Patchy Patch Cables

Have you ever found that your videoconference equipment has unexplained packet loss? Do you know how to find out if you are losing packets during a videoconference? Do you know what packets are?

I’m starting to teach my building coordinators how to pay attention to these things. This is the way I explain packet loss to them: Everything on the Internet is broken into little packets to send over the wire. With email, if a packet gets lost along the way, the receiving end asks for it again and eventually you get the whole email. With videoconferencing, if a packet is lost or arrives too late, it’s thrown away because the information is real time. Late information isn’t useful. This is what causes colored blocks on the screen. The information for that block didn’t come through.

Then I show them how to look at the packet loss during a connection. Most of my schools have Polycom VSXs. So I show them how to press the yellow Help button during a call to get the call statistics. (Unless that button has been reprogrammed for another feature. Also can someone reply & share how to do this on other units?)

I tell my building coordinators also that usually they can’t do anything about it and neither can I. However it can give us useful information.

For example, if usually you get 1% of less packet loss and suddenly you’re getting 5-7%, then you should tell your techs. Something might be up with the network. They say that 2% and below is tolerable; but if you get higher than 2% you really start to notice and it can affect the educational quality of the experience. Sometimes the packet loss in a videoconference is an early warning of problems with a router or switch. In this way, VC can be the “canary in the coal mine” for network health.

In two of my buildings this fall, we had some unexplained packet loss. In theory everything else on the network should have meant that they would get a solid 0% packet loss connection. But they were still losing packets to an annoying level.

Come to find out in both situations, the patch cable (also known as the ethernet cable) from the Polycom to the jack in the wall was bad. In one situation I actually saw the cable. It was quite mangled and the cart wheels had rolled over it enough to flatten one section. We swapped out the cable, and voila! 0% packet loss like it should have been.

So, if you have unexplained packet loss, check out your patch cable! Sometimes we forget about the wear and tear on technology in schools. That cable might be due for a change.

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