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About a month or two ago my main PC (also HTPC) started having some intermittent latency issues.

PC:

  • Win7 Pro 64
  • TRENDnet Wireless N 450Mbps USB adapter (TEW-684UB) - connected at 2.4Ghz
  • SABnzbd
  • uTorrent
  • Pulseway service
  • Dropbox
  • Carbonite backup
  • ESET Nod32
  • Malwarebytes Anti-Exploit
  • Windows Firewall disabled

... and more

Router:

  • Asus RT-N66U running Tomato Shibby v121 K26AC AIO-64K
    • 2.4Ghz @ 40Mhz channel width
    • 5Ghz @ 20Mhz channel width
    • WPA2

Now I've all but eliminated the router and the wireless connection as the problem. The PC is quite close to the router and inSSIDer shows a very strong connection. I'm reasonably confident that the issue is on the PC. Both SABnzbd and uTorrent are always running, but only occasionally downloading. Their activity doesn't seem to correspond to the problem. I've disabled and even uninstalled the AV to no avail.

Basically, what happens is that the latency will randomly spike way up (~1000ms) and stay that way for a while, then come back down to normal. None of my other LAN clients experience any issues whatsoever. One way to reliably trigger this is to connect to the PC via RDP with the Performance setting set to "LAN". Even after disconnecting the latency will remain high for a while. This isn't necessary to trigger the problem, though.

I'm at a bit of a loss as to how to troubleshoot this. I've updated the NIC driver. I've looked at active connections using Resource Monitor and didn't see anything out of the ordinary. Is there some other piece of software that might help? Perhaps something to look at all TCP connections to see if it's being flooded or something? Any other ideas?

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  • What latency? Latency to what? Mar 30, 2015 at 15:30
  • Latency to any endpoint, LAN or WAN.
    – jluce50
    Mar 30, 2015 at 15:35
  • BTW, your channel bandwidth settings seem backwards. In the small, crowded 2.4GHz band, it's best to use 20MHz-wide channels to leave room for Bluetooth and other users. In the large, uncrowded 5GHz band, it's fine to use 40MHz-wide channels for speed.
    – Spiff
    Mar 30, 2015 at 17:56
  • As a troubleshooting step, go into the advanced settings for your Wi-Fi driver (on your PC with the problem) and disable power save mode. Power save mode increases latency, and can introduce interop problems. Also look for anything on your PC that may be doing Wi-Fi scans ("stumblers", geolocation tools), or otherwise cause your radio to go off-channel (Wi-Fi peer-to-peer things), and disable them.
    – Spiff
    Mar 30, 2015 at 18:04
  • Regarding the channel width, crowding isn't an issue on 2.4Ghz for me. I do, however, want the maximum possible throughput since I stream high bitstream video. I have a device on the 5Ghz band that doesn't handle 40Mhz well for some reason, so I'm forced to have it at 20Mhz. There is no power save mode under the Advanced tab I don't think I have any tools of that sort. I do have Wifi Direct, but it is disabled.
    – jluce50
    Mar 30, 2015 at 18:25

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