tag:blogger.com,1999:blog-1988432060681510848.post2505306273804781969..comments2024-03-25T23:51:47.067-05:00Comments on Revolution Wi-Fi: Cisco CleanAir ReviewAndrew von Nagyhttp://www.blogger.com/profile/12658799453646609565noreply@blogger.comBlogger15125tag:blogger.com,1999:blog-1988432060681510848.post-22967989111016342402010-10-28T22:20:18.851-05:002010-10-28T22:20:18.851-05:00Thanks for the update James. It looks like CleanAi...Thanks for the update James. It looks like CleanAir is a solid competitive advantage and differentiator for Cisco.<br /><br />-AndrewAndrew von Nagyhttps://www.blogger.com/profile/12658799453646609565noreply@blogger.comtag:blogger.com,1999:blog-1988432060681510848.post-13903185713875074282010-10-28T09:04:12.157-05:002010-10-28T09:04:12.157-05:00Hi Andrew,
Good catch on the deployment guide - I...Hi Andrew,<br /><br />Good catch on the deployment guide - I think I can get that fixed. Now - as for third party comparisons, Check out the Miercom test report. It is located here. <br /><br />http://www.cisco.com/en/US/solutions/collateral/ns340/ns394/ns348/ns1070/Miercom_Report_DR100409D_Cisco_CleanAir_Competitive_for_22Apr10.pdf<br /><br />There just are not a lot of wi-fi based solutions actually released AND shipping at this time - I am sure that will change though.Florwjhttps://www.blogger.com/profile/02173064770356425805noreply@blogger.comtag:blogger.com,1999:blog-1988432060681510848.post-42246421698002059042010-10-18T11:03:32.155-05:002010-10-18T11:03:32.155-05:00Hi WiFi guy,
If interference detection is all you ...Hi WiFi guy,<br />If interference detection is all you want, not automated network changes, then I think deploying an overlay would be feasible. If you're going to deploy an overlay anyways, I would bundle it with WIPS functionality too. That just makes sense.<br /><br />As far as external antennas, that should provide increased range for detection. The downside would be that interference from potentially very far away could be detected, which may or may not be impacting your network.<br /><br />I would deploy the spectrum sensor with the same gain as my infrastructure APs, or attempt to tune it so that it only detects interference that will impact your APs. If you throw a high-gain antenna on it and it detects distant interference sources, those may end up being false positives.<br /><br />-AndrewAndrew von Nagyhttps://www.blogger.com/profile/12658799453646609565noreply@blogger.comtag:blogger.com,1999:blog-1988432060681510848.post-73783133513319512622010-10-18T10:58:19.947-05:002010-10-18T10:58:19.947-05:00Hi Devin,
Like you stated, there is no 3rd party c...Hi Devin,<br />Like you stated, there is no 3rd party comparisons available between Wi-Fi chipset and dedicated chipset spectrum analysis accuracy that I am aware of. <br /><br />However, from my experience with traditional RRM from multiple vendors, Wi-Fi chipsets do a good job of detecting other Wi-Fi neighbors and adjusting channel and power accordingly. <br /><br />We tested with a few different interference sources (video camera, baby monitor) and the Wi-Fi chipset could only detect a raised noise floor. And comparing it to a spectrum analysis laptop card, it appeared to be vague in determining the severity. Also, reacting to interference seemed slow since the noise floor value bounced around quite a bit. I can only suspect that the Wi-Fi chipset had a hard time determining whether or not to make an adjustment because of this. Traditional RRM was forced to wait for a the next slotted RRM update interval, which also made reaction slower. Typically, I have seen companies set RRM intervals anywhere from 10 minutes to 24 hours.<br /><br />Can you imagine detecting interference and having to wait upwards of 24 hours to adjust settings. Ouch!<br /><br />In my opinion, CleanAir does seem to do a much better job of being able to classify interference sources. This gives it much better accuracy and gives the system the inherent "trust" in itself to make a change immediately. That's Event-Driven RRM's job, to make the change right now and avoid waiting for the next RRM interval.<br /><br />I think it all boils down to how trustworthy the data is, and I'm not sure I would trust network operational changes from interference based off Wi-Fi chipset data. Maybe thats just me.<br /><br />I think other vendors will eventually follow-suit and place dedicated spectrum chipsets into access points. If MetaGeek is any indication, dedicated chipset prices should be low enough to make this a possibility without a huge uptick in cost.<br /><br />-AndrewAndrew von Nagyhttps://www.blogger.com/profile/12658799453646609565noreply@blogger.comtag:blogger.com,1999:blog-1988432060681510848.post-46101842478504282472010-10-17T08:58:34.426-05:002010-10-17T08:58:34.426-05:00Great review Andrew,
