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Ensuring resiliency in wireless LANs

By Ozer Dondurmacioglu
October 12, 2012 05:52 PM ET

Network World - This vendor-written tech primer has been edited by Network World to eliminate product promotion, but readers should note it will likely favor the submitter's approach.

The latest challenge confronting IT organizations is managing the influx of mobile devices and real-time applications that rely on the enterprise wireless LAN. The WLAN has to be resilient enough to enable mobile devices to stay connected and applications like voice and videoconferencing to work without interruption.

To increase resiliency in any network infrastructure, it's good to start by employing a network design ready for high availability. But designing for high availability is not always enough to ensure WLANs are ready for mission-critical applications.

ANALYSIS: It's time for wireless LANs to evolve

In wired access networks, we hardly worry about the user devices disconnecting from the network in case of a network failure, because the cable always stays connected as recovery takes place within the redundancy infrastructure. With WLANs this can be a challenge because traditional wireless access points (APs) turn off their Wi-Fi radios during a controller failover and mobile devices then start to search for a new AP.

So the easiest way to achieve a wired-like resiliency for WLANs is to not give mobile devices any chance to roam -- that is, to never drop them off the Wi-Fi network until WLAN recovery is complete. To achieve this, wireless APs should continue to broadcast SSIDs so mobile devices won't resort to scanning for other APs or SSIDs to connect to. This greatly reduces the possibility that a mobile device will disconnect from the network.

Without this approach end users are forced to manually adjust (i.e., physically turn Wi-Fi off and back on again) their mobile devices to re-establish connectivity, resulting in unsatisfied Wi-Fi users and potentially increasing IT support costs. The easy test when you are evaluating WLAN gear -- the WLAN infrastructure should not disconnect any mobile devices after a redundancy failover event takes place.

A high-availability approach that does not drop devices will also deliver sustained connectivity for real-time mobile applications as well. Video streaming, unified communications and voice/video calling are all examples of applications where end users expect consistently reliable service and don't want to be asked to re-initiate a voice/video call. We've all experienced this frustration with dropped connections on cellular networks. As recovery times for WLANs decrease, real-time mobile applications have a greater chance to stay connected in case of network failures without requiring manual intervention by the end users.

Therefore, another valuable test would be to measure amount of time (and effort) it takes to recover any real-time application after a simulated failure within the redundant WLAN infrastructure.

Originally published on www.networkworld.com. Click here to read the original story.
Reprinted with permission from NetworkWorld.com. Story copyright 2012 Network World, Inc. All rights reserved.
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