Solutions To Internet Traffic Jams

Win Treese

During one week in July, users on the Internet downloaded more than 300,000 files, many of them megabyte-size images, from the Comet Shoemaker-Levy 9 server at NASA's NSSDC (National Space Science Data Center) in Greenbelt, Maryland. In the past year, the total number of bytes transferred on the Internet has doubled. Such levels of network traffic, both in number of users and amount of information transferred, have many Internet observers concerned about ``traffic jams'' on the network. Others are busy working to prevent network overloads in the future.

From a user's point of view, the symptoms of a traffic jam are obvious: The desired network service is either unavailable or painfully slow. This symptom masks various possible problems, including failure of network components and limitations of the server computers, as well as network congestion.

Several traffic jams are caused by the popularity of a particular service. During the collision of Comet Shoemaker-Levy with Jupiter in July, NASA's NSSDC supplied images and other information to the Internet community. During the peak hour, the NASA server handled nearly 6000 requests. ``The load on our primary server was sufficiently high for us to consider closing down the service,'' says Syed Towheed, a systems programmer with NASA. Instead, engineers brought additional systems on-line to handle the load. By the end of the week, the traffic jam was over.

Service providers can often eliminate overloads when they expect a service to be popular. For example, release 6 of the X Window System software from the X Consortium was available earlier this year on dozens of servers around the world. As a result, the X Consortium computers and network were not overwhelmed, as they have been in earlier releases.

New services on the Internet often experience heavy traffic intermittently, much as a stadium parking lot gets jammed after a football game. But what about the underlying networks? Can the wires that make up the Internet handle the traffic? Rick Adams, founder and chief technology officer of UUNet Technologies (Falls Church, VA), thinks they can. UUNet operates AlterNet, one of the largest private Internet providers. Adams says that AlterNet's networks are engineered with plenty of capacity for high-load times. However, he notes, ``It's like the telephone system. If everyone picks up the phone at the same time, you won't get a dial tone.''

To stay ahead of the load, AlterNet has invested in expanding the capacity of its network. So far, according to Adams, AlterNet has been able to keep up with its part of the rapid growth in Internet traffic.

One change that has some Internet observers concerned is the increase in multimedia applications. The past year has seen dramatic growth in the use of images , audio, and video across the Internet. The Multicast Backbone, or MBone, is one way of sending audio and video to many receivers on the network at once. As more users install the hardware and software needed to use audio and video, the demand for network resources will increase. To meet the near-real-time requirements of multimedia applications, researchers and network vendors have been working to develop new network protocols, such as the RSVP (a bandwidth reservation protocol), to share the available network bandwidth among competing applications.