Cisco 2504 & 3602i Mesh Throughput Issues

[phosgene]

Hello all,

I have an indoor mesh network comprising of several 3602i access points and a 2504 wireless controller. Referencing the diagram below; I'm having throughput issues from "test pc 2" and "test pc 1", where I'm only getting around 50-70Mbps on an iperf3 test.

I'd expect the throughput to be somewhere near the bridge data rate of the two access points "prd-3602-ap01" and "prd-3602-ap02", which should be around 400Mbps (looking at the MCS numbers for the 3600 series).

Can someone help me with troubleshooting this for me? I'm lost as to why the throughput is so bad.

[Scott Fella · Accepted solution]

Keep in mind that wireless is half duplex. That means throughout is at max half of the “rate”. Also depends on the amount of traffic that is crossing the link. If the backhaul is also client access, that can reduce the overall throughput on the backhaul link. So don’t think that the backhaul is like a full duplex cable link, it is not. It’s more of a hub to hub connection.

[phosgene]

Hi Scott,

Thanks for the clarification on wireless being half duplex... I did find this article which states that serial backhaul links loose 30-40% throughput per hop. So say the RAP is roughly 200Mbps (accounting for half duplex), the first hop could be 120Mbps, and the second hop (which the switch is connected to) could be 72Mbps?

Accounting for a few 5GHz clients on the backhaul and that gets me 60Mbps on average... Am I calculating this correctly?

[patoberli · Accepted solution]

That sounds possible yes. It's also one of the reasons why it's advisable to reserve the 5 GHz interface only for backhaul/uplink and the 2.4 Ghz for client access. It's well possible that the APs here don't support any other mode anyway. And a 2.4 GHz link with those models limits the throughput to about 70 Mbps (802.11n with 20 MHz channel)