First Stage Approved For WLAN Switching Protocol

MANHASSET, N.Y. — The Internet Engineering Study Group (IESG) has approved a taxonomy of wireless LAN architectures. The approval is the first of a three-stage process to define a protocol that will allow access-point interoperability between the myriad vendors of WLAN switches.

Startups Aruba, Trapeze, Airespace and Chantry as well as more established companies such as Cisco, Symbol, Proxim, Foundry and Nortel are participating. The WLAN switch vendors have been polarized over whether the media access control should be separate or not.

Splitting the MAC and putting the intelligence on the central switch lowers the cost of the AP and provides better control of the network, said Partha Narasimhan, wireless architect at Aruba Networks (Sunnyvale, Calif.). Such control, he added, allows for such features as simplified security upgrades and smoother hand-off between APs when clients roam.

However, according to Dan Simone, vice president of product management at Trapeze Networks, keeping the MAC intact allows better scaling of security. "You won't find any WLAN chips that don't have encryption embedded on them already, so why turn that off just so you can do it on the switch?" According to Simone, the full MAC approach allows better scaling of APs as each has their own encryption core, and also enhances quality of service. "When you want to do real-time services, it's better to do so where the antenna is located," he said.

To help settle the dispute and enhance interoperability to lower costs for customers, the companies gathered together 18 months as the Control and Provisioning of Wireless Access Points (Capwap) group. Working under the guidance of the IESG, the group's first charter was to define a taxonomy of the various WLAN approaches so that work could begin to define protocol requirements.According to Simone, the taxonomy defines three basic WLAN approaches: autonomous, also called "fat"; centralized; and distributed, or meshed.

The next step, according to Simone, is to decide on the functionality of the AP and it's interfaces. This may require the help of the IEEE 802.11 working group. Once decided, the Internet Engineering Task Force will then help define the protocol that will communicate between the AP and the switch.

According to Narasimhan, a single protocol could cater to both a split and full MAC approach. "When you split the MAC, you have to define a protocol that will span L2 and L3 boundaries," he said.

Objectives have to be defined by May at the latest, he added. After that, Narasimhan predicted the standard will be largely complete by early 2006.

If the objectives of the standard have not been set by May, then the Capwap group will most likely dissolve. Given all the work on the taxonomy definition, Simone said he doubts dissolution will occur. "We don't want to lose momentum," he said.0