Clear To Send: Wireless Network Engineering

Things are evolving again at Cisco. This time with the certifications. Cisco is further driving the Intent-based networking model into certifications. There’s the need to drive multi-domain policy, introduce APIs and programmability. It could change the way we do things every day. Infrastructure engineers are becoming software developers? Maybe not completely but there are those who may want to do both. New Cisco & DevNet Certs with Mandy Whaley Organizations want more speed, more agility, and more simplicity but what happens underneath that simplification is not that simple. Chuck Robbins, during his keynote, mentioned the certifications have not evolved in 26 years. And that’s when he introduces the Cisco Certified DevNet certifications. Bringing software skills to networking and networking skills to software. Cisco wants you to build applications and capabilities. Which will bring value on top of the platforms Cisco is building. The DevNet Associate certification covers 80% software skills and 20% networking skills. The CCNA covers 80% networking skills and 20% software skills. The two are complimentary if you were to pursue NetDevOps. Cisco then took those CCNA specializations and turned them into technology concentrations. CCNP certifications are now available in enterprise, service provider, data center, security, and collaboration, which you need to pass the core exam and a concentration exam. DevNet Professional is earned by passing core exam and DevNet Specialist What does that mean for wireless? * The CCNA Wireless won’t be available anymore* There will be a Cisco Concentration certification in Wireless* Concentration exams exist under the Enterprise Track* 300-425 ENWLSD Enterprise Wireless Design* Focuses on site surveys* Collecting requirements and constraints* Predictive and post-deployment surveys* Determining infrastructure requirements such as * PoE* RRM* RF Profiles* RxSOP* Designing per requirements* High density* Mesh* Mobility* High availability* 300-430 ENWLSI Enterprise Wireless Implementation * Focuses on actual configuration* FlexConnect* QoS* Multicast* Location Services* MSE* CMX* Security* ISE* Portals (not security really)* 802.1X* AAA* Monitoring* DNAC* PI* Device Hardening* CCNP Enterprise contains two wireless concentration exams* 300-425 ENWLSD Designing Cisco Enterprise Wireless Networks* 300-430 ENWLSI Implementing Cisco Enterprise Wireless Networks* At the CCNP level, the R&S and Wireless track have merged. So it will be the same core exam covering both tracks and it will be called CCNP Enterprise. It will test you on:* Dual Stack (IPv4 IPv6) architecture* Virtualization* Infrastructure* Network assurance* Security* Automation* CCIE Wireless becomes CCIE Enterprise Wireless* There is no more CCIE written, the CCNP ENCOR exam qualifies you to sit the CCIE Enterprise Wireless Lab* The policy to sit the lab 18 months after the written exam is gone. Now you have 3 years after you passed your ENCOR to sit in the lab.* The CCIE Enterprise Wireless Exam will cover (link):* Radio Frequency and Standards* Enterprise Wired Campus* Enterprise Wireless Network* Wireless Security and Identity Management* Wireless business applications and services* Automation, Analytics and Assurance New exams go live on February 24, 2020. Training for these new certifications will start this year (probably more towards the end of the year.) All certifications will now be valid for 3 years.

In this episode, we are interviewing Hendrik Lüth on the state of Wi-Fi security today. Hendrik works as a System Engineer for CANCOM in Germany. You can follow him on Twitter @DO9XE and on Linkedin. You can also visit and read his blog at https://linux-nerds.de/. Agenda * Start conversation with the “2018” status of WiFi security* WPA2 is widely supported* WPA2-Enterprise too complicated for home/guest solutions* Headless IoT devices only support PSK, because of hardware limitations* MPSK/PPSK/DynPSK* Short Recap on 4-way handshake* We just need to mention that there is Nonce and a MIC, that’s all

