I know it's been awhile but things have been a bit slow around here so I've been using my spare time to learn Linux inside and out the best I can. Figured another technology under my belt surely can't hurt anything. Last week however was a change of pace with a strange issue.
I have a customer that is experiencing choppy audio when dialing their analog paging system. They are on 10.5(2) so everything in place works and is supported even prior to their upgrade. Their 8841s go off hook and dial a paging number that hits a voice gateway and then pushes out an FXO port to their paging system. Every time they call the number the overhead paging sounds like crap. At first, they thought the paging system was bad but with a buttset hooked up to the POTS line going to the paging system, everything sounded fantastic. That leaves Cisco's side of things.
I had to rule out the DSPs and the FXO port. I had them make a call and after a "show voice call x/x/x" and saw nothing out of the ordinary. Logs on the gateway were also fine so what the heck? They only have a two port FXO card so I wasn't about to ask them to pull their primary line inbound to test. I instead asked a coworker to go on-site and with a spare FXO card that we know works. We swapped out the card and the same thing still happened, so piss!
After that fiasco, we went back to the drawing board and tried dialing from a phone that isn't an 8841 and everything sounded good. That old 7912 from over ten years ago still works and pointed the finger to the 8841. I don't know if it's the G.722 codec, firmware, or somehow and someway SIP is screwing up the call setup using a weird codec but I will need to pull logs to find out for sure. I need to schedule another test call with them and pull logs relevant only to that time period so I can get a fresh cap.
Hopefully this pans out to be firmware but with it suddenly happening who knows. I don't see SIP screwing up since it's just a SIP phone pushing to an H.323 gateway. At that point CUCM should have already done the heavy lifting of protocol conversion.
