Clear To Send: Wireless Network Engineering

Wireless is a half-duplex medium. Unlike Ethernet, wireless devices must contend for air time to transmit their frames. To avoid collisions, there are a number of mechanisms used: * Physical Carrier Sense * Virtual Carrier Sense * a Coordination Function In this episode, I go over these mechanisms and describe their purpose. Here is a screenshot of a wireless frame showing the Duration value within the header. This Duration value is used to set a device’s NAV timer. Links and Resources * 802.11 Arbitration

Part of having a healthy and rewarding career involves taking a break every once in a while. In this episode, Francois and I talk about work/life balance. We provide our insight and tips for achieving a work/life balance that works for us and hopefully you can gain from these tips. If you would like to add anything additional, please leave a comment in the show notes. Francois and I are both working fathers. Francois is self-employed and I (Rowell) work for a university. The biggest takeaway from us is to aim for efficiency and maintain a good calendar or to-do list. Take a step back and determine how much we love to do for work such as studying for certifications, researching, performing analysis, blogging, podcasting, etc. But of course, you have to spend time with the family and your partner. So how do you make it all work? While this is a very personal subject, everyone’s workflow is different. To get a sense of what your day looks like, write down what you do each day. The goal is to become efficient while working so you can spend more time with family and friends. So here are some tips: * Create a to-do list * Organize your tasks and priorities * Take care of the important tasks first * Utilize your calendar * Celebrate the small accomplishments * Gain some energy by getting active in sports or exercise * Set due dates for every task * Try to keep your to-do list short! * Take a vacation!

Thank you for joining us on another great episode. The topic of episode 39 is when and how to use spectrum analysis. Spectrum analysis is a crucial part of wireless site surveys and for troubleshooting. When performing spectrum analysis as part of a wireless site survey, an engineer can determine which areas contain sources of interference that can greatly degrade the performance of a wireless network. Some interference is non-802.11 traffic. Wireless NICs within devices cannot demodulate these signals. If a transmission occurs with interference present, the frames are corrupted. It’s important to know the different kinds of interferences that can exist. * Sporadic (happens only at specific times). An example is bluetooth * Constant (the interference is there all the time). Example: Wireless Video Camera — Both can be disruptive to the Wi-Fi if the duty cycle is high — There is also the width of the interference to validate. * Do not forget to watch out for interference from other Wi-Fi networks (even yours…) * Duty cycle * ACI Links and Resources * David Coleman, WLPC 2016, Wi-Fi Troubleshooting * Metageek Chanalyzer * Spectrum XT * Ekahau * Tamograph

Robert Boardman is my special co-host for Episode 38. Robert is the creator of Hub Holster which is a great alternative to using velcro on your laptop to hold up a USB hub during a wireless site survey. I assisted in providing measurements for my own USB hub and after a few back and forth in communication I have a fully functional USB hub holder. It was printed using a 3D printer. We discuss how the idea of the hub holster came to mind, the process that goes into building a hub holster, and other features we may want to see. Both Robert Boardman and I will be heading to Cisco Live 2016 in Las Vegas. This will be my first time attending. I’m excited to meet others in networking and hope to get a podcast episode recorded with other attendees. If you are attending Cisco Live 2016, please let me know! Our last topic of discussion is about RRM. Robert and I have been thinking about really learning the ins and outs of RRM. Our goal is to deploy RRM and collect the necessary metrics to determine whether or not RRM helped in our scenario. Links and Resources * Robert’s blog * Hub Holster Page * Robert’s Twitter, robb_404 * Cisco Live * RRM White Paper

I have the pleasure of having Francois Verges co-hosting with me as he discusses his journey to CWNE. It was recently announced on Twitter, Francois became CWNE #180. Francois first started his journey to becoming CWNE about 3 years ago. He talks about this experience and how he got introduced into the CWNP program. In this episode, Francois provides his tips and insights into starting out with CWNA and what steps to take in becoming a CWNE. Links and Resources * CWNA * CWSP * CWAP * CWDP * CWNE * CWNE Requirements

Following up with Wes Purvis’ talk from MFD1 on getting started in wireless, I wanted to do my own on the same topic. In this podcast, I will go over my own experiences in a high level step by step on how I got started in wireless. I didn’t take a direct path to wireless and I actually don’t do wireless ful time. I am currently a network engineer who does do quite a bit of wireless work. But the path to this point took a while. It wasn’t instant. I started from the very bottom working as a computer parts salesman. My next role I began working as tech support. Working in tech support allowed me to learn how the end users worked on the network, what kind of applications they use, and how they use it. After my tech support role I then landed a systems administration job. From there I learned about servers and operating systems. What’s great about knowing sysadmin work is that I was able to understand Active Directory for authentication. Many wireless systems use Active Directory for authenticating users. Listen in on this episode to hear more about how to get started in wireless. There are just eight steps I highlight here which I go into briefly. Each one can certainly have its own episode. * Get experience dealing with end user issues. * Learn networking from the wire perspective. * Pick up a CWNA book. * The learn vendor material. * Get a lab. Use wireshark. * Start volunteering yourself for wireless work. * Write about wifi * Network with other wifi professionals

