standard transit arrangements


I just wanted to find out what the "standard" arrangements are when
one buys transit traffic. I've been left in charge of this now,
without haven't been doing this before :frowning:

So what normally you buy x amount of bandwidth over a physical line
e.g. 45Mb/s over FastEthernet or so. They then charge you for excessive
usage based on 95th percentile.
Is there anything else I need to keep an eye on?


Thanks for all answers/comments.