MAGMA Working Group B. Haberman Internet Draft Caspian Networks draft-ietf-magma-igmpv3-and-routing-03.txt J. Martin October 2002 Netzwert AG Expires April 2003 IGMPv3/MLDv2 and Multicast Routing Protocol Interaction Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 [RFC 2026]. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." 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. Abstract The definitions of IGMPv3 and MLDv2 require new behavior within the multicast routing protocols. The additional source information contained in IGMPv3 and MLDv2 messages necessitates multicast routing protocols to manage and utilize the information. This document will describe how multicast routing protocols will interact with these source-filtering group management protocols. 1. Introduction The definitions of IGMPv3[IGMP3] and MLDv2[MLDv2] require new behavior within the multicast routing protocols. The additional source information contained in IGMPv3 and MLDv2 messages necessitates multicast routing protocols to manage and utilize the information. This document will describe how multicast routing protocols will interact with these source-filtering group management protocols. 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. Haberman, Martin 1 Internet Draft IGMPv3/MLDv2 and Multicast Protocols October 2002 2. Multicast Forwarding State Existing multicast routing protocols utilize the group management database in determining if local members exist for a particular group. In the case of IGMPv3 and MLDv2, these routing protocols may now build multicast forwarding state based on the source filter information available for each multicast group that has local membership. The source filter state available in the group management database should be utilized when generating forwarding state for a multicast group. If the source address in the multicast packet is included in the database for the specified multicast group, the multicast routing protocol should add the interface to the list of downstream interfaces, otherwise it should not be added based on local group membership. 3. Version Transitions and Routing Protocol Interaction IGMP version 3 and MLD version 2 specify that if at any point a router receives an older version query message on an interface that it must immediately switch into a compatibility mode with that earlier version. Since none of the previous versions are source aware, should this occur and the interface switch to compatibility mode, any previously learned group memberships with specific sources (learned via the INCLUDE or EXCLUDE mechanisms) MUST be converted to non-source specific group memberships. The routing protocol will then treat this as it would the receipt of an IGMPv3 or MLDv2 report message with a zero-length EXCLUDE list. 4. DVMRP Interaction The DVMRP protocol[DVMRP] interaction with source-filtering group management protocols is important in two areas: multicast distribution tree pruning and multicast distribution tree grafting. The following sections will describe the behavior needed in DVMRP to interoperate with IGMPv3 and MLDv2. 4.1 DVMRP Prunes DVMRP prune messages are generated when a router determines that there are no longer any interested downstream listeners. The DVMRP protocol builds prune information that contains both destination group address and source network information. When DVMRP routers implement a source-filtering group management protocol, the source filter information in the group management database must be used in the creation of DVMRP prune messages. When group state changes (e.g. Report message received with EXCLUDE state), and forwarding state exists for a particular (S,G), DVMRP Haberman, Martin 2 Internet Draft IGMPv3/MLDv2 and Multicast Protocols October 2002 will create a prune containing the specified group and source information. 4.2 DVMRP Grafts DVMRP graft messages are generated when local group membership state changes and a DVMRP prune is in place for the requested group address. The graft message overrides the prune state and should result in the resumption of multicast flow for the requested group. When DVMRP routers implement a source-filtering group management protocol, the source filter information in the group management database must be used in the creation of DVMRP graft messages. State changes in the database that renders existing prune state obsolete must result in the creation of a DVMRP graft message. 