CleanAir Live Webcast : FAQ from live webcast

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Jun 30, 2011 12:01 AM
Jun 30th, 2011

Introduction

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Nicolas Darchis is a wireless and authentication, authorization, and accounting expert for the Technical Assistance Center at Cisco Europe. He has been troubleshooting wireless networks, wireless management tools, and security products, including Cisco Secure Access Control Server since 2007. He also focuses on filing technical and documentation bugs. Darchis holds a bachelor's degree in computer networking from the Haute Ecole Rennequin Sualem and a master's degree in computer science from the University of Liege. He also holds CCIE Wireless certification number 25344.

The related Ask The Expert sessions is available here - Cisco Wireless CleanAir Technology : 3500 APs. Click the Snapshots to view the Complete Recording of this live Webcast.

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Cisco Wireless CleanAir Technology : 3500 APs

Q. Does all your APs have to be 3500?

A. No.you will have clear information on 3500 AP's. the others will work fine the way they have been working before.

1.

2. Q. It says WLC on the slide. I've heard that Cisco Prime NCS is the great new thing. How is that different?

A.NCS is the new WCS version. There is no WCS 8.0, now it will be NCS because NCS will now manage both wireless and Wired networks at the same time. So all the clean air features will be present in NCS. We can consider it as WCS which will manage both wireless and wired with more integrated features. We need the controller (WLC) to handle the access points and WCS/NCS will be extra feature for location and have the historical data.

3. Q. If APs are dual band. Is the sage running in both 2.5GHz and 5 GHz at the same time?

A. Yes they are.

4. Q. Are there issues with mixing the Clean AIr AP and non-Clean Air?

A.No. Their RRM algorithm is working on different triggers. The CleanAir AP will be able to use the real severity of the interference but the others will choose their best guesses. You may have performance issues while selecting the channels but no issues are discovered so far.

5. Q. Is the Monitor mode still needed? How it differentiate from ELM (Enhanced Local Mode)?

A. They are still different things. The monitor mode AP will not be RF-active so it does not represent an overhead for the network (not serving clients) and it can dedicate all its time to scan all channels.

ELM is made for wips reporting while still serving clients. It's a separate thing from cleanair. An ELM AP will be able to report attacks against the network (authentication flood, spoofings, etc ...).

Cleanair on ELM AP is still identifying interferer only on the current channel for that AP, while Cleanair on Monitor mode AP identifies interferer on all channels.

6. Q. What functionality does MSE add to CleanAir?

A.We will have the interference marked on the map and historical data is kept. Controller will have only 15 mins of information. But MSE will allow to keep weeks and weeks of data.

3. Q. If APs are dual band. Is the sage running in both 2.5GHz and 5 GHz at the same time?

A. Yes they are.

8. Q. Do all APs need to have clean air? Do I need to replace everything I already have?

A.No we don't need to replace. We need to decide whether you want to deploy CleanAir AP with or without the CleanAir chipset. We can add one CleanAIr capable access point on each point to get good idea of interference on that floor.

9. Q. Is there any price incentives to upgrading our current APs?

A. Please contact your local Cisco reseller/partner get more information. We do have online tool but that may not show local country price.

10. Q. Can you view the PMAC from the WLC CLI?

A.Yes we have the same information available on CLI the way we have on GUI.

11. Q. Do we need WCS for cleanAir to function?

A.No. The minimum requirement for cleanAir is controller running 7.0 and at least one cleanAir (3500) access point. So that you can have information of interference of that access point over the period of 15 mins.

12. Q. Is it only 3500 supports CleanAir technology, what about other APs like 1252AG and 1400s?

A.No. Cisco will come up with new cleanAir AP's that will be 3500 and 3600. in parallel we will have other like 1200 or 1400 available but without cleanAir technology.

CleanAir is a hardware technology and thus will never be available on APs where the feature was not present (1200, etc...)

13. Q. This CleanAir technology, when is it introduced by CISCO?

A. It has been introduced 1 year ago.

14. Q. Only CISCO has this kind of technology or is there any other vendor working on this kind of technology, say Motorola?

A.No this is Unique. So if you hear other competitors saying they detect interference, it's with best guess only. If you don't have resolution with 150khz you can't be precisely detect. E.g would be microwave oven with bluetooth device. Cisco only has stage shifters which does miracles and so far no one has come up with this kind of technology.

15. Q. What is the advantage of the plus license?

A. It is required if you want to use WCS and MSE to use the cleanAir . Normally the plus licence is used to get the location informaiton so if you want the WCS for management and not for location then you can have WCS base. But for cleanAir we need to have Plus licence for WCS.

16. Q. Are there plans to do Clean Air with MESH?

A. yes, the 1550 11n mesh AP is actually having CleanAir technology already !

17. Q. Can you summarize briefly of the clean air technology?

A.It is a Hardware chipset present on some models of the AP's and it allows to precisely identify what is the interference source and it merge information from all access points about this. So it allows you to know what all interference are there in your network, how many AP's are interfering and how bad they are interfering your AP's. Thanks to this information, the AP's can take much smarter decision on changing channels and taking RRM decisions.

