SXT 5HnD asymmetric throughput

Hardware MikroTik hardware general
1

Hi,

I have a problem with a wireless link using two SXT 5HnD connecting two (all switches are GigE Switches, all LAN Ports except the SXT 5HnD ones are 1Gbps) LANs using subnets 192.168.1.0/24 and 192.168.173.0/24 respectively. The distance is very short (on Google it shows 168m). The link is stable and when I use the built in bandwidth test I get full speed in both directions: When selecting 20MHz channels I get over 100Mbps in either direction and when selecting 20/40MHz HT Below I get over 200Mbps using UDP test with UDP Packet size 1500 and 500bytes.

However when I try to send data between 2 stations on the LAN I get asymmetric results. In one direction (remote → local) I get full 100Mbps throughput. In the other direction I only get approx. 35Mbps. (Using either FTP, iPerf or Ixia Chariot does show the same result)

I checked various stations on both LANs and regardless of the combination I always get the same results. The LAN stations are definitively not the bottle necks (in the most preforming setup they are a Quad XEON and Quad i7 running MacOSX 10.6).

I also tried connecting the stations directly to the SXT 5HnD. No change.

I also swapped the Mode of the SXT 5HnD (bridge / station bridge). No change.

Has anybody an idea what could cause this asymmetric behavior or any hint where I should look at?

Regards

Peter

2

What is the CPU usage like on both SXT’s when performing these tests?

3

reaim the antennas, even if you get a worse signal. you might be getting reflections / bounces on one unit. try moving one of the units a few feet away from where it is now.

if you are only 200m away from the other side you probably need to turn down the power.

4

When performing the good direction the highest CPU I have observed on the station side is 77%/73% and on the bridge side 60%/59%. In the bad direction with only 35Mbps the highest CPU I have observed is 37%/32% and 18%/17% (CPU/IRQ). Lower throughput seems to have another reason. But thanks for the hint, I did not even check that before.

The point with the antenna/reflection and the power is very good. I’ll try another position/angle and settings for power. Thanks as well. I’ll keep you informed about the results.