Fixing VoIP on Comcast

Due to recent business troubles with Vonage, we thought it prudent to change phone providers. On the recommendation of Jeremy, we made the switch to Packet8. Unlike Vonage, Packet8 doesn’t offer VoIP devices that include a network hub or wireless capabilities. No problem, I pulled out my reliable Linksys WRT54G router and updated it to the latest firmware.

The new Packet8 device is a bit of an unknown to me, so I thought it best to place it behind my WRT54G rather than expose it to the wilds of the internet. Unfortunately, I found that the call quality was not very good when I was uploading files to my server. I tried adjusting the QoS settings on my router but with no luck…until today.

My theory is related to my previous post on how Comcast is bursting bandwidth, which means that your upload and download speed vary. (Isn’t it convenient for them that the speeds are really fast for duration all of the typical speed tests available on the internet?) Apparently, my router isn’t very good at auto-calculating the upstream bandwidth when it varies. This probably won’t apply to you if you have a static upload speed (like most DSL lines.)

Here’s what I did to fix the problem:

  1. Update to the latest firmware
  2. Find your long-term upload speed – All of those tests I found on the internet don’t run long enough to find this number. I had to copy a large (~20MB) file up to my server and see what the upload speed was for the last 5-10 MB.
  3. Edit your QoS settings – Enter in your upstream bandwidth and give your device “High” priority. I’ve included a screenshot of mine here:
    QoS Settings

I estimated my upload bandwidth to be ~40KB/s which is 320kbs (remember 8 bits in a byte.) I also have my Packet8 device plugged into Port 3 on my router.

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