It takes up to 21 seconds for SL multicast to be authorized.

The description in the original article is relatively difficult. It takes up to 21 seconds for me to test and verify it.

A simple understanding after the test is as follows. A maximum of three announcements can be sent. A maximum of three seconds can be sent after the first two announcements are sent, and a maximum of 12 seconds can be sent after the third announcement is sent. 3 seconds after the first announcement is sent.

The time sequence is described as follows. Assume that you have not been authorized to send the announcement for 3rd Times:

Send the first announcement in 0th seconds,

No authorization in 3rd seconds. wait 3 seconds.

Send the second announcement in 6th seconds, wait 3 seconds,

9th seconds without authorization, send the third announcement, wait 12 seconds,

21st seconds without authorization, enter the 60 seconds retreat period, that is, the next 60 seconds cannot repeatedly send announcements.

 

The original msdn text is described as follows:

If the Silverlight runtime does not receive a matching authorization message within 3 seconds, the Silverlight runtime assumes that the announcement has been deleted and a new announcement will be resending. If no matching authorization is received, the same request will be resent in 6 seconds. If no matching authorization message is received 12 seconds after the third resend, the Policy Check is deemed as failed and the ApplicationProgramReceiveSocketexceptionAndSocketerror.Accessdenied. If a matched authorization message is received at any time point before the timeout, the Policy Check succeeds and the application is allowed to access multicast groups.

Any other attempt initiated by the application to join multicast groups during the policy check will wait until the Policy Check is complete. If a policy check fails, another attempt to join the multicast group within the next 60 seconds will wait until the 60-second backoff period expires. This prevents malicious applications or poorly written applications from using repeated policy checks to cause excessive traffic on the network.