INTERNET-DRAFT Source-Specific Multicast H. Holbrook Expires Jan 18, 2005 Cisco Systems B. Cain Storigen Systems 18 Jul 2004 Source-Specific Multicast for IP Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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. Holbrook/Cain [Page 1] INTERNET-DRAFT Source-Specific Multicast 18 Jul 2004 Abstract IP addresses in the 232/8 (232.0.0.0 to 232.255.255.255) range are designated as source-specific multicast (SSM) destination addresses and are reserved for use by source-specific applications and protocols. For IP version 6 (IPv6), the address prefix FF3x::/32 is reserved for source-specific multicast use. This document defines an extension to the Internet network service that applies to datagrams sent to SSM addresses and defines the host and router requirements to support this extension. 1. Introduction The Internet Protocol (IP) multicast service model is defined in RFC 1112 [RFC1112]. RFC 1112 specifies that a datagram sent to an IP multicast address (224.0.0.0 through 239.255.255.255) G is delivered to each "upper-layer protocol module" that has requested reception of datagrams sent to address G. RFC 1112 calls the network service identified by a multicast destination address G a "host group." This model supports both one-to-many and many-to-many group communication. This document uses the term "Any-Source Multicast" (ASM) to refer to model of multicast defined in RFC 1112. RFC 2373 [RFC2373] specifies the form of IPv6 multicast addresses with ASM semantics. IP addresses in the 232/8 (232.0.0.0 to 232.255.255.255) range are currently designated as source-specific multicast (SSM) destination addresses and are reserved for use by source-specific applications and protocols [IANA-ALLOCATION]. For IPv6, the address prefix FF3x::/32 is reserved for source-specific multicast use, where 'x' is any valid scope identifier, by [IPV6-UBM]. Using the terminology of [IPv6-UBM], all SSM addresses must have P=1, T=1, and plen=0. [IPv6-MALLOC] mandates that the network prefix field of an SSM address also be set to zero, hence all SSM addresses fall in the FF3x::/96 range. Future documents may allow a non-zero network prefix field if, for instance, a new IP address to MAC address mapping is defined. Thus, address allocation should occur within the FF3x::/96 range, but a system should treat all of FF3x::/32 as SSM addresses, to allow for compatibility with possible future uses of the network prefix field. Addresses in the range FF3x::4000:0000 through FF3x::7FFF:FFFF are reserved in [IPv6-MALLOC] for allocation by IANA. Addresses in the range FF3x::8000:0000 through FF3x::FFFF:FFFF are allowed for dynamic allocation by a host, as described in [IPV6-MALLOC]. Addresses in the range FF3x::0000:0000 through FF3x::3FFF:FFFF are invalid IPv6 SSM addresses. ([IPV6-MALLOC] indicates that FF3x::0000:0001 to FF3x:3FFF:FFFF must set P=0 and T=0, but for SSM, [IPV6-UBM] mandates Holbrook/Cain [Page 2] INTERNET-DRAFT Source-Specific Multicast 18 Jul 2004 that P=1 and T=1, hence their designation as invalid). The treatment of a packet sent to such an invalid address is undefined -- a router or host MAY choose to drop such a packet. Source-specific multicast delivery semantics are provided for a datagram sent to an SSM address. That is, a datagram with source IP address S and SSM destination address G is delivered to each upper-layer "socket" that has specifically requested the reception of datagrams sent to address G by source S, and only to those sockets. The network service identified by (S,G), for SSM address G and source host address S, is referred to as a "channel." In contrast to the ASM model of RFC 1112, SSM provides network-layer support for one-to-many delivery only. The benefits of source-specific multicast include: Elimination of cross-delivery of traffic when two sources simultaneously use the same source-specific destination address. The simultaneous use of an SSM destination address by multiple sources and different applications is explicitly supported. Avoidance of the need for inter-host coordination when choosing source-specific addresses, as a consequence of the above. Avoidance of many of the router protocols and algorithms that are needed to provide the ASM service model. For instance, the "shared trees" and Rendezvous Points of the PIM-Sparse Mode (PIM-SM) protocol [PIM-SM] are not necessary to support the source-specific model. The router mechanisms required to support SSM are in fact largely a subset of those that are used to support ASM. For example, the shortest-path tree mechanism of the PIM-SM protocol can be adapted to provide SSM semantics. Like ASM, the set of receivers is unknown to an SSM sender. An SSM source is provided with neither the identity of receivers nor their number. SSM