There have been a lot of questions raised here that we want to answer and summarize with regards to uploading files to iTunes U. We have worked with a couple of individual schools to get more detail on their reported problems. Let me explain what we've found.
First, a few facts about the iTunes U servers and policies. Yes, there is a limit on the overall file size that can be uploaded to iTunes U - 500 MB. And this currently cannot be detected before the file starts uploading. So if your users begin uploading a file that's too big, our upload page will not display an error until the 500 MB limit is reached. This may result in an error that feels like a timeout, but actually is not.
The iTunes U server does not have a rate limit, cap or minimum on how fast or slow files can be uploaded.
There are a lot of factors that can be part of the problem if you are seeing or hearing of upload failures, timeouts or slow activity. While working with a few schools we have uncovered a few factors to consider.
Some people's expectations of how fast a file should upload can be off. This may be due to how fast they can download a file (which is often faster due to asynchronous network rates) or based on how fast they can upload a file to a system on campus (which may be faster due to the proximity of the server and the fact that the upload may take place entirely on the campus WAN or LAN making it more efficient). We recommend doing some speed tests with a 3rd party to see if you can upload data to other points on the Internet at a comparable rate (keep in mind the difference between a bit and a byte). The following web site can measure upload and download speeds from your point on a network to other locations around the country and world. We recommend picking the San Jose, California node to do a test that is roughly equivalent to uploading a file to the iTunes U server (due to the proximity of San Jose to our data center):
http://www.speedtest.net/
We have found in one case where a school's network administrators have placed rules on their firewall and network routers which limit the speed at which files can be sent out of the campus network and onto the commodity Internet. We understand this is an effort to thwart peer-to-peer file swapping activities by slowing them down, but has the collateral effect of slowing down other upload activity.
Another factor could be a known bug/behavior of Microsoft Internet Explorer browsers on Windows. The details are provided in the link below:
http://support.microsoft.com/default.aspx?scid=kb;en-us;329781
For those of you who are looking for even more technical information on bandwidth throughput, you may find the following articles and tools helpful:
http://articles.techrepublic.com.com/5100-6346_11-5034413.html
http://www.dslreports.com/tweaks
