Glossary
IP Multicast Stub Routing in AOS
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Copyright © 2005 ADTRAN, Inc.
61200890L1-29.3A
Glossary
Broadcast: A transmission addressed to all receivers, usually contained within the given broadcast
domain.
Broadcast Domain: A layer 2 domain, separated by layer 3 devices (routers). A VLAN or LAN segments
connected layer 2 switches and/or bridges typically form a broadcast domain. An IP subnet is typically
contained within a broadcast domain.
Content: The information being conveyed by a source via transmission of a multicast stream.
Downstream: With regard to IP multicast stub routing (IGMP forwarding), the router interface that
connects to multicast client devices.
DVMRP: Distance Vector Multicast Routing Protocol. A multicast routing protocol similar in operation to
RIP. DVMRP creates its own unicast route table.
Group: A set of devices that request to receive a particular content being transmitted in a stream addressed
to that specific group address. A host uses IGMP to communicate with the local multicast router and join a
specific group, becoming a group member. The group member then listens for IP multicast packets
addressed to that specific group address.
Group Address: The IP multicast address to which a specific multicast stream is transmitted. Somewhat
analogous to the frequency on which a particular TV or radio channel is transmitted. End devices use
IGMP to join (subscribe) a specific group to receive packets transmitted to that group address. In doing so,
they become group members.
IGMP: Internet Group Management Protocol. Used between end devices and multicast routers allowing
the end devices to join and leave a multicast group. The multicast router performs IGMP router mode. The
end devices perform IGMP client mode.
IGMP Forwarding: A function that allows a device (multicast stub router) to forward or proxy IGMP
activity from a client on one interface to a router on another interface.
IGMP Helper: See IGMP Forwarding.
IGMP Proxy: See IGMP Forwarding.
Listener: A device that has joined a particular multicast group and is listening for packets addressed to the
group address. Also referred to as a receiver or subscriber.
Media Player: An application that receives streams, reads the content, and presents it to the user.
Media Server: An application that manages content streams and transmits them to or toward devices in the
network.
MOSPF: Multicast Open Shortest Path First. A multicast routing protocol based on OSPF that uses OSPF
for unicast route information.
