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Thin AP Standards Proposed

Last week was the deadline for draft of a new thin AP protocol with the IETF. Information on at least one of those drafts is in from two vendors—Trapeze Networks and Aruba Networks —that are usually rivals, but in this case they let their engineers work together to their (hopefully) mutual benefit.

Over a year ago, the Internet Engineering Task Force (IETF) began a working group called CAPWAP—the Control and Provisioning of Wireless Access Points. The goal was to set a standard that could be used for "thin APs"—those wireless access points that would not only be centrally controlled, but would have most of their "smarts" residing on the central controller, usually a WLAN switch.

Originally, many of the WLAN switch startups were backing the Light Weight Access Point Protocol (LWAPP), but when the IETF Internet-Draft for LWAPP expired, CAPWAP was formed as a "Birds of a Feather" (BoF) group that would eventually work toward a final protocol. The deadline for new Internet-Drafts was last week, and that's when Trapeze/Aruba proposed SLAPP—Secure Light Access Point Protocol.

According to Aruba's Partha Narasimhan (who co-authored the SLAPP proposal with Trapeze's Dan Harkins), SLAPP will be different from other thin AP protocol proposals because it's somewhat technology-agnostic. It will work not just with 802.11 but with future wireless technologies like ultrawideband, RFID, and WiMax/802.16.

"We've split [the protocol] into two components," says Narasimhan. "A base across multiple access technologies, with extensions on the base. The base is agnostic—we don't care what the technology is. The extensions will come in and be more aware of the details of an 802.11 access point versus an 802.16 base station." He compares it to the way the Extensible Authentication Protocols (EAP types) work with 802.1X authentication.

Trapeze vice president of marketing Bruce Van Nice adds that SLAPP is "compatible with anything the CAPWAP Working Group would do."

SLAPP would feature an "image download," so that whatever the AP is, if it recognizes the WLAN switch on the network, software would be downloaded to that AP so it could boot up and work with that switch instantly.

Sounds good, but it doesn't mean SLAPP is a shoe-in for becoming the standard as is. The CAPWAP Working Group has to first assign an editor that will pick and choose from the existing proposals and create a final draft that will become the IETF's RFC (Request for Comment document). From there, the arguments start. While Van Nice thinks things could move quickly, the IETF calendar doesn't specify that a final protocol be proposed until January 2006. In fact, the calendar says the CAPWAP Working Group could be shut down in May of this year if objectives have not been finalized.

IETF Internet-Draft documents have a six month shelf life before they must either be renewed or they expire (the latter is what happened to LWAPP originally).

Existing Internet-Draft documents that the CAPWAP editor could choose from include one from Panasonic, one from Chantry (the WLAN switch vendor recently bought by Siemens), and LWAPP is still out there, probably backed by Cisco, which recently acquired Airespace, the switch startup that was originally behind LWAPP.

Trapeze and Aruba both recently provided limited access to the proprietary software running their APs, so third parties can turn inexpensive APs into thin units that can be used with their respective switch products—in fact, Aruba's firmware uses a SLAPP implementation. Publication of a final CAPWAP protocol could render those projects unnecessary, as any vendor could use the actual standard to make hardware that works with any switch that supports CAPWAP.