18. Q. What is the max and min distance that is configurable for AP distance?

A.Coming back soon on this one. I'm verifying.

19. Q. I've read different information regarding the number of clients per 3500 ap. Can you tell me what the recommended numbers of data clients and also the recommended numbers of voice clients?

A.Ap with CleanAir or without CleanAir technology will handle same number of clients. The number of clients supported on Ap depends upon what clients are doing, either browsing or checking mails for example. Since we are sharing the same medium so number of clients will not increase. The numbers are still around 20 clients max per AP for data applications.

20. Q. With 5GHz, is the same chip able to scan all 40MHz if bonded?

A.Yes. It scans the same channel that the AP is serving so the AP with 40 Mhz, the same chipset will be 40mhz.

21. Q. Is this a special chip for CleanAir, does it give burden to CPU of Access point? mean does it impact the CPU performance of AP ?

A. it is totally independent. It doesn't bring any load. The only load on access point is to send a packet every 15 sec with detected interference. It works normally power on Ethernet, so it uses same power as normal access point.

22. Q. Is there any comparison how the performance improves with this technology, like diagram etc.?

A.No because that means you need to know the interference you have. You could present an environment so full of interferers that CleanAir will do miracles. It's hard to present objective data.

23. Q. What is so specific about CleanAir? Wasn't Rogue detection doing the same before?

A.No. Rogue detection is only on Wifi signals. So what we were detecting is only rogue AP's , only wifi AP's. So if somebody is on overlapping channel, this is called Noise and can't be decoded and wifi chip can't differentiate the different noise generated by Bluetooth or microwave oven etc.

All the same Wips and rogue features are still there. CleanAir tackles the only problem that was not taken care of yet : non-wifi interference.

24. Q. Can I use AP with spectrum expert?

A.Yes. We can connect the machine with any CleanAir capable Ap and it does the same job as spectrum expert. Download the spectrum utility from Cisco.com on local machine and use the CleanAir capable Ap. That is the reason we don't have any new spectrum release. The Spectrum Expert 4 can connect to any Clean Air AP, the AP acting as a remote sensor for your spectrum expert application.

This also allows manual site survey/spectrum analysis without moving a foot !

25. Q. Other than number of devices, is there difference between MSE 3310 and 3355, with regards to Clean Air?

A. No there is no difference apart from computing power or limit of the device tracked.

26. Q. Will the WLC change the channels the APs run on to avoid the detected interference?

A.

yes depending on the severity of the interferences. It's the whole point of CleanAir : sometimes the interference is not worth changing channel (remember that changing a channel means disconnecting clients briefly and also impacting the whole channel plan of APs around).

Competitors usually demonstrate how fast they change channel in case of an interference. But sometimes, changing the channel means that this AP will sit on the same channel as the AP in the next room and that may be less desirable in some cases.

Knowledge is power.

27. Q. 15X more granular than what?

A. more granular than a Wifi chipset doing noise analysis (Wifi chipset sees chunks of 5mhz signal, Cleanair goes down to 150khz)

28. Q. Do AP's automatically adjust frequency in response to interference information?

A. yes depending on the severity of the interferences. It's the whole point of CleanAir : sometimes the interference is not worth changing channel (remember that changing a channel means disconnecting clients briefly and also impacting the whole channel plan of APs around).

Competitors usually demonstrate how fast they change channel in case of an interference. But sometimes, changing the channel means that this AP will sit on the same channel as the AP in the next room and that may be less desirable in some cases.

Knowledge is power.

29. Q. What's the real functions of the clean air technology?

A. identifying what type of device is the interferer in order to better mitigate it (automatically or manually by going onsite Commando style)

30. Q. Do you require a quiet period for sufficient detection? "

A.No it's immediate. Upto 30 seconds in case of many interferers.. But usually in5 seconds. So very fast. It does not interrupt normal work. The CleanAir chipset doesnt' require the AP to be silent to detect interferers. Fully parralel work.

31. Q.How many channels will 802.11n support and is CleanAir only supported on 3500?

A. CleanAir is only supported on 3500 yes. It's a hardware feature . 11n on CleanAir AP is just identical to 11n on 1140 or 1260 AP. Same amount of channels, etc.

32. Q. What is MSE stands for?

A.Mobility Services Engine . It's the "new" Location Appliance.

33. Q. I've heard that there is am issue with 3500 AP's and 1142 AP's in the same spectrum, can you comment on that, regarding clean air offcourse ?

A.Frankly speaking, I am aware of one issue regarding the violation of load threshold message between the models, you've mentioned. But we do not have any bugs found, specific to this scenario. If there was an issue discovered, it could easily be solved because there is theoretically no issues in having 1140s living with 3500s.

34. Q.Can 3500 or CleanAir feature work on IOS?

A.No, CleanAir is not available on IOS. There is no merging point in IOS such as the WLC who merges all the reports from APs so the feature would be much less interesting.

It seems that IOS image have been published for the 3500 but those are basically 1260 images (the 1260 is a 3500i without cleanair), so it works the same but no cleanair available.