is particularly well-suited to dissemination-style applications with one or more senders whose identities are known before the application begins. For instance, a data dissemination application that desires to provide a secondary data source in case the primary source fails over might implement this by using one channel for each source and advertising both of them to receivers. SSM can be used to build multi- source applications where all participants' identities are not known in advance, but the multi-source "rendezvous" functionality does not occur in the network layer in this case. Just like in an application that uses unicast as the underlying transport, this functionality can be implemented by the application or by an application-layer library. Holbrook/Cain [Page 3] INTERNET-DRAFT Source-Specific Multicast 18 Jul 2004 Multicast resource discovery of the form in which a client sends a multicast query directly to a "service location group" to which servers listen is not directly supported by SSM. 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 [RFC 2119]. This document defines the semantics of source-specific multicast addresses and specifies the policies governing their use. In particular, it defines an extension to the Internet network service that applies to datagrams sent to SSM addresses and defines host extensions to support the network service. Hosts, routers, applications, and protocols that use these addresses MUST comply with the policies outlined in this document. Failure of a host to comply may prevent that host or other hosts on the same LAN from receiving traffic sent to an SSM channel. Failure of a router to comply may cause SSM traffic to be delivered to parts of the network where it is unwanted, unnecessarily burdening the network. 2. Semantics of Source-Specific Multicast Addresses The source-specific multicast service is defined as follows: A datagram sent with source IP address S and destination IP address G in the SSM range is delivered to each host socket that has specifically requested delivery of datagrams sent by S to G, and only to those sockets. Where, using the terminology of [IGMPv3], "socket" is an implementation-specific parameter used to distinguish among different requesting entities (e.g., programs or processes or communication end-points within a program or process) within the requesting host; the socket parameter of BSD Unix system calls is a specific example. Any host may send a datagram to any SSM address, and delivery is provided according to the above semantics. The IP module interface to upper-layer protocols is extended to allow a socket to "Subscribe" to or "Unsubscribe" from a particular channel identified by an SSM destination address and a source IP address. The extended interface is defined in section 4.1. It is meaningless for an application or host to request reception of datagrams sent to an SSM destination address G, as is supported in the any-source multicast model, without also specifying a corresponding source address, and routers MUST ignore any such request. Holbrook/Cain [Page 4] INTERNET-DRAFT Source-Specific Multicast 18 Jul 2004 Multiple source applications on different hosts can use the same SSM destination address G without conflict because datagrams sent by each source host Si are delivered only to those sockets that requested delivery of datagrams sent to G specifically by Si. The key distinguishing property of the model is that a channel is identified (addressed) by the combination of a unicast source address and a multicast destination address in the SSM range. So, for example, the channel S,G = (192.0.2.1, 232.7.8.9) differs from S,G = (192.0.2.2, 232.7.8.9), even though they have the same destination address portion. Similarly, for IPv6, S,G = (2001:3618::1, FF33::1234) and S,G = (2001:3618::2, FF33::1234) are different channels. 3. Terminology To reduce confusion when talking about the any-source and source- specific multicast models, we use different terminology when discussing them. We use the term "channel" to refer to the service associated with an SSM address. A channel is identified by the combination of an SSM destination address and a specific source, e.g., an (S,G) pair. We use the term "host group" (used in RFC 1112) to refer to the service associated with "regular" ASM multicast addresses (excluding those in the SSM range). A host group is identified by a single multicast address. Any host can send to a host group, and similarly, any host can send to an SSM destination address. A packet sent by a host S to an ASM destination address G is delivered to the host group identified by G. A packet sent by host S to an SSM destination address G is delivered to the channel identified by (S,G). The receiver operations allowed on a host group