The numbers we present here reflect performance in a wireless network configured without encryption. Administrators should expect increased delays with security enabled, and these numbers may vary depending on the type of security selected. The 802.1x protocol that provides strong port-based authentication to the WPA and WPA2 WLAN security specifications may add significant delay when a client initiates a roam between access points. In a worst-case scenario, the wireless client device must re-authenticate to the RADIUS server for each handoff.Many wireless switch vendors also include proprietary features to help load balance the wireless network and ensure QOS for users, particularly voice clients. For example, Meru Networks Inc.s WLAN System works to remove the burden of roaming from the client devices almost entirely. Using a single MAC (media access control) address and one radio channel for an entire wireless network, roaming decisions are instead initiated by the central switch. Client devices view the entire network as a single radio cell, which minimizes delay in handoffs because the client does not need to reassociate and reauthenticate. Technical Analyst Andrew Garcia can be reached at email@example.com. Check out eWEEK.coms for the latest news, views and analysis on voice over IP and telephony.
The IEEE 802.11i security standard, ratified last year, includes a few optional parameters to help speed roaming in a secured environment. Implementers should check with their wireless vendor as to whether preauthentication to neighboring access points or proactive key caching is supported.