cwna

CTS 156: 802.11 Service Sets

802.11 has different topologies to be aware of.  They describe how 802.11 radios may be used to communicate with each other. Many are familiar with the most common ones such as BSS and ESS. But additionally, a client can operate in an IBSS, PBSS, and MBSS.

  • IBSS: Independent Service Set
  • BSS: Basic Service Set
  • ESS: Extended Service Set
  • PBSS: Personal Service Set
  • MBSS: Mesh Basic Service Set
  • QBSS: QoS Basic Service Set

What is a Basic Service Set?

The BSS is the foundation of a WLAN. It is the most common 802.11 topology. The BSS is 1 AP with one or more client stations associated. The BSA (Basic Service Area) is the coverage area of an AP.

SSIDs have a unique BSSID. The BSSID is a MAC address of the AP’s radio of a particular SSID. The SSID is advertised in beacons (here’s a BSS!)

The 802.11 standard references BSS in various ways

  • HT BSS
  • VHT BSS
  • HEW BSS (802.11ax)

Clients move between BSAs as they roam, negotiating rates dynamically as RSSI and SNR changes. There is no sharp cutoff of a BSA as it depends on external factors.

What is an ESS

It is the Extended Service Set. Or multiple BSSs with the same SSID (ESSID) connected to the same infrastructure. An example would be running a WLAN for an entire campus or running WLAN for a large office. Clients roam from one BSS to another within the same ESS

Overlap of BSA is for roaming. Hopefully, efficiently done with Fast BSS (802.11r)

IBSS

The Independent BSS. Sometimes, but not often, you aren’t connecting to a ESS. It is a basic WLAN consisting of only two clients. An ad hoc network created by, for example, a laptop.

Another client, say a laptop or tablet, communicates directly with the other client. It consists of clients that are directly connected which, technically, there is only one BSS.

There is no AP, just client radios. The BSSID is randomly generated by the first station which setup the IBSS

PBSS

The Personal BSS. Similar to IBSS but for DMG (Directional multi-gigabit) – 60GHz and clients communicate directly with each other. One client will be a PBSS control point (PCP).

PBSS is established through DMG clients. DMG is 802.11ad (directional multi-gigabit), commonly in mmWave

MBSS

The Mesh BSS. All clients in an MBSS establish links with neighboring clients. They determine hop capabilities.

An AP can both provide connectivity to clients and be a client of another AP to provide a mesh backhaul connection. There are a lot of consumer APs using mesh.

QBSS

The Quality of Service Basic Service Set. Simply a BSS that implements QoS.

Any enterprise AP manufactured in the past 10 years supports QoS, therefore, each BSS in most enterprise deployments is considered an QBSS.

CTS 153: Recap of 2018 & Starting 2019

We made it to the end of 2018! In our final episode of the year, we wanted to recap the show and its top episodes. There are some good episodes to listen to or if you already have, listen to them again!

Additionally, we wanted to share some brief stats about the show and how we’ve grown. Then we’ll share about what’s to come in 2019 for Clear To Send.

Top 10 Episodes of 2018

1 – CTS 137: MIMO
2 – CTS 106: 802.11ax with Broadcom
3 – CTS 108: Useful Wi-Fi Metrics To Track
4 – CTS 109: Ekahau Sidekick, Spectrum Analysis, & Finnish Rap
5 – CTS 123: Design Principles for Stadium Wi-Fi
6 – CTS 130: RF Characteristics
7 – CTS 107: What’s The Purpose of Cisco CleanAir
8 – CTS 138: CWNA with Coleman and Wescott
9 – CTS 134: Understanding the 4-Way Handshake
10 – CTS 125: 802.11 Frame Captures for Windows

Some stats:

  • 52 episodes for this year!
  • Now over 14k downloads per month
  • 4900 downloads in January 2018

Top countries:

  • 1 – US
  • 2 – UK
  • 3 – Australia
  • 4 – Portugal
  • 5 – Canada

Looking into 2019:

We are looking at providing some sort of Deep Dive into topics. Some of the content involved would include examples from real world data, how tests were performed, and the results we learned from the Deep Dive.

Additionally, we will look at including some video content to supplement the audio podcast.

When it comes to video, we may plan on doing a few webinars to answer questions from the listeners.

