Meru Muddies 802.11e

Months before the release of a final 802.11 specification that helps enable voice services over wireless LANs, startup Meru Networks Inc. has suggested the standard might not be scaleable enough for large enterprise implementations.

However, the Institute of Electrical and Electronics Engineers Inc. (IEEE) and other vendors suggest that the startup, which is still in stealth mode and working on its own enterprise WLAN product line, is only serving its own interest in promoting fear, uncertainty, and/or doubt about the standard known as 802.11e.

802.11e will add quality-of-service (QOS) extensions to the existing wireless LAN standard. This will help to enable voice services by allowing the voice data to be prioritized over regular data on a wireless LAN network. In theory, this should improve the quality of voice services over WLAN networks.

The 802.11e specification is expected to be ratified in the summer or fall of next year.

Kamal Anand, the VP of sales and marketing for Meru, says that the IEEE is currently working on channel access mechanisms that can only prioritize traffic across four "access channels." This will make the specification more suitable for small business and home applications than corporate networks, Anand claims.

When client devices try to broadcast over existing 802.11b (11 Mbit/s over 2.4GHz) networks, the data packets are tagged with an "access channel" number of 0 to 32, which indicates when that data can be transmitted. However, of the two QOS mechanisms currently in 802.11e specification most think that the Enhanced Distribution Coordination Function (EDCF) protocol will be the one implemented in enterprise environments.

In essence, EDCF tags higher priority data -- such as voice or video -- at the client and then sends those packets out first. The other access channel method in the spec, Hybrid Coordination Function (HCF), negoiates packet transmission on both sides of the link between the device and access point. However, most think that this will require a stable environment, where the type of data being routed over the network doesn't change frequently. This points to HCF implementations being more useful for home applications like video-over-WLAN.

But Meru claims that -- in fact -- neither of the techniques will be suitable for large enterprise QOS applications. "[EDCF] doesn't scale up [for enterprise deployments] -- basically, that's the problem," Anand says, although he stresses that Meru supports the IEEE's 802.11e work and his company's product will be compatible with the standard.

The system won't be scaleable, claims the Meru man, because there will be more traffic collisions when more than four clients broadcasting high-priority traffic converge on a single access point using the 802.11e specification.

The IEEE's publicity chairman, Brian Mathews, says that he cannot comment on the technical details of the work that is going on at the 802.11e working group.

However, he did point out that wireless LAN is being widely deployed now in the enterprise, without any kind of QOS extensions. "For business reasons there are those that will try to extrapolate the extremes of implementing 802.11," Mathews expostulates.

"Its a little bit of a tempest in teapot," agrees Bob O'Hara, director of systems engineering at wireless LAN switch startup Airespace Inc. and one of the authors of the 802.11e specification.

— Dan Jones, Senior Editor, Unstrung