[Contents]
[Prev]
[Next]
[Index]
[Report an Error]
Broadband Subscriber Management IGMP Model Overview
In an IPTV network, channel changes occur when a set-top
box (STB) sends IGMP commands that inform an upstream device (for
example, a multiservice access node [MSAN] or services router) whether
to start or stop sending multicast groups to the subscriber. In addition,
IGMP hosts periodically request notification from the STB about which
channels (multicast groups) are being received.
You can implement IGMP in the subscriber management
network in the following ways:
-
Static IGMP—All multicast
channels are sent to the MSAN. When the MSAN receives an IGMP request
to start or stop sending a channel, it performs the request and then
discards the IGMP packet.
-
IGMP Proxy—Only multicast
channels currently being viewed are sent to the MSAN. If the MSAN
receives a request to view a channel that is not currently being forwarded
to the MSAN, it forwards the request upstream. However, the upstream
device does not see all channel change requests from each subscriber.
-
IGMP Snooping—Only multicast
channels currently being viewed are sent to the MSAN. The MSAN forwards
all IGMP requests upstream, unaltered, even if it is already receiving
the channel. The upstream device sees all channel change requests
from each subscriber. Using IGMP snooping enables the broadband services
router to determine the bandwidth requirement of each multicast group
and adjust the bandwidth made available to unicast traffic.
-
IGMP Passthrough—The
MSAN transparently passes IGMP packets upstream to the broadband services
router.
IGMP hosts (sources) also periodically verify that they
are sending the correct traffic by requesting that each client send
information about what multicast groups it wants to receive. The responses
to this IGMP query can result in
a substantial upstream traffic burst.
IGMPv2 is the minimum level required to support IPTV, and is
the most widely deployed. Emerging standards specify IGMPv3.
Related Topics
[Contents]
[Prev]
[Next]
[Index]
[Report an Error]
