Author: Jim's Wireless World

I like radios, and networking when it suites me. Love watching baseball with my son!

The Real Benefit of 802.11ax

This week is Aruba Atmosphere 2019, #ATM19, in what I am assuming is sunny and hot Las Vegas.  I’m not there for numerous of reasons, one of them not being I didn’t want to go, but since no one opened up a GoFundMe to get me there, I am sitting in what I can tell you is sunny Colorado enjoying the weather but missing the Wi-Fi talk.  What I am seeing is a fair amount of talk on social media about 802.11ax or Wi-Fi 6 both from the technical side and from the marketing side.  How can I tell which one is which? It’s easy.

Marketing guys talk about speed, and when they are done talking about speed, they talk more about speed.  Speed is sexy, and sex sells.  I didn’t go to any marketing classes and I’m pretty sure that is year 1 and 2 or marketing school.

Technical guys talk about how angry they are that 1) it’s called Wi-Fi 6 and 2) how the marketing guys got it wrong.  See, now you too can distinguish between the two when you go to parties and talk about the latest and greatest 802.11 standard.  Top Tip: if you are talking about 802.11ax at a party you are definitely the nerdy guy of your group.)

What I want to talk about, as a technical guy, is the letters that come after the 802.11ax part.  Some people don’t know it, but since 802.11n there have been letters that came after signifying something:

  • 802.11n HT
  • 802.11ac VHT
  • 802.11ax HE

HT stands for High Throughput, and VHT stands for Very High Throughput.  Since 802.11 is indeed wireless, we can draw the correlation to the radio world that if we had HF (High Frequency) and then came VHF (Very High Frequency) the next set of letters on the old (and I mean OLD) TV dial was UHF (Ultra High Frequency). Why then did the IEEE decide to go with HE instead of UHT for 802.11ax?  Turns out the crowd that runs in the IEEE circle (the REALLY nerdy ones at parties) understood what most Wireless Professionals do; speed is awesome but more speed isn’t the answer right now.  What is the answer?  HE, or High Efficiency.  Keep this in mind, as it is really important for the next 4 years or so in the world of Wi-Fi.

While 802.11ax indeed has 1024 QAM and in theory and in labs can achieve some crazy throughput numbers on the old speed test, most of realize that with the exception of most corner cases, it’s 100% useless and is there to help the marketing guys put their first 2 years of school to use.  What we professionals really want is efficiency and stability.  Stability is in the hands of the vendors and their code but efficiency is in the IEEE wheelhouse, and they crushed it on this one!  What does all this rambling really mean?  Let me try to put it in a story you can tell at parties when you decide to bring this conversation up (and probably seal your fate of never being invited back!)

I have been at my current place of employment for almost 11 years, and have lived in my current house for almost 4 years.  My drive to and from work, up until recently, consisted of a pretty long stretch of a 2 lane road.  I go to work REALLY early in order to avoid the traffic but in the afternoon, the only good answer was the countries most expensive toll road or this 2 lane disaster.  Driving 4 or 5 times a week, I generally found myself on the disaster more often than not.  The difference in my commute times between the morning and the afternoon was easily 20 minutes.  The problem was there was one lane heading north, and a bunch of vehicles wanting to use that one lane.

Let’s go ahead and correlate this to a Wi-Fi Access Point (AP).  There is generally one channel that everyone wants to use (5 GHz) and no matter how wide that channel is, only one device can use it at a time.  Whether that device (vehicle) is a jumbo frame (extra wide load tractor trailer) or the newest, shiniest device (hypercar) or the cheapest (scooters), by the rule of the road, only one can use that lane at one time, no matter the payload or speed.

Back to my commute.  When this was a 1 lane road, vehicles would back up all over the place, and it was a real disaster.  Entire exit ramps would back up, the road would be clogged, and almost useless, for hours every afternoon.  It really made that super expensive toll road look AWESOME!  I spent more money than I care to admit on that toll road to avoid the congested disaster that was that 2 lane road with 1 lane headed north.

Luckily, just recently, they completed an expansion of that disastrous 2 lane road, and now it’s a whole FOUR lanes, 2 headed north and 2 headed south.  Now, on my road, 2 vehicles can occupy what used to be one lane, at the same time.  The difference?  It’s beyond extraordinary!  I can now breeze through what used to be a solid 5 minute backup without even stopping!  The difference between my morning and evening commute, the one that used to be 20 minutes?  Gone.  Takes me the same amount of time now.  The toll road?  It’s still there but I don’t have to use it any longer.

On my road, the speed limit wasn’t changed from what it was before.  There isn’t any more, or less, stop lights than before, and if anything, the number of vehicles using that road has actually increased instead of decreased, but my evening commute was almost cut in half by the addition of one single lane going my way.  What used to be 20 minutes of stop and go traffic has now turned into a normal drive that I can accomplish sometimes without even stopping, and at the same time, handling more vehicles.

It can do it, because just like in the trunked radio world that I spoke about here, an addition like this is not a linear addition, it’s logarithmic, meaning it is more than the simple sum of the 2 parts.  Taken in a single snapshot in time, it might appear to be simple multiplication, but over time, the ability of the traffic (frames or vehicles) to adjust and better utilize the resource (channel or lane) means that the overall impact is massive when you go from a single to multiple.