are called "join(G)" and "leave(G)" (as per RFC 1112). The Holbrook/Cain [Page 5] INTERNET-DRAFT Source-Specific Multicast 18 Jul 2004 receiver operations allowed on a channel are called "Subscribe(S,G)" and "Unsubscribe(S,G)." The following table summarizes the terminology: Service Model: any-source source-specific Network Abstraction: group channel Identifier: G S,G Receiver Operations: Join, Leave Subscribe, Unsubscribe We note that, although this document specifies a new service model available to applications, the protocols and techniques necessary to support the service model are largely a subset of those used to support ASM. 4. Host Requirements This section describes requirements on hosts that support source- specific multicast, including: - Extensions to the IP Module Interface - Extensions to the IP Module - Allocation of SSM Addresses 4.1. Extensions to the IP Module Interface The IP module interface to upper-layer protocols is extended to allow protocols to request reception of all datagrams sent to a particular channel. Subscribe ( socket, source-address, group-address, interface ) Unsubscribe ( socket, source-address, group-address, interface ) where "socket" is as previously defined in Section 2, and, paraphrasing [IGMPv3], "interface" is a local identifier of the network interface on which reception of the channel identified by the (source-address,group- address) pair is to be enabled or disabled. A special value may be used to indicate a "default" interface. If reception of the same Holbrook/Cain [Page 6] INTERNET-DRAFT Source-Specific Multicast 18 Jul 2004 channel is desired on multiple interfaces, Subscribe is invoked once for each. The above are strictly abstract functional interfaces -- the functionality can be provided in an implementation-specific way. On a host that supports the multicast source filtering application programming interface of [MSFAPI], for instance, the Subscribe and Unsubscribe interfaces may be supported via that API. When a host has been configured to know the SSM address range, (whether the configuration mechanism is manual or through a protocol) the host's operating system SHOULD return an error to an application that makes a non-source-specific request to receive multicast sent to an SSM destination address. Widespread implementations of the IP packet reception interface (e.g., the recvfrom() system call in BSD unix) do not allow a receiver to determine the destination address to which a datagram was sent. On a host with such an implementation, the destination address of a datagram cannot be inferred when the socket on which the datagram is received is Subscribed to multiple channels. Host operating systems SHOULD provide a way for a host to determine both the source and the destination address to which a datagram was sent. (As one example, the Linux operating system provides the destination of a packet as part of the response to the recvmsg() system call.) Until this capability is present, applications may be forced to use higher-layer mechanisms to identify the channel to which a datagram was sent. 4.2. Requirements on the Host IP Module An incoming datagram destined to an SSM address MUST be delivered by the IP module to all sockets that have indicated (via Subscribe) a desire to receive data that matches the datagram's source address, destination address, and arriving interface. It MUST NOT be delivered to other sockets. When the first socket on host H subscribes to a channel (S,G) on interface I, the host IP module on H sends a request on interface I to indicate to neighboring routers that the host wishes to receive traffic sent by source S to source-specific multicast destination G. Similarly, when the last socket on a host unsubscribes from a channel on interface I, the host IP module sends an unsubscription request for that channel to interface I. These requests will typically be Internet Group Management Protocol version 3 (IGMPv3) messages for IPv4, or Multicast Listener Discovery Version 2 (MLDv2) messages for IPv6 [IGMPv3,MLDv2]. A host that supports the SSM service model MUST implement the host portion of [IGMPv3] for IPv4 and [MLDv2] for IPv6. It MUST also conform to the Holbrook/Cain [Page 7] INTERNET-DRAFT Source-Specific Multicast 18 Jul 2004 IGMPv3/MLDv2 behavior described in [GMP-SSM]. 