Home > Uncategorized > “The odd call drops” of the Mediation Server

“The odd call drops” of the Mediation Server

“The odd call drops” of the Mediation ServerStandardI had a very annoying issue lately when an installation of a new gateway resolved in some calls (specifically to US numbers) dropped by the Skype for Business mediation server saying “A call to a PSTN number failed due to non availability of gateways.”The cause, according to the mediation server, was that “All gateways available for this call are marked as down“, and the resolution, surprisingly, was to “Verify that these gateways are up and can respond to calls.”It seemed funny, because all other calls were successful, I have not exhausted the available PRI channels I had, the gateway didn’t seem to lose connectivity for a split second and SIP options are accepted and replied to on both ends.Looking further at the Lync Monitoring Reports, I noticed the following:Reported by Client12000; reason=”Routes available for this request but no available gateway at this point”Reported by Server12000; reason=”Routes available for this request but no available gateway at this point”I went to the gateway (AudioCodes M1000B) for answers and the logs were showing something very weird;Every call starts with the same flow:Flow1The mediation server sends a SIP Invite that will normally be answered immediately by the gateway with a “100 Trying”. This, for me, will close the deal on the “Gateway no responding” – this is a great response if you ask me.The next phase would be the gateway immediately sending a “PSTN Place call” to the PSTN, hopefully receiving a “Proceeding” instantly from the PSTN, meaning so far we’re fully communicating. So for the time being I’m not really buying what the Lync mediation server is selling.Looking further at the logs, I see the following strange behaviour:As I’m still waiting for the PSTN to connect the call (this would normally be a “PSTN Call Alerting” message), I see that the mediation server decided to abandon ship!This is what I see in the logs:WrongWithin 10 seconds after initiating the call, the mediation server will send a “Cancel” request to the gateway and will terminate the call:19:25:49.640 [S=660986] [SID:1327438938] INVITE sip: 353857560598@;user=phone SIP/2.0 19:25:49.729 [S=661027] [SID:1327438938] SIP/2.0 100 Trying 19:25:49.730 [S=661035] [SID:1327438938] ( lgr_psbrdif)( 656225) pstn send –> PlaceCall19:25:50.087 [S=661039] [SID:1327438479] ( lgr_psbrdex)( 656229) pstn recv PSTNDisconnectCallClearly, the gateway is available and responding, but the mediation server is somewhat impatient.Doing a bit of digging around, it appears there’s a setting for this.

Source: “The odd call drops” of the Mediation Server

Categories: Uncategorized
  1. No comments yet.
  1. No trackbacks yet.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: