cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
2813
Views
0
Helpful
4
Replies

Per client bandwidth calculation help

istvan.kelemen1
Level 1
Level 1

Hello,

Assuming that "Air Time Fairness" is on, how can I calculate the real bandwidth per AP per channel?

Let's say we are on 5Ghz. Channel for N is set to 40Mhz, for AC is set to 80Mhz. GI is set to short.

4 clients are associated at 877.5Mb/s, 5 clients are associated at 450Mb/s and 7 clients are associated at 300Mb/s.

What would be the maximum per client throughput when all the devices are talkin at the same time?

How to calculate it?

Thanks you,

István

4 Replies 4

Philip D'Ath
VIP Alumni
VIP Alumni

Well, there are 16 clients attached.  Maximum per-client bandwidth would be achieved if 15 of those connected were silent and did not generate or send traffic.  The maximum throughput would happen on the "best" connected  client.

So I would say the maximum per client bandwidth in this case would be 877.5Mb/s.

Hello,

I have a theory.

Let's assume that max 5G rate may be 1300Mb/s and 2.4 may be 216.7Mb/s.

In this case the real BW would be 650Mb/s and 108Mb/s respectively.

So the max BW what AP would require may be 758Mb/s when the clients are associated at the highest speed, regardless of the number of the clients.

Let's take a real word example, assuming Airtime fairness is enabled.

For simplicity, let's say all the clients transmit for 1 second in a round-robin fashion.

Case 1, mixed clients:

5Ghz:

Client 1 : 1300Mb/s associated rate - 650Mb is sent

Client 2 : 877Mb/s associated rate - 438Mb is sent

Client 3 : 780Mb/s associated rate - 390Mb is sent

Client 4 : 292Mb/s associated rate - 146Mb is sent

Average speed in 4 seconds is: 406Mb/s

2.4G

Client 5 : 216Mb/s associated rate - 108Mb is sent

Client 6 : 144Mb/s associated rate - 72Mb is sent

Client 7 : 72Mb/s associated rate - 36Mb is sent

Average speed in 4 seconds is: 72Mb/s

Total AP average BW: 478Mb/s

Case 2:

5Ghz:

Client 1 : 1300Mb/s associated rate - 650Mb is sent

Client 2 : 1300Mb/s associated rate - 650Mb is sent

Client 3 : 1300Mb/s associated rate - 650Mb is sent

Client 4 : 1300Mb/s associated rate - 650Mb is sent

AVG: 650Mb/s

2.4G

Client 5 : 216Mb/s associated rate - 108Mb is sent

Client 6 : 216Mb/s associated rate - 108Mb is sent

Client 7 : 216Mb/s associated rate - 108Mb is sent

AVG: 108 Mb/s

Total: 758Mb/s

Let's add few more slow clients:

5Ghz:

Client 1 : 1300Mb/s associated rate - 650Mb is sent

Client 2 : 877Mb/s associated rate - 438Mb is sent

Client 3 : 780Mb/s associated rate - 390Mb is sent

Client 4 : 292Mb/s associated rate - 146Mb is sent

Client 5 : 292Mb/s associated rate - 146Mb is sent

Client 6 : 292Mb/s associated rate - 146Mb is sent

Client 7 : 292Mb/s associated rate - 146Mb is sent

Average speed in 4 seconds is: 294Mb/s

So my conclusion is that slower clients slow down all the faster clients which are connected to the same AP Radio in a directly proportional fashion.

Am I correct?

Yes, you are correct.

Apologies on hijacking the thread as its been some time. I am curious and wondering on how the values are dervied? Is there a methodology/forumul for it?

 

Appeciate for the help :)

Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community:

Review Cisco Networking products for a $25 gift card