Information Technology’s side to a technical story

In regards to the recent article involving music sharing, it was suggested by a student that the school (or should I say, the IT Services department) is preventing the sharing of iTunes music between residence halls. This is not the case.There are a couple factors that prevent iTunes sharing, the main one being that Windows XP and Mac OS X come configured with a personal firewall that allows the iTunes application to work for downloads, but not the sharing portion of it. There are two ports (3689 for TCP and port 5353 for UDP) that need to be opened on the personal firewall for iTunes sharing and doing a Google search will provide details and instructions

The other factor is that Apple themselves removed the ability to share across “subnets”. Since each residence hall is in it’s own different subnet, this accounts for the problem. Without launching into a full-scale networking 101 seminar, let me just say that this design is necessary since there is a maximum of 250 available ip addresses in each subnet. With approximately 150+ students in each residence hall (some with multiple computers), you can easily do the math to see why it’s easiest to have each hall in it’s own subnet. However, there are software applications that supposedly make sharing across subnets work. Again, a Google search will provide the answers – but all the configuration, coordination, and decision-making is in your hands – not ours.

Finally, I will say that IT Services does block Windows filesharing across residence halls. This is done in an effort to contain certain destructive viruses that use the Windows-sharing ports to proliferate. These viruses often perform denial-of-service attacks on network devices and can take down an entire residence hall. Without the block, it would enable a virus to take down more than just one residence hall – even the entire campus.

Any other questions you have will be answered to the best of our ability by emailing

Jonathan Czar
LAN Admin – IT Services

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