Latest 802.11 standards: Too little too late?

* Utility of 802.11r and 802.11k to be determined

Both 802.11k for radio resource measurement/management and 802.11r for fast handoff among wireless LAN access points have recently been ratified. Their arrival reminds me a little of the discussions surrounding IPv6 a few years ago, in that many of the problems these standards were designed to address have, in the meantime, been solved in alternative ways.

As a result, the Wi-Fi Alliance is currently evaluating which components of both standards to include in its interoperability testing - with an eye toward its Enterprise Voice certification, to begin next year.

802.11r shortens handoff delays associated with 802.1X authentication by reducing the time it takes to reestablish connectivity after a client transitions from one 802.11 AP to another while roaming. Particularly in WLANs supporting voice, lengthy handoff times are problematic, in that voice really can only tolerate delays in the order of milliseconds. The Pre-Shared Key (PSK) capability in consumer-class WLANs addresses this handoff delay problem; however, the security is not as robust as the 802.1X authentication-based security required for enterprise-class networks, which introduces the delay problem.

And at least as big a problem in voice WLANs as roaming is the related “stickiness” factor. In traditional networks, clients tend to hold fast to the AP with the strongest signal, even when that AP is overloaded and there isn’t enough capacity to sustain the call. 802.11r doesn’t solve the stickiness issue; rather, this is where 802.11k comes in. 802.11k detects whether a given AP is loaded to its full capacity and redirects the client association to an AP with more capacity, making more efficient use of overall network resources.

In the meantime, the makers of traditional microcell WLANs have created sophisticated adaptive resource management of their own to deal with these issues in the absence of standards for the past several years. And makers of single-channel WLANs (Meru and Extricom, to be specific) use a network management model similar to that of the cellular network operators. In these networks, the WLAN controller decides, top-down, which AP a given client associates with for optimum traffic load balancing and performance WLAN-wide.

So what role will 11k and 11r play in networks going forward? The Alliance is evaluating that as we speak.

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