Computing Services Restricts Outbound Traffic on Network

Outbound traffic on the Faculty of Arts and Sciences network has been restricted to a maximum of 10 percent of total bandwidth, making it much harder for those outside Harvard to access materials on students' computers through the University's speedy connection.

According to Kevin S. Davis '98, coordinator of residential computing for FAS Computer Services, the decision was made in response to recent delays and sluggish network response times.

"We received a large number of complaints from students, faculty and staff and noticed problems such as the failure of several Crimson Cash systems earlier in the week," said Davis.

Such delays and failures were primarily the result of enormous outbound network traffic--traffic caused by the flow of information from Harvard students' computers to outside sources.

MP3s and other files downloaded from Harvard computers by non-Harvard Internet users are one example of information that moves in the outbound direction. Harvard students using Napster and other music-sharing Internet services to download files weren't causing a problem--but users who get their music from Harvard computers were taking up enough bandwidth to slow the network.

Student websites posted through the Harvard network and videos uploaded by Harvard users to the Internet also lie under the category of outbound traffic.

The FAS network can be understood as an open highway, according to Davis, who is also a Crimson editor. Normally, the network is a highway free of dividers--traffic is allowed to flow freely in either direction.

At its worst, network congestion was at the point where at 3 p.m. on a typical day, outbound traffic was taking up 85 percent of the network. Davis pointed out that at most Harvard students are not using their computers at that time, so this enormous amount of outbound traffic was very likely the result of outsiders downloading MP3s, videos or other files from Harvard computers--sometimes without users even realizing it.

The new restriction, known as traffic shaping, essentially erects a divider on the information highway. According to Davis, the alteration has seen enormously positive response in speeding up the network.

Network performance is determined by measuring ping times. One computer sends a ping out to another computer and sees how long it takes the other computer to respond. If the network is highly congested, then it's like trying to get from Cambridge to Boston during rush hour--it will take longer and result in a higher ping time.

According to Davis, ping times of 20 milliseconds or more indicate that the network is overloaded. Earlier this week, ping times were a whopping 150-200 milliseconds. That number dropped to roughly 1-6 milliseconds after the change was made Tuesday night.

But those Harvard network users who frequently upload information to the Internet may be experiencing some delays in the days to come. For example, many student groups on campus post their websites through the network, and Davis said that several of these groups experienced problems following Tuesday's change.

Those trying to access the student groups' websites experienced delays and connection failures, for example. But adjustments were quickly made to accommodate these exceptions, Davis said.

Although Davis said that at least 95 percent of the Harvard population uses the network primarily to download from the Internet, he said that students who need to send information in the outbound direction should be accommodated.

"Tuesday's change is not a perfect solution--this is only a stop-gap measure while we look for permanent solution," he said. "Students deserve good network access, and we need to find a way to ensure that the network is used and not abused."

Tuesday's change was not the first time that Harvard Arts and Sciences Computer Services (HASCS) has placed restrictions on network access.

In October, HASCS restricted Napster access by limiting outbound network traffic for the music-sharing service.

But Davis said that Napster has since then found ways to get around such restrictions, and he emphasized that other websites such as Scour.com, Gnutella and CuteMX, have gained a place in the hearts of Harvard students--and have contributed to clogging up the network in the process.

--Staff writer Kate L. Rakoczy can be reached at rakoczy@fas.harvard.edu.