The 1st thing that needs to happen is to be sure your PRI isn't having issues.
You can do this by typing DTS READ <PLID OF PRI> last 24.
It will show you if your PRI has been up/down during the last 24 hours.
Next, go to your maintenance & software logs and export them into Excel.
Do a search for "congestion". This will show you if you're getting a busy because of all trunks being used.
Now you'll need to figure out if you're loosing your network connections.
Check the logs you down loaded and do a search for 'lost'. See if your systems are loosing connections to each other. If yes, they you do have a network problem.
Another test you can do here is to call a phone on site B from site A (as an internal call, not as an outside call) and then leave them both on speaker phone. All day if you need to. If the call drops then you probably do have a network issue.
Ralph
Check them once in a while to see if they've dropped the call. If yes,