1. BitStorm 2400 Overview
2400-A2-GB20-10
December 2002
1-15
IGMP Leave Messages
IGMP V2 Leave messages received from subscriber ports indicate that a host on a
subscriber port has lost interest and no longer wishes to participate in a multicast
group. The BitStorm 2400, upon receiving this message from a port, determines if
there are any remaining hosts interested in this group on the port or VLAN
interface.
The BitStorm 2400 extracts the IP group address from the message and looks it
up in the group-to-interface forwarding table. If the table indicates that an IGMP
Version 1 host is active for this group on this interface, no further processing is
performed. If the table indicates that only IGMP V2 hosts are on this interface, the
BitStorm 2400 immediately issues a Group-Specific Query message on that
interface. If there are no report messages received for that group in response to
the Query message, the group entry for that interface may be deleted or
invalidated from the interface table.
Configurable parameters are made available to specify an interval and retry count
to control the process of removing an entry after an IGMP Leave message is
received. The parameter sets a number of retries (default 3) and interval (100 ms)
that would be allowed to attempt to locate remaining hosts on the BitStorm 2400 or
VLAN interface before removing the entry from the forwarding table. Tuning this
parameter would be one of the tools for minimizing the effects of ‘channel surfing’
on the links.
Group-to-Interface Table Processing
In the presence of an IGMP enabled router, IGMP General Query messages
should be received about every 10 seconds or less. The BitStorm 2400 notes the
relative time of the last Query message.
As General Query messages and reports are being processed and forwarded, the
group-to-interface table will be updated. At least every 10 seconds, the
BitStorm 2400 reviews the group-to-interface table entries, looking for rows that
have not seen a report message from a host on that interface in 3 Query cycles or
30 seconds.
If entries are found that have expired, they may be invalidated or deleted. If
General Query messages have not been received in 15 seconds, the data pump
generates its own IGMP General Query message.
Summary of Contents for BitStorm 2400
Page 1: ...BitStorm 2400 User s Guide Document No 2400 A2 GB20 10 December 2002...
Page 10: ...About This Guide viii December 2002 2400 A2 GB20 10...
Page 42: ...3 Using the Asynchronous Terminal Interface 3 14 December 2002 2400 A2 GB20 10...
Page 70: ...4 Using the Web Interface 4 28 December 2002 2400 A2 GB20 10...
Page 86: ...C MIB Support C 12 December 2002 2400 A2 GB20 10...
