Duplicate 200 OK from client is dropped - Another ACK should be sent since the duplicate OK implies the previous ACK was lost.

[elbow]

Hi Dave,

I investigated a "caller couldn't hear me" report from two internal users.

The call was being processed via B2BUA with the simringer.

In the trace - which I can send - you can see that the callee returned a 200 OK; we sent an ACK.

Then, another 200 OK came from the callee. Drachtio-srf logged :

2020-07-09 09:07:46.550047 SipDialogController::processResponseOutsideDialog - unable to match invite response with callid: [email protected]:5060

and apparently dropped the OK with no further action.

I think that another ACK should have been sent since the duplicate OK implies that the previous ACK was not received.

Do we have to take a special action to deal with this?

Thanks

[davehorton]

Yes, if possible would like to see the trace

Unless you continued receiving retransmitted 200 OKs I don't think this would have been the cause of the audio loss.

I can look into why an ACK was not retransmitted by the server though

[elbow]

Hi Dave,

Is this going to be something in drachtio itself or in drachtio-srf? Since the message was logged in my drachtio-srf-using client I had assumed that drachtio-srf or my own code was where the problem would be found.

But I will send you the logs.

[davehorton]

Its going to be a drachtio server thing