Troubleshooting Internet Quality Of Service And VOIP Call Quality

Last week I suddenly started experiencing poor outgoing sound quality on my Vonage phone. The incoming sound was fine for me, but people on the other end could barely make out what I was saying. Evidently it sounded something like a bad cell phone call, where every few words would drop out, or several seconds of sound was lost.

Other internet service seemed OK, maybe a bit sporadic, but I’m not sure I would have noticed a problem except for the complaints about my phone service. I checked my internet speed with a couple of those online “speed test” web sites, and the download speed was very consistent, while the upload speed was generally consistent, but occasionally much slower. Based on this, I assumed that there was a problem with my Vonage box or the service itself.

So I contacted their technical support and gave them my account information, and pretty much immediately the support engineer said something like “You’ve got big-time problems with your Internet service”. Apparently they can call up your device and query it for data, and he reported that I was suffering from 1) High latency (time to respond), 2) Jitter (high variability in the latency), and 3) Dropped Packets.

I noted that I had done a “speed test” and everything seemed fine, and he responded that that was a very common scenario. To demonstrate, he had me dust off the ol’ Ping Test, using a couple of additional command-line switches to perform a poor man’s connection quality test. The command-line syntax was:

ping -t -l 600 8.8.8.8

which will continuously ping a Google DNS resolver (or whatever IP address or hostname you supply) with 600 bytes of data.

The test basically involved just letting it sit and run for awhile and observing the Ping statistics. You can enter Ctrl+Break to get the intermediate statistics while the test is running, or press Ctrl+C to abort the test and see the final results.

When everything is working correctly, you should see consistent response times and zero (or very close to zero) packet loss, as shown below:

Sample ping data

When I was experiencing my problem, however, I was seeing consistent 10% or higher packet loss, wildly varying response times (40 ms to 3000 ms or higher), and in general very graphic evidence of what the Vonage engineer was seeing. He said that anything over about 1% packet loss begins to result in poor call quality for them, also latency and jitter affect them, but I don’t recall specific numbers he cited for those. This was enough to convince me that the problem existed with Comcast rather than Vonage.

One cable modem plus one outdoors cable drop, as well as an elevation of my ticket to the “network team” later, that was proven to be the case. As it turns out, another Comcast customer around one mile away was experiencing “irregularities” and had to be physically disconnected from the network. Once that was done, the periodic blasts of data they were emitting stopped and everything returned to normal.

Comcast’s phone technical support was unable to connect the dots between this known problem, which had been occurring for two days, and my Quality of Service issues. They reported that because my modem signal strength was OK, the problem HAD to be inside my house. Despite the fact that I was giving them explicit information about the symptoms I was seeing, they were unable or unwilling to investigate the issue from a Quality of Service perspective.

Oh well, I’m sure their service and support will get better once Net Neutrality is destroyed and they can FINALLY make a little money from their monopoly.