Welcome to this episode where we do a quick recap of how Cisco Live went this year in San Diego. This is one of the few rare moments when both hosts are in the same city. Cisco Live Recap with Rasika and Stephen Check out this short video we recorded with Rasika and Stephen getting their thoughts at the end of the conference. Wi-Fi 6 The Cisco Live conference was not using the new Catalyst 9100 series access points. Stability is a big thing for a huge conference. But they were seen over at the Whisper Suites. It’s just too soon to be using the C9100’s for a large conference. Cisco Live Wi-Fi We do have some interesting stats near the end of the conference. There were over 28,000 attendees. The Cisco Champions were able to join a NOC Talk with the folks running the network. Just to note, during the NOC talk there were only five Wi-Fi 6 clients on the network. Cisco Live Photos by Rowell Dionicio. https://rowelldionicio.com/clusphotos Some Cisco Live Wi-Fi details * 6 WiFi guys* 91% of clients were 802.11ac* Running Aironet in convention* Hyatt running Meraki* Took over Hilton’s Meraki network* OpenRoaming debuts – 3000+ devices on Monday before keynote* DNA Assurance deployed. Sensors deployed all over.* Cisco 8540s servicing convention center* Running 8.5.140.0 code Cisco Live Photos by Rowell Dionicio. https://rowelldionicio.com/clusphotos DevNet Certifications Announced during the opening keynote were the certification changes across the board along with new DevNet certifications announced. We’ll address the new certifications in a future episode but you can check out the details on Cisco’s developer site. Cisco Live Photos by Rowell Dionicio. https://rowelldionicio.com/clusphotos Cisco + Intel + Samsung + Boingo Cisco Champions were fortunate to take part in conversations between Cisco, Intel, Samsung, and Boingo. We received insight into the partnership between each company and how they are all working together to bring a better user experience to devices and infrastructure as it pertains to Wi-Fi. It was a short conversation but a good one nonetheless. Cisco Live Photos Check out Rowell’s photos from Cisco Live.

This week’s episode is the eve of Cisco Live. Rowell & François will be headed to San Diego for a week of learning, recording, and networking with other likeminded individuals. In this episode, we talk about various topics of Wi-Fi. You can take a look at an example of sessions we’re looking forward to at Cisco Live. François’ #CLUS Schedule Captive Portals are a necessary evil. Most are still done in a way that prevents users from getting connected. Whether that’s requesting every single kind of personal information or maybe it’s a simple splash page with terms and conditions. Either way, there’s now a page which describes how different devices behave with captive portals. It was created by the Wireless Broadband Alliance and it’s a good read if you’d like to understand how a device’s behavior is to be expected with Captive Portals. Captive Portals Wi-Fi 6 testing continues over at CTS headquarters. Rowell now has a Samsung S10 and an Intel AX200NGW in a Lenovo laptop. You can upgrade your laptop for a reasonable price. Rowell purchased his for $30 and it shipped from China. We’re learning whether what we’ve read from the draft is being implemented by the Wi-Fi vendors. When it comes to capturing these frames, you have to remember to capture with another Wi-Fi 6 capable device. You’ll need to demodulate Wi-Fi 6 frames. Rowell used a Cisco C9115AX access point in sniffer mode to see what can be gathered. There’s a little caveat with these access points which we will look into further before putting something out public. We will have more information after #CLUS. The Wi-Fi Alliance expands with the Wi-Fi Certified Home Design which is aimed toward home builders. In a highly connected world, why not have Wi-Fi built with a new home? Builders can get educated in Wi-Fi design and have homes certified for Wi-Fi. What are your thoughts on that? Let us know in the comments.