Mobility Field Day 1 brought together different minds in the wireless industry in one room and one presentation. We saw presentations from different vendors and other wireless leaders. Actually, not even all of them were really wireless but had their ties back to wireless in one way or another. All I have to say is that it is a great time to be alive. We’re seeing wireless advance greatly and many vendors are doing creative work in this space. I’ll let you listen to the podcast episode to hear what I’m talking about. If you haven’t seen any of the videos from MFD1, please head over to the [Vimeo page] to get educated. This Week In Wireless * 2015 Wi-Fi Alliance Annual Report * Gogo’s Airborne Wireless Test Lab * Cisco fixes three denial of service vulnerabilities in WLCs. one, two, three * If you missed it, watch my webinar on Challenges and Solutions for Higher-Ed Wi-Fi * Read my Best Practices for High Density Wi-Fi for Education * Francois Verges is CWNE #180

The beacon frame is used by access points, and stations in an IBSS, to communicate their characteristics for connection. A beacon frame is sent periodically, called the target beacon transmission time (TBTT). Default time is 102,400 microseconds (102 ms). 100 time units (TUs) is 1,024 microseconds. APs also contend for airtime while sending beacon frames. If the network is busy when an AP wants to send a beacon frame, then the AP will delay the beacon transmission. Stations use access point beacons as a time reference for each beacon has a time stamp and an indication of when the next beacon will be sent. A station will use use the time stamp to make sure their clock uses the same tempo as the access point. This is called the timing synchronization function (TSF). In an IBSS, the first station to create the ad hoc network defines the beacon interval and all stations joining the IBSS learn this interval. To see an example beacon frame, download my pcap file captured from my laptop. Links and Resources * CTS 028: Management Frames * Wireshark Display Filters via SemfioNetworks

Have you thought about joining the wireless community but aren’t sure how to get started? You want to help educate others but can’t decide on a platform to use. Giving back to the wireless community is one of the reasons why we have a great group of people. We like to share and discuss topics with passion. In this episode, I list out some ways you can participate in the wireless industry. Create A Blog You can start off by guest blogging on someone else’s blog. It’s a great way to get started and share your content with the community. The next best thing is to start your own blog for free using WordPress or Blogger. This is a place to write about your experiences, provide tutorials on how to do something, or even a place to keep your notes for the certification you are studying for. Twitter Probably the least required effort to get involved. Only requires 140 characters or less to get your thoughts out there. Many wireless professionals are on Twitter participating in a lot of great wifi discussions. Twitter has become the go-to method of communicating with other professionals. Many conversations get heated and it can be interesting to watch and learn from those discussions if you feel that you are unable to provide any other value. Additionally, the wireless community is very supportive in sharing others’ blog posts with their followers. Conferences If there’s any place where you can meet those you communicate with on social media in person. Put a name and a voice to the person behind the avatar. The most valuable part of a conference are the tabletop discussions that occur over a couple of drinks. That’s in addition to the presentations scheduled throughout a conference. Videos Video tutorials are a great way to contribute back to the community in a learning way. Many people, including myself, are visual learners. Reading how to do something sometimes isn’t the best way to learn but with the support of a video it can become a powerful duo. Podcast This is the route I took, obviously. A podcast enables you to fully participate in the community in meaningful ways. Audio is an easy way for a listener to consume content. It can be listened to anywhere. Doing a podcast also forces you to learn subjects to create content. All you need is a microphone and a voice. This Week in Wireless * Join my upcoming webinar with Ekahau on Challenges & Solitons in Higher-Ed. * Mobility Field Day 1 is coming soon and yours truly is a delegate. * Brocade Aquires Ruckus

