address +2.4.1. Manual RP Configuration It is often easiest just to manually configure the RP information on the routers when PIM-SM is used. Originally, static RP mapping was considered suboptimal since it required explicit configuration changes every time the RP address changed. However, with the advent of anycast RP addressing, the RP address is unlikely to ever change. Therefore, the administrative burden is generally limited to initial configuration. Since there is usually a fair amount of multicast configuration required on all @@ -698,39 +701,41 @@ These options are discussed in this section. 2.7.1. Router-to-Router Flooding Reduction A proprietary solution, Cisco's RGMP [RFC3488] has been developed to reduce the amount of flooding between routers in a switched networks. This is typically only considered a problem in some Ethernet-based Internet Exchange points or VPNs. There have been proposals to observe and possibly react ("snoop") PIM - messages [I-D.tsenevir-pim-sm-snoop][I-D.serbest-l2vpn-vpls-mcast] to - achieve the same effect. + messages [I-D.ietf-l2vpn-vpls-pim-snooping]. 2.7.2. Host/Router Flooding Reduction There are a number of techniques to help reduce flooding both from a router to hosts, and from a host to the routers (and other hosts). Cisco's proprietary CGMP [CGMP] provides a solution where the routers notify the switches, but also allows the switches to snoop IGMP packets to enable faster notification of hosts no longer wishing to receive a group. IPv6 is not supported. IEEE 802.1D-2004 specification describes Generic Attribute Registration Protocol (GARP), and GARP Multicast Registration Protocol (GMRP) [GMRP] is a link-layer multicast group application of GARP that notifies switches about IP multicast group memberships. - GMRP requires support at the host stack and implementation status - especially on hosts is unknown. Some further information about GARP/ + GMRP requires support at the host stack and it has not been widely + implemented. Further, IEEE considers GMRP obsolete having been + replaced by Multicast Multiple Registration Protocol (MMRP) that's + being specified in IEEE 802.1ak [802.1ak]. MMRP is expected to be + mainly used between bridges. Some further information about GARP/ GMRP is also available in Appendix B of [RFC3488]. IGMP snooping [RFC4541] appears to be the most widely implemented technique. IGMP snooping requires that the switches implement a significant amount of IP-level packet inspection; this appears to be something that is difficult to get right, and often the upgrades are also a challenge. Snooping switches also need to identify the ports where routers reside and therefore where to flood the packets. This can be @@ -751,21 +756,21 @@ reduction inside a single link for router-to-router and last-hop LANs. +--------+-----+---------------------------+ | R-to-R | LAN | Notes | +-----------------------+--------+-----+---------------------------+ | Cisco's RGMP | Yes | No | Replaced by PIM snooping | | PIM snooping | Yes | No | Security issues in LANs | | IGMP/MLD snooping | No | Yes | Common, IGMPv3 or MLD bad | | Multicast Router Disc | No | Yes | Few if any implem. yet | - | IEEE 802.1D-2004 GMRP | No | Yes | Impl. status unknown | + | IEEE GMRP and MMRP | No | No | No host/router deployment | | Cisco's CGMP | No | Yes | Replaced by other snooping| +-----------------------+--------+-----+---------------------------+ 3. Acknowledgements Tutoring a couple multicast-related papers, the latest by Kaarle Ritvanen [RITVANEN] convinced the author that up-to-date multicast routing and address assignment/allocation documentation is necessary. Leonard Giuliano, James Lingard, Jean-Jacques Pansiot, Dave Meyer, @@ -786,24 +791,24 @@ However, there has been analysis of the security of multicast routing infrastructures [I-D.ietf-mboned-mroutesec], IGMP/MLD [I-D.daley-magma-smld-prob], and PIM last-hop issues [I-D.savola-pim-lasthop-threats]. 