WLAN protocol hits standards trail

FRAMINGHAM (11/07/2003) - At the Internet Engineering Task Force meeting next week in Minneapolis, the standards group is expected to clear the last hurdles before launching work on a new wireless LAN protocol.

The group will review the latest draft for the Lightweight Access Point Protocol (LWAPP), which is intended to create a standard way for WLAN switches to communicate with streamlined radio access points. Proponents are convinced they have addressed a range of technical and editorial concerns that the IETF's Internet Engineering Steering Group raised in July.

If the Steering Group is satisfied, it seems likely the IETF will assign a working group responsible for crafting a document for formal consideration. It is anticipated that the working group will rename the protocol as Control and Provisioning of Wireless Access Points (CAPWAP), which is a succinct summary of what the protocol is intended to do.

A standard protocol, in theory, should let network executives mix different brands of access points and switches on their networks.

But it's unclear how important that actually will be to network executives, even if they're fans of the centralized WLAN security and administration that the emerging class of WLAN switches has made possible. One such supporter is Rene Lopez, manager of IT operations for Experience Music Project, a Seattle rock-and-roll museum who has evaulated WLAN products from several vendors.

"I've chosen a homogenous solution from (from Trapeze Networks Inc.)," Lopez says. "I'm not too concerned about buying different brands of access points."

But he wonders if existing protocols can fill the need for automatic discovery and provisioning.

Not surprisingly, the vendors backing the protocol say "no." Today, they use various discovery or tunneling protocols, either of their own making or by borrowing one, such as Generic Routing Encapsulation. In each case, the intent is to create a more or less automatic interaction between centralized switches and hundreds of relatively inexpensive access points that are little more than 802.11 radios.

Pat Calhoun, CTO for vendor Airespace Inc., and one of the original LWAPP authors, acknowledges that the protocol mimics existing tunneling technologies, but does more. It also creates a standard framework for centrally configuring large numbers of access points, handling firmware upgrades and supporting session management, all secured by IEEE 802.1x authentication.

Even so, vendors are expected to quickly use CAPWAP - assuming it becomes an IETF standard - as a kind of lowest-common denominator. "It likely will be a base-level standard, with vendor-specific features added above that," says Michael Banic, vice president of marketing at Trapeze Networks, a WLAN switch vendor.

The rock museum's Lopez is puzzled as to why LWAPP is an IETF project rather than an IEEE one, the traditional domain of Layer 1 and 2 wireless networking. "Being the son of an IEEE member, I'd rather see LWAPP come out of there," Lopez says. "You may have to communicate over Layer 3, but the functionality is all at Layer 2."

Airespace's Calhoun says the IETF and IEEE coordinated unusually closely on this issue. The IEEE concluded, he says, that because LWAPP proposed no changes to the media access control or physical layers, which are the IEEE's keenest interest, the protocol development could be left to another group. "The IEEE is very comfortable with this," he says.

The Layer 3 component of LWAPP is a critical difference, says Michael Vakulenko, director of software engineering at WLAN switch vendor Legra Systems, and author of the Layer 3 section. "Layer 3 gives you flexibility, so you can put the switch in one building and have access points in other buildings," he says. "They can communicate over any network, as long it talks IP."

Assuming no missteps, Calhoun says 18 months is a reasonable time frame for final IETF approval. But customers probably can expect to see early implementations from vendors before then. "You can't get things rubber-stamped in the IETF," he says.

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