4.3. Allocation of Source-Specific Multicast Addresses The SSM destination address 232.0.0.0 is reserved, and a system MUST NOT send a datagram with a destination address of 232.0.0.0. The address range 232.0.0.1-232.0.0.255 is currently reserved for allocation by IANA. SSM destination addresses in the range FF3x::4000:0000 through FF3x::7FFF:FFFF are similarly reserved for IANA allocation [IPv6-MALLOC]. The policy for allocating the rest of the SSM addresses to sending applications is strictly locally determined by the sending host. When allocating SSM addresses dynamically, a host or host operating system MUST NOT allocate sequentially starting at the first allowed address. It is RECOMMENDED to allocate SSM addresses to applications randomly, while ensuring that allocated addresses are not given simultaneously to multiple applications (and avoiding the reserved addresses). For IPv6, the randomization should apply to the lowest 31 bits of the address. As described in Section 6, the mapping of an IP packet with SSM destination address onto a link-layer multicast address does not take into account the datagram's source IP address (on commonly-used link layers like Ethernet). If all hosts started at the first allowed address, then with high probability, many source-specific channels on shared-medium local area networks would use the same link-layer multicast address. As a result, traffic destined for one channel subscriber would be delivered to another's IP module, which would then have to discard the datagram. A host operating system SHOULD provide an interface to allow an application to request a unique allocation of a channel destination address in advance of a session's commencement, and this allocation database SHOULD persist across host reboots. By providing persistent allocations, a host application can advertise the session in advance of its start time on a web page or in another directory. (We note that this issue is not specific to SSM applications -- the same problem arises for ASM.) This document neither defines the interfaces for requesting or returning addresses nor specifies the host algorithms for storing those allocations. One plausible abstract API is defined in RFC 2771 [RFC2771]. Note that RFC 2771 allows an application to request an address within a specific range of addresses. If this interface is used, the starting address of the range SHOULD be selected at random by the application. Holbrook/Cain [Page 8] INTERNET-DRAFT Source-Specific Multicast 18 Jul 2004 For IPv6, administratively scoped SSM channel addresses are created by choosing an appropriate scope identifier for the SSM destination address. Normal IPv6 multicast scope boundaries [SCOPINGV6] are applied to traffic sent to an SSM destination address, including any relevant boundaries applied to both the source and destination address. No globally agreed-upon administratively-scoped address range [ADMIN- SCOPE] is currently defined for IPv4 source-specific multicast. For IPv4, administrative scoping of SSM addresses can be implemented within an administrative domain by filtering outgoing SSM traffic sent to a scoped address at the domain's boundary routers. 5. Router Requirements 5.1. Packet Forwarding A router that receives an IP datagram with a source-specific destination address MUST silently drop it unless a neighboring host or router has communicated a desire to receive packets sent from the source and to the destination address of the received packet. 5.2. Protocols Certain IP multicast routing protocols already have the ability to communicate source-specific joins to neighboring routers (in particular, PIM-SM [PIM-SM]), and these protocols can, with slight modifications, be used to provide source-specific semantics. A router that supports the SSM service model MUST implement the PIM-SSM subset of the PIM-SM protocol from [PIM-SM] and MUST implement the router portion of [IGMPv3] for IPv4 and [MLDv2] for IPv6. An SSM router MUST also conform to the IGMPv3/MLDv2 behavior described in [GMP-SSM]. With PIM-SSM, successful establishment of an (S,G) forwarding path from the source S to any receiver depends on hop-by-hop forwarding of the explicit join request from the receiver toward the source. The protocol(s) and algorithms that are used to select the forwarding path for this explicit join must provide a loop-free path. When using PIM- SSM, the PIM-SSM implementation MUST (at least) support the ability to use the unicast topology database for this purpose. A network can concurrently support SSM in the SSM address range and any- source multicast in the rest of the multicast address space, and it is expected that this will be commonplace. In such a network, a router may receive a non-source-specific, or "(*,G)" in conventional terminology, request for delivery of traffic in the SSM range from a neighbor that does not implement source-specific multicast in a manner compliant with this document. A router that receives such a non-source-specific request for data in the SSM range MUST NOT use the request to establish Holbrook/Cain [Page 9] INTERNET-DRAFT Source-Specific Multicast 18 Jul 2004 forwarding state and MUST NOT propagate the request to other neighboring routers. A router MAY log an error in such a case. This applies both to any request received from a host, e.g., an IGMPv1 or IGMPv2 host report, and to any request received from a routing protocol, e.g., a PIM-SM (*,G) join. The inter-router case is further discussed in section 8, Transition Considerations. It is essential that all routers in the network give source-specific semantics to the same range of addresses in order to achieve the full benefit of SSM. To comply with this specification, a router MUST treat ALL IANA-allocated SSM addresses with source-specific semantics. 