This Week In Wireless * Rowell recorded a video on Wi-Fi 6 on David Bombal’s YouTube channel* Long version: https://www.youtube.com/watch?v=uZMA4p00c9g* Short version: https://www.youtube.com/watch?v=r62vs2uyQjM* Huawei* Huawei is temporarily pushed out of the Wi-Fi Alliance* Wi-Fi Alliance is fully complying with the recent U.S. Department of Commerce order without revoking Huawei Technologies membership. Wi-Fi Alliance has temporarily restricted Huawei Technologies participation in Wi-Fi Alliance activities covered by the order.* https://www.androidauthority.com/huawei-wi-fi-bluetooth-990610/* SpaceX Launches 60 Starlink Internet Satellites Into Orbit* https://www.nytimes.com/2019/05/23/science/spacex-launch.html* “The Starlink satellites will orbit much lower — between 210 and 710 miles above the surface. That reduces the lagginess, or latency. SpaceX has said performance should be comparable to ground-based cable and optical fiber networks that carry most internet traffic today. Starlink would provide high-speed internet to parts of the world that currently are largely cut off from the modern digital world.”* CWNP new certification: Solution Administration* https://www.cwnp.com/certifications/cwsa* Certification on non-802.11 technologies (BLE, Cellular, Zigbee, wired-side technologies, location services, APIs, Project Management)* First class will be in September 2019* In the future, additional certifications will address key areas in greater depth, such as automation/integration, IoT, private 5G, etc.* Wi-Fi Images* Instagram @cleartosend* https://www.instagram.com/cleartosend/* iBwave webinar* How to Design Wi-Fi for Higher Education* https://www.cleartosend.net/designing-wifi-networks-higher-education/ Conference Wi-Fi Challenges * Very Dynamic environment! * Very High Density of devices* There are a lot of ad hoc requests throughout the event* ROGUES* Very intense, long hours, little sleep Prep Work – A lot of it! * Understand the type of event* Understand what type of people will be attending* Understand which application will be used over the Wi-Fi. Any critical ones?* Understand the layout of the conference* Where will the stages be* Where will the VIP zone be* Where will the media zone be* Where will the TV broadcaster zone be* Where will the registration zone be* Understand the flow of people* Prepare the LAN* Size it properly so it can handle the number of devices expected (2.5 devices per person)* Make sure the basics are covered* DHCP* DNS* Firewall* Core network* PoE budget* Prepare alternative plans just in case something goes wrong with the basics* What do I do if the internet goes down? Maybe plan for a backup internet link* What do I do if my DHCP server goes down?* What do I do if my DNS server goes down?* What do I do if run out of PoE power?* Make sure that you have enough internet bandwidth* Prepare the Wi-Fi* Understand the limitation of AP placement* Leverage the APs installed under the ceiling* Understand where to place temporary access points if required* Do you have access to cables from the floor* Plan to have APs ready to go and being deployed fast* Size your controller properly* Forget 2.4GHz, plan for 5GHz. Expect to see a lot of 802.11ac devices (and a few 802.11n devices)* Stage as much equipment ahead of time as possible* Organize the APs, name them properly and keep track of them in a document* Tweak the RF on the under ceiling APs as much as you can.

Recently, I joined the wonder folks at iBwave to deliver a webinar on the topic of designing Wi-Fi networks in Higher Education. Thanks so much iBwave for providing me the opportunity to discuss Wi-Fi design in front of their audience. The agenda items I cover in this webinar: * Challenges we see today* Approach to Wi-Fi design* Designing for capacity in large spaces* Wi-Fi 6 Considerations To follow along with this episode you can download my slides. Designing Wi-Fi Networks in Higher Education from Rowell Dionicio My slides Why must we design Wi-Fi? Why can’t we just install access points and call it a day? That’s something I go into with this webinar. But the short story is you don’t want to guess. We’re delivering a service that is used by thousands of people and whom rely on this service. And some of those people have over 30k clients per day. What if 1/3 of those people had poor Wi-Fi experiences and put in a ticket for each incident? When it comes to Wi-Fi, we should follow a process or a lifecycle in order to continue delivering a good user experience. I go into each of these on the webinar. I provide examples from my own environments. Share my solutions to temporary Wi-Fi deployments for events. I also share some Bad-Fi

Historically, AP-on-a-Stick (APoS) surveys were the only way to find out where to place the access points. We didn’t have any of the fancy software we have today to predict how the Wi-Fi signal will behave in our space. However, we still perform APoS today. In this episode, we will explain why we still use them and how they can be beneficial to us Wi-Fi Engineers. APoS utilizes an AP that will be deployed on-site. The AP would be installed on a “stick” and is used to measure how the Wi-Fi signal behaves in the space that is being surveyed. The advantages are it takes into consideration the behavior of an RF wave and the attenuation, reflection, diffraction, scattering, etc. The disadvantage is it takes time and materials to achieve. Historically, that was the way we used to define where to place the APs. We would start in a corner of a building and place the first AP, measure the signal to define the edge of the Wi-Fi cell and go on to the next measurement until you covered the whole site and defined the different AP locations. The introduction of tools allowed us to model and predict how the Wi-Fi signal will propagate in a given space. This allows us to plan and perform our Wi-Fi design “on paper” so to speak. In order for this type of predictive design to be accurate, we still need to understand the physical environment. However, we can predict the signal prediction in the software and save some time. Why do we still use APoS then? In some environment and cases, the predictive design will not be accurate enough for us to be confident in the design. In these cases, we now use the APoS to validate some of the AP locations defined during the predictive design phase. How much validation do we need to do? It depends