6. References 6.1. Normative References - [I-D.ietf-idmr-dvmrp-v3] - Pusateri, T., "Distance Vector Multicast Routing - Protocol", draft-ietf-idmr-dvmrp-v3-11 (work in progress), - December 2003. + [I-D.ietf-idr-rfc2858bis] + Bates, T., "Multiprotocol Extensions for BGP-4", + draft-ietf-idr-rfc2858bis-10 (work in progress), + March 2006. [I-D.ietf-isis-wg-multi-topology] Przygienda, T., "M-ISIS: Multi Topology (MT) Routing in IS-IS", draft-ietf-isis-wg-multi-topology-11 (work in progress), October 2005. [I-D.ietf-mboned-addrarch] Savola, P., "Overview of the Internet Multicast Addressing Architecture", draft-ietf-mboned-addrarch-04 (work in progress), March 2006. @@ -824,64 +829,69 @@ March 2006. [I-D.ietf-ssm-arch] Holbrook, H. and B. Cain, "Source-Specific Multicast for IP", draft-ietf-ssm-arch-07 (work in progress), October 2005. [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9, RFC 2026, October 1996. - [RFC2858] Bates, T., Rekhter, Y., Chandra, R., and D. Katz, - "Multiprotocol Extensions for BGP-4", RFC 2858, June 2000. - [RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A. Thyagarajan, "Internet Group Management Protocol, Version 3", RFC 3376, October 2002. [RFC3618] Fenner, B. and D. Meyer, "Multicast Source Discovery Protocol (MSDP)", RFC 3618, October 2003. [RFC3810] Vida, R. and L. Costa, "Multicast Listener Discovery Version 2 (MLDv2) for IPv6", RFC 3810, June 2004. [RFC3956] Savola, P. and B. Haberman, "Embedding the Rendezvous Point (RP) Address in an IPv6 Multicast Address", RFC 3956, November 2004. [RFC3973] Adams, A., Nicholas, J., and W. Siadak, "Protocol Independent Multicast - Dense Mode (PIM-DM): Protocol Specification (Revised)", RFC 3973, January 2005. 6.2. Informative References + [802.1ak] "IEEE 802.1ak - Multiple Registration Protocol", + . + [CGMP] "Cisco Group Management Protocol", . [GMRP] "GARP Multicast Registration Protocol", . [I-D.daley-magma-smld-prob] Daley, G. and G. Kurup, "Trust Models and Security in Multicast Listener Discovery", draft-daley-magma-smld-prob-00 (work in progress), July 2004. + [I-D.ietf-idmr-dvmrp-v3] + Pusateri, T., "Distance Vector Multicast Routing + Protocol", draft-ietf-idmr-dvmrp-v3-11 (work in progress), + December 2003. + [I-D.ietf-idmr-dvmrp-v3-as] Pusateri, T., "Distance Vector Multicast Routing Protocol Applicability Statement", draft-ietf-idmr-dvmrp-v3-as-01 (work in progress), May 2004. - [I-D.ietf-idr-rfc2858bis] - Bates, T., "Multiprotocol Extensions for BGP-4", - draft-ietf-idr-rfc2858bis-10 (work in progress), - March 2006. + [I-D.ietf-l2vpn-vpls-pim-snooping] + Hemige, V., "PIM Snooping over VPLS", + draft-ietf-l2vpn-vpls-pim-snooping-00 (work in progress), + August 2006. [I-D.ietf-magma-igmp-proxy] Fenner, B., He, H., Haberman, B., and H. Sandick, "IGMP/ MLD-based Multicast Forwarding ('IGMP/MLD Proxying')", draft-ietf-magma-igmp-proxy-06 (work in progress), April 2004. [I-D.ietf-mboned-ipv6-multicast-issues] Savola, P., "IPv6 Multicast Deployment Issues", draft-ietf-mboned-ipv6-multicast-issues-02 (work in @@ -906,31 +916,20 @@ Lehtonen, R., "Requirements for discovery of dynamic SSM sources", draft-lehtonen-mboned-dynssm-req-00 (work in progress), February 2005. [I-D.savola-pim-lasthop-threats] Lingard, J. and P. Savola, "Last-hop Threats to Protocol Independent Multicast (PIM)", draft-savola-pim-lasthop-threats-02 (work in progress), June 2006. - [I-D.serbest-l2vpn-vpls-mcast] - Serbest, Y., "Supporting IP Multicast over VPLS", - draft-serbest-l2vpn-vpls-mcast-03 (work in progress), - July 2005. - - [I-D.tsenevir-pim-sm-snoop] - Senevirathne, T. and S. Vallepali, "Protocol Independent - Multicast-Sparse Mode (PIM-SM) Snooping", - draft-tsenevir-pim-sm-snoop-00 (work in progress), - April 2002. - [RFC1075] Waitzman, D., Partridge, C., and S. Deering, "Distance Vector Multicast Routing Protocol", RFC 1075, November 1988. [RFC1584] Moy, J., "Multicast Extensions to OSPF", RFC 1584, March 1994. [RFC1585] Moy, J., "MOSPF: Analysis and Experience", RFC 1585, March 1994.