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1900-A2-GN20-00
The 10306 IP Multicast Operation works in the following manner:
1. The client issues an IGMP Join Request (Unsolicited report)
Layer 2 broadcast.
2. The 10306 modem listens for any IGMP packets (IGMP snooping)
and maintains a table mapping the IP Multicast stream to the port.
3. The 10306 forwards the IGMP Join Request upstream through the
MIU to the IGMP-enabled switch.
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 10306 replicates and forwards IP Multicast streams ONLY to
the ports with subscribing clients.
9. When the member clients issues an IGMP Leave, the 10306
receives that message, forwards it to the upstream IGMP-enabled
Switch, and then generates a series of "quick query" packets on the
downstream port (default response time of 100 milliseconds,
repeated 3 times.) This query will allow the 10306 modem to deter-
mine 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 10306 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 10306 modem relies on an upstream IGMP enabled router or
switch to send Group Membership query messages.
BitStorm 1900 Installation and Maintenance Guide
1. BitStorm 1900 IP DSLAM
1-15
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