Rowell and François were invited to Cisco Headquarters, along with many others, as part of the #JustTheTech event which was planned in coordination with the Wi-Fi 6 announcement that happened on April 29, 2019. It was a jam packed day of discussions with key people from Cisco. The folks in attendance for #JustTheTech were: * Rowell Dionicio* François Vergès* A.J. Murray* Sam Clements* Evan Mintzer* Hayden Andrews* Shaun Bender* Kevin Blackburn* Amy Arnold* Network Chuck* David Bombal* Phillip Gervasi* Dave Benham We kicked off the event with a tour of the Customer Experience Center. Taking a look at the possibilities using Cisco solutions. It’s an impressive facility on the first floor of one of many Cisco buildings. There’s an entry way with a large Cisco logo on the wall. On the other side of the wall is the beginning of the Customer Experience Center. Big Cisco logoHop aboard the Cisco busVirtual ConciergeIndustrial switchesThe Customer Experience WallCisco’s first product, the AGS.BGP on a napkin During our tour we ran into Todd Nightingale who is an SVP, General Manager of Meraki. It was a delightful surprise but he was able to talk to us for a bit and even tour with us. So the main purpose of #JustTheTech was to take part in the coordinated announcement of Wi-Fi 6 products from both Cisco and Meraki. But instead of marketing material, we were able to speak directly to engineers. This means taking a look at the new Wi-Fi 6 access points up close * Catalyst 9115, 9117, 9120* Meraki MX55, MX45 The actual event started off with Sacha Gupta, Senior Vice President, Product Management – Cisco Enterprise Networking. He talked about Reinventing Access, Unplugged and Uninterrupted. Reinventing Access, Unplugged and Uninterrupted by Sacha Gupta Next, Jérôme Henry, Principle Engineer, Office of the CTAO, talked about OpenRoaming which is an interesting concept in today’s world where 5G and Wi-Fi 6 will converge.

With Wi-Fi 6 and 5G now taking the stage, one has to think – what about the coexistence of the two technologies? Rowell and François met together at Cisco HQ to speak with Jérôme Henry about OpenRoaming and Cisco’s vision of seamless roaming. François Vergès (left), Jerome Henry (center), Rowell Dionicio (right) Rowell and François participated at an event called #JustTheTech at Cisco HQ in Milpitas, CA. At this event we were table to speak to technical experts just about the technology and how it works in regards to Wi-Fi 6, switching, testing, and more. In this episode, François talks with Jérôme Henry, following his presentation on OpenRoaming. In the room is Rowell Dionicio, Sam Clements, and Dave Benham – all who participated at #JustTheTech. OpenRoaming What is OpenRoaming? According to Cisco: Cisco, along with other vendors and enterprises, is working to provide a better bridge between mobile devices and Wi-Fi networks. With frictionless and secure guest onboarding, users can roam across Wi-Fi 6 and 5G networks, automatically maintaining connectivity with security and achieving the ultimate experience.https://www.cisco.com/c/en/us/solutions/enterprise-networks/802-11ax-solution/openroaming.html OpenRoaming also bridges the network operator with the provider. A way to seamlessly onboard users to Wi-Fi with existing credentials. Learn more about OpenRoaming from Jerome Henry by listening to this episode today. To see more about OpenRoaming check out Cisco’s website.

