Specifications

1 BitStorm 1900 Access Multiplexer Elastic Networks
1-18 BitStorm 1900™ Installation and Maintenance Guide 08-01101-01, Rev. 1.50
4. The IGMP-enabled Switch “snoops” for the IGMP messages and
builds a mapping of IP Multicast streams to its Ethernet port inter-
faces.
5. The Switch forwards the IGMP report on behalf of the IP Multicast
client to the upstream Multicast Router
6. The Multicast Router utilizes a multicast routing protocol (such as
MOSPF, DVMRP, etc.) to route available multicast streams.
7. Once the IP Multicast stream is received at the IGMP-enabled
Switch, it replicates and forwards the packets on all ports with
active members of that IP Multicast group.
8. The 6306 replicates and forwards IP Multicast streams ONLY to
the ports with subscribing clients.
9. When the member clients issues an IGMP Leave, the 6306 receives
that message, forwards it to the upstream IGMP-enabled Switch,
and then generates a series of “quick query” packets on the down-
stream port (default response time of 100 milliseconds, repeated 3
times.) This query will allow the 6306 modem to determine if there
are any remaining client members of the IP Multicast group being
left on that port, such as a second set-top box. If no IGMP Group
Membership response is received, the 6306 modem will update the
IP Multicast bridge table and no longer forward that IP Multicast
stream to that port.
10. The query response time value and number of quick queries sent
are provisionable parameters, and can be adjusted to better interop-
erate with a variety of client devices, such as IP television set-top
boxes. Refer to the StormTracker-Site Manager and Administration
User Guide for more information.
11. The 6306 modem relies on an upstream IGMP enabled router or
switch to send Group Membership query messages.