I am trying to work through a rather puzzling SIP issue on my CUCM 8.6 system at the moment. We have 10 non cisco SIP phones connected to our Call Manager, and we are experiencing a bit of jitter on certain inbound/outbound external calls (there doesn't sem to be a clear pattern though) and the audio on one side will sound robotic (we call it autotuning).
We use 2 x Cisco 2811 routers, one hosting a SIP trunk to our Telco (runs CUBE, and has DSPs for codec translation), and the other is for a ISDN PRI trunk (also have enough DSPs to cover the channels). Calls that hit the PRI trunk seem to do ok, so I think this is narrowed to a SIP phone => CUCM => SIP trunk issue. We use G.722/711 within the region/device pool assigned to the phones and CUCM, and we also use G.722/711 between the phones/CUCM and the region/device pool the CUBE is assigned to.
For our switching infrastructure, we use 3750s for access layer with fiber uplinks to our 6509 distribution/core switch. The 2811s are connected to the 6509. Both sets of switches have QOS enabled, but I profess that I do not understand it at all well enough to mentally picture how it would affect traffic flows on this issue.
With the above in mind, I'd appreciate any suggestions on:
1.) Some good methods I could use to track down where the jitter delay is being introduced.
2.) What path could I expect the SIP traffic to take? (I think the SIP legs go like: SIP phone <=> CUCM <=> CUBE <=> SIP provider, but I am not sure).
Thanks in advance,