35. Q.What is the accuracy for locating sources of RF interferences?

A.Theoretically it's less accurate than the client location. Why is this ? Because for a wifi client you can triangulate the position from the received signal strength of 3 of your APs. You also know the original transmit power of the client.

For interferer, a bluetooth device could be transmitting full power or could be low on battery and transmitting very low. The transmit power can also vary a lot. How can you figure out the original transmit power of a microwave oven ? you can't.

But thanks to a nice algorithm and stastical values collected in our labs, it turns out that interferer location is usually as good as a client location (so a few meters precision). However, Cisco does not provide guarantees or numbers due to the high variety of interferer that could exists.

36. Q.Which AP modes do we use for CleanAir and what are the differences?

A.. Monitor Mode : AP is not serving client, does not transmit anything over the air (totally passive). On the other hand it scans all the channels for wifi and non-wifi information (interferers,rogues, location of your clients, ...). MSE is required to enjoy CleanAir because merging reports require to know the location of the AP on the map.

Local Mode : AP is serving clients normally. CleanAir chipset is scanning for interferer only in the current channel that the AP is serving. CleanAir and Wifi chipset don't "interfere" with each other. The CleanAir chipset knows when the AP is transmitting so it knows what is interference and what is not.

37. Q.Once an RF interference is detected, what actions can we take?

A.No "magic" is happening. Contrary to popular belief, the AP is not shooting a laser towards the interferer (as in a certain youtube video you may have seen). But you have 2 advantages :

-the automatic RRM decision (power level, channel assignments) are taken in a much smarter way. Nothing you have to do there, it's just the system adapting better to inteferences

-You know where exactly (with a few meters precision) is an interferer and what it exactly is. Knowing that it's an analog camera on floor 2, room 3 in the corner of the room makes it much easier for you to send security there and remove the illegal interferer.

38. Q.Which licenses do we need for CleanAir?

A.There is only one type of license on the controller, so that is ok. For WCS, you need a PLUS license to get the cleanair features.

39. Q. I heard the Persistent interference avoidance and Spontaneous interference avoidance (ED RRM) are only available with full CleanAir enabled installation –not overlay. Can you confirm and commend on that?

A. Only CleanAir APs can take RRM decisions based on CleanAir information. That means for example, that your 1130 AP cannot use the AirQuality information of a 3500 located close for interference avoidance. The 1130 will still avoid interference but without the enhanced algorithm that CleanAir allows, so it will still act like it was behaved.

It is not possible because the CleanAir APs know how the interferers are affecting themselves. they can't know how interferers are affecting non-CleanAir APs.


And if your overlay deployment is dense enough to allow for Location of the interferers (so 3 cleanair APs observing the interferer), then you have enough CleanAir APs to do your whole deployment with Cleanair and not an overlay anymore :-)


Overlay network typically allows to buy less CleanAir APs, to have those APs working in monitor mode (scanning all channels, improving location and monitoring of the network). If you're buying plenty of CleanAir APs, just use a 100% cleanair deployment then.

40. Q. I want to know the coverage of Cisco Aironet 1140 Wireless AP?

A. Why is Cisco not giving numbers ? Well that's because it's an indoor AP and there are not 2 indoor deployments that are the same. The range could vary from 10 meters in a bank with super thick walls to 50 meters in an office space, maybe more if you put the AP outdoor (which you're not supposed to). So what's the point of giving a number that will not be right for you in the end ?


It reminds me of Bluetooth devices sold with a sticker "up to 100 meters". Right, right ... if I move into the next room, it stops working.


I guess you're asking this question because you are planning for a deployment. How to know then ? :

-Use WCS planning tool

-Get 2-3 1140s and go on site and do a site survey to verify the actual coverage in that precise environment.

If you're asking to compare with competitors then you're choosing the wrong number to compare. You should rather look into transmit power and antenna gain. But since this is a regulation maximum, there should not be differences between brands (except if one brand goes beyond the regulatory maximum).

41. Q. Is it recommended to enable all access points in a specific area for CleanAir, or just a few? Could there be performance degradation on APs that are CleanAir enabled and servicing clients? For example, if you have a floor with 30 access points how many should be enabled for CleanAir?


A. I can't imagine any reason why you would want CleanAir on all APs. As explained in the video, there is no performance degradation at all :

-Spectrum sampling is done by the SaGe chipset (same as in the Spectrum Expert) that is inside the CleanAir AP, so wifi chipset is not involved.

-Calculations and device identification is done by this dedicated chipset, still no overhead on the AP CPU.

-Only Air Quality reports and Interference Device Reports are sent by the AP to the WLC. So the AP doesn't spam a lot of traffic on the network. Merely a small "Air quality is 70% in the last minutes and I detected a microwave oven and a Bluetooth device with these characteristics". So totally negligible.


The more CleanAir AP you have, the more interferer you can detect/identify and locate.

Related Information

General description

Access point information

Configuration guide about Cleanair

If you believe it's all marketing, check out independent CWNP review

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