WLAN QoS standard approved

A specification that could improve voice and video on wireless LANs has received approval from the IEEE, ending a long standards-setting process but possibly setting the stage for more work on the problem.

The standards board of the full IEEE approved the 802.11e specification for publication in late last month, according to Geri Mitchell-Brown, Wi-Fi strategist at SpectraLink, a maker of voice over Wi-Fi systems.

The standard is a set of technologies for prioritizing traffic and preventing packet collisions and delays, which should improve the experience of users making VoIP calls and watching video over WLANs.

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A specification that could improve voice and video on wireless LANs has received approval from the IEEE, ending a long standards-setting process but possibly setting the stage for more work on the problem.

The standards board of the full IEEE approved the 802.11e specification for publication in late last month, according to Geri Mitchell-Brown, Wi-Fi strategist at SpectraLink, a maker of voice over Wi-Fi systems.

The standard is a set of technologies for prioritizing traffic and preventing packet collisions and delays, which should improve the experience of users making VoIP calls and watching video over WLANs.

Mitchell-Brown expects vendors, and the Wi-Fi Alliance , to adopt specific elements of the standard as appropriate for common demands by users. The Wi-Fi Alliance has adopted a subset of the standard, called WMM (Wi-Fi Multimedia), which has been adopted by several WLAN vendors.

On WLANs that are based on standard 802.11, all users share the network's capacity, and no packet gets priority over any other. This usually isn't a problem with typical data applications, such as exchanging e-mail and browsing the Web, but with voice calls and streaming video, packets have to get across the network at the right time.

The 802.11e specification allows packets to gain priority by defining four traffic classes, each with its own queue. By default, these are voice, video, best effort and background, says Ben Guderian, vice president for market strategies and industry relations at SpectraLink. The definitions of the four classes could be changed from the default. To identify the class of each packet, the standard uses markers similar to those used in wired Ethernet, he says. Seeing those markers, an access point could give voice packets top priority for transmission, followed by video and so on, he says.

That piece combines with other mechanisms for preventing collisions between packets, Guderian adds. Another key element of the standard is a way of timing communications with client devices intended to conserve battery life in handheld devices, he says.

The new standard is a good start, according to IDC analyst Abner Germanow.

"It's a fairly good standard for small wireless LAN deployments where you have a need to prioritize certain traffic types, but it may not be the right standard for doing QoS in large-scale enterprise environments," Germanow says.

The problem with 802.11e is that it puts the power to request priority in the client, Germanow says. As a result, "anyone has the ability to mark e-mail as high-importance," he says. In larger deployments more control will have to reside in centralized servers or network mechanisms, he says.

As a result, the process of standardizing priority in WLANs may be just beginning, Germanow says. Vendors such as Meru Networks already offer mechanisms better suited to large enterprises, and it's likely that vendors will try to put more advanced technology into another standard that would go into WLAN gear alongside 802.11e, he says. "

Read more about wireless & mobile in Network World's Wireless & Mobile section.