PLANET EPL-1000 - Manual (Page 75)

4.7 IGMP
EPON chipsets include an RFC 2236 compliant IGMP solution that leverages the power of
the underlying hardware classifiers, shapers and priority FIFOs to deliver high quality IP
multicast content over EPON. From a functional perspective the feature set may be roughly
divided into 4 broad classes of functionality:
1. Control over IP multicast data traffic at the network and customer edge.
2. Burst protection for customer premise equipment (CPE.)
3. Scheduling of IP multicast data traffic.
4. Aggregation of reports sent by CPE, greatly limit the burdon placed on RFC 2236
queriers such as a video server residing in the CO.
These 4 primary functions are distributed between the OLT and the several ONUs, based
on the design principle that functionality should be implemented, as much as possible, at
the network’s edges. Thus preserving the bandwidth of the PON and taking maximum
advantage of the combined resources of the several ONUs.
4.7.1 Brief Overview of Proxy Concepts
On the customer edge the OLT acts as an RFC 2236 querier. Hosts connected to one of the
ONUs UNI ports perceive the queries sent by the OLT as originating from a media server
behind the OLT. On the network edge the OLT behaves as an RFC 2236 “non-querier,”
aggregating the reports sent by the several connected hosts, and making the system
appear to an attached video server or other device connected to the OLT’s NNI as if there
existed only a single STB behind the OLT.
„ Behavior of ONU
By default the ONU shall block all IGMP multicast data traffic preserving the bandwidth of
the user network. When an STB or other host attached to one of the ONU’s UNI ports
requests to join a multicast group, the query is snooped by the ONU’s CPU before being
forwarded to the EPON port without modification.
Report Received from UNI
If no host is joined to the group on the attached interface, the ONU will install a new rule to
forward the group to the provisioned IGMP multicast data FIFO.
Leave Received from UNI
If the LMQC variable is set to 0 (“fast leave”) and at least one host is joined to the group on
the attached interface, the ONU will remove the forwarding rule for the associated group.
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