1024-QAM Evolution of the modulation techniques we are using today with 802.11ax (256-QAM). With 1024-QAM, we are now able to encode 10 bits per cycle on each subcarrier. The way we are able to do that is by increasing the number of different levels of amplitudes used to encode the data. If you want to learn more about the different types of modulations used by Wi-Fi and how they work, there is a great video where Keith Parsons explains it on youtube: https://www.youtube.com/watch?v=W5DMfEuY2Vg&t=8s Due to the addition of a new modulation technique (QAM-1024), 2 new MCS indexes are now available with 802.11ax: * Index 10: when the 1024-QAM modulation is used with a coding of 3/4* Index 11: when the 1024-QAM modulation is used with a coding of ⅚ FEC (Forward Error Correction). Send more than the data bits. If you lose some of the sequence, the remaining bits will help you to understand what you were supposed to be sent. What is the challenge with more complex modulation techniques? How well will 1024-QAM in real life? Will we be able to take advantage to it? Interesting talk on twitter around the subject (Troy Martin, Andrew, Hendrik Lüth & Jim Vajda). We tend to think that a smaller communication bandwidth will give us a better SNR. But it is not necessarily the case here since the receiver in 802.11ax will still be listening to the whole 20MHz wide channel even if its RU is smaller. Link here: https://twitter.com/VergesFrancois/status/1113779145731977216 HE-MCSs Download the updated MCS Table With 802.11ax, we are getting a whole new set of data rates (or MCSs). If we want to understand why, we need to understand how these data rates are calculated. The amount of data we can transfer through a Wi-Fi link will depend on: * The channel width (or the number of subcarriers)* The modulation and coding use* The amount of spatial streams used* The guard interval used* The duration of the symbol And we can actually take all these different variables and calculate the different data rates using the following formula: 802.11n/ac Data Rate Formula You can take a look at the blog post and see which values can each of these variables can have for 802.11n and 802.11ac: HT & VHT Parameters Now, the reason why we have a new set of data rates for 802.11ax is because some of the key variables are changing: * A new symbol duration is used: 12.8µs* Different Guard Intervals are used: 0.8µs, 1.6µs and 3.2µs* The size and number of data subcarriers is not the same (especially with the different RU sizes introduced by ODFMA. Also, with the introduction of OFDMA and the use of Resource Units, we might be using smaller numbers of subcarriers which impact the data rates. This is why the draft identify the OFDMA and non-OFDMA MCS differently. The draft even use specific variables related to each resource unit. And we can therefore define this new formula: 802.11ax ODFMA Data rate Formula And here are the different values each of these variables can have for 802.11ax communications.

There are multiple functions in which a client or AP can gain access to the channel. What we’re going to discuss is in addition to the HCF and DCF. * TXOP duration-based RTS/CTS* Intra-BSS or inter-BSS frame determination* SRG PPDU determination* Two NAVs* MU-RTS/CTS* EDCA using MU EDCA parameters GOOD NEWS, CTS IS NOT GOING ANYWHERE! It’s all new ways of thinking about channel access but with added complexity. You’re dealing with multi-access, TXOP, BSS coloring which complicates the channel access process. TXOP Duration-based RTS/CTS HE AP can use TXOP duration-based RTS/CTS exchanges to mitigate interference for dense environments. RTS/CTS is now under TXOP Duration RTS Threshold. There is a TXOP Duration RTS Threshold subfield within the HE Operation element. To disable TXOP Duration RTS Threshold, the AP can set this subfield to a value of 1023. A client receiving a non-zero value from the AP will set its TXOP Duration RTS Threshold to the value of the TXOP Duration RTS Threshold subfield. A client shall use an RTS/CTS exchange to initiate a TXOP if the feature is enabled and: * The client intends to transmit unicast frames to the AP or to a TDLS peer client* The transmission opportunity duration is greater than or equal to 32 μs * RTS/CTS threshold. (Ex: RTS/CTS threshold = 300 & duration is 12345. Then 12345 μs > 32*300=9600) The RTS and CTS frames contain a Duration field that defines the period of time that the medium is to be reserved to transmit the actual Data frame and the returning ACK frame. The AP can also send a MU-RTS and simultaneous CTS responses by clients prior to the actual Data frames is another means of distribution of the medium reservation information. Otherwise, the client follows the normal DCF rules used today by 802.11ac. Intra-BSS and Inter-BSS Frame Determination Client determines if received PPDU is an inter-BSS PPDU based on the following: * BSS_COLOR is not 0 and is not the same BSS color which the client is a member. Pretty much is the client doesn’t have the same BSS color.* BSS_COLOR is not 0 and if HE client is associated with a non-HE AP. If the client is not associated to a 802.11ax AP Client determines if received PPDU is an intra-BSS PPDU based on the following: * BSS color is the same as the client * The frame carries an RA/TA/BSSID field value that is equal to the BSSID the client is associated with Essentially, in order for a transmitter to determine whether it can obtain access to the shared medium, it must determine if a received frame is within its own BSS color or not. SRG PPDU Identification A client looks to the Spatial Reuse Parameter Set element to see if the SRG Information Present subfield has been set to 1. It’s used to identify BSSs that are members of the client’s SRG. It will be used by the client to identify if the received inter-BSS frame is a SRG frame. It is used during Spatial Reuse Parameter (SRP) OBSS (Overlapping Basic Service Set) PD operation. We will have a dedicated episode on Spatial Reuse. Updating Two NAVs HE clients must maintain two NAVs. A HE AP can maintain two NAVs. Those two NAVs are: * intra-BSS NAV* Basic NAV

