When I do an Omnipeek capture of an iPerf TCP throughput test over WiFi, I only see TCP Acks from the iPerf server to the client. How come I don't see any TCP frames from the client to the server? I thought iPerf traffic moves from client to server.

  • Also, how can I add a file (.pcap) to this post?
    – elin05
    Sep 25, 2013 at 0:57
  • 1
    You can use cloudshark.org to upload a pcap and share the link here.
    – Teun Vink
    Sep 25, 2013 at 6:44
  • 2
    Some pcap's won't work in promiscuous mode on wifi adapters. If the pcap is done directly on the client, try disabling that. Sep 25, 2013 at 8:37
  • From what I remember, as generalnetworkerror said, only a select few WIFI adaptor permit promiscuous mode, and if you're using window, you might need one of those particular adaptor combined with specific drivers, as windows do not let hardware access to the WIFI adaptor directly. You still should be able to see frames to/from your adaptor MAC address though. Jun 11, 2014 at 18:02
  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
    – Ron Maupin
    Aug 8, 2017 at 21:05

1 Answer 1


It seems that your omnipeek client card cannot capture higher data rate traffic. The ACK frames are sent with basic data rates and the DATA frames are sent with higher data rates. The issue can come up if your client and AP are transmitting on 3 stream and 40 MHz and omnipeek can listen on 1 stream and 20 MHz. This can also happen if the omnipeek client card is at a distance as it may not see the date frames.

Please make sure the the Omnipeek client card supports 3 (or at-least 2 streams) and it also supports 40MHz channel bandwidth

  • I am using OmniWifi (wildpackets.com/products/omniwifi_adapter) which supports 3-stream and 40Mhz. I wonder: is there some sort of calibration mechanism between the client and AP to help the client differentiate the three unique streams? What if my OmniWiFi adapter simply cannot distinguish the three streams well enough?
    – elin05
    Oct 15, 2013 at 23:15

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.