I agree with Chuck about the need for better information about WLAN scalability. It's an issue I've struggled with for many years but I'm not optimistic about a resolution. I've discussed this issue extensively with Phil Belanger, the author of the Novarum report, and I just can't see any way to get all the vendors to agree to a single test plan and commit the resources necessary for such ambitious tests.
Although it's clear that Meru designed these tests to best reflect their competitive advantage, I also believe Phil played the role of objective analyst, which is not always the case with "pay for test" projects. Phil pressured Meru to include test runs that were not part of their original plan and he was very transparent in disclosing his role in these tests. Still, it's highly likely that the results would have been different if Cisco and Aruba had been directly involved. Personally, I still think Meru would have performed better, but I don't think the differences would have been as great. Although the issue of co-channel interference is an important one, I think it may be reasonable to assert that its importance will be reduced with the adoption of 5 GHz 802.11n. With over 20 non-overlapping channels, I believe it will be possible to design high-density, micro-cellular WLANs that do not suffer from performance degradation as a resulting of co-channel interference. Over time, I believe 2.4 GHz will be thought of as a best-effort legacy technology for most enterprises. I'd be curious how others are viewing this. dm -----Original Message----- From: The EDUCAUSE Wireless Issues Constituent Group Listserv [mailto:[EMAIL PROTECTED] On Behalf Of Charles Spurgeon Sent: Monday, March 31, 2008 4:31 PM To: [email protected] Subject: Re: [WIRELESS-LAN] Aruba's SCA vs. MCA whitepaper [was: Open Wireless in Higher Ed] On Wed, Mar 26, 2008 at 10:31:50PM -0500, Frank Bulk - iNAME wrote: > I wish it was easier to evaluate the performance (not only aggregrate > throughput, but also QoS) of the MCA and SCA products in various scenarios > and density and usage, but unfortunately examining the impact of co-channel > interference on a large scale in variety of building types and architectures > with lots of APs and clients with realistic traffic patterns (in terms of > type and longitudinally over time) is not currently possible with the tools > available. I think we would learn that there certain scenarios where one > performs generally better over another. I, for one, would like to see more vendors step up and do the kind of testing of co-channel interference issues that was described in the recent Novarum whitepaper: http://www.novarum.com/documents/WLANScaleTesting.pdf As a user of typical multi-channel equipment, I'm not focussed on the SCA versus MCA debate. Instead, I would very much like to see more real-world test results on how the typical multiple APs on multiple channels (MCA) approach works at scale and under traffic loads. I think it's very interesting that the author of the Novarum whitepaper is also one of the developers of the 802.11 MAC, and that he states that he was "surprised at how easily we could drive these systems to unstable behavior." I've heard complaints from the vendors whose gear was used in the Novarum test. But I haven't seen any third-party tests commissioned by those vendors to replicate the tests and show where the problems were in the Novarum tests. I would be much more impressed by actual third-party test results based on a significant scale layout like the one used in the Novarum tests, rather than hearing complaints about the how the test was unfair since it was done under the auspices of Meru. The problems of co-channel interference and wireless channel meltdown under load are too important to be left to the marketing departments of the wireless vendors. On our campus the community has been adopting wireless networking at extremely high rates, and this technology has become much too important to allow it to be supported this poorly. Isn't it long past time for more real-world scale testing like the Novarum tests to be done to investigate the issues with CCI and channel meltdown under load in 802.11b/g systems and to develop some approaches for identifying and dealing with those issues? -Charles Charles E. Spurgeon / UTnet UT Austin ITS / Networking [EMAIL PROTECTED] / 512.475.9265 ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/. ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/.
