User`s guide

Introduction
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addressing (i.e., those IP addresses with 1110 as their high-order
four bits). Using Internet standard dotted decimal notation, host
group IP addresses range from 224.0.0.0 to 239.255.255.255. The IP
address 224.0.0.1 is assigned to the permanent group of all IP
hosts.
Members of a host group can:
• Join and leave the host group at any time
• Be included as a member in multiple host groups.
A host group can be permanent or temporary. A permanent host
group maintains a single IP address regardless of how many
members it has. A temporary host group is one that must have at
least one member, a permanent host group can exist with zero
members. Currently the ATX supports only temporary host
groups.
Note: There are no restrictions on the location or number of members
assigned to a host group.
IP multicasting provides the following benefits:
• When the same information must be sent to more than one
destination, IP multicasting reduces both network overhead and
the time it takes for all destinations to receive the information.
• When information must be sent to one or more hosts whose
address is either unknown or changeable, IP multicasting can
reduce the need for complicated configuration files because
permanent host groups maintain a single IP address.
Group membership reports are not forwarded across the network.
Instead, routers learn of the existence of other routers on the
network, and forward all IP multicast packets to the downstream
neighboring router.
When a route receives an IP multicast packet, it verifies the route’s
origin, and then forwards the IP multicast packet only if there is a
downstream neighboring router and/or there is a host group
member on the outgoing port.