While I understand Cisco'...Great review Andrew,<br /><br />While I understand Cisco's stance on not intermingling CleanAir with non-CleanAir APs, it still seems valid to deploy an overlay model with a single central CleanAir AP (perhaps in dedicated Monitor or SE-Connect mode) per floor as a detection strategy. This has been the approach of other IDS vendors including AirMagnet if locating a source and mitigating with EDRRM are not priorities. Would external antennas increase its interference detection capabilities?WiFi guyhttps://www.blogger.com/profile/10210647833085361757noreply@blogger.comtag:blogger.com,1999:blog-1988432060681510848.post-3892925489072069332010-10-16T22:02:21.635-05:002010-10-16T22:02:21.635-05:00Andrew,
This is a killer write-up. Nice work. I...Andrew,<br /><br />This is a killer write-up. Nice work. I loved your comments on how they could improve the product and how thorough your analysis was. I'm left only with one comment/question:<br /><br />Since there have been no 3rd party verified comparisons between Wi-Fi chipset-based spectrum analysis and Cisco's dedicated chipset, how do we know that one is better than the other in real-world application?<br /><br />Stated differently, for clarity:<br /><br />Is Wi-Fi chip-based analysis accurate and granular enough to make appropriate and accurate RRM changes and to appropriately visually display the RF environment?<br /><br />Thanks!<br /><br />Devin Akin<br />Chief Wi-Fi Architect<br />Aerohive NetworksDevinatorhttps://www.blogger.com/profile/02969739263236315747noreply@blogger.comtag:blogger.com,1999:blog-1988432060681510848.post-46125535529811023412010-10-15T18:39:15.510-05:002010-10-15T18:39:15.510-05:00Hi James,
Thanks for the clarification. It looks l...Hi James,<br />Thanks for the clarification. It looks like the CleanAir Design Guide on Cisco's website has incorrect information on the resolution bandwidth in the Glossary section. It has the values backwards, the same as in my original post. Perhaps this is something that you can get updated?<br /><br />http://www.cisco.com/en/US/products/ps10315/products_tech_note09186a0080b4bdc1.shtml#t9<br /><br />I will update my post accordingly.<br /><br />AndrewAndrew von Nagyhttps://www.blogger.com/profile/12658799453646609565noreply@blogger.comtag:blogger.com,1999:blog-1988432060681510848.post-17680050808191436602010-10-15T18:19:16.375-05:002010-10-15T18:19:16.375-05:00Hi cutlerite,
It is important to remember that onl...Hi cutlerite,<br />It is important to remember that only some device classifications are considered "persistent" devices and will be remembered for 7 days. Since these types of devices cause severe issues and are very likely to recur, CleanAir can be configured to avoid them using the persistent device avoidance feature. This feature can be turned off on the 802.11a/b/g/n RRM > DCA page, but you risk having the AP go back to that channel and being affected by the same interferer again. <br /><br />Essentially, it's the worse of two evils: complete channel disruption by the interferer, or more co-channel contention which is not as harsh to clients.<br /><br />Also, to clear persistent devices prior to the 7 day mark, Cisco states that the AP can be rebooted to clear its list on both radios. Unfortunately, there is not method to simply clear this list without rebooting the AP. The list can be viewed from the Wireless > 802.11a/b/g/n Radios > AP Radio Blue Drop Down > CleanAir RRM.<br /><br />I agree that once severe sources of interference are found, they should be removed by the administrator. That's part of the real benefit of CleanAir, giving administrators visibility into interference sources for removal. EDRRM is really a mitigation technique that should be used temporarily by the system only until the administrator removes the source of the problem.<br /><br />AndrewAndrew von Nagyhttps://www.blogger.com/profile/12658799453646609565noreply@blogger.comtag:blogger.com,1999:blog-1988432060681510848.post-60557994746299826352010-10-15T16:19:37.225-05:002010-10-15T16:19:37.225-05:00Good catch! yeah sorry about that. That is the fie...Good catch! yeah sorry about that. That is the field I had to change before adjusting the filter bandwidth. It was a hasty mistake.<br /><br />I should have clarified my question. Let's say there is an AV transmitter disrupting transmission on Wi-Fi channel 1, all of the affected APs must move to channels 6 and 11 increasing co-channel interference. Must you deal with that for 7 days?<br /><br />It seems to me that if you have serious interference issues, you must go to the location of it and eradicate the source - no matter what. <br />Once you have gotten rid of the device, why wait 7 days?<br /><br />I really like what spectrum analysis can add in the AP, but 7 days seems like an excessive wait time - especially in a mission critical Wi-Fi set up.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-1988432060681510848.post-5738254866953745562010-10-15T13:44:15.157-05:002010-10-15T13:44:15.157-05:00Hi Andrew,
