Traffic shaping tools at a dead end

As broadband usage expands in Australia IT managers will face an exponential threat from bandwidth-intensive applications, a network expert has warned.

But the pickings are slim locally for network traffic management tools, Gartner's program director Geoff Johnson said.

"We will need more of these techniques, including traffic shaping and forward error correction, as broadband becomes more prevalent in Australia," Johnson said.

However, there is more than one way to prioritise and control burdensome traffic. Policy management of networks is available from Cisco, Computer Associates, Lucent and Nortel Networks.

Using server-based policy managers, IS staff can define which classes of applications or end users will get priority treatment, and when.

The rate control approach, using traffic shaping tools, identifies troublesome, low-priority applications and limits the amount of bandwidth these applications can consume.

This approach lets a network manager classify and prioritise different types of traffic on a network and give each class a predetermined amount of bandwidth.

Another approach is the differentiated services (diff serv) method, which identifies the applications that are the highest priority to an organisation and sets the bandwidth requirements for these applications.

Low-priority applications 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.

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 year with Windows 2000.

Taming Napster bandwidth grab

By Carolyn Duffy Marsan

The experience colleges in the US have had taming Napster offers an important lesson to corporate network managers facing similar threats from other bandwidth-intensive applications such as Gnutella, iMesh, Freenet and CuteMX. All these applications let users swap large files including music, images and software over the Internet, creating heavy, bursty traffic patterns on LANs and Internet connections.

"This Napster class of applications can be bandwidth-intensive for small periods of time," John McConnell, a consultant specialising in network bandwidth management, said.

"From a network administrator's point of view, you don't know when loads are coming, how long they will last and what the demand is going to be. . . If you allow these applications to have uncontrolled access and usage, you can start starving out your business processes."

That's what happened to Plattsburgh State University, which began blocking Napster last November after the application saturated its outbound Internet bandwidth. The university has two T-1 lines that provide Internet access to dormitory and administrative networks.

Network manager Hap Wheeler recently bought two Packeteer PacketShapers to control the amount of bandwidth Napster can consume on each network.

"The Packeteer device lets me automatically classify applications . . . to get a list of incoming and outgoing traffic so I can set priorities," Wheeler said.

Wheeler used PacketShaper to place the highest priority on traffic from the university's online research applications. Below that he rated http traffic for general Web surfing and America Online traffic for e-mail services. Further down were incoming file transfers. The lowest priority was given to bandwidth-intensive file-sharing applications such as Napster, iMesh, CuteMX and Gnutella.

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