Many of the problems experienced with VoIP usage can be blamed on the LAN. The things you need to look at are the following:
- Inside wiring - cat3 wiring won't work any more. It maxes at 10MB in good condition. And most is not in good condition.
- Are you using 100MB switches on full duplex or hubs or 10/100 switches set to half-duplex?
- Do you have enough Internet bandwidth? And how many hops are you from the VOIP Gateway?
- Does your router perform QOS or do you need an Edgewater?