Ekahau Connect Jussi joins us on the show to talk about the latest announcement of Ekahau Connect and new products. Jussi has been on the show multiple times before: * CTS 009: Jussi Kiviniemi of Ekahau* CTS 069: Jussie of Ekahau* CTS 109: Ekahau Sidekick, Spectrum Analysis, and Finnish Rap* CTS 142: Jussi Kiviniemi Discusses the Ekahau Acquisition* Story Behind the Ekahau Hat New Ekahau Products There are 5 new products under the suite of Ekahau Connect that are now available. Let’s take a look at what’s new from Ekahau: ESS becomes Ekahau Pro (v10) and comes with interference detection (placed them on the map). There’s faster heatmap calculations, support for 802.11ax (Wi-Fi 6). New Features on the Sidekick includes 128 GB of storage unlocked. They Sidekick has always had the storage internally but now it can be used to store projects and other files. And as long as you’re using Ekahau Pro 10, you’ll be able to survey for Wi-Fi 6. Ekahau Survey for iPad has been in development for a while and is now ready to be used in production. Carrying a laptop has been always a struggle. Now survey data can be collected by using an Ekahau Survey iPad app. It’s a lighter version of Ekahau focused on data collection only. You will not be able to do any design work on the iPad app. The Ekahau Survey for iPad requires the Sidekick to collect Wi-Fi data. The Sidekick connects to the iPad using a USB-C to Micro USB cable. It’s easy enough for anyone to collect survey data. Wi-Fi experts will be doing more designing and optimization and another team member can perform the actual data collection. Ekahau Cloud allows users to easily collaborate with any Ekahau project file. You can share project files through the Ekahau Cloud and collaborate in real time. The project uploads to the cloud automatically. Ekahau Capture will allow a user to perform frame captures using the Sidekick. The pcap files can be stored on the Sidekick or locally on the laptop. There is a standalone tool to allow someone to select which channels they want to perform a capture on. It’s a dead simple capture tool. Ekahau University is a course to learn how to use the new Ekahau Connect suite of applications. Joel Crane will be the instructor for Ekahau University. Licensing If you’re new to Ekahau, here are your options: Ekahau Connect * Ekahau Connect Pack (SKU: EC-PACK)* Ekahau Pro* Ekahau Sidekick* Ekahau Connect Subscription (SKU: ECS-1YR or ECS-3YR)* Ekahau Survey for iPad* Ekahau Capture* Ekahau Cloud* Ekahau Support* Ekahau Connect Training

