[SIPForum-discussion] Delayed 100 Trying
Paul Kyzivat
pkyzivat at alum.mit.edu
Tue Aug 11 19:44:52 UTC 2015
On 7/21/15 3:11 AM, Raj Kumaradass wrote:
> Hello,
>
> I have observed a case where in 100Trying & 180ringing response for a
> initial INVITE message is delayed beyond 32seconds(TCP transport being
> used here) causes the client B to remain in a hung call state, as the T1
> timer expiry eventually causes dialog cleanup at the server side as below.
>
>
> Client A ------ Server ------- Client B
>
> --- INVITE ----->
> @32seconds(T1 timer) fires and cleansup the dialog
> after say 40 seconds
> <---100 Trying---
> <--- 180 Ringing --
>
> In such case, is there any standard described way to get this cleaned up
> at Client B side as well? Is this covered up in any drafts?
Unless the 180 is reliable, there is nothing more for B to do about it.
And there is nothing to do about the 100. But B will eventually need to
send some sort of final response. (Success or failure.) When that
happens, A will presumably drop it, without sending an ACK. When B
doesn't get the ACK it will retransmit the final response. After all the
retries have been sent B should time out and terminate the dialog.
Thanks,
Paul
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