HP 2610, Advanced Traffic Management Manual

Page: 96 / 364

Multimedia Traffic Control with IP Multicast (IGMP)
How IGMP Operates
assume this function in order to elicit group membership information
from the hosts on the network. (If you need to disable the querier feature,
you can do so through the CLI, using the IGMP configuration MIB. See
“Configuring the Querier Function” on page 4-10.)
■
Report (Join): A message sent by a host to the querier to indicate that
the host wants to be or is a member of a given group indicated in the report
message.
■
Leave Group: A message sent by a host to the querier to indicate that the
host has ceased to be a member of a specific multicast group.
IGMP Operating Notes
IGMP identifies members of a multicast group (within a subnet) and allows
IGMP-configured hosts (and routers) to join or leave multicast groups based
on the following process.
■ An IP multicast packet includes the multicast group (address) to which
the packet belongs.
■ When an IGMP client connected to a switch port needs to receive multi­
cast traffic from a specific group, it joins the group by sending an IGMP
report (join request) to the network. (The multicast group specified in the
join request is determined by the requesting application running on the
IGMP client.)
■ When a networking device with IGMP enabled receives the join request
for a specific group, it forwards any IP multicast traffic it receives for that
group through the port on which the join request was received.
■ When the client is ready to leave the multicast group, it sends a Leave
Group message to the network and ceases to be a group member.
■
When the leave request is detected, the appropriate IGMP device will
cease transmitting traffic for the designated multicast group through the
port on which the leave request was received (as long as there are no other
current members of that group on the affected port).
Displaying IGMP Data.
To display data showing active group addresses, reports, queries, querier
access port, and active group address data (port, type, and access), see the
appendix on monitoring and analyzing switch operation in the
Management
and Configuration Guide .
4-12