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Airman
Premium
join:2001-12-15
Bay Area

[Speed] File transfers and speed slow-downs

Hi,

For the past three days, I've noticed that when I use a file transfer service such as YouSendIt or LargeFileASAP, my whole Internet connection slows down.

For instance, when a transfer is in progress, the upload/download speeds are dramatically reduced and the latency sky-rockets. According to the Comcast speed test results, my upload speed is 0.2 Mbps, download is 0.43 Mbps and ping is 524 ms.

What's interesting is that the upload speed of the actual transfer averages about 2 Mbps which is where it's supposed to be. I never noticed this until 3 days ago. All computers connected to the network are affected, not just the one doing the transfer.

As soon as the transfer is completed, the speeds and latency return to normal (~21 ms ping instead of the 500 ms above).

I looked at my data usage and it's currently at 230GB out of 250GB and I'm wondering if this could be the issue.


graysonf
Premium,MVM
join:1999-07-16
Fort Lauderdale, FL
kudos:2
Reviews:
·Comcast
This is typical TCP behavior. When the link is saturated in one direction, performance in the opposite direction is reduced, often to the point of being unusable.

If your gear has the ability to prioritize TCP ACKs, the problem can be reduced or eliminated.


pclover

join:2008-08-02
Santa Cruz, CA
reply to Airman
You could also implement QOS or throttle the connection.

Airman
Premium
join:2001-12-15
Bay Area
reply to Airman
Thank you for the replies. I didn't realize this was typical behavior, especially since it didn't seem to bother me before.

How would I go about prioritizing TCP ACKs, QOS or throttle the connection?

Modem: Motorola Surboard 6121
Router: Linksys Cisco EA3500
Mac OSX 10.7.4

Thanks for the help!