6. Link-Layer Transmission of Datagrams Source-specific multicast packets are transmitted on link-layer networks as specified in RFC 1112 for IPv4 and as in [ETHERv6] for IPv6. On most shared-medium link-layer networks that support multicast (e.g., Ethernet), the IP source address is not used in the selection of the link-layer destination address. Consequently, on such a network, all packets sent to destination address G will be delivered to any host that has subscribed to any channel (S,G), regardless of S. And therefore, the IP module MUST filter packets it receives from the link layer before delivering them to the socket layer. 7. Security Considerations This section outlines security issues pertaining to SSM. The following topics are addressed: limitations of IPSec, denial of service attacks, source spoofing, and security issues related to administrative scoping. 7.1. IPSec and SSM The IPSec Authentication Header (AH) and Encapsulating Security Payload (ESP) protocols [IPSEC] can be used to secure SSM traffic. As of this writing, however, the IPSec protocols have some limitations when used with SSM. This section describes those limitations. [IPSEC] specifies that every incoming packet that requires IPSec processing is ultimately looked up in a local Security Association Database (SAD) to determine the Security Association (SA) that is to be applied to the packet. The resulting SA determines the decryption and/or authentication key to use and the anti-replay window, if one is used. The key used for the SAD lookup is: - the packet's destination IP address - the IPSec protocol (ESP or AH) Holbrook/Cain [Page 10] INTERNET-DRAFT Source-Specific Multicast 18 Jul 2004 - the Security Parameter Index (SPI) A problem arises for SSM because the source address is not included in the SAD lookup. IPSec does not currently provide any way to ensure that two unrelated SSM channels will have unique SAD entries at all receivers. Two senders that happen to choose the same SSM destination address and the same Security Parameter Index will "collide" in the SAD at any host that is receiving both channels. Because the channel addresses and SPIs are both allocated autonomously by the senders, there is no reasonable means to ensure that each sender uses a unique destination address or SPI. In practice, this problem only arises if a receiver subscribes simultaneously to two unrelated channels using IPSec whose sources happen to have chosen the same IP destination address (IPDA) and the same IPSec SPI. The tuple, however, consists of 56 bits that are generally randomly chosen, and a conflict is unlikely to occur through random chance. But when this problem occurs, however unlikely, a host will not be able to simultaneously receive IPSec-protected traffic from the two colliding sources under the current IPSec model. This problem is under investigation and a solution will appear in a separate document. One possible solution is to include the source address in the SAD lookup when the destination is an SSM address. 7.2. Denial of Service A subscription request creates (S,G) state in a router to record the subscription, invokes processing on that router, and possibly causes processing at neighboring routers. A host can mount a denial of service attack by requesting a large number of subscriptions. A denial of service can result if: - a large amount of traffic arrives when it was otherwise undesired, consuming network resources to deliver it and host resources to drop it - a large amount of source-specific multicast state is created in network routers, using router memory and CPU resources to store and process the state - a large amount of control traffic is generated to manage the source-specific state, using router CPU and network bandwidth To reduce the damage from such an attack, a router MAY have configuration options to limit, for example, the following items: Holbrook/Cain [Page 11] INTERNET-DRAFT Source-Specific Multicast 18 Jul 2004 - The total rate at which all hosts on any one interface are allowed to initiate subscriptions (to limit the damage caused by forged source-address attacks) - The total number of subscriptions that can be initiated from any single interface or host. Any decision by an implementor to artificially limit the rate or number of subscriptions should be taken carefully, however, as future applications may use large numbers of channels. Tight limits on the rate or number of channel subscriptions would inhibit the deployment of such applications. A router SHOULD verify that the source of a subscription request is a valid address for the interface on which it was received. Failure to do so would exacerbate a spoofed-source address attack. We note that these attacks are not unique to SSM -- they are also present for any-source multicast. 