Troubleshooting Using One of the Three Essential WI-Fi Troubleshooting Tools - Discovery Software
Who wants some free stuffffffff?!?
You're reading a free blog, so I'm guessing the answer is, "all of us". And that's good. You've come to the right place. Because the first part of my three-part series on Essential Wi-Fi Troubleshooting Tools is going to be about the free (or, very inexpensive) one: Discovery Software.
Discovery software, which is also called Scanner software, is software that records and displays information that a Wi-Fi radio gathers during 802.11 Discovery. There are two ways that 802.11 Discovery can be done: Active Scanning and Passive Scanning. (Hence, the term "Scanner" software.) Passive Scanning involves a device listening for Beacon frames that have been sent by APs. Active Scanning involves a device sending Probe Request messages as a broadcast in the hopes of getting APs to respond with Probe Response messages. Beacon frames and Probe Response frames carry essentially the same thing: information about the AP.
(Pop Quiz: Why does the 802.11 standard have two different types of frames that carry essentially the same information?
A: Probe Request/Response frames allow devices to connect to hidden/non-broadcasting SSIDs, while Beacon frames do not carry the SSID when the SSID is hidden/non-broadcasting.
B: Probe Request/Response frames allow devices to initiate 802.11 Discovery, thus potentially making roaming faster and giving devices a higher likelihood of connecting quickly in congested Wi-Fi areas.
C: The designers of the 802.11 standard are stupid, and stupid people do things like creating two different frames that essentially do the same thing.
D: All of the above.
Answer below.)
Discovery software is either free or cheap. If you want details about the options, read my previous post. To summarize:
iOS: Airport Utility (Apple)
Mac OS X: Wireless Diagnostics (Apple), WiFi Explorer (Adrian Granados - $15)
Windows: Acrylic WiFi (Tarlogic), inSSIDer (Metageek - $20)
Android: WiFi Analyzer (farproc)
Chrome OS: NONE
An important note to remember when using Discovery software is to always use Discovery software that runs ON A PRODUCTION DEVICE. (I know that sucks for Chrome OS people because Chrome OS has no Discovery software. On the other hand, if you're using Chrome OS then you're used to things that suck, so you should be fine.) It does you no good (and it can actually end up being COUNTER-PRODUCTIVE) to run Discovery software on a laptop if you're trying to support someone's iPhone. For example, I'm sitting in my friend's office and my Apple MacBook laptop shows an RSSI of -62 dBm. My iPhone 5, being held in my hand right in front of my laptop, shows an RSSI of -55 dBm. That's a big difference.
Once Discovery software is installed on a PRODUCTION DEVICE, then it's time to use Discovery software. When using Discovery software, remember it's limitations: it only gathers 802.11 Discovery information. Basically, that means it gathers AP information. It doesn't tell you about frames (commonly called "packets", but in the world of Wi-Fi the correct term is "frames") or other Wi-Fi devices or non-WiFi interferers (such as wireless speakers, microphones, headsets and the like). But that's fine. AP information is important. You just need to know what to do with it.
Discovery software can be used for a lot of things. You can check your current RSSI, look to see which channels your neighbors' APs are on, try to find unencrypted SSIDs and, if you're using a more advanced Discovery tool like WiFi Explorer, even view Information Elements from Beacon frames to figure out what your APs are capable of. All of those things are nice, but in the enterprise I find that I end up using Discovery software for two main purposes: to figure out whether my device is connecting to the best AP and to see if I need to adjust settings on deployed APs.
Devices that don't connect to the best AP are frustrating because you often can't do anything about it. In Wi-Fi, devices -- not APs -- manage connections. So, if a smartphone decides that it wants to stay connected to an AP that's two rooms away or latch on to an AP that's on a congested channel or gravitate towards an AP that always seems to deliver inconsistent Wi-Fi, there's not much you can do about it. You can disable an AP radio (or even an entire AP, in extreme cases), but that may trigger a game of Wi-Fi whack-a-mole. (I call it "Wi-Fi whack-a-mole" when you adjust one AP, solve a problem in one place, create a problem in another place and then keep repeating the process ad infinitum.)
Unfortunately, Discovery software can't solve the problem of devices connecting to unstable APs, but it can at least identify the problem. For example, you might find that a certain type of low cost laptop seems to always gravitate to 5 GHz connections, even in areas where 2.4 GHz coverage is much more reliable. Discovery software will allow you to see that your low cost laptop's RSSI is much lower than the signal coming from other APs in the area. Once you know that, you might be able to run a test to see if you'd be better off disabling the 5 GHz radios on some of your APs. Or maybe you'll find that your Wi-Fi can be improved by installing an extra AP that has only the 5 GHz radio enabled. Whatever the result, Discovery software can be part of finding a solution.
