I’ve been experiencing some network issues for the past few weeks. The upload for my Comcast cable internet connection would turn unresponsive for a short period of time, ranging from 2-10 seconds, every few minutes or so. This turned from an annoyance in to a huge problem after a week or so. I use Skype as my primary home phone service, using the Netgear SPH200D. During the upload interruption every few minutes or so I can hear the caller’s voice perfectly fine but they can’t hear me for that 2-10 seconds, which is no doubt frustrating on both ends. It also meant that firefox would essentially freeze for the period of time my upload doesn’t work, if I try to access a site when my upload is down. It is especially frustrating in Ubuntu since it grays out the entire firefox window till my upload is restored, since it thinks firefox has crashed.
I initially thought it was an issue with my ClarkConnect(Red Hat based) linux gateway that my network access to internet is routed through since it was experiencing some high loads due to squid trying cache too much resources. The server load returned to normal after disabling squid but the problem did not improve. I also suspected it was the network card since I popped in a new intel gigabit card around that time but was able to rule out the server completely and connecting my computer directly to the modem. Ping Plotter still showed constant interruptions where pings to google.com was completely unresponsive(red bars).
I read on the Vonage forum about someone who was having a similar problem and after 4-5 visits from Comcast techs, it turns out there was a problem with a network cable on his street and was fixed after Comcast replaced the cable. It actually turns out that this happens pretty often; the thread regarding this issue is a hundred pages long. But I didn’t have the time to put up with the required 4-5 visits from Comcast before they can fix the issue and gave up for the time being.
I noticed that the coax cable to the modem was off a 1-to-3 splitter(1 for internet and the other 2 for TVs) and decided to bypass the splitter and plug the coax straight in to the modem. I expected it to alleviate the problem since the signal will no doubt improve but to my surprise, the problem was for the most part fixed. I was no longer receiving ping reports littered with red bars, but the ping plotter graph was still pretty jumpy with a occasionally upload downtime of a second or two which should not be very disruptive
To my surprise I found another splitter(1-to-2) hidden behind some boxes piled on some shelves today and removed that from the path to the modem also and the situation further improved with the ping times stabilizing a bit more. The screen shot above shows the before and after of removing the 1-2 splitter with the big red bar representing the downtime from having to remove the splitter. With both splitters, all of the spikes in ping time would have been red bars.
However, the ping is still not as stable as I would like it to be and Ping Plotter is still showing some packet loss so I may still need to call Comcast to replace the aged coax cable running in to my apartment. I also recall a similar problem with my neighbor’s internet connection that I helped call in. The tech spent an hour making sure all the coax cables were working correctly and the culprit ended up being a aged cable filter installed in a metal box a hundred feet away. There has also been reports of bad modems, although removing splitters will almost always help with your cable connection.