Two ways to control 'hogs'

At the iBAND4 conference in San Francisco next week, network equipment vendors will demonstrate two ways of prioritizing and controlling Napster and similarly burdensome traffic using products available today.

"Our goal is to show network managers that there are ways to manage the bandwidth consumed by an application like Napster rather than turning it off," says Jeffrey Scheaffer, a technical consultant for Hewlett-Packard and organizer of the iBAND4 demonstration.

The first, a rate control approach, identifies troublesome, low-priority applications such as Napster and limits the amount of bandwidth these applications can consume. Usually implemented in network traffic shapers, this approach allows a network manager to classify and prioritize different types of traffic on his network and give each class a predetermined amount of bandwidth.

The second, a differentiated services approach, identifies the applications that are the highest priority to an organization and sets the bandwidth requirements for these applications. Low-priority applications such as Napster fight it out among themselves to consume the leftover bandwidth. The diff serv approach requires that applications are marked according to their priority at the server, and that switches, routers and policy managers on the network maintain the priority.

Each approach has pros and cons, according to Schaeffer.

The rate control approach is more common and is available through traffic shapers from Packateer, Allot Communications and Top Layer Networks that range in price from $4,500 to $18,000. These devices let network managers offer access to bandwidth-intensive applications like Napster - albeit at a slower speed - without harming the rest of the applications on the network. However, this approach doesn't respond well to new threats. Like antivirus software, a time lag exists between when a new threat like Napster emerges and when it is implemented in traffic shapers.

The diff serv approach, on the other hand, is not affected by new threats because it focuses on mission-critical applications that have already been identified. However, the diff serv approach is not as precise as rate control. And diff serv is just becoming available in products. Hewlett-Packard introduced policy management software that supports diff serv and rate control about six months ago, but Microsoft didn't begin shipping a diff serv marking capability until this spring with Windows 2000.

Long-term, diff serv may be a more scalable and less expensive approach because it doesn't require special appliances installed throughout the network, Shaeffer says. However, diff serv is not yet supported by ISPs, so use is limited to local-area networks.

"At HP, we're really convinced that the diff serv model will become very prevalent," Schaeffer says. "Eventually, you'll be able to pay your ISP an extra fee for high-priority traffic and it will be delivered."