The second -- and most important -- use for Discovery software when troubleshooting in the enterprise is to identify overused and underused channels. This is what the stuff if really good for.
Let's take an example. The other day I was in an area of Los Angeles that TimeWarner Cable covers with their "CableWiFi" Wi-Fi network. It's a network that is supposed to be a value-add for TimeWarner Cable Internet customers, but unfortunately it's often a point of ridicule and frustration for TWC subscribers like myself. If you connect your smartphone to it once you might get good WiFi and you might not. But it often ends up being a big annoyance because of its inconsistency.
You're reading a free blog, so I'm guessing the answer is, "all of us". And that's good. You've come to the right place. Because the first part of my three-part series on Essential Wi-Fi Troubleshooting Tools is going to be about the free (or, very inexpensive) one: Discovery Software.
Discovery software, which is also called Scanner software, is software that records and displays information that a Wi-Fi radio gathers during 802.11 Discovery. There are two ways that 802.11 Discovery can be done: Active Scanning and Passive Scanning. (Hence, the term "Scanner" software.) Passive Scanning involves a device listening for Beacon frames that have been sent by APs. Active Scanning involves a device sending Probe Request messages as a broadcast in the hopes of getting APs to respond with Probe Response messages. Beacon frames and Probe Response frames carry essentially the same thing: information about the AP.
(Pop Quiz: Why does the 802.11 standard have two different types of frames that carry essentially the same information?
A: Probe Request/Response frames allow devices to connect to hidden/non-broadcasting SSIDs, while Beacon frames do not carry the SSID when the SSID is hidden/non-broadcasting.
B: Probe Request/Response frames allow devices to initiate 802.11 Discovery, thus potentially making roaming faster and giving devices a higher likelihood of connecting quickly in congested Wi-Fi areas.
C: The designers of the 802.11 standard are stupid, and stupid people do things like creating two different frames that essentially do the same thing.
D: All of the above.
Answer below.)
Discovery software is either free or cheap. If you want details about the options, read my previous post. To summarize:
iOS: Airport Utility (Apple)
Mac OS X: Wireless Diagnostics (Apple), WiFi Explorer (Adrian Granados - $15)
Windows: Acrylic WiFi (Tarlogic), inSSIDer (Metageek - $20)
Android: WiFi Analyzer (farproc)
Chrome OS: NONE
An important note to remember when using Discovery software is to always use Discovery software that runs ON A PRODUCTION DEVICE. (I know that sucks for Chrome OS people because Chrome OS has no Discovery software. On the other hand, if you're using Chrome OS then you're used to things that suck, so you should be fine.) It does you no good (and it can actually end up being COUNTER-PRODUCTIVE) to run Discovery software on a laptop if you're trying to support someone's iPhone. For example, I'm sitting in my friend's office and my Apple MacBook laptop shows an RSSI of -62 dBm. My iPhone 5, being held in my hand right in front of my laptop, shows an RSSI of -55 dBm. That's a big difference.
Once Discovery software is installed on a PRODUCTION DEVICE, then it's time to use Discovery software. When using Discovery software, remember it's limitations: it only gathers 802.11 Discovery information. Basically, that means it gathers AP information. It doesn't tell you about frames (commonly called "packets", but in the world of Wi-Fi the correct term is "frames") or other Wi-Fi devices or non-WiFi interferers (such as wireless speakers, microphones, headsets and the like). But that's fine. AP information is important. You just need to know what to do with it.
Discovery software can be used for a lot of things. You can check your current RSSI, look to see which channels your neighbors' APs are on, try to find unencrypted SSIDs and, if you're using a more advanced Discovery tool like WiFi Explorer, even view Information Elements from Beacon frames to figure out what your APs are capable of. All of those things are nice, but in the enterprise I find that I end up using Discovery software for two main purposes: to figure out whether my device is connecting to the best AP and to see if I need to adjust settings on deployed APs.
Devices that don't connect to the best AP are frustrating because you often can't do anything about it. In Wi-Fi, devices -- not APs -- manage connections. So, if a smartphone decides that it wants to stay connected to an AP that's two rooms away or latch on to an AP that's on a congested channel or gravitate towards an AP that always seems to deliver inconsistent Wi-Fi, there's not much you can do about it. You can disable an AP radio (or even an entire AP, in extreme cases), but that may trigger a game of Wi-Fi whack-a-mole. (I call it "Wi-Fi whack-a-mole" when you adjust one AP, solve a problem in one place, create a problem in another place and then keep repeating the process ad infinitum.)
Unfortunately, Discovery software can't solve the problem of devices connecting to unstable APs, but it can at least identify the problem. For example, you might find that a certain type of low cost laptop seems to always gravitate to 5 GHz connections, even in areas where 2.4 GHz coverage is much more reliable. Discovery software will allow you to see that your low cost laptop's RSSI is much lower than the signal coming from other APs in the area. Once you know that, you might be able to run a test to see if you'd be better off disabling the 5 GHz radios on some of your APs. Or maybe you'll find that your Wi-Fi can be improved by installing an extra AP that has only the 5 GHz radio enabled. Whatever the result, Discovery software can be part of finding a solution.
The second -- and most important -- use for Discovery software when troubleshooting in the enterprise is to identify overused and underused channels. This is what the stuff if really good for.
Let's take an example. The other day I was in an area of Los Angeles that TimeWarner Cable covers with their "CableWiFi" Wi-Fi network. It's a network that is supposed to be a value-add for TimeWarner Cable Internet customers, but unfortunately it's often a point of ridicule and frustration for TWC subscribers like myself. If you connect your smartphone to it once you might get good WiFi and you might not. But it often ends up being a big annoyance because of its inconsistency.
You can tell that the CableWiFi network is going to deliver inconsistent Wi-Fi by looking at Discovery Software. In this case, I used iOS Apple Airport Utility's scan while outside the Starbucks on the corner of Detroit & LaBrea to create this output:
Of course, the big caveat here is that switching TWC's APs that cover the corner of Detroit & La Brea in Los Angeles to channels 1, 6 and 11 might start it's own game of Wi-Fi whack-a-mole. I might start getting usable Wi-Fi when I'm outside Starbucks, but if I cross the street to Lulu's Cafe, one or more of those APs might run into interference or congestion.
The way to avoid Wi-Fi whack-a-mole when using Discovery software is to do a holistic survey, if possible. If I have a problem area, I want to run Discovery software on an actual user's device in the problem area, and also in other areas that are covered by the same APs. It can end up being an involved process, but if you have accurate floorplans (marked with AP placements, of course) and if you annotate those floorplans carefully, it can be done. Discovery software can be used to identify areas where your APs are interfering with one another and give you an idea of which channels those APs can be re-configured to.
As one might expect, free software on its own isn't going to be enough to do the toughest Wi-Fi jobs. Discovery software applications are very helpful, but the other two Essential Wi-Fi Troubleshooting Tools (Protocol analyzers and Spectrum analyzers) will often be needed as well. I'll talk about those other Essential Tools in upcoming blog posts.
***
Look at that mess. Three AP radios in the 2.4 GHz band covering my iPhone 5 at RSSI above -80 dBm (which is typically the threshold that I use when determining whether an AP is "covering" a space), and they're on channels 2, 3 and 2. What the heck?!?! (Actually, I know "what the heck". Ruckus's ChannelFly is "what the heck". And I've had enough, ahem, discussions with my main man GT Hill [a Ruckus VP] on why I RESPECTFULLY disagree with using ChannelFly for guest Wi-Fi in public spaces that I'm going to save my arguments for another time.) This CableWiFi network would almost certainly be improved by manually configuring the APs that use BSSIDs ending in "CB", "68" and "18" to channels 1, 6 and 11. (And, oh by the way, check out the piddly coverage that 5 GHz is offering: only ONE AP above the -80 dBm threshold, compared to three in 2.4 GHz. Yuck! I'm telling you, 5 GHz is for high-density only. Get those offices and schools on 2.4, baby! You'll thank me when LTE-U comes in.)
Of course, the big caveat here is that switching TWC's APs that cover the corner of Detroit & La Brea in Los Angeles to channels 1, 6 and 11 might start it's own game of Wi-Fi whack-a-mole. I might start getting usable Wi-Fi when I'm outside Starbucks, but if I cross the street to Lulu's Cafe, one or more of those APs might run into interference or congestion.
The way to avoid Wi-Fi whack-a-mole when using Discovery software is to do a holistic survey, if possible. If I have a problem area, I want to run Discovery software on an actual user's device in the problem area, and also in other areas that are covered by the same APs. It can end up being an involved process, but if you have accurate floorplans (marked with AP placements, of course) and if you annotate those floorplans carefully, it can be done. Discovery software can be used to identify areas where your APs are interfering with one another and give you an idea of which channels those APs can be re-configured to.
As one might expect, free software on its own isn't going to be enough to do the toughest Wi-Fi jobs. Discovery software applications are very helpful, but the other two Essential Wi-Fi Troubleshooting Tools (Protocol analyzers and Spectrum analyzers) will often be needed as well. I'll talk about those other Essential Tools in upcoming blog posts.
***
Quiz answer: B.
Hiding the SSID is not part of the 802.11 standard and the designers of 802.11 are not stupid.
***
If you like my blog, you can support it by shopping through my Amazon link. You can also donate Bitcoin to 1N8m1o9phSkFXpa9VUrMVHx4LJWfratseU or to my QR code:
Twitter: @Ben_SniffWiFi
Twitter: @Ben_SniffWiFi
ben at sniffwifi dot com
Comments
Post a Comment