CCNP Wireless Certification Update In March 2016, Cisco announced new updates to the CCNP Wireless exam. After looking through the objectives, I came to the conclusion that the new CCNP Wireless looks appealing. Cisco changed the objectives to meet the exam closer to the real world. The new CCNP Wireless exams are: * 300-360 WIDESIGN * 300-365 WIDEPLOY * 300-370 WITSHOOT * 300-375 WISECURE Be prepared for the lab simulations in any of these exams as there is an emphasis on it based on the objectives. Additionally, the candidate will need to know at least the following: * AireOS v8.0 * IOS-XE v3.6 * ISE v1.3 * Prime Infrastructure v2.2 If a physical lab is in sight for you, be sure you can work with the list of technologies above. 300-360 WIDESIGN The CCNP Wireless WIDESIGN exam focuses a lot on designing WLANs. From gathering requirements to predictive and validation surveys. You may even see a question or two relating to Ekahau Site Survey. I’d say this exam is the most important out of all the CCNP Wireless exams. Study Material 300-365 WIDEPLOY The focus of the deployment exam targets Cisco technologies specifically. We’re talking about the deployment of access points, controllers, mesh, and more Cisco proprietary subjects such as FlexConnect. It would be advantageous to have a physical lab setup to practice these objectives. Study Material 300-370 WITSHOOT The TSHOOT exam is new to CCNP Wireless. In the existing exam, troubleshooting was scatterred across all the exams. New with the 2016 update, troubleshooting shines on its own. Troubleshooting is a big part of wireless. I’d go far to say it’s just as important as designing. There’s going to be a large focus on debug messages, show commands, log messages, etc. So sit tight and lab it up. Study Material 300-375 WISECURE The security aspect of wireless. Cisco has removed previous technologies such as NAC, WCS, and ACS. There’s a large focus on standards such as 802.1X, EAP, AAA, and policies. Taking those standards in mind, you will need to translate that into a Cisco configuration. Study Material Links and Resources * Join me and Ekahau for a webinar: Challenges and Solutions for Higher-Ed Wi-Fi * Wireless Network Engineers can expect a 9.7% increase in starting pay. * Extreme Networks going into wireless industry. * Wireless Packet Analysis using CloudShark and Airtool (Video) * Webinar: Gigabit Wi-Fi: Not So Fast with Andrew von Nagy (Video)

Band Steering What is wireless band steering? Band steering is a method or feature within enterprise access points to sending dual-band stations to the 5 GHz band instead of the 2.4 GHz band. Band Steering enabled access points delay responses to 2 GHz probe response frames. Why would you want to enable band steering? The most common reason is to encourage 5 GHz capable stations to leave the congested 2.4 GHz band thus leaving legacy devices behind. The 2.4 GHz band has three non-overlapping channels which provides wireless engineers with a less channels to re-use. The 5 GHz band has 24 non-overlapping channels using 20 MHz channel-widths. Francois Verges joins me as the special guest on the show to discuss the merits of band steering, why you should use it and also what you should look out for if you do implement this feature. As I work primarily with Cisco wireless networks, I’ve provided an example of how to configure band steering. Cisco’s terminology for band steering is called Band Select. I won’t go into the differences between Band Select and Band Steering in this episode. This is simply to show everyone where band steering can be enabled. To view Cisco WLC Band Select settings: Cisco Band Select is enabled by default on the Cisco WLC./caption Band Select is enabled by default on a Cisco WLC. The global settings for Band Select are located at Wireless > Advanced > Band Select. Although Band Select is enabled globally on the controller, the setting itself must be enabled on the WLAN. This Week In Wireless Cisco Revises the CCNP Wireless Certification

The wrap up of a three part series on wireless frames. In previous episodes, I discussed Management and Control frames. Within those episodes I mentioned the frame subtypes contained in each of those frames. This episode is about Data frames and the data frame subtypes. There are fifteen data frame subtypes which I will briefly go over in the podcast episode. Data Frames * Data * Data + CF-Ack * Data + CF-Poll * Data + CF-Ack + CF-Poll * Null * CF-Ack (no data) * CF-Poll (no data) * CF-Ack + CF-Poll * QoS Data * QoS Data + CF-Ack * QoS Data + CF-Poll * QoS Data + CF-Ack + CF-Poll * QoS Null (no data) * QoS CF-Poll (no data) * QoS CF-Ack + CF-Poll (no data) The data frame image above highlights the frame type, shown as data, the subtype as a QoS data frame. The image also shows the additional QoS Control field that is part of the data frame because of the subtype that it is (QoS). This Week In Wireless CWAP-402 will launches June 28th, 2016 replacing the current PW0-270. Last day to take PW0-270 is June 27th, 2016. Study guide will be available end of May 2016. You can register for the webinar outlining whats new in the CWAP exam which occurs on April 21st

