Vassar Technology Today | Battle of the bandwidth: Shaping Vassar’s network

Matthew Leung Managing Editor

Vassar’s connection to the Internet uses a T3 line that has a bandwidth of 45 megabits per second (Mbps) for each outgoing and incoming Internet connection. At this speed, while the outgoing connection is almost never used to full capacity, the incoming connection is usually full, especially in the late afternoon and evenings.

During these peak times, many computers may be fighting to use more bandwidth than is available. For example, peer-to-peer (P2P) applications and other protocols used to download files compete to consume whatever amount of bandwidth is necessary to download files in the quickest time.

Computing and Information Services (CIS) moderates this fight for bandwidth by bandwidth shaping. Bandwidth shaping is accomplished with a device called PacketShaper 6500, which monitors all traffic going in and out of Vassar. Data is identified by its protocol, or the way it is formatted. For example, data for video streaming have a different protocol from data for program downloads.

PacketShaper identifies the protocols for all data going in and out of the network and determines how much of the bandwidth they can consume based on two kinds of rules: priority and cap.

The type and amount of outbound Internet traffic is more restricted than inbound traffic. For example, individual users cannot use their own connections to host Web sites.

For inbound traffic, different kinds receive different priorities. For example, data for Web browsing, e-mail, and iTunes receive a high-priority, while data for streaming videos receive average priority, and data for P2P applications receive the lowest priority. This means that if the bandwidth is close to maximum consumption, then high-priority traffic will still get to use the remaining small amount of bandwidth, and availability for average and low-priority traffic might be very limited.

In addition to having an assigned priority, some data have a maximum usage limit, or cap, so that they are kept from using too much bandwidth. Even though data used for online gaming, for example, receives a high priority so that the user can better see instantaneous results of the game, the usage is capped so that other high priority traffic can also get through. The cap rules apply at all times regardless of bandwidth availability. The College does not actively block any protocols except for ones known to carry viruses.

According to Vice President for CIS Bret Ingerman, other institutions also manage their bandwidth in order to prevent over-consumption. Cornell University, for example, limits the amount of data each individual user can send or receive via the Internet and requires payment for usage beyond a specified limit.

There are ways to maximize your bandwidth consumption that are perhaps more effective than just complaining about not being able to watch Lost on abc.com.
First, check CIS’s traffic page (computing.vassar.edu) for times of the day when fewer people use the Internet, such that more bandwidth will be available. This is usually from 4 a.m.-7 a.m. Traffic use also tends to be the lightest during holidays and breaks. If you are using a specific protocol but experiencing slowness, you can contact CIS (helpdesk@vassar.edu) to try to receive a higher priority on it.

Vassar provides video conferencing space
If the purpose is for business or education, use Vassar’s video conferencing center in College Center 204 instead, to which CIS has specifically assigned a high priority on its bandwidth usage. This is a free resource for everyone and is managed by CIS.

Use video protocols given higher priority
Standard video protocols such as Windows Media, QuickTime, and Flash Video are prioritized and given 22 percent of the total bandwidth. This will allow about 40 high-quality 250 kilobits per second videos to be streamed in total. This means that if more than 40 users try to stream high-quality video, streaming might be slow. Since the FTP protocol has a higher priority than protocols for streaming, downloading the video might be quicker.

Browse Web content without creating a new Internet connection
CIS uses a local caching proxy server to store contents of frequently viewed Web content. Browsing the web from this cache avoids having to use the bandwidth. Also, the proxy server has a higher bandwidth priority to retrieve content from the Internet than other computers. Instructions for using this proxy server can be found on the CIS website.