7.3. Spoofed Source Addresses By forging the source address in a datagram, an attacker can potentially violate the SSM service model by transmitting datagrams on a channel belonging to another host. Thus, an application requiring strong authentication should not assume that all packets that arrive on a channel were sent by the requested source without higher-layer authentication mechanisms. The IPSEC Authentication Header [IPSEC] may be used to authenticate the source of an SSM transmission, for instance. Some degree of protection against spoofed source addresses in multicast is already fairly widespread, because the commonly deployed IP multicast routing protocols [PIM-DM, PIM-SM, DVMRP] incorporate a "reverse-path forwarding check" that validates that a multicast packet arrived on the expected interface for its source address. Routing protocols used for SSM SHOULD incorporate such a check. Source Routing [RFC791] (both Loose and Strict) in combination with source address spoofing may be used to allow an impostor of the true channel source to inject packets onto an SSM channel. An SSM router SHOULD by default disallow source routing to an SSM destination address. A router MAY have a configuration option to allow source routing. Anti- source spoofing mechanisms such as source address filtering at the edges of the network are also strongly encouraged. Holbrook/Cain [Page 12] INTERNET-DRAFT Source-Specific Multicast 18 Jul 2004 7.4. Administrative Scoping Administrative scoping should not be relied upon as a security measure [ADMIN-SCOPE]; however, in some cases it is part of a security solution. It should be noted that no administrative scoping exists for IPv4 source-specific multicast. An alternative approach is to manually configure traffic filters to create such scoping if necessary. Furthermore, for IPv6, neither source nor destination address scoping should be used as a security measure. In some currently-deployed IPv6 routers (those that do not conform to [SCOPED-ARCH]), scope boundaries are not always applied to all source address (for instance, an implentation may filter link-local addresses but nothing else). Such a router may incorrectly forward an SSM channel (S,G) through a scope boundary for S. 8. Transition Considerations A host that complies with this document will send ONLY source-specific host reports for addresses in the SSM range. As stated above, a router that receives a non-source-specific (e.g., IGMPv1 or IGMPv2 or MLDv1) host report for a source-specific multicast destination address MUST ignore these reports. Failure to do so would violate the SSM service model promised to the sender: that a packet sent to (S,G) would only be delivered to hosts that specifically requested delivery of packets sent to G by S. During a transition period, it would be possible to deliver SSM datagrams in a domain where the routers do not support SSM semantics by simply forwarding any packet destined to G to all hosts that have requested subscription of (S,G) for any S. However, this implementation risks unduly burdening the network infrastructure by delivering (S,G) datagrams to hosts that did not request them. Such an implementation for addresses in the SSM range is specifically not compliant with Section 5.2 of this document. 9. IANA Considerations Addresses in the range 232.0.0.1 through 232.0.0.255 and IPv6 addresses in the range FF3x:4000:0000 to FF3x::7FFF:FFFF are reserved for services with wide applicability that either require or would strongly benefit if all hosts used a well-known SSM destination address for that service. IANA shall allocate addresses in this range according to IETF Consensus [IANA-CONSIDERATIONS]. Any proposal for allocation must consider the fact that, on an Ethernet network, all datagrams sent to any SSM destination address will be transmitted with the same link-layer destination address, regardless of the source. Furthermore, the fact Holbrook/Cain [Page 13] INTERNET-DRAFT Source-Specific Multicast 18 Jul 2004 that SSM destinations in 232.0.0.0/24 and 232.128.0.0/24 use the same link-layer addresses as the reserved IP multicast group range 224.0.0.0/24 must also be considered. Similar consideration should be given to the IPv6 reserved multicast addresses. Except for the aforementioned addresses, IANA SHALL NOT allocate any SSM destination address to a particular entity or application. To do so would compromise one of the important benefits of the source-specific model: the ability for a host to simply and autonomously allocate a source-specific multicast address from a large flat address space. 