Hi John,
I am curious what you mean when you say “it’s just not how clients work.” With a single channel, the clients and APs see and send probes just like they would if you were using more channels. If anything, the single channel helps the clients by not having to change channel as they roam between APs. As always, I’ll happily disclose that we have been running a Meru 11n deployment for almost two years. We do stack channels for extra capacity, but the large majority of our APs run on the same channel and have since the beginning. Take care, Matt Barber Network Analyst Morrisville State College 315-684-6053 From: The EDUCAUSE Wireless Issues Constituent Group Listserv [mailto:[email protected]] On Behalf Of John W Turner Sent: Wednesday, July 29, 2009 1:35 PM To: [email protected] Subject: Re: [WIRELESS-LAN] Single Channel vs Multi-Channel Architecture We have been running a 4 channel plan for 3 years with ARM (Aruba) and have had no problems. This is across 850 AP's in 100 buildings. The single channel plan seems like a good idea, but it's just not how clients work.... -- John W. Turner Director of Networks & Systems Brandeis University ----- Original Message ----- From: "Ken Connell" <[email protected]> To: [email protected] Sent: Wednesday, July 29, 2009 12:15:17 PM GMT -05:00 US/Canada Eastern Subject: Re: [WIRELESS-LAN] Single Channel vs Multi-Channel Architecture I don't have much experience with a single channel deployment, but without even getting into vendor preferences or specifics I can't see how a single channel can gain any perfomance in such an unpreditctable and dynamically changing environment as far as other devices, and wireless networks that will come and go probably a daily basis with little or no control. The channel you decide on today, may not be the best suited channel tomorrow, and if you then need to make a change at that point, then you've jsut come full circle and are right back where you started. In my opinion it just makes sense to go with an automated RF type deployment (Aruba ARM for us) and be able to sleep at night ;) Ken Connell Intermediate Network Engineer Computer & Communication Services Ryerson University 350 Victoria St RM AB50 Toronto, Ont M5B 2K3 416-979-5000 x6709 ________________________________ From: Ryan Holland Date: Wed, 29 Jul 2009 09:04:34 -0400 To: <[email protected]> Subject: Re: [WIRELESS-LAN] Single Channel vs Multi-Channel Architecture ...interesting thread... When we were making our decision 3+ years ago, we discounted Meru primarily on scalability information in their RFP response. So unfortunately, we did not get a chance to bring them in for a demo. I am still quite skeptical about a single-channel architecture but believe I understand why it is promoted: to assist devices in roaming by creating a seemingly single BSSID. However, once we see more devices supporting standards such as 802.11k and 802.11r, such efforts, to me, are negated. Again, however, I have not had the opportunity to play with this gear, so [disclaimer]. We have been deploying Aruba for sometime and have learned a great deal about their technology, so I will caution the trusting of intelligent radio management solutions. Instead, I would suggest one utilize this technology while maintaining a tight supervision of it. Using Aruba with whom I am most experienced, their adaptive radio management (ARM) is quite powerful, as it allows for dynamic remodeling for channel and power based on the environment. This means that as other building tenants bring in their own wireless systems, our network can modify its channel configuration accordingly. Also, in the event of an AP failure, adjacent APs will likely perceive a lower aggregate signal strength of neighboring APs, boost their power, and thus help alleviate the loss of coverage from said failed AP. The reason I cautioned earlier is that many administrators simply "turn on ARM" and leave it. Doing so is assuming the defaults are applicable for all environments, which I would argue is not true for most educational institutions. Examples: the range of chosen transmit power is likely too expansive; the noise threshold at which an AP would change channels may be too low, especially for "research areas" like Illinois mentioned; the target coverage index may be too low for densely deployed installations or too high for sparsely deployed installations. Aruba is great in that administrators can configure different ARM profiles for all these different circumstances and use them suitably. But again, to just turn it on and expect it to "work" can lead to false assumptions. I would also add that there are still a lot of those that state static channel/power assignments is the best way to go. While I would agree that is true assuming the environment is identical at installation as it was during survey, it is incredibly likely that the environment will change and therefore negate the initial survey. Because our environments are largely unpredictable, I find a dynamic solution to be preferable. Now, if we had complete control over RF across campus, my opinion may be different. (Oh, and because people seem to be concerned with these sorts of numbers: ~5,000 APs, ~40 controllers). ========== Ryan Holland Network Engineer, Wireless CIO - Infrastructure The Ohio State University 614-292-9906 [email protected] ********** 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/.
