Podcast

CTS 033: Community

CommunityHave 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

CTS 032: Cisco Updates CCNP Wireless

Title text over image of buildings.

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:

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

CTS 031: Band Steering with Francois Verges

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:

Band Select settings from the Advanced menu. 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.

Enabling Band Select on a WLAN.

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

CTS 030: Data Frames

Title over blurred text.

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

  1. Data
  2. Data + CF-Ack
  3. Data + CF-Poll
  4. Data + CF-Ack + CF-Poll
  5. Null
  6. CF-Ack (no data)
  7. CF-Poll (no data)
  8. CF-Ack + CF-Poll
  9. QoS Data
  10. QoS Data + CF-Ack
  11. QoS Data + CF-Poll
  12. QoS Data + CF-Ack + CF-Poll
  13. QoS Null (no data)
  14. QoS CF-Poll (no data)
  15. QoS CF-Ack + CF-Poll (no data)
QoS Data Frame

Wireshark capture of a wireless data frame.

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

CTS 029: Control Frames

 Blurred image of a capture control frame.

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