Measure load of pipes?

[Shawn Barnhart]

I've been trying to reign in our internet connectivity (multilink
aggregation of 2 T1s) using a FreeBSD box bridged between our border router
and our firewall.

One thing that's not clear to me is if there's any way to measure the load
on a specific pipe.  "ipfw pipe show" lists the number of drops associated
with the pipe.  I'm thinking there might be a script I could kludge that
would parse out the bytes on the pipe display and use that as mrtg input or
something.

Any other way to do this?