Wireless Infrastructure

04:59 PM
Dave Molta
Dave Molta
Commentary
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Air Time: Cisco vs. Meru: You Make the Call

Are Cisco's allegations that Meru isn't playing by the rules of 802.11 true? The debate continues.

At the heart of the controversy is the issue of fair sharing of WLAN spectrum when multiple APs (access points) coexist on the same radio channel. This issue has surfaced over the years in various forms as the 802.11 standard has evolved. It's also a central issue in the delay associated with the emergence of 802.11n, though in the case of 802.11n, the issues are much different than what we were dealing with in our tests of Meru and Cisco.

In our testing, we measured the performance of both Cisco and Meru equipment on a simple WLAN consisting of two 802.11g clients and one 802.11b client. When two Cisco APs were co-located on the same channel, one AP achieved aggregate throughput of 6.3 Mbps while the other achieved throughput of 5.5 Mbps. The numbers weren't identical, but they were close. On the other hand, when we ran a Cisco AP and a Meru AP on the same channel with the identical client configuration and traffic mix, Cisco's throughput dropped to 2.7 Mbps while Meru's was 8 Mbps.

According to Cisco, this provided proof that Meru equipment was operating in a manner that unfairly suppressed Cisco's performance. Meru asserted that it was doing nothing wrong; the results simply proved that Meru's design was superior and that Cisco's implementation of 802.11 was buggy.

Cisco's claim suggested that Meru was playing fast and loose with 802.11 rules, prioritizing its own traffic at the expense of Cisco's. Meru vehemently denied it was doing anything outside the standards. After hearing both sides of the argument, we rendered a somewhat tentative verdict that Cisco's claims were credible; but we also stated that more analysis was required.

As IT professionals and wireless product testers, we are knowledgeable about how 802.11 operates. But the issues associated with this debate are so complex and ambiguous that we weren't able to come to a definitive conclusion by our publishing deadline. Because of this, we did not accuse Meru of violating standards. Instead, we presented all of the findings available to us as of our publication deadline, along with a tentative judgment that Cisco's claims appeared to have some merit. Ironically, while Meru was extremely upset about our article--calling into question our competence and editorial objectivity--some of our findings cast Meru in a positive light. In fact, the company has even extracted some of our quotes and included them on its Web site.

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