Objectives of TWT Objectifs of 802.11ax * Increase the performance of the Wi-Fi network by a factor of 4 while improving or not impacting power requirements* Provide power saving mechanisms for new emerging IoT devices All the current power saving mechanisms defined today remain usable with ax. In addition, the 802.11ax draft defines a new mechanism called Target Wake Time or TWT. Target wake time (TWT) is used to help minimize contention between clients and reduce the amount of time a client in power save mode to be awake. Clients will operate in non-overlapping times and/or frequencies and the frame exchanges are coordinated. TWT was introduced in 802.11ah and is particularly useful for battery-powered devices that communicate infrequently. TWT Modes of Operations There are three modes of operation: * Individual TWT* Broadcast TWT* Opportunistic PS TWT Power-save options in 802.11ax from Aruba 802.11ax White Paper: TWT Power-Save options in 802.11ax Individual TWT Client will be assigned specific times to wake up and exchange frames. The schedule is determined and delivered by the AP. There is a different mode of TWT such as explicit TWT. A client doesn’t need to know about another client’s TWT values. Simple process: * A client wants to establish a TWT agreement* A client communicates its waking schedule information to the AP* The AP devises a schedule and delivers TWT values to the client* The client wakes up and transmit a frame according to the schedule* The AP send the client the next TWT information on when to wake up again (explicit mode)* The client wakes up again at the next scheduled time to send a frame and receive a new TWT information* When TWT implicit is used, the client calculates the Next TWT by adding a fixed value to the current TWT value A client can go off of the AP’s TWT parameters. Or a client can “demand” a TWT with indicated parameters for agreement. If agreed upon, the AP will respond with “Accept TWT”. The AP can counter the offer with an Alternate TWT. A client wanting to utilize TWT will indicate what channel to use as a primary channel during a TWT SP. Broadcast TWT The AP will be in charge. The AP will send TWT parameters in the Beacon frame using the TWT Element. The TWT Element might be sent in other management frames as well such as the (Re)Association frame or the probe response frame. The clients will use the TWT parameters from the most recently received TWT element carried in the Management frames of its associated AP. The client is also called “TWT Scheduled STA” in this case in the draft. The AP is called “TWT Scheduling AP” The AP will provide the schedule to all the clients that supports broadcast TWT. The AP will send a trigger frame to discover which clients are awake. The AP will then send frames to these clients that will, then, be able to doze again. This is called a trigger-based TWT SP (Service Period). Clients can device to join or leave a broadcast TWT. This is done by an exchange of frame that carry TWT elements. Find the information in 802.11ax Frames Subfields to identify client support of TWT modes:

Cisco Live We have an episode full of Cisco goodness. Recently, Cisco released the data sheets to two 802.11ax access points. We have the details on these two APs, their capabilities, and some of our opinions. And speaking of Cisco, right around the corner is Cisco Live. We have our tips and the sessions we’re looking forward to. Cisco Live Tips The following Cisco Live tips were written on Rowell’s blog – Attendee Guide to Cisco Live 2019. It’s going to be hosted in San Diego, CA this year which should be a fun event. Check out the blog and register for Cisco Live if you haven’t done so already! Attendee Guide To Cisco Live 2019 * Bring a smile!* Meetups* Cisco Champions* Twitter* Friends* Exams – book early* Bring walking shoes.* Bring a jacket – sometimes the A/C is blasting inside the conference.* Portable battery packs – for your mobile devices.* Drink plenty of water – it’s best you bring your own reusable. I like to use my Hydro Flask. Empty out the contents before you pass through TSA.* Tylenol might be useful for those headaches. Either from learning so much by the fire hose or from partying the night before.* Book your sessions once they’re available. Some fill up quickly and you’ll be let on the waitlist.* Book your exam early! Schedule it on Saturday or Sunday before the chaos of the conference begins.* Download the Starbucks app. The lines for coffee get really long. Download the app and do mobile purchase. Skip the lines.* Don’t bring a backpack. You’ll get one at Cisco Live.* Leave room in your luggage. If you plan on grabbing swag, this is the conference that will fill up your bag, easily.* Hang around after each of your sessions and thank the presenter.* Check out DevNet Create and get hands on. Sessions on Wi-Fi to Look Out For Roadmap: Wireless and Mobility – CCP-120 Hear about the future of wireless, and how Cisco bridges 5G and WiFi 6. And, learn how our open platform delivers network and location analytics to support IT and business use cases. Securely Designing Your Wireless LAN for Threat Mitigation, Policy and BYOD- BRKEWN-2005 The session will cover effective strategies to build a defence-in-depth security model and the role of network segmentation in implementing Software-Defined Access (VLANs, VRF and TrustSec) for wireless networks. Participants will learn the principles of secured wireless networks (encryption, 802.1X, guest access, etc.) and the latest identity services available to securely onboard different kinds of devices (laptops, tablets, smartphones, IoT etc.) and users (employees, guests, contractors, etc.). This session will guide you through designing a fabric-integrated wireless deployment enabled for security, mobility and policy. Introduction to Next Generation Wireless Stack – BRKEWN-2010 This session will introduce the Next Generation Wireless Stack for enterprise and branch office WLAN deployments, i.e. the core technologies that drive and enable mobility services. Topics covered include protocol details like CAPWAP, deep-dives into new controller Catalyst 9800 features like High Availability, Security and integration with Cisco DNA Center and Cisco 11ax Access Points. We will also introduce Cisco DNA spaces and integration with the next generation stack. Introduction to Catalyst 9800 Wireless Controllers – BRKEWN-2670 Your next generation Wireless controller is the Catalyst 9800, available as an appliance,

