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I have two Windows 7 machines on the same wireless LAN. When I try pinging from one machine to the other, the round trip times range from 1ms to 300ms, with lots of variation in between. Is it normal to see such high latencies and jitter?

I tried multiple brand routers as well as different WiFi channels, and the results are the same. If I switch the machines to wired, the problem goes away and it's always in the 1ms range.

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How busy is the RF environment where you are testing these PCs? –  Skyhawk Feb 3 '11 at 1:08
    
I'm in an office complex. My office itself is small (7 people), so I can control my environment, but there are dozens of AP's in the complex spread across various channels. I used inSSIDer to pick the least crowded channel, but I'm not sure how to gauge the activity level within a channel. –  Ravi Feb 3 '11 at 1:24
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Yes. This is normal. Wifi is a shared media network and you'll get lots of jitter when multiple clients want to talk at the same time and buffering occurs.

Things to try to reduce jitter:

  • change the wifi channel to the three non overlapping channels (1,6 or 11) These are generally better bets - use a wifi scanner to check your environment

  • look for potential sources of interference and turn them off or move them (microwaves, cordless phones, bluetooth, baby monitors)

  • remove other wifi devices from the same network (iphones, tivos, etc) - less devices means less radio interference

  • If you access point supports it: connect one host using a 5ghz channel and the other using a 2.4Ghz channel.

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Thanks, I haven't tried 5GHz, I'll give that a shot. Would having two clients on the same WiFi make the problem much worse, since they would have to bounce packets off the same router in infrastructure mode? Maybe they both transmit at the same time, collide, and then backoff for a long time? –  Ravi Feb 3 '11 at 1:27
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