We have a routed T1 cx between two buildings terminated by Cisco 1700s. Main Building houses servers.
Main Building has 100MB switched network on a single subnet with no apparent congestion issues. There's about 100 nodes. Nobody has trouble grabbing files off the servers 24hrs/day.
Secondary building has 100MB switched network on a single subnet. About 40 nodes. Secondary Building network displays classic evidence of congestion in morning and late afternoon. Main test is a file transfer between a client in the Secondary Building with a server in the Main Building. A file that normally takes 1 minute to transfer takes 20 minutes at these times.
Intuition says the T1 is getting congested as the world logs on and gets email in the AM and wraps up in the PM. (If it were the servers, then everybody would see an impact, not just Secondary Building.)
So I had NPM watch the serial interface on Main Building's router for a week. While I did see peak utilization spike above 90% in the mornings and evenings, the average utilization for those times was a very acceptable 20%.
Now, from everything I've been lead to understand, this T1 isn't saturated, so here's my question: what might be causing my Secondary Building's problems, if it's not the T1? Or could it still be the T1?
Anybody got a suggestion?
JB