SEATTLE -- Wireless LAN roaming was a hot topic this Tuesday morning on the first leg of Unstrung's whirlwind conference tour of the West Coast of the U.S.

Roaming is important for the most elementary application offered by wireless LAN networking -- allowing the user to move between access points without losing the connection -- and crucial for what many consider to be the killer app for corporate 802.11 networks: Voice-Over-WLAN (VOWLAN).

Yet panelists at today's Unstrung's live show in Seattle -- Wireless LANs: Business Plans -- say that a basic issue is still causing problems for users trying to roam.

The problem stems from how fast a client's NIC cards can roam between two APs. "Roaming depends on the NIC cards," notes Fanny Milnarsky, the CTO of wireless LAN testing startup Azimuth Networks.

Yet, she notes, her company has found that some cards can take up to 23 seconds to roam between access points. This would make them totally unsuitable for use in VOWLAN applications, where roaming times of between 50 milliseconds and a second -- depending on whom you ask -- are required if a customer is to successfully implement such apps (see SpectraLink Seeks New Standard).

Phil Kwan, director of enterprise applications at Foundry Networks Inc. (Nasdaq: FDRY), says that the roaming speed offered by a NIC card is usually determined by how closely a card's driver software confirms to the 802.11 standard. Some cards -- particularly older models -- "just don't stick very closely to it," he says.

It’s a problem that the panelists expect to become pressing as roaming on a wireless LAN network becomes more important for a variety of voice, video, and data applications.

Some suggest that more interoperability testing could make for smoother client-side roaming.

But, as Michelle McLean, director of product marketing for Trapeze Networks Inc., notes, this could be a monumental task with all the legacy cards already on the market and a vast amount of new WiFi-enabled devices expected to arrive over the next couple of years.

McLean says that the Wi-Fi Alliance would be the natural candidate to undertake such a task. "But where do they draw the line?" she asks. "There's so much to test."

— Dan Jones, Site Editor, Unstrung