Quality of Service

FRAMINGHAM (07/31/2000) - Quality of service (QOS) is a concept that's been around for years. One can argue that without QOS, a service-level agreement and a dollar gets you a cup of coffee.

When traffic is heavy, load balancing can help by redirecting traffic to another server and easing bottlenecks. Some switches can distinguish types of traffic, such as file transfer protocol and the HTTP Web protocol, and direct each according to defined rules.

The resulting network utilization reports can look pretty good. But put your head in the fireplace and your feet in a bucket of ice, and the average temperature looks good, too.

QOS lets managers direct, at a more granular level, how traffic for a particular application moves through the network's routers and switches.

But QOS involves more than specifying which traffic gets through the gate first. It's the foundation for policy-based networking. A policy defines how to use network resources under specific conditions and how much bandwidth to allot. A network manager can provide resources based on the data flow's business value - for example, giving a stock-trading transaction priority over an information request.

Policies can recognize that some data flows vary in amount and importance at different times. For example, sales traffic could be given precedence over accounting except at the end of every quarter, when the accounting department must calculate and generate reports.

Policy definitions depend on several existing QOS standards. The Resource Reservation Protocol (RSVP) lets an application inform routers and switches about the QOS requirements for a particular transmission - bandwidth, jitter (packets arriving out of sequence) and latency (delay between a packet's arrival and its forwarding). Depending on these requirements and on the policies that have been set for routers along the path, resources are either reserved for or denied to the transmission.

RSVP ropes off network resources even if they're not fully used. That's good for applications like telephony, where dropped packets can make a transmission unintelligible.

The 802.1p standard lets a message header specify a packet's QOS, which is crucial for time-critical applications like videoconferencing.

Differentiated Services (DiffServ) technology reads packet headers to determine which QOS level the message should receive. Most communication today is "best effort" - no guarantee, just a promise to deliver the message as quickly as possible. That may not be helpful if you're trying to complete a sales transaction when everyone else is checking e-mail.

DiffServ allows varying service levels for different applications over the same network at the same time. A policy can ensure that a sales application is first in line for the transmission speed and quality it needs. What's left over gets apportioned to other applications.

Common Open Policy Service technology is used to communicate QOS parameters between devices.

Because of this multiplicity of standards, there's confusion over which standards need to be supported by devices and management software. Cisco Systems Inc., Nortel Networks Inc. and 3Com Corp. all make policy management software, but it's specific to their hardware. Vendors such as Framingham, Mass.-based IP Highway Inc. make multivendor policy-management software.

In Windows 2000, Microsoft Corp. supports QOS standards and has included application programming interfaces to implement QOS. Version 2.0 of CiscoWorks 2000, due later this year, will support QOS.

Support should also grow with the Directory Enabled Network (DEN) initiative.

DEN standards allow the association of applications - including QOS data - and let users with network resources store the information in a directory that other applications, devices and services can access.

A further barrier to QOS implementation is that service providers need to implement QOS peering agreements by agreeing on which standards to use and on how to implement them. But the biggest impediment may be that QOS hasn't been needed on LANs, where bandwidth is cheap and overprovisioning relatively easy.

But with bandwidth hogs like voice and streaming video coming, QOS will likely become far more important. definitionQuality of service is a measure of the ability to control and assign network bandwidth to specific traffic so as to provide predictable levels of IP-based data throughput based on the importance of the business process associated with that traffic.

QOS is for Web Sites, Too

QOS began as a way to control network bandwidth, but end-to-end QOS demands that information technology managers extend the concept to application performance.

"Certainly, the increased interest in networking open standards has raised a new level of challenges around QOS," says Warren Wilson, an analyst at Summit Strategies Inc. in Boston. "Customers are going to want their Internet applications to perform as well as their in-house applications."

For Web applications, slowdowns can be traced to servers more often than to networks, says Rosemarie Chiovari, Hewlett-Packard Co.'s WebQOS alliances manager. "If you have a reasonably fast Internet connection and you're trying to complete a transaction such as a stock trade over the Web, of a 10-second wait, two seconds is the network and the rest is the server," she says.

HP's WebQOS 2.2, which was released in July for HP-UX, Windows NT and Windows 2000, assigns priority to Web browsing sessions based on transaction activity.

When site traffic spikes, priority can automatically shift from browsing sessions to revenue-producing transactions, Chiovari explains.

Tests by San Mateo, Calif.-based Keynote Systems Inc., a Web site performance monitoring service, "show an average increase of 40 percent in the number of completed transactions during times of heavy demand," Chiovari says.

During a peak hour, one grocery-buying Web site saw a 30 percent increase in completed shopping-cart checkouts, resulting in US$12,000 more revenue for the hour, she says.

WebQOS 2.2 for Windows NT and Windows 2000 is $8,000 per box. The HP-UX version and WebQOS 2.2 for Solaris, set for release in August, are processor-based and start at $12,000.

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