There's only one reliable tool... (Score 1)

A line tester will tell you if you've got a physical T1 but can't tell you how much upstream bandwidth is available. Unless the provider is willing to give you SNMP read access to their network (uh, yeah, right, that'll happen), MRTG isn't going to be very helpful either.

The best and most reliable tool for hop-by-hop bandwidth determination we've found is PCHAR:

http://www.employees.org/~bmah/Software/pchar/