WLAN QoS specification 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 September, 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 already 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 isn't usually 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, they would be for voice, video, best-effort and background, said 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 ones used in wired Ethernet, he added. Seeing those markers, an access point could give voice packets top priority for transmission, followed by video, and so on, he said.

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

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

"It's a fairly good standard for small WLAN 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 said.

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

As a result, the process of standardizing priority in WLANs may be just beginning, Germanow said. 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 said.

The IDG News Service is a Network World affiliate.