I have a number of IP softphones setup connected back to an AVAYA pbx. I have ruled it out being a network issue as I have tried a number of different types of PC,s into the same port on a catalyst switch.
One particular model of PC works fine with the softphone and has an average Jitter level of zero.
Another model of PC works but has high Jitter resulting in bad conversation. Jitter can be as high as 21 average.
Bear in mind both these PC's have traveresed the same path back to the AVAYA, with me even trying both PC's into the same switch port.
The PC that works is a Lenovo Thinkcentre 8107.
The PC that does not work is a Fujitsu Siemens Esprimo E3510.
Both PC's have QOS enabled on the network card. I can't see any other difference but must be something PC related.
Any suggestions ??