5. MOSPF Interaction In MOSPF[MOSPF], the consideration of source filter information in the group management database is limited to the building of forwarding state (discussed above). This is due to the flooding of group-membership-LSAs within MOSPF. 6. PIM-DM Interaction Like DVMRP, PIM-DM[PIMDM] must utilize the source filter information when generating Prune and Graft messages. The following sections describe the creation of these message types. 6.1 PIM-DM Prunes PIM-DM prune messages are initiated when a PIM-DM router determines that there are no entities interested in the data flowing on the (S,G) forwarding state. If the multicast router is running IGMPv3 or MLDv2, this is determined by the source S being EXCLUDED in the source filter for the destination G or all interest in G being terminated by a Leave message for an existing (S,G) forwarding entry. 6.2 PIM-DM Grafts PIM-DM graft messages are sent in order to override an existing PIM- DM prune. In the case of IGMPv3 or MLDv2, this occurs when prune state exists for (S,G) and a state change occurs in which the source filter state for S changes to INCLUDE for the specified G. 7. PIM-SM Interaction A PIM-SM interaction takes place when a PM-SM [PIMSM] router receives an IGMP or MLD message regarding a group address that is in the Any Source Multicast (ASM) range. This range is defined as the Haberman, Martin 3 Internet Draft IGMPv3/MLDv2 and Multicast Protocols October 2002 entire multicast address space excluding the global SSM range [SSM] and any locally defined Source Specific space. 7.1 PIM-SM Joins (ASM Behavior) PIM-SM join messages are initiated when a PIM-SM router determines that there are entities interested in a specific group or a specific source sending to the group. If this is due to a IGMPv3 or MLDv2 report with a zero-length EXCLUDE list, then the join is sent as a (*,G) join towards the RP. If the join is triggered by the reception of an IGMPv3 or MLDv2 report that contains source specific information, the join is sent as a (S,G) join towards the specific source. This behavior optimizes the join process, as well as facilitates the adoption of the SSM model. It also can cause failures in some specific network architectures, and thus, can be overridden by local policy. If this is the case, then all triggered joins are sent towards the RP as (*,G) joins. The initiating router is responsible for filtering the data before forwarding to the requesting network. 7.2 PIM-SM Prunes (ASM Behavior) PIM-SM prune messages are initiated when a PIM-SM router determines that there are no entities interested in a specific group, or a specific source sending to the group. If this is triggered by either receiving a report with an EXCLUDE or if a specific Source/Group times out, then an (S,G) prune is sent towards the upstream router. If all of the IGMPv3 or MLDv2 derived requests for a group time out, then (S,G) and (*,G) prunes are sent upstream as needed to stop all flow of traffic for that group. 8. PIM-SSM Interaction A PIM-SSM interaction takes place when a PIM-SM router receives an IGMPv3 or MLDv2 message regarding a group address that is in the Source Specific Multicast range. This range is defined as the global SSM range and any locally defined Source Specific space. This behavior is not defined in this document, but rather in [PIMSM]. 9. Security Considerations This document does not introduce any additional security issues above and beyond those already discussed in [PIMSM], [IGMP3], and [MLDv2]. 10. Acknowledgements The authors would like to thank Murali Brahmadesam, Leonard Giuliano, and Hal Sandick for their feedback and suggestions. 11. Authors' Addresses Haberman, Martin 4 Internet Draft IGMPv3/MLDv2 and Multicast Protocols October 2002 Brian Haberman Caspian Networks bkhabs@nc.rr.com Jim Martin Netzwert AG An den Treptowers 1 D-12435 Berlin jim@Netzwert.AG +49.30/5 900 800-180 12. References [IGMP3] B. Cain, et al, "Internet Group Management Protocol, Version 3", work in progress. [MLDv2] Vida, R., et al., ôMulticast Listener Discovery Version 2 (MLDv2) for IPv6ö, work in progress. [DVMRP] T. Pusateri, "Distance Vector Multicast Routing Protocol", work in progress. [MOSPF] J. Moy, "Multicast Extensions to OSPF", RFC 1584, March 1994. [PIMDM] A. Adams, et al, "Protocol Independent Multicast - Dense Mode: Protocol Specification (Revised)", work in progress. [PIMSM] B.Fenner, et al, "Protocol Independent Multicast -Sparse Mode (PIM-SM): Protocol Specification (Revised)", work in progress. [SSM] G. Shepard, et al, "Source-Specific Protocol Independent Multicast in 232/8", work in progress. Haberman, Martin 5