The most common and biggest problem for WLAN Performance is layer 2 retransmissions.
So what are layer 2 transmissions? As you might already know in wireless networking we are using 802.11 frames. Unicast 802.11 frames have to be acknowledged, so if we have an access point talking to a client device it will be sending that transmission as an 802.11 unicast frame.
If a collision occurs or any partition of a unicast frame is corrupted, the cyclic redundancy check (CRC) will fail and the receiving 802.11 radio will not return an acknowledgement (ack) frame to the transmitting 802.11 radio. So we now have the original transmitting radio not receiving an ack so it will then begin retransmitting.
Excessive layer 2 transmissions will affect your WLAN performance in a number of ways. The two most common reasons are:
· Layer 2 retransmissions increase overhead on the access point and therefore decrease throughput, leading to calls to the helpdesk.
· Users of VoIP over the wireless will experience latency and jitter due to them being time sensitive applications.
So how do you solve the problem and what else causes layer 2 transmissions. So any good 802.11 protocol analyser can track layer 2 retry statistics.
Unfortunately, layer 2 transmissions are a result of many different variables and I will be creating some short articles telling you what they are. In each article there will be details on how to best try solve the problem. In most instances you will need the assistance of a trained wireless administrator who can use the appropriate tools to work out what is causing the problem.
If you have issues with your wireless network and would like to learn more about how computerworld can help, please do get in touch with us.