Links & Resources

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CTS 138: CWNA with Coleman and Westcott

David Coleman and David Westcott join the show to discuss the new release of the Sybex CWNA Study Guide.

Sybex CWNA Study Guide, 5th Edition

Sybex CWNA Study GuideDavid Coleman and David Westcott have released an updated version of the Sybex CWNA Study Guide, 5th Edition. It’s been refreshed for the CWNA-107 exam and it’s packed with a lot of content.

As Coleman and Westcott will describe in this episode, it’s been quite the process completing the study guide. With so much Wi-Fi technology out there, and being backwards compatible, there’s a lot to include. What you’ll also find is information for the upcoming 802.11ax.

With the 5th Edition of the Sybex CWNA Study Guide, there has been a complete overhaul. The study guide doesn’t follow the objectives in order. Coleman and Westcott have reorganized the content in order for it to have a natural flow. There’s more of a logical chapter order.

There’s a new chapter about WLAN design concepts and a new chapter on WLAN troubleshooting.

In addition to hearing about the book, Coleman and Westcott talk about how they got into Wi-Fi and ended up writing the CWNA Study Guide together. We discuss the process in writing such a technical book which includes a lot of research of the 802.11 standard, testing, and editing.

You’re not getting a regurgitated version of the 802.11 standard in this study guide. You’re getting a lot of real world information that will be more than useful for the CWNA-107 exam. It will be a study guide and a reference.

Links and Resources

Enter To Win a Copy of the Sybex CWNA Study Guide, 5th Edition

CTS 060: Road to CWNE

The journey to CWNE is not a straight path. It takes preparation, determination, and patience with a lot of studying. This is my summary to CWNE #210.

CWNE LogoDeciding to tackle the CWNP certifications towards CWNE is a task you do not take on lightly. In 2015, I had decided to create a personal goal of fulfilling my Wi-Fi dreams of becoming CWNE. While the certifications were not required for my job at my employer I was wanting to complete them for myself and to have the credibility of a CWNE.

In December 2016, I received the confirmation email of becoming CWNE #210 and was filled with a lot of joy from the sweat from the hard work.

CWNA

The CWNA cemented a foundation in Wi-Fi and proved there was much to learn in this space.

I used the CWNA study guide from Sybex which helped me pass the exam the first time. The book covered all the topics and provided more information beyond the scope of the exam.

During this time, I had also begun doing a Wi-Fi podcast to help me stay on track by constantly talking about the topic. The Clear To Send podcast has definitely helped me stay focused on Wi-Fi topics. I believe that teaching others is a way to also help yourself really understand the technology.

My CWNE Timeline

 

My timeline for CWNP to CWNE

CWNE Requirements

The requirements for becoming CWNE are straightforward and outlined on the application PDF.

CWNE requirements as of January 2017:

  • You must pass CWNA, CWAP, CWDP, and CWSP and they must be current.
  • Have three years of experience (verifiable) Wi-Fi administration, Security, Protocol Analysis, and Quality of Service
  • Have three endorsers
  • Meet listed achievements such as a published book, white paper, recorded instructional presentation, updated blog, etc
  • Write three essays (each over 500 words but not longer than 1000 words) which speak to your knowledge in Wi-Fi

  • Hold two valid non-CWNP certifications

CWAP

After completing CWNA, the next task is figuring out which professional level certification to go with next. My recommendation is to knock on CWAP. The analysis portion will arm you with the knowledge to pass the other exams with a little more ease. Analysis requires you to know more about design and security which is why I recommend this path. Within the CWAP you will dive into the frames and know more about frames than you ever wanted to.

When I first started tackling CWAP, I had tried to rush myself into passing before CWNP made the exam changes. Rushing is definitely a recipe for failure as I didn’t pass on my first attempt. What made things worse is that I couldn’t review fast enough for a second attempt before the exam changes.

Without giving up, I ended up purchasing the CWAP Study Guide by CWNP. While the book was much thinner, it did contain enough information to pass the exam.

I highly recommend capturing many wireless frames to help solidify the topics for CWAP. I lived and breathed in Wireshark during my CWAP. Anytime I needed to troubleshoot a Wi-Fi issue I always opened Wireshark just to see what was going on.

Something I always remember was when I solved a slow Wi-Fi issue due to a client constantly sending out CTS-to-Self frames with large duration values. I wouldn’t have seen this if I hadn’t gone through CWAP and applied what I learned.

