Avaya’s IPOffice platform provides a monitor application to troubleshoot all sorts of issues with calls and phones.
A nice reference for IP Office’s Monitor application is hosted at this link.
http://www.oc-stuff.com/mergedProjects/monitor/
Another handy reference when troubleshooting dropped calls are the ISDN cause codes.
http://www.oc-stuff.com/mergedProjects/monitor/htm_cause_codes_(isdn).htm