Wi-Fi Roaming Techniques

 

Wi-Fi Roaming Techniques : Pre-Authentication, PMK Caching, OKC, Fast Transition - 11r

What is Roaming:

Roaming is one of the most crucial aspect of Wi-Fi. Roaming in simple terms is Handing off Client connectivity from one Access point to another without losing connectivity. When the Client sees that the RSSI ( signal Strength ) of connected AP is decreasing, the Client does a roam Scan and sees if there are other APs with better RSSI. Once it identifies the better AP, it starts association with this AP. This process is called Roaming.  

Why is Roaming Important:

Wi-Fi is mostly used in devices which are mobile such as mobile phones, Laptops etc. User intend to use these device while moving from one place to another and it is expected that the devices are always connected to Wi-Fi and the user can continue his work seamlessly. It would not be desirable that Wi-Fi keeps disconnecting and connecting to other Access Point while the user is moving, there should be a way where in the client can remain connected to Wi-Fi network while it moves. This issue is addressed by Wi-Fi Roaming.

Another important reason for Why Roaming is important is to understand that Wi-Fi is now immensely used for Voice calls. We would not like to lose connectivity and have a crackling sound during a voice call. For this, the Roaming activity should be as soon as possible so that there is no significant disturbance to the user during the voice call.

A complete 802.1x Authentication process takes approximately more than 300 ms and voice packets are sent every 20 ms If the voice packets aren't sent for such a long time then there will be significant crackle in the voice. Just imagine that an officer says "Don't Shoot" over a voice call and there is a crackle in the call and the other officer only gets to hear "Shoot". This crackle can cost a life, and as reliable test Engineers we need to make sure that the quality of Wi-Fi that we provide is reliable.