IN some buildings where hundreds of people are all using the same T1 line, it can slow down tremendously when lots of people get on the net. The more people using the line, the slower it goes.. If you connect at 7:00 A.M. things zip right along.. At noon, it crawls. Our office also has T1 lines and have created internet policies that prevent employees from doing certain things. A few steps to break bad habits helps a lot.. They can't watch streaming videos.. or leave an internet window open and minimized..or use P2P file sharing...avoid downloading files in the middle of the day....set antivirus updates times to first thing in the morning.., etc.
Hope this helps.