Control frames assist with delivery of data and management frames. They only have layer 2 header and trailer.  The function of a frame is identified in the Frame Control field which will have the Type and Subtype fields. * RTS * CTS * ACK * Block ack request (BlockAckReq) * Block ack (BlockAck) * PS-Poll * CF-End * CF-End + CF-Ack * Control wrapper RTS and CTS Both help prevent collisions from occurring by improves upon virtual carrier sense. Before a station transmits, it must do an RTS/CTS exchange. Prior to transmitting, the station will send an RTS control frame. Within the RTS frame, the Duration value has the time needed for the next frames to transmit (in microseconds). Listening stations will change their NAV timers to this value. Stations cannot contend for the medium or transmit data until their NAV counts down to 0.  After the RTS frame, the receiving station responds with a CTS control frame. Acknowledgement Frame Every unicast frame, if received properly, is responded to with an acknowledgement frame. This lets the original station know that the frame transfer was successful. Unacknowledged unicast frames will trigger the original transmitter to retransmit its frame. Affects of excessive layer 2 retransmissions on WLANs: • Increases overhead and therefore decreases throughput • Application traffic becomes delayed or inconsistent Block Acknowledgement Request Improves efficiency by aggregating several acknowledgements into one single acknowledgement frame. NAV reservation is performed so a block of frames can be sent. Each frame has the Ack Policy subfield in the QoS Control field set to Block ACK. Originator requests acknowledgement of all outstanding QoS data frames by sending a block acknowledgement request (BlockAckReq) frame. Block Acknowledgement Used to acknowledge a block of QoS data frames instead of acknowledging each unicast frame independently.  PS-Poll When client is in Power Save mode, some of the transceiver components will shut down to conserve power. The station tells the AP it is using Power Save mode by changing value of Power Management bit to 1.  Station is in one of two states (awake or doze): • During awake state, client can receive frames and transmit frames • During doze state, client station cannot receive or transmit any frames and operates in a very low power state Station receiving a beacon will check if its AID is set in the TIM. If so, station will remain awake and will send a PS-Poll frame to the AP. AP receives the PS-Poll frame, and sends buffered unicast frames to station. If station received unicast frame with a 1-bit field called More Data field, then the station will stay awake until it receives all buffered data. Contention Free CF-End is used to indicate the end of a contention-free period. Announces the end of the contention-free period and indicates that virtual carrier sense does not have to be extended.  The CF-End+CF-ACK frame is used to indicate the end of a contention-free period and acknowledge receipt of a frame. Control Wrapper Defined in 802.11n for HT. Used to carry any other control frame, other than another Control Wrapper frame. Carried Frame field contains fields that follow the Address 1 field for the control frame that is being carried. Links and Resources Mentioned * Congratulations to James Garringer on becoming CWNE #179 * Congratulations to Gustavo Mastroianni on passing CWSP * Pedestrian Patterns...

There are three types of wireless frames used for wireless communications. In this episode, I begin talking about one of them and its frame subtypes. The three types of frames are Management, Control, and Data. In this episode I go into the Management frames. Management frames are used to either for notification or for request and response. Management Frame Types There are twelve subtypes of the management frame. Each playing a key role in wireless communications. Some of them you may have heard of, such as the Beacon frame. If you are are studying for the CWAP exam, knowing each of the twelve management frame subtypes is important and knowing the purpose of each subtype is equally important. Listen to the podcast for a little more detail on each of the twelve management frame subtypes. 12 Management frame subtypes: – Beacon – Probe request – Probe response – Authentication – Deauthentication – Association request – Association response – Reassociation request – Reassociation response – Announcement traffic indication message (ATIM) – Disassociation – Action Links and Resources Mentioned * Sample wireless capture * Check out a fun way to create SSIDs, emoticons. I created a test SSID using a sushi emoticon to express my love for raw fish. Download the wireless capture to see what the SSID looks like in a Beacon frame. * Xirrus Unveils New MSP Offering * Configuring EAP-PEAP on Apple TV * Ekahau RTLS Acquired by AiRISTA * WLPC 2016 Videos Available Thanks For Listening Thank you to everyone who listens to the show. If there are any topics you would like to hear about please feel free to submit them using the contact form. Also, please subscribe to the show to get the latest episode delivered, automatically, to your Podcast listening app.

Josh Gerst, Vice President of Engineering at RF Connect, joins me on the podcast today to talk about outdoor wireless and DAS. He has over 15 years in RF engineering. His previous experience comes from a small smart antenna startup called Metaware, Sprint, Powerwave, to Ericsson, a large wireless equipment OEM. He goes into how he got his start in wireless and his experience working at various RF related positions at different companies. Today he is the VP of Engineering at RF Connect and he provides insight into how he and his team works on configuring wireless systems for different cities such as public WiFi over 12 square miles in Michigan. Some of the same kind of issues we see in WiFi are a little different when doing WiFi outdoors such as trees and hills. Josh goes into how they add this data into their surveys. Josh provides a comparison between WiFi and DAS and why one may be used over the other. When deploying either system, Josh talks about how to achieve success by gathering the scope of work and requirements. You can find more about RF Connect from their website, LinkedIn, and Twitter. This Week In Wireless * WLPC is complete. Waiting for the videos to come online * @jolla moves to Ekahau. * Eero is now for sale. * Google OnHub home WiFi. * Apple and Cisco WLAN Enterprise Best Practices updated for February 2016 * Ekahau Certified WiFi Master Thanks For Listening Thank you for listening to another great interview. If you enjoyed this episode, please do share it with the links below this article. What are your thoughts on outdoor wireless and DAS? Leave a comment below to start a discussion.