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Doc ID: FAQ15377
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Spirent TestCenter: What is the setting "Unsolicited Report Interval" in IGMP used for?
Setting this parameter sets the time between the initial STC IGMP host's "initial report" and subsequent repetitions of it.
The Help file describes the “Unsolicited Report Interval" (URI) with:
period of time (in seconds) between sending repetitions of the initial report of membership
in a group
Next, RFC 2236 - IGMP, section 6, "start timer", indicates that the URI is used to specify an interval (0, URI].
"start timer" for the group on the interface, .... If this is an unsolicited Report, the timer is set to a delay value chosen uniformly from the interval (0, [Unsolicited Report Interval] ].
so when a device sends its initial join (i.e., after the user clicks on the "Send report for IGMP groups" command):
a delay value is chosen between (0, URI]
the "start timer" begins to count down
when the "start timer" expires, the next join (assuming the robustness variable is > 1) is sent
This is what it'd look like in a timeline:
^ ^ ^
| <------ | -----> |
initial report delay chosen URI
(i.e., join) when next join the upper bound
sent is sent on the delay
Now, the number of subsequent joins are set with the "Robustness variable" parameter.
The default of the robustness variable is 2.
This value can be changed to a higher value but still this is only used for the initial report.
After these <robustness variable> reports are sent, the only other reports he will see is if the client receives a query from the DUT.
the response from the STC IGMP host is a Solicited Report.
Of course you could also resend reports either manually or use the command sequencer.
A client would not periodically send any other unsolicited reports.
If the router needs to know if a client still wants to receive multicast traffic, then the router will send a query to the client.
Once the client receives the query it will respond with a report.
If you are seeing the IGMP routes disappearing please check article
Product : Spirent TestCenter,IGMP/MLD,Multicast
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