With OFDMA in 802.11ax, the size of the subcarriers has been divided by 4. Going from 312.5KHz wide with OFDM to 78.125KHz wide. The symbol duration has been increased by 4 times in the meantime. Going from 3.2 microseconds with OFDM to 12.8 microseconds. Zooming into the subcarriers of a 20 MHz channel width View the full image here Advantages of having more subcarriers * Allow OFDMA to extend to small sub-channels. Each sub-channel requires at least one (usually two) pilot subcarriers, and with a 2 MHz minimum sub-channel size, a smaller subcarrier spacing loses a much smaller percentage of the overall bandwidth to pilots.* * The number of guard and null subcarriers across a channel can be reduced as a percentage of the number of usable subcarriers, again increasing the effective data rate in a given channel. The figures above show a ~10% increase in usable subcarriers compared to 802.11ac, after allowing for the 4x factor. Example: OFDM: 64 subcarriers, 12 GuardNull subcarriers = 18.75%, OFDMA: 256 subcarriers. 22 GuardNull subcarriers = 8.5%.* The longer OFDM symbol allows for an increase in the cyclic prefix length without sacrificing spectral efficiency, which in turn enables increased immunity to long delay spreads, especially in outdoor conditions. The cyclic prefix can be reduced to a smaller percentage of the symbol time, increasing spectral efficiency even while more robust to multipath conditions. And it reduces the jitter-sensitivity of uplink multi-user modes. The smallest sub-channel is composed of 26 subcarriers. Type of subcarriers: * Data subcarriers* Pilot subcarriers* DC subcarriers* Guard subcarriers* Null subcarriers A 26-tone RU consists of 24 data subcarriers and 2 pilot subcarriers. A 52-tone RU consists of 48 data subcarriers and 4 pilot subcarriers. A 106-tone RU consists of 102 data subcarriers and 4 pilot subcarriers. A 242-tone RU consists of 234 data subcarriers and 8 pilot subcarriers. A 484-tone RU consists of 468 data subcarriers and 16 pilot subcarriers. A 996-tone RU consists of 980 data subcarriers and 16 pilot subcarriers. DC (Direct Current) subcarriers are used for the subcarriers located in the center of the channel. Depending on the channel width and the number of tone used, the number of DC subcarriers can vary (Ex: 3 or 7 for a 20MHz wide channel). Most of the time it will be 7 for the 20MHz and 80MHz wide channels and 5 for the 40MHz wide channels. A 20MHz wide channels has 11 guard interval: the first 6 and the last 5 of the channel. Here are the diagrams extracted from the 802.11ax draft document detailing the structure of the subcarriers for each channel width using different RUs sizes: Links & Resources * Acceltex Portable Battery* FCC Plans to Open Large Amount of Frequency for Experimental Purposes.* https://venturebeat.