Tag Archives: firewalls

A Little VC Technical Knowledge

After the discussions that arose from my posts last week about mentoring, I thought it might be helpful to share some of the ways that I work with the tech coordinators in our districts.

A Little History
First, a little history. I’m at heart and by training a teacher, and the technology scared me at first. When we started with VC in 1999, my supervisor did all the technical stuff. I didn’t want to touch it. But over time I learned more about it, and sometimes say that I’ve learned more about networks than I ever wanted to know! Experience was my teacher. So I encourage you to try to learn what you can about how VC works on your network!

Background Knowledge

Word Wall from Jazz Workshop
Word Wall in the Jazz Workshop

I really started to learn more when we made the switch to IP videoconferencing in 2005. An early workshop that I attended in 2006 was “Understanding and Troubleshooting Videoconferencing Networks.” I thought for sure I wouldn’t get anything out of it and that it would be over my head. But surprisingly, I’d experienced enough situations in our IP calls that I learned something and actually understood it! Some basic concepts (written in my lay language!) include:

  • IP numbers that start with 10. are internal addresses and people