i have E1-PRI running on a 2851 voice gateway, the gateway is connected to a port on a core switch, this port belongs to vlan 10.
IP phones are in voice vlan 20
when a call is made from any IP Phone to pstn via this E1-PRI after some time during the call the jitter suddenly begins to rise to a huge values and i can see these values when pressing ? twice on the phone during that call.. the Avg jitter sometimes exceeds 900 !!
at this time the user experiences a bad voice quality and most times the call then is dropped.
i'm trying to investigate why this happens and solve this problem... could any body help me how can i investigate such a jitter problem, could it be Telco problem or since it's a jitter problem means it is something with the IP side of the call not the TDM (Telco side) of the call?
please help me