I have one main office and two satelite offices. Both satelite offices are connected to the main via point to point T1 line. There are routers on site at the satelite offices and at the main office. There are multiple times during the week where one of the offices is complaing about performance. During normal times ping times to a server/router/workstation there around roughly 4ms. During the performance issues they are 300-500ms. What are the best tools/ways to determine what is causing the performance issues and to narrow down the problem exactly.