There are two main reasons why gaming systems won't connect to the wired network:
1) One of the main reasons that gaming systems wont connect to the network is because the SafeConnect manager that regulates what can and cannot use the network sees them as an unknown device. So a way to tell Safe*Connect that your device is in fact a PS3 (and allowed to connect) is to run the Internet Connection Test.
If you are not able to connect to the internet with your PS3, open the PS3 Settings and choose Network Settings followed by Internet Connection Test. This should create enough traffic to have the system recognized as a gaming system.
2) If you still can't connect to the network after following the instructions in #1, call the ITS Help Desk at 619-260-7900 or email firstname.lastname@example.org The port in your dorm room may have been deactivated due to inactivity and ITS will need to reactivate it.