Source-specific multicast
Encyclopedia
Source-specific multicast (SSM) is a method of delivering multicast
packets in which the only packets that are delivered to a receiver are those originating from a specific source address requested by the receiver. By so limiting the source, SSM reduces demands on the network and improves security.
SSM requires that the receiver specify the source address and explicitly excludes the use of the (*,G) join for all multicast groups in RFC 3376, which is possible only in IPv4's IGMPv3 and IPv6's MLDv2
.
Source-specific multicast is best understood in contrast to any-source multicast
(ASM). In the ASM service model a receiver expresses interest in traffic to a multicast address
. The multicast network must
This behavior is particularly well suited to groupware applications where
The source discovery burden on the network can become significant when the number of sources is large.
In the SSM service model, in addition to the receiver expressing interest in traffic to a multicast address, the receiver expresses interest in receiving traffic from only one specific source sending to that multicast address. This relieves the network of discovering many multicast sources and reduces the amount of multicast routing information that the network must maintain.
SSM requires support in last-hop routers and in the receiver's operating system
. SSM support is not required in other network components, including routers and even the sending host. Interest in multicast traffic from a specific source is conveyed from hosts to routers using IGMPv3 as specified in RFC 4607.
SSM destination addresses must be in the ranges
or
.
Multicast
In computer networking, multicast is the delivery of a message or information to a group of destination computers simultaneously in a single transmission from the source creating copies automatically in other network elements, such as routers, only when the topology of the network requires...
packets in which the only packets that are delivered to a receiver are those originating from a specific source address requested by the receiver. By so limiting the source, SSM reduces demands on the network and improves security.
SSM requires that the receiver specify the source address and explicitly excludes the use of the (*,G) join for all multicast groups in RFC 3376, which is possible only in IPv4's IGMPv3 and IPv6's MLDv2
Multicast Listener Discovery
Multicast Listener Discovery is a component of the Internet Protocol Version 6 suite. MLD is used by IPv6 routers for discovering multicast listeners on a directly attached link, much like IGMP is used in IPv4. The protocol is embedded in ICMPv6 instead of using a separate protocol. MLDv1 is...
.
Source-specific multicast is best understood in contrast to any-source multicast
Any-source multicast
Any-source multicast is the more traditional form of multicast where you can have multiple senders on the same group/channel, as opposed to source-specific multicast where a single particular source is specified....
(ASM). In the ASM service model a receiver expresses interest in traffic to a multicast address
Multicast address
A multicast address is a logical identifier for a group of hosts in a computer network, that are available to process datagrams or frames intended to be multicast for a designated network service...
. The multicast network must
- discover all multicast sources sending to that address, and
- route data from all sources to all interested receivers.
This behavior is particularly well suited to groupware applications where
- all participants in the group want to be aware of all other participants, and
- the list of participants is not known in advance.
The source discovery burden on the network can become significant when the number of sources is large.
In the SSM service model, in addition to the receiver expressing interest in traffic to a multicast address, the receiver expresses interest in receiving traffic from only one specific source sending to that multicast address. This relieves the network of discovering many multicast sources and reduces the amount of multicast routing information that the network must maintain.
SSM requires support in last-hop routers and in the receiver's operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
. SSM support is not required in other network components, including routers and even the sending host. Interest in multicast traffic from a specific source is conveyed from hosts to routers using IGMPv3 as specified in RFC 4607.
SSM destination addresses must be in the ranges
232.0.0.0/8 for IPv4IPv4
Internet Protocol version 4 is the fourth revision in the development of the Internet Protocol and the first version of the protocol to be widely deployed. Together with IPv6, it is at the core of standards-based internetworking methods of the Internet...
or
FF3x::/96 for IPv6IPv6
Internet Protocol version 6 is a version of the Internet Protocol . It is designed to succeed the Internet Protocol version 4...
.