Atlantis Land Compact Router ADSL A02-RA110 - Manual (Page 45)

COMPACT ROUTER ADSL
A02-RA110 Pag. 37
5.4.4 Multicast
Traditionally, IP packets are transmitted in one of either two ways - Unicast (1
sender - 1 recipient) or Broadcast (1 sender - everybody on the network).
Multicast delivers IP packets to a group of hosts on the network - not everybody
and not just 1.
IGMP (Internet Group Multicast Protocol) is a network-layer protocol used to
establish membership in a Multicast group - it is not used to carry user data.
IGMP version 2 (RFC 2236) is an improvement over version 1 (RFC 1112) but
IGMP version 1 is still in wide use. If you would like to read more detailed
information about interoperability between IGMP version 2 and version 1, please
see sections 4 and 5 of RFC 2236. The class D IP address is used to identify host
groups and can be in the range 224.0.0.0 to 239.255.255.255. The address
224.0.0.0 is not assigned to any group and is used by IP multicast computers.
The address 224.0.0.1 is used for query messages and is assigned to the
permanent group of all IP hosts (including gateways). All hosts must join the
224.0.0.1 group in order to participate in IGMP. The address 224.0.0.2 is assigned
to the multicast routers group.
The ADSL Router supports both IGMP version 1 (IGMP-v1) and IGMP version 2
(IGMP-v2). At start up, the ADSL Router queries all directly connected networks to
gather group membership. After that, the ADSL Router periodically updates this
information. IP multicasting can be enabled/disabled on the ADSL Router LAN
and/or WAN interfaces in the web configurator (LAN; WAN). Select None to
disable IP multicasting on these interfaces.