10. Acknowledgments The SSM service model draws on a variety of prior work on alternative approaches to IP multicast, including the EXPRESS multicast model of Holbrook and Cheriton [EXPRESS], Green's [SMRP] and the Simple Multicast proposal of Perlman et. al. [SIMPLE]. We would also like to thank Jon Postel and David Cheriton for their support in reassigning the 232/8 address range to SSM. Brian Haberman contributed to the IPv6 portion of this document. Thanks to Pekka Savola for a careful review. 11. Normative References [ETHERv6] Crawford, M., "Transmission of IPv6 Packets over Ethernet Networks", RFC2464, Dec 1998. [GMP-SSM] H. Holbrook and B. Cain, "IGMPv3/MLDv2 for SSM", draft- holbrook-idmr-igmpv3-ssm-07 (Work in Progress), June 2004. [IGMPv3] Cain, B., Deering, S., and A. Thyagarajan, "Internet Group Management Protocol, Version 3," RFC 3376, October 2002. [IPSEC] S. Kent, R. Atkinson, "Security Architecture for the Internet Protocol.", RFC 2401. [IPV6-UBM] B. Haberman, D. Thaler, "Unicast-Prefix-based IPv6 Multicast Addresses.", RFC 3306, August 2002. [IPV6-MALLOC] B. Haberman, "Dynamic Allocation Guidelines for IPv6 Multicast Addresses", RFC 3307, August 2002. [MLDv2] R. Vida, and L. Costa. "Multicast Listener Discovery Version 2 (MLDv2) for IPv6," RFC3810, June 2004. [PIM-SM] B. Fenner, M. Handley, H. Holbrook, and I. Kouvelas. "Protocol Independent Multicast-Sparse Mode (PIM-SM): Protocol Specification (Revised)," draft-ietf-pim-sm-v2-new-10.txt (Work in Progress), July 2004. Holbrook/Cain [Page 14] INTERNET-DRAFT Source-Specific Multicast 18 Jul 2004 [RFC791] Postel, J., ed., "Internet Protocol, Darpa Internet Program Protocol Specification," September 1981. [RFC1112] Deering, S., "Host Extensions for IP Multicasting," RFC 1112, August 1989. [RFC2373] Hinden, R. and Deering, S. "IP Version 6 Addressing Architecture." RFC 2373, July 1998. 12. Informative References [ADMIN-SCOPE] Meyer, D., "Administratively Scoped IP Multicast", BCP 23, RFC 2365, July 1998. [DVMRP] Waitzman, D., Partridge, C., and S. Deering., "Distance Vector Multicast Routing Protocol," RFC 1075, Nov 1988. [EXPRESS] Holbrook, H., and Cheriton, D. "Explicitly Requested Source- Specific Multicast: EXPRESS support for Large-scale Single-source Applications." Proceedings of ACM SIGCOMM '99, Cambridge, MA, September 1999. [IANA-ALLOCATION] Internet Assigned Numbers Authority, http://www.iana.org/assignments/multicast-addresses. [IANA-CONSIDERATIONS] Narten, T., and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs," RFC 2434, October 1998. [IGMPv2] Fenner, W., "Internet Group Management Protocol, Version 2," RFC 2236, November 1997. [MSFAPI] Thaler, D., Fenner, B., and Quinn, B. "Socket Interface Extensions for Multicast Source Filters." Work in Progress. [PIM-DM] Deering, S., Estrin, D., Farinacci, D., Jacobson, V., Helmy, A., Meyer, D., and L. Wei, "Protocol Independent Multicast Version 2 Dense Mode Specification," Work in Progress. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels," RFC 2119, March 1997. [RFC2710] S. Deering, W. Fenner, B. Haberman, "Multicast Listener Discovery (MLD) for IPv6", RFC 2710, October 1999. [RFC2771] Finlayson, R., "An Abstract API for Multicast Address Allocation," RFC 2771, February 2000. Holbrook/Cain [Page 15] INTERNET-DRAFT Source-Specific Multicast 18 Jul 2004 [SCOPINGV6] Deering, S. et. al, "IP Version 6 Scoped Address Architecture", Work in Progress. [SIMPLE] R. Perlman, C-Y Lee, A. Ballardie, J. Crowcroft, Z. Wang, T. Maufer, C. Diot, and M. Green. "Simple Multicast: A Design for Simple, Low-Overhead Multicast." Work in Progress. [SMRP] Green, M. "Method and System of Multicast Routing for Groups with a Single Transmitter." United States Patent Number 5,517,494. Authors' Addresses Brad Cain Storigen Systems 650 Suffolk St. Lowell, MA 01854 bcain@storigen.com Hugh Holbrook Cisco Systems 170 W. Tasman Drive San Jose, CA 95134 holbrook@cisco.com Intellectual Property Rights Notice The IETF has been notified of intellectual property rights claimed in regard to some or all of the specification contained in this document. For more information consult the online list of claimed rights. The IETF takes no position regarding the validity or scope of any intellectual property 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; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards- related documentation can be found in BCP-11. 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