CWDP

My decision to go with CWDP next had to do with the work I was doing with my employer. At the time I was doing quite a bit of design work so it was only natural that I took this path.

When I looked into book resources for learning CWDP I learned the book for the previous exam version was much bigger than the new version by CWNP. I decided to pick up both for the purposes of learning more.

The CWNP book is what I used to study for the CWDP and the previous version, by Sybex, I use as reference.

CWSP

I left the CWSP as the final professional level certification to tackle. This was in part of security being one of my weaker areas.

After reviewing the objectives I knew there would be quite a lot of terms to be familiar with. One of those being 802.1X and the security methods.

When you study for the CWSP be sure you know each of the authentication and encryption methods. Know what the difference is between them and which ones should and should not be used. What helped me learn the topics really quickly was building a Wi-Fi lab and experimenting with each method.

At home I have an Intel NUC which has VMware ESXi installed. I deployed a FreeRADIUS server and learned how to setup 802.1X with different access points and with a Cisco WLAN controller. Then during the authentication process of a device I would capture the wireless frames and analyze them.

If you take this route you will remember the topics much easier.

CWNE Application

In parallel to my CWSP studies I began working on my CWNE application. Why do it in parallel? It made it faster to apply after passing the last required exam.

The easiest task to do here is find three endorsers who can attest to your knowledge in Wi-Fi.

My three endorsers were:

  • Colleague
  • Manager
  • A CWNE

I recommend you at least find one CWNE to endorse you. You should really find a CWNE to guide you through this process when you are early on into your CWNP studies. I’ll talk more about this later.

Experience

A requirement of the CWNE is having the experience. Get exposed to working on Wi-Fi networks in areas of administration, design, analysis, and security. You may even be able to volunteer your expertise to non-profits who do not have the funds or capacity to do Wi-Fi networks properly. Look out for Episode 61 on this topic.

If you haven’t already, start a blog talking about your Wi-Fi experience. Talk about the subject as if you were teaching someone. You can see some examples on my own blog.

Other ways to get experience is to have published Wi-Fi articles. I have a few on Network Computing.

If you have questions about whether something is eligible you can contact CWNP and get verification.

Essays

You’re required to write three essays that show your knowledge in Wi-Fi. A simple way to approach this is to look at the three professional level certifications. You can write three topics on Design, Analysis, and Security.

I don’t recommend writing three essays on the same topic. For example,  you write three essays all on Design. That only speaks to your design knowledge.

You will want to show that you’ve been able to learn from the CWNP certifications and have applied that on a project or in the workplace.

Reach out to a CWNE and ask for guidance. You may even want them to review your essays to provide any input and recommendations for improvement.

Mentors

Early on in my Wi-Fi career I had indirect mentors. What I mean is I followed some of industry experts by reading their blogs, listening to their podcasts, and engaging with them on social media.

What I wish I had done when I first started was actually reach out to specific individuals and ask them to become mentors. These are CWNE’s who have the time to provide guidance to someone starting out in the CWNP path.

First you must be a good mentee. I always always always emphasis on doing the research first. Try to find the answers to your questions. And then when you have hit that wall you can approach your mentor with the results you found and ask for the push towards the right direction. A mentor will never give you a straight up answer. They are there to guide you.

A good mentor will be someone who is approachable and has the time (many CWNE’s are very busy with work travel and family). They provide guidance, input, recommendations, and experience. A mentor does not give you all the answers. They will encourage you along the path and push you to do better.

I want to thank one person specifically who has guided me throughout my CWNE journey and that is Francois Verges. He was patient with me, reviewed my essays and provided valuable input. Thanks Francois!

Resources Used During CWNE Journey

CWNA

CWAP

CWDP

CWSP

Applications

Hardware

Blogs

CTS 020: 5 New Year’s Resolutions For Wireless Engineers

In This Episode

We’ve made it through the first week of 2016. It’s a good time to look back at our accomplishments of 2015 and to look forward for 2016.

I’ve created a short list of 5 New Year’s resolutions for wireless engineers. It is not in any particular order.

  1. Attend an in-person event
  2. Become a speaker/presenter
  3. Get certified
  4. Start a blog
  5. Be Bold

Bonus: Start your own lab

Links and Resources Mentioned

What are your New Year’s resolutions? Are you going to take up one of the ones listed above? Let me know in the comments below.