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Without a program doing uploads, my 64-bit Windows 7 laptop does great - 40 ms ping time, 5 MB download rate.

If anything starts uploading (Dropbox, for instance), ping times suddenly increase over 2000 ms! Download rate, once a connection is eventually established, doesn't seem to be too affected.

I turned off Windows Firewall, no change. Why is this problem occurring? Is there anything I can do to prevent major latency increases while I upload files?

Thanks!

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    Almost all ISPs relatively low transfer upload rates. If you saturate your link then your performance is going to suffer. There is nothing to trouble shoot. You have just filled the tubes.
    – Zoredache
    Jan 13, 2014 at 21:17
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    Is this happening over WiFi? Have you tried to upload files on a wired connection to see if there is an improvement?
    – root
    Jan 13, 2014 at 21:19
  • @Zoredache Dropbox has QoS and will not fill his 'tube'.
    – Rik
    Jan 13, 2014 at 21:21
  • @Zoredache I can understand it slowing the network, but I don't really see that. I see a 50x increase in latency.
    – eplictical
    Jan 14, 2014 at 0:41

2 Answers 2

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This sounds like the symptoms of Bufferbloat.

Basically, what happens is that somewhere on your network link, there is a large buffer which is holding your outgoing packets. When a ping packet is sent out, it ends up in this buffer and has to wait a long time before all the packets in front of it can be sent first. The actual network speed is not affected by this, meaning that the rate of packets going through the buffer is the same as normal.

Imagine this like a thin pipe with a fat bulge in the middle. As small amounts of water flow through, no effect is noticed. Only when a large amount of water is flowing, will the bulge fill with water. The rate of water going in and coming out is the same, but water spends more time inside the pipe than normal.

The cure for this is to find out where the problem lies, and reduce the size of this buffer to limit the amount of packets that slow down the ping traffic. This may be easier said than done. If the problem is in your router, then you could try using CeroWRT and adjust the buffer sizes. If the problem is in your ISP, you can adjust your router to send data slightly slower than your available bandwidth, which prevents the buffer from ever being filled.

More advice can be found on this question: How to mitigate BufferBloat on an ADSL connection?

Check your connection with The ICSI Netalyzr (Java required). It will let you know what is going on with your network connection.

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  • Awesome utility! So my buffer depth pretty much matches my bad ping times. Where do I go from here? I specifically bought a DD-WRT router. Here's what the util says: "We estimate your uplink as having 2100 ms of buffering. This is quite high, and you may experience substantial disruption to your network performance when performing interactive tasks such as web-surfing while simultaneously conducting large uploads. With such a buffer, real-time applications such as games or audio chat can work quite poorly when conducting large uploads at the same time."
    – eplictical
    Jan 14, 2014 at 0:54
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This should be expected, since you're using the network adaptor to upload files. Your system's network response time will be delayed, especially if you're uploading.

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    I disagree. I'm currently uploading 900Mb to dropbox while on the background my torrents are on 3MBps download and 0,5MBps upload and still i get around 50ms with ping google.com. I agree there might be some difference but a ping of 2000ms is not due to this traffic alone.
    – Rik
    Jan 13, 2014 at 21:19
  • Disagree all you want, but there's nothing 'shocking' about this issue.
    – MDT Guy
    Jan 13, 2014 at 21:35
  • If you upload a file... do you see pings of 2000ms? (There was no bandwidth specified... so... with any file you upload you see that kind of degradation in your network traffic. nice)
    – Rik
    Jan 13, 2014 at 21:42
  • @MDT Guy It's 50x increase in ping time. Something different is going on. It's not limited to Dropbox, any kind of upload from any program is causing this.
    – eplictical
    Jan 14, 2014 at 0:42

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