QoS face-off: On the desktop

What's the best way to handle QoS over multiservice networks?

Quality of service seems to be a widely used but poorly understood term. However, ensuring that business applications and critical users get priority use of constrained resources is an easily understood necessity. The only way to really meet this requirement is to control applications and users right at the desktop. The alternative, trying to control traffic after it is out on the network, is like trying to herd cats. Once packets are released onto the network, the only management options available are queuing, delaying or dumping.

For years, companies have tried to ensure application delivery by overprovisioning network and server resources. But you can't continue to spend money on upgrades without some justification to the CFO. Ultimately, you must build a business model that says, "This application drives X dollars of revenue, so we can justify spending Y dollars to deliver the application." Overprovisioning fails to address this basic fact of life.

If companies try instead to ensure delivery using intervening network devices, they run into capacity and capability issues. When every packet must receive individual treatment at a box, the box becomes a bottleneck as traffic loads increase. In addition, a physical box can't control every kind of network.

Controlling applications at the desktop gives you a solid head start in ensuring profitable application delivery. With a desktop system, agents enforce policy at the session layer (Layer 5) of the Open Systems Interconnection model, prioritizing traffic above the network and encryption protocols. You're no longer limited to specific topologies or particular applications. This session-layer approach controls TCP and User Datagram Protocol (UDP) traffic, and networks as diverse as frame relay, broadband, wireless and dial-up. Simple policies based on users and applications, instead of complex packet rules, let anyone easily specify the application priorities appropriate for their environment. Finally, because prioritization occurs at each desktop instead of a centralized box, the delivery system scales easily as the network grows.

For example, a distributed enterprise customer recently built a frame relay network to support more than 10,000 branch-office sites. After browser-based applications were added, demand for bandwidth exceeded network capacity. Management had to choose between a desktop-based delivery system and upgrading the entire network. The network upgrade would have taken two years and cost more than $100 million. Desktop delivery software could be rolled out at a fraction of the cost and the project completed within three months. The answer was very clear - do it on the desktop.

Most net managers find a simple software system more attractive than wrestling with packets inside the network. So before you stake your business on net-based approaches, evaluate the desktop approach. You'll be glad you did.

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Nye is CEO and founder of Centricity Software, which provides software products for the differentiation and control of applications and services. He can be reached at lynn@centricitysoftware.com.

The opposing view
By Todd Krautkremer, vice president of marketing for Packeteer.

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