I have a UC500 with SIP trunk. I have intermitent voice qualtity problems in the form of broken speech, typically on the far end.
The SIP trunk provider claims the issue is not with him and points to widely varying ping times from his server to my UC500.
The ISP claims he can ping the cable modem consistantly in less that 70ms while the UC500 takes 100-800ms. The ISP will not reveal the IP address of the cable modem (Linksys CM100) so I cannot test this for my self.
The network consists of one phone one PC and one wireless cam so it seems an overloaded connection issue.
How can I find out why my router is doing this?
Here is a good document (you will also see it is part of the bigger QoS Design Guide):
Your shaping needs to match whatever is guaranteed upstream by the circuit. In your case, since there are no guarantees, I would just apply the "Bottom" service policy to the WAN interface directly and avoid shaping (Top).
You can determine which codec is being used, by pressing the blue "?" button or "i" button on the IP phone itself while on a call.
Regarding multiple trunks support, this is OK ONLY IF THE SECOND PROVIDER DOES NOT REQUIRE AUTHENTICATION. UC500 can only register with one provider at a time.