Great post. I would like to clarify t...Hi Andrew,<br /><br />Great post. I would like to clarify the remarks on resolution. 78 KHz is for a 20 MHz dwell and applies to the full 2.4 Ghz and 5 Ghz spectrum. 156 KHz is for a 40 MHz dwell - which is wider - and so well double. 10 KHz resolution is available of the 3500 AP - it is not exposed to the customer for various reasons - but is in the hardware.Florwjhttps://www.blogger.com/profile/02173064770356425805noreply@blogger.comtag:blogger.com,1999:blog-1988432060681510848.post-9773388714992247202010-10-15T13:35:16.044-05:002010-10-15T13:35:16.044-05:00Hi cutlerite,
Resolution bandwidth is only one imp...Hi cutlerite,<br />Resolution bandwidth is only one important component in a spectrum analyzer solution. In your referenced image, it would be the "Res BW" field, not the step size. Also, looking at the Metageek products, my post referenced the older Wi-Spy 2.4i model. I will update the post to include the newer Wi-Spy DBx product, which has better resolution down to 24KHz.<br /><br />Also, CleanAir does not wait 7 days to mitigate an interference source, it does so immediately IF the source causes the AQI to drop below the configured sensitivity threshold. The 7 day wait period is a wait timer before an AP will be allowed to us a channel on which a persistent interference source has been detected. The persistent interferer must not be detected for 7 days, then the AP will consider using that channel again. In effect, CleanAir waits to make sure that fixed/stationary interferers are really gone before trusting that channel in the surrounding area again.<br /><br />Thanks for your input!<br />AndrewAndrew von Nagyhttps://www.blogger.com/profile/12658799453646609565noreply@blogger.comtag:blogger.com,1999:blog-1988432060681510848.post-60267683126739481352010-10-15T10:56:43.793-05:002010-10-15T10:56:43.793-05:00Andrew, Thank for the post.
The MetaGeek Wi-Spy...Andrew, Thank for the post. <br /><br />The MetaGeek Wi-Spy's resolution that you posted is the resolution of the entire 2.4 GHz band and not 40MHz. I'll admit the Wi-Spy may not be as fast as the cognio or spectrum xt, but if all you care about is resolution. here:<br /><br />http://i51.tinypic.com/213irnm.png<br /><br />You talked a lot about hypothetical situations, but if someone brought in a narrow band av transmitter wouldn't you be better off fixing it manually than waiting 7 days for your set up to fix itself?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-1988432060681510848.post-13429811421923316682010-10-14T22:25:15.431-05:002010-10-14T22:25:15.431-05:00Thanks for the great review of CleanAir from Cisco...Thanks for the great review of CleanAir from Cisco. I learned a lot that I didn't know. The best kind of read!<br /><br />Well done.Keith Parsonshttps://www.blogger.com/profile/00403558343082565874noreply@blogger.comtag:blogger.com,1999:blog-1988432060681510848.post-32779811855254712352010-10-14T20:21:48.725-05:002010-10-14T20:21:48.725-05:00Andrew,
Thanks for the great write up. We are abo...Andrew,<br /><br />Thanks for the great write up. We are about to start our first deployment in a couple of weeks. It is encouraging to hear about your real-world success and limited concerns. Now if I can only make it through the design guide without falling asleep.Chad Tealhttps://www.blogger.com/profile/04299039267795617635noreply@blogger.comtag:blogger.com,1999:blog-1988432060681510848.post-20312191857094470542010-10-14T17:56:31.560-05:002010-10-14T17:56:31.560-05:00Andrew,
You wrote an excellent post on CleanAir, t...Andrew,<br />You wrote an excellent post on CleanAir, this is something I will refer to later whenever I have a chance to put my hands on the technology. I've been using both Cisco's Spectrum Expert Cardbus and AirMagnet's Spectrum XT and find these great for troubleshooting. But deploying a full scale AP 3500 scenario provides a proactive environment where one can pinpoint problems as they occur.Anonymousnoreply@blogger.com