Roaming with Ruckus
Wireless roaming can be difficult to get right. Wireless voice handsets are extremely sensitive to delays and jitter. When roaming within a wireless network, calls can be disrupted or dropped altogether. These problems are usually caused by different subnets on a network. When roaming between access points on different subnets a client device will need to re-associate, re-authenticate and obtain a new IP address. This whole process causes traffic delays and VOIP calls suffer.
Ruckus solve the problem in 2 ways;-
- WLAN Tunnelling - LWAPP - based (LightWeight Access Point Protocol)
- 802.1X PMK Caching
WLAN tunnelling cuts out inter subnet roaming by creating a layer 2 WLAN that directs VOIP clients directly back to the controller. The VOIP client can now keep the IP address as it roams from an access point to an access point within a layer 3 WLAN.
802.1X PMK Caching
802.1X EAP enabled clients have to authenticate when moving from one access point to another, which is usually handled by a Radius Server in a remote location. This process can cause delays and VOIP call disruptions. Ruckus gets around this problem by caching Pairwise Master Keys (PMK) to reduce or eliminate the delay caused by a re-authentication process.
The process starts with the first authentication with the remote radius server. A PMK is then cached by the client and the controller and creates PMK ID which includes the AP MAC address. When the VOIP client roams away from the AP and then back again and performs a handshake with the Zone Director controller, cutting out the re-authentication with the Radius server.
PMK's can be shared with neighbouring AP's by the controller and creates new PMK ID's with the AP MAC address of new AP's and sends them back to the controller. When roaming to these new access points, the PMK matches the PMK ID of the AP and performs a handshake with the controller. Disruptions are eliminated, and seamless roaming is achieved. This process is called opportunistic PMK caching. iscalledopportunistic oppOpportunistcvopportunistic PMK caching.