OnSIP, the virtual PBX service that we use, has a web page that allows you to test your VoIP connection.
It simulates a voice conservation to OnSIP’s remotes, measuring packet loss and jitter or variation in transit times.
My performance over my information cable provided by Comcast here in NJ was pretty good: no packet loss and .9 ms in jitter.
I got an overall MOS (Mean Opinion Score) in the 4.2 range, which is very good, although this metric is a crude one
And by the way, my SIP invite and register transit times were a speedy .1 seconds.
Thank you Comcast.