Screen Shot 2019-04-03 at 4.33.55 PM

Courtesy National Instruments (link below)

With 802.11ax HE, the HE part is allowing what used to be a single lane road to be utilized as if they made it into a NINE LANE road?  Can you image what your commute would be like if all of a sudden every single lane road you drove was now NINE LANES?  That simply crazy talk right there!  The best part about this new technology that is allowing this to happen, OFDM  vs OFDMA (as pictured above), is that the AP can finally be in charge of something and can dynamically adjust the lanes as needed, on the fly, giving those oversized loads (1500 byte frames) the space they need while the rest of us on our mopeds (300 bytes) only use what we need, and allow more of us to get through at the same time, reducing congestion, and improving everything overall.

Screen Shot 2019-04-03 at 4.34.42 PM

Courtesy National Instruments (link below)

This is accomplished by utilizing something that has always been there, but never utilized efficiently in Wi-Fi, called subcarriers.  These subcarriers are grouped into what are termed Resource Units, or RU’s.  Each RU will consist of no less than 26 subcarriers per RU, but if needed all subcarriers can be utilized, dynamically, to accomplish the task. Very efficient you say?  Maybe those IEEE guys are on to something with their naming convention!

What this means the end result will be faster speeds that what you experience today, even if it isn’t the 1.21 jigabytes per second that 1024 QAM can do.  But be honest, wouldn’t you simply be happier driving your Honda Accord at 60 MPH in a 45 MPH zone?  Do you really need to do 150 MPH on your evening commute?  So when will this construction be over and your evening commute speeded up?  That is still being debated within many the circles.  I was going to write a second post, but I’m going for the gold now, and in a down and dirty fashion.

I have heard some people say we won’t really see the expected results that I have explained above until nearly 40% of all clients in a given space can use this new eight lane freeway that comes with 802.11ax/Wi-Fi 6/OFDMA.  My prediction?

12%, or at least 2 clients, of saturation in a given space and you will see a noticeable improvement

Put in the books, write it in the clouds, I am saying it here, the number of clients needed to see an improvement utilizing this new technology is WAY less than everyone else I have heard say.  My reasoning is just like with my evening commute.  When things are very inefficient, like they are today, it doesn’t take much to improve everyone’s life greatly.  The next step in efficiency after this jump it will take a lot more, but for now, this is a huge addition.

Am I advocating that anyone run out and buy these brand new shiny AP’s to see this improvement before your neighbor?  Not even close.  As most of you know, vendor code has just as much to do with device performance as chip manufacturers, the IEEE, and the Wi-Fi Alliance ever thought about.  Don’t believe me?  I would like to introduce you to Lee Badman and his blog site and you can read all about it!  For now, if you are in the cycle to buy new hardware, do your research and you should be fine.  If you can wait, or you just refreshed your hardware, then for goodness sakes, WAIT!  I believe that sweet spot will happen around the spring of 2020.  You have time, and maybe, even by then, we will be talking about 802.11ax Wave 2!

So the next time you hear a sales guy start talking speed, nod quietly to yourself and know that while technically they are correct, and it will make things faster, it has nothing to do with 1024 QAM and 1.21 jigabytes per second, but all about being efficient.

Graphics courtesy of National Instruments and their PDF; PDF can be sourced here 802.11ax.

The Title Of Your Blog Posts Matter

When I first started writing my bog, I tried to get really cute with the title of my blog posts.  Some of them worked, others not so much.  Likewise, some of these blog posts were more of my musings and not really technical, while others I felt like getting really technical and in depth.  My problem, I have since realized, is I didn’t always get the serious posts paired together with serious titles.

This thought was hammered home to me last week while reading an online message board where someone asked if there were any down and dirty write up’s about 802.11k/v/r.  I didn’t know of any, but what caught my attention is that this would:

  1. make a really cool title for a blog post and
  2. if typed in a search engine might not pull up much, unless that was the title of your blog.

Recently, I participated in the CWNP CWSP JTA (for those who don’t speak acronym that is the Certified Wireless Network Professional, Certified Wireless Security Professional, Job Task Analysis.). During our three days of “discussions” one of the topics turned to how we as wireless professionals deal with products or terms that we come across in our day to day activities that we aren’t familiar with.  The obvious answer is we turn to the internet and we search for what we don’t know and educate ourselves, or at least that should be the answer, in my opinion.  Sometimes we turn to online message boards, like my example above, but that should really be the second or third option.  Again, my opinion.  If you call yourself a professional do your own searching first.

*Disclaimer: I have been known to ask my coworker something because I’m too lazy to look it, and they call me on that every time.  It’s ok, our office functions like this.

As the discussion went on at the JTA, I was reminded of a sticker I saw, and still want to get, that looked like this: sticker-b222a421fb6cf257985abfab188be7d6746866850efe2a800a3e57052e1a2411

As it turns out, that links to a website (that I got the image from by the way) called and is an acronym for “Let Me Google That For You.” Why you would go to a website called that to search for something instead of just going to the actual website it references, is beyond me, but to each their own.  What this does reinforce is the idea that the term “Google” has now evolved from the name of a company into an actual verb that is globally recognized as going to the internet and searching for something to find your answer.  In the end, if I remember correctly, we refrained from using the term Google and instead referenced online research or something like that.

This brings me back to the title of this blog post, and my first paragraph.  I realized that I have written some pretty good blog posts, and those that saw the link’s posted on Twitter probably went and read them, but if someone was searching for something on a topic I had written on, but due to my “cuteness” in my title, they will probably never see it.  If the goal of your blog is to help bring knowledge and preserve your experiences for the world to relate to later, then don’t be like me.  If the goal is to share your knowledge, is it really sharing if you hide that information.  If your goal is to keep your information private and not to share, then be as cute and obscure as you want, just realize that your work will probably blend into the rest of the minutia on the internet and never been again.

Very similar to my thoughts on the new Wi-Fi Alliance naming scheme, what you name something really does matter.  I’ve never searched for my topics or blog titles on a search engine to see how well my previous posts rank in search engines, but that’s not really my intent.  Even if my previous posts really could use a new name, I’m not going to go back and edit it.  If you go back and read my blog posts from the beginning, you should be able to see how I progressed as a “blogger” from the beginning to this point, and hopefully I will get better in the future.  Going back and changing my previous mistakes to clean it up seems very 1984 to me, and not something I am comfortable doing.

Oh, and if the reference to 1984 doesn’t immediately “click” with you, might I suggest a quick internet search looking for a book with that title, because I’m certainly not going to “Google” it for you!

You Should Care About DHCP Option 51

Edit 4 Jan 2019 – It has been pointed out to me that instead of packets, these are frames.  You can read more about how I was mistaken here.  The link to RFC 2131, Dynamic Host Configuration Protocol, can be found here.  I’m not going to go through and change all the words, just replace them in your head as you read through!

Dynamic Host Configuration Protocol, or DHCP, is one of the first things you learn about with IP devices and the super basics of how they work; even before you learn binary and MAC addresses and layer 3’s and LAN vs WAN and, and, and, and…

Hopefully you get where I am going with this.  DHCP is one of the building blocks of IP networking, and most people know just enough to survive.  As WLAN Professionals maybe you have heard of DHCP Option 43 (Vendor Specific information) or Option 60 (Class ID) but did you know about Option 51?  It’s OK, neither did I. 

The point of this diatribe is to point out how much most people, including me, don’t know about DHCP and the different options that are defined within the protocol itself, and how this can affect clients on a WLAN.  My interest in this was piqued by a conversation on the WLAN Pro’s Slack site (more on that at the end) and how Apple devices negotiated their DHCP lease.  Didn’t know that there was a negotiation during the DHCP process?  Neither did I.  Let’s get at it.

Basic Options

Some of the basic options that most people already know about, but probably didn’t know their defined option numbers are:

  • Option 3 – Router
  • Option 1 – Subnet Mask.
  • Option 4 – Time Server.
  • Option 6 – Domain Server.
  • Option 15 – Domain Name.
  • Option 51 – Address Time.
  • Option 53 – DHCP Message Type.
  • Option 138 – CAPWAP Access Controller Address

Honestly, the list of options that are available, and what they do, is pretty astounding when you start to dig into it.  It makes me think about some of the different things I could configure on my DHCP servers to try and help my clients negotiate the network easier and faster, improving customer experience.  At least that’s the “pie in the sky” thought.  The honest answer is the ever classic and pervasive It Depends™.  Hence the conversation on Slack about Apple devices and how they “negotiate” their DHCP lease from the DHCP server.

There are a myriad of things that happen within the DHCP process, starting with the typical 4 way exchange that most are aware of:

  1. DHCP Discover (A client transmitting an initial BootP packet)
  2. DHCP Offer (The intitial response from the DHCP server)
  3. DHCP Request (The client requesting the IP offered in Step 2)
  4. DHCP Ack (the DHCP server confirming the IP as being assigned to that client)

What surprised me was the number of options and things that happen within those 4 “simple” packets and how they differed between vendors.  Now as anyone who has dealt with client devices can attest, different vendors can wreak havoc within an infrastructure, but did you realize how much it can do just to a DHCP scope?

Option 51

With just a little bit of experience, and some time staring iPad DHCP Discoverat packet captures, this is a pretty easy exchange to watch, and then take for granted.  For the sake of this conversation, I performed a bunch of captures on my test DHCP server (pfSense – I should probably do a post about that) and focused on Option 51.  This is the part where an Apple device will “negotiate” its lease time.  On the right is a look at my new iPad as it starts the DHCP process with a DHCP Discover message (Option 53).  Notice the time in Option 51?  This is in the initial packet of the process and this Apple device is requesting 90 DAYS (!) for its lease.  I tested this with multiple Apple products and found this to be the same across the board.  Every time an Apple product that I tested sent a discover packet to the DHCP server, it asked for 90 days.

Greedy buggers!

Conversely, the Android devices I tested asked for what the leaseWindows DHCP Req Packet time was as part of the Option 55 section (Parameter Request List), but never asked for a time as a specific option.  Windows devices, pictured here, never even inquire about Option 51; either as a standalone option request or part of the Option 55 Parameter Request List.  This becomes critical when we get to the “DHCP Request” packet or #3 in the process. 

Now while a lot of the parameters requested in this DHCP Request packet on the right aren’t configured on my test DHCP server, the device is still asking for them.  That’s fine, the server will only respond with what it knows.  The cool thing about a pfSense DHCP server is that it knows about TWO different timers for the DHCP Lease Time.  A “default time” and a “maximum time.”  These are configurable through the the GUI and until recently, I never knew why this was such an important thing.

Apple Devices and Option 51

Enter the Apple discussion on Slack that I referred to earlier.  The conversation centered around the fact that Apple devices didn’t like having short lease times for its DHCP.  I don’t have the conversation to post, but I need to give credit to Kristian Roberts for originally bringing light to this subject.  I couldn’t find him on Twitter but he is on Slack (more at the end.)

What Kristian discovered, and I confirmed, is that Apple products will always request for 90 days.  What gets weird is when it request 90 days.  As part of the standard 4 packet exchange, the discover and request (1 & 3) in the exchange come from the clients, the offer and acknowledge (2 & 4) come from the server. An Apple device will only request the 90 days in the discover packet of an initial DHCP process.  In the request packet, it doesn’t include Option 51 for the initial request.  Where this changes is the renewal that happens at the half life of the lease time as defined in the last packet of the exchange, the acknowledge packet.

In my scenario with 2 different lease times defined, this is what an Apple Mac Book Pro looks like from a DHCP scenario:

mbp 75 min dhcp overview

Mac Book Pro DHCP Summary

I did the math for you, and 7,776,000 really is 90 days.  3,600 seconds is an hour that the server responds with, which in pfSense is defined as the maximum lease time.  Notice that the request packet (#3) has no value?  Apple devices don’t request a time in their initial  DHCP request packet so the server responds with 1,800 seconds, or the default time of 30 minutes.

900 seconds after the first DHCP ACK from the server, the client sends a DHCP Request packet when it starts the renewal process; half life of the 30 minute lease that both the server and client respect from the first ACK packet.  If the client didn’t respect that value, the renewal wouldn’t have come in until later.  What I want to call your attention to is the IP Address Lease Time for packet numbers 5 through 10.  In the initial request packet (line 3) the Mac Book Pro didn’t ask for a time but in every subsequent request it asks for 90 days.  The server, programmed with a maximum lease time of 60 minutes, keeps offering it.  The other oddity happens at line 7.  The request comes 900 seconds after an ACK with a 3,600 second (1 hour) lease.  The source and destination IP address revert to a broadcast like the initial request, but it’s a renewal.  This time, however, the client “accepts” the 3,600 second lease because the renewal at line 9 happens 1,800 seconds (30 minutes) later.

The one thing that I can state is that Apple definitely has some “negotiation” happening within their DHCP process.  What I saw above I saw on multiple Apple products so it’s not just a one off.  When the same type of test is compared to a Windows laptop, it’s easy to see the similarities, and the differences.

Windows and Option 51

After examining the Apple products in depth, I wanted to contrast that to other devices.  In environments that support a mix of devices and can’t just focus on a single vendor, this might come in handy in the future.  What I learned, and have alluded to earlier, is that Windows and Android devices just don’t care about Option 51.  This is why, in my opinion, that Windows DHCP servers don’t offer a second lease time in the normal configuration.  We are still playing around with the Windows server to see if we can add a max lease time, but for now I can’t find it.

windows 75 min dhcp overview

Windows Laptop DHCP Summary


What we have here is the same test as before, but this time with a Dell laptop running Windows 10.  The only things that changed was the client device and the time of day.  While the general look is the same; starting with the standard 4 packets and then going into the renewal process.  The first thing that jumps out is there isn’t 90 days anywhere in the IP Address Lease Time (Option 51) so even though the server will allow a lease of 3,600 seconds, it only ever offers the 1,800 second lease.  At no point in this test does the laptop EVER request a time.  The only time values come from the server.  The test I did with an Android device looks identical to the summary above.  The only way to tell the difference is to look into the request packet and see that the Android device included Option 51 in the Option 55 Parameter Request List.

That’s it.  Windows and Android devices just don’t care to use Option 51 the way that Apple does.

The last thing that I can draw from comparing the 2 summaries above is why the DHCP Request during the renewal process every once in a while comes as a broadcast from to  For both Apple, Windows, and Android, even though the packet is a DHCP “renewal”, the device still remembers the initial lease time.  When you see the request from without a preceding offer packet, it means that it is the end of the initial lease period.  I’m pretty sure that if I went and read an RFC it would explain that, but I learn so much better doing it this way!


So what does all of this mean?  That’s an easy answer!

It Depends™

I spent a bunch of time digging into what was really happening with Apple devices on my network, and made an adjustment to allow those devices to eventually gain a longer lease.  I don’t have empirical evidence it made a difference, but I feel like it did.  I still have some more work to do, but one thing I can tell you is I have a much better idea of what happens during this process than I did two weeks ago.  All it took was some free software, some time, and a bunch of different wireless devices to play around with.

In an environment with almost all Apple, I could see some benefit to having 2 different lease times, and adjust those to find a sweet spot based on how long the clients stay in the environment.  If you only have Windows or Android, this won’t help you.  What I hope it does is to prod you to do your own testing and see what options you can use for your environment.  It’s not difficult, just takes some dedication and some curiosity.

If you aren’t on the Wi-Fi Pros Slack and want to be, contact the infamous Sam Clements and he can hook you up.  The conversations are more detailed and thorough, and you can even meet Kristian Roberts!

My site won’t let me upload the actual packet captures I collected during my research, but if you want them send me a message and I will work to get them to you.

Thanks for reading!

The Wi-Fi Community Is The Best There Is

The the day after Christmas, 2018, found me at work at my usual time (05:45 in case you were wondering) pondering the previous 5 days.  For most, the four days before Christmas of 2018 were probably spent with friends and family, having a joyous time and focusing on all that was good with their year and looking forward to the new year.  Not so much for me.

I spent that weekend sick, along with my wife, all while trying to take care of our four year old granddaughter who lives with us.  I had also been gathering some information about some news I had been waiting on for the past couple of months, and by the afternoon on Christmas I received some round about information that confirmed what I had long suspected.  I don’t want to get into the details about what “that” was; it isn’t crucial to where I am headed with this later, just know that it contributed to where my head was on the morning of 26 December, 2018, when I posted this tweet:


I was serious.  As I sat at my desk in a very quiet office, waiting on co-workers that wouldn’t appear for another 2 1/2 hours, I was stuck in my own head.  On a good day it’s a hectic place to be, but on this particular morning it wasn’t a good place at all.  That’s where that tweet came from.

Fast forward 24 hours.  Maybe my brain knew something subconsciously that I couldn’t figure out in the moment, that turning to my online support group was the best solution to where I was at that moment.  Alcoholics, gamblers, and a myriad of other groups in society that have issues have different 12 step programs they can turn to for support.

Wi-Fi folks have Twitter.

Where as others go to actual meetings in their community, Wi-Fi people turn to their support group, which is Twitter.  Luckily for me, the Wi-Fi community on Twitter responded to my tweet, and 14 hours later I was back on the path.  Between public responses to my tweet, private messages, and a few contacting me directly on my cell to check up on me, my online community came through for me.

It’s comforting to know that we aren’t in this alone.  If you do Wi-Fi in any capacity you need to be on Twitter and start following the community there.  I don’t care if you focus on Wi-Fi as a primary responsibility and thrive in the details or you happen to be the person who drew the short straw and are stuck staring and these weird numbers called “Minimum Basic Rates”, there is help out there.

For those that reached out to me, either on Twitter or text messages, I truly appreciate the effort.  My wife didn’t understand why such simple messages meant so much to me but the fact they came from people I consider to be the titans of the industry, the fact that they took the time meant everything in the world to me, especially at that moment.

We don’t have 12 steps, but what we have is the best online tech community there is.

Bar none.

Tenerife-North Airport and the World of Wi-Fi

I’m currently sitting the Tenerife-North Airport on the island of Tenerife after attending the Ekahau Masters meeting for 2018.  It took me over an hour in a taxi to get here from the hotel so it gave me time to reflect on where I was going, and it made me wax philosophical.  Let me explain by going backwards in time for a moment.

When I was first invited to attend the Ekahau Masters meeting this year, and when I found out where it was, I was a little giddy.  I’m kind of an aviation buff, and Tenerife, particularly the North airport, holds a special, maybe unique spot in the history of aviation and I was excited to have the opportunity to maybe visit the North airport.  I have been anticipating this moment for close to 8 months, so it’s been building for a while now.

That explains my giddiness, although a weird one I will admit.

To give you some background, the Canary Islands, of which Tenerife belongs, is to Europe as the Hawaiian Islands are to the USA.  It’s a tropical holiday spot where Europeans have been coming to for hundreds of years.  First, as a last stop before crossing the Atlantic on the voyage to the west and more recently as a holiday getaway location for people trying to escape Europe to some place a little warmer.  See, while technically being ruled by Spain, the Canary Islands actually sit on the African tectonic plate and are much closer to Morocco than they are to Spain.

This sets the stage for what happened here in March of 1977, the 27th to be exact.  I won’t go into the full details but a terrorist bomb detonation on one of the other islands in the chain forced that airport to close and all aircraft inbound to that location to divert.  Tenerife-North Airport (then called Los Rodeos Airport, and the only one on the island at the time) was the closest airport so many of the aircraft diverted to this single runway airport in the Atlantic Ocean.

This event led to what happened, and while not the only factor involved, it was one of the many leading to the end result.  To wrap this up, what happened was when the aircraft that had diverted to this small airport were finally able to depart and head to their original destination, at one point in the middle of a heavy fog, two Boeing 747 aircraft ended up on the single runway facing each other and the KLM flagged airplane started it’s takeoff roll, heading directly towards the Pan Am aircraft taxiing straight at it.

What happened next is pretty easy to guess, and the result is, to date, the deadliest accident in the history of aviation.  583 people between the two aircraft died in the accident.

International Tenerife Memorial, March 27, 1977

International Tenerife Memorial By Jesús Manuel Pérez Triana – Own work, CC0

Right, now why do I tell you such a morbid tale right before I board a flight taking off from this exact airport, and still its only runway?

  1. I love history and really like aviation, so it fits.
  2. If there is one thing I have learned, most of the people in wireless are a little off kilter, just like me. Don’t deny it, own it, you know you are!
  3. I have many hours of waiting and wanted to write about my experience.

The real truth is during the cab ride, I started to compare what happened on that fateful day on this little island to what I do in my everyday job.  What I realized is while I sat there and thought about everything I had to go back and work on after my trip, there were a lot of little things that led to where that particular issue currently stands.  I also realized that, just like with the Tenerife Airport disaster, all of these seeming little occurrences, had they happened in a bubble, wouldn’t lead to where I am today.  It’s only when many, little occurrences start to happen, all in the “correct” order and lined up exactly, do you get to moments when really, REALLY bad things happen.

Picking vendor A over vendor B.  Using virtual controllers instead of bare metal. Not doing that last AP-on-a-Stick survey, Picking one redundancy strategy instead of another. While independently, and if nothing goes wrong, most of these decisions are benign and don’t result in anything other than success.  Only in those unique moments when the stars align against us as Wi-Fi Professionals do we realize the times that make us earn our pay.

This leads me back to the airport that I’m sitting in, and what happened here 41, almost 42 years ago, and how I can relate that to my Wi-Fi career.  Unlike that disaster, if I make the wrong call in my job, and make every little mistake possible, it’s not going to lead to what happened here.  It’s only in the aftermath of what happened here can I compare the two worlds.

After the crash, aviation as it was known back then changed drastically.  Much of what you know of today in the aviation world, and most of the safety measures you don’t know of, but happen in the background, are a result of the investigation of that accident.  Aviation learned from what happened and then applied those lessons learned to what we have today.  Most people know that aviation today is the safest way to travel, bar none.  It’s only like that because of people who look into the disasters and figure out how do we learn from our mistake.

As I sat in a conference room for 2 days and listened to some very, VERY smart people talk and share their experience and wisdom I realized that even as a select member of the Wi-Fi community invited to be in the room, I still needed to stay focused and learn.  Disasters happen (we had 2 controllers go down at the same time while I as here, one still to be RMA’d) and I know there will be fallout from that.  What did I do right, what did I do wrong, and what can I learn from that.

While successes are fantastic and great, most of our learning comes from our failures.  If you are new to Wi-Fi, you are going to fail.  It’s not meant to be accusatory, it’s just going to happen.  I know because it still happens to the best of us.  And by “us” I mean even the people I hold in high regard and look to as mentors.  Even, and I know this is shocking, to me.  Don’t hang your head and give up.  If you have the desire, there will always be someone in the community ready and willing to help you up and dust you off.

The real test and measure of a true professional is what do you do after that failure.

Aerohive and their 802.11ax Roadshow

A couple of days (now weeks) ago I had the opportunity to attend an Aerohive roadshow that was focused on the new 802.11ax standard.  My reason for attending was to listen to Aerohive’s “Senior Technical Evangelist”, the great David Coleman, CWNE #4 and also the co-author of the Sybex CWNA Study Guide, of which the 5th edition was recently released.  If you haven’t seen it, just take a gander at it.  All told, the page count is north of 1,000 pages!  Anyways, I went because I wanted to hear more about the new 802.11ax standard, listen to Mr. Coleman, and get out of the office, pretty much in that order.  It’s OK, I even put that on my comment card so this isn’t news to anyone involved.

As an event, it was very well done.  My previous experience with Aerohive was limited to knowing they had a “HiveManager” but not knowing anything about it and their little stress ball “bees” that my granddaughter loves to play with.  My biggest fear was that the whole discussion was going to de-evolve into a marketing talk about Aerohive, but with David Coleman involved, I was pleasantly surprised.  David is super smart, and he was able to keep the topic centered on the IEEE standard (that as of November 2018 hasn’t been ratified yet) with just enough marketing to keep the people footing the bill happy.  I was also happy to see that there were administrators of other vendors present; all there just to learn about 802.11ax.  Kudos to Aerohive for keeping the proper mix of technical and marketing, I never felt the pressure of a sales pitch, just good ol’ fashioned arguing about the finer points of Wi-Fi!

Technical Learning

Since I was there primarily to learn more about 802.11ax, I was happy with the technical part of the afternoon.  I also heard other attendees say the same thing so I know it wasn’t just me that thought that.  My biggest takeaways from what I learned, and not just what I knew already is this:

  1. 802.11ax is officially known as “802.11ax High Efficiency Wi-Fi.”  I knew that while marketing people were banging away at the 1024 QAM modulation scheme that provides a jillion bytes per second of throughput the real improvement was centered around improving spectral efficiency.  The fact that someone was smart enough to to include that in the name was a pleasant surprise.11ax RU chart
  2. Resource Units (RU’s) are at the heart of Orthogonal Frequency Division Multiple Access (OFDMA) which is the 802.11 change that allows 802.11ax to be highly efficient.  This was “borrowed” directly from how LTE works, so it’s not like this is a new concept in the RF world, just in the 802.11 world.  As far as the standard goes, the smallest allocation of these Resource Units is 26 subcarriers (or tones).  I’m not going to get into subcarriers here but I will include a link at the end if you want to read more.  It’s nice to know that there is a standard to point to when vendors start to stray from that to improve their marketing jargon.  Why 26 subcarriers being the smallest resource units allowed is important because in the future as this will be akin to the 20 MHz channel width that we know today.  When looking at the chart above, it looks similar to what we know about the channel graphs that go from 20 MHz wide channels to 160 MHz wide channels.  Hopefully this reinforces the idea that 802.11ax is about going smaller to better utilize the spectrum, not going bigger.
  3. There are some new frames that have been introduced in the 80211ax Trigger DL Trigger.11ax standard called “trigger frames.”  On the surface these trigger frames seem innocuous but upon deeper inspection, you come to find out that these new frames actually provide a level of control that previously hasn’t been seen in previous 802.11 standards.  AP’s can now use these trigger frames to learn what type of data, and how much of it, a client wants to send so it can calculate how many Resource Units the AP needs to allocate to each client and make a plan on who it can combine together into a single time slot.  This is at the heart of the high efficiency and I can’t wait to dig deeper into these trigger frames.  All told there are 7 different types of these new trigger frames and I believe will provide additional features going forward.  That’s mere speculation on my part, but I can see how these frames could be leveraged once 802.11ax hits the mainstream.
  4. BSS “Coloring“. This will come as a surprise to no one, but “coloring” is a marketing term, not a technical term.  There are actually numbers for each “color” but it’s easy to see why they added color to the slide so it’s easier to show non-techie people.  What coloring actually does is focus on spatial reuse and the Clear Channel Assessment (CCA) that exists in the 802.11 today.  This new coloring introduces a new “color bit” into the PHY header that can only be interpreted by 802.11ax clients.  This also introduces two new terms to the lexicon known as intra-BSS and inter-BSS transmissions.  Intra-BSS transmissions are both on the same color so nothing changes from what happens today.  Inter-BSS transmissions are when a device determines that what it heard was actually from a different color BSS and treats the medium as busy “only for the time it took to determine the color bit was different.”  Understanding this from a textbook perspective is one thing, it will be really interesting to see what happens when this is deployed in real world scenarios.  Stay tuned in 18 months when we finally have AP’s AND clients available to test this one out!
  5. While PoE is nothing new to WLAN folks, the new AP’s that are being announced are coming with new bells and whistles and are going to require more power to operate.  What has just now started to become an issue with 802.11ac AP’s is only going to get worse.  Designers and engineers are now going to have to pay special attention to power requirements per port, total power per switch, power supplies for the switch, and then UPS requirements for these new higher power demands on the switches.  If you have gotten rusty on your understanding of Ohm’s law, it’s time to break that out and dust it off!

Aerohive Marketing

I knew this couldn’t be avoided, but was happy that it was kept at a respectable level.  If you are avoiding going to this because you don’t want to sit through a bunch of marketing, that’s a mistake.  Don’t get me wrong, it’s there because someone has to pay for it, but David does a good job keeping it from being overwhelming.

One of the things that was interesting to see was the mounting solution that Aerohive has.  I am a big fan of vendors who pay attention to the little things like mounting.  You don’t really understand why until you are standing on the top step of a 10 foot step ladder at 4 AM trying to hang the last AP before you are shut down and some hokey mounting solution slows you down.  It’s frustrating and I always like to look at that when I can.

The other thing I learned about Aerohive is they are going to support WPA3 SAE (the “upgraded” WPA2-PSK) before the end of 2018 and allow older hardware to support it with a code upgrade.  WPA3 Enterprise will also be supported but sadly Opportunistic Wireless Encryption will not be something Aerohive will support unless it becomes mandatory.

I know, I talked with David Coleman about this at length both before and after his presentation, and we parted agreeing to disagree.  While I don’t like the stance that Aerohive has taken in this regard, at least I know their reasoning.  Aerohive supports PPSK and feels that this is the best option for guest Wi-Fi security options.  For 95% of the applications, they are right.  PPSK is a better option and it’s something they support today. Why re-invent the wheel?  Sadly, I fall into the 5%.  I get it, I ALWAYS fall into that 5% outlier so I fight the uphill battle everyday.  I know that in a perfect world every vendor would support every option, but it ain’t happening.


While I won’t advocate that everyone should run out and purchase Aerohive gear to deploy everywhere (simply because I am firmly in the “It Depends™” camp) it was a pleasant surprise to learn about Aerohive, their gear, and to meet David Coleman in person.  Another pleasant surprise, albeit one I should have expected, was meeting some folks in my area that also work in Wi-Fi.  Sometimes, sitting out here where I do, I forget there are other folks who do Wi-Fi for a living in the city I work in.  Honestly, look at a map, where I work is technically “in the city.”  I will give you that it takes some crazy gerrymandering map work to make it happen, but it is in the city.

Now, if you want to learn more, here are some links that I promised earlier.

  1. Read more about David Coleman’s take on 802.11ax.
  2. Get the Aerohive 802.11ax book for dummies.
  3. Learn more about Aerohive and their gear here.

802.11ax is a thing (WiFi 6) so if you don’t take advantage of great resources like this then you are really missing out!

Meraki Is Now In The “F’ACK” Game

I live in Colorado, and for the past couple of years, Fracking has been a HUGE issue, both physically and politically.  I don’t really understand it, but that’s OK, I’m not going to talk about that in this post.  It’s a rabbit hole I don’t want to go to down.  I bring this up because during Mobility Field Day 3, #MFD3, Meraki introduced “FAST-ACK” and the first thing I thought of, both in name and potential impact, was fracking.

For those of you that don’t know what fracking is or didn’t click on the link earlier, fracking is the process of injecting high pressure liquid into rock deep underground to release trapped natural gas that are in tiny pockets that makes traditional drilling financially unfeasible.  It’s easy to reason both the pros and cons to this (pro = access to natural resources, con = “you are doing what?!?!”) but nonetheless, it’s a thing and it is happening.  As I sat in the Meraki presentation during #MFD3 this immediately sprang to mind.

Now that I have covered natural gas extraction using fracking, let me get to the technology of “FAST-ACK” which was quickly reducing to any number of shorter versions, but other than my witty title we are going to stick with FAST-ACK.  FAST-ACK is a patented technology that Meraki introduced at #MFD3 as a way to speed up your wireless network.  To really understand it, you need to be aware that in a traditional Ethernet connection, there is an ACK packet to a TCP packet, and that has always been there.  In wireless, there is an ACK to most frames as wireless professionals are well aware of, but there will still be a TCP ACK that happens; not to a received frame but from the client to the remote end to acknowledge that it received the TCP payload.  In wireless, it’s not flagged as an ACK, it’s a normal frame.  You would need to dig into the payload to figure out that it’s a TCP ACK.Screen Shot 2018-10-06 at 7.58.58 AM

Meraki’s approach to this is quite simple from a high level.  In order to speed up the delivery of content from a remote device (like a Netflix server), the AP will proxy the TCP ACK from wireless client to the remote end based on the fact that it received a Layer 2 ACK from the wireless client.  While the wireless client is processing the received payload to verify that it can send a TCP ACK, the remote end has already received that proxied TCP ACK and is queuing up the next batch of packets to send to the client.  This means that by the time the wireless client is ready to receive the next batch of traffic, that traffic is already cached in the AP, waiting to be sent.  Over time, this saves time and will get the client the movie they are wanting to download FASTER than the traditional manner.  According to Meraki, TCP FAST-ACK offers up to 38% improvement in throughput!  If you know me, I am a huge fan of getting people their content faster, so now you have my attention!Screen Shot 2018-10-06 at 8.09.59 AM

Now, if you are anything like the group that was in the room when all this was explained, there are some immediate questions that spring to mind, as well as additional questions that arise the more you think about it, just like with fracking in the oil and gas business.  One of the first questions, and this was covered during the presentation, was what about roaming?  Meraki has thought about that and the AP that processes the original TCP frames will cache the next batch until the client is ready to receive them.  If the client roams, the AP will transfer that TCP data to the next AP so that the new AP is ready to send it the moment the client is ready.  So that is covered, no problem.  My lingering question surrounding that is what does that do to the price of an AP when it is discovered that the AP will need additional storage to cache more and more data in certain venues, like LPV?  I could see a highly mobile environment with clients downloading a lot AND moving around a lot, there might be problems.  Time will tell, and I’m afraid that only time will tell about that.  Maybe this means that in certain environments, FAST-ACK shouldn’t be turned on.  Does that limit the market for Meraki?  Again, only time will tell.

After the presentation, as the delegates were packing up and talking, the majority of the conversation was focused on FAST-ACK and potential ramifications of this new technology.  Just like with any wireless centric conversation, there were multiple opinions and just like normal, none of them were wrong, per se, they were just different.  What happens if the client doesn’t send the TCP ACK to the remote end but asks for that payload again?  Does the AP send the next batch and then waits for the repeat batch?  All this TCP payload is numbered, so it will be received out of order, but that’s one of the reasons that TCP number is there to begin with.  If that happens, what is the trickle down effect of that?  What else suffers?  Is that throughput performance improvement worth the risk?  Again, only time will tell, because I don’t think we know what that risk is in the wild.  Too many times I have been burned with technology that works great in a lab setting or in an environment that was hand picked for testing, only to find out that in the wild, it’s not really worth the time and investment.  I’m not saying that is what is going to happen with FAST-ACK, I’m just being cautiously optimistic for the time being.

To watch the full Meraki presentation, go here and see for yourself.  To really understand the impression that FAST-ACK made on me, notice that the FAST-ACK portion doesn’t start until the 15 minute mark.  Before that there was a conversation about external antennas for ALL the radios in an AP – client serving, scanning and BLE.  If you know me at all you know that I love antennas so the fact that my first post about the Meraki presentation wasn’t about the fact that they are dealing with one of my pet peeves but instead introducing a mechanism to speed up the TCP flow should tell you something.

I still think that only time will tell on the real impact of Meraki’s FAST-ACK so if you like to be on the bleeding edge of technology, jump in and tell me how the water really is after you have done a couple laps, I am really interested in how this plays out.

In the mean time, I think I need to re-think the name of my blog.  The fact that I typed an entire blog post centered around TCP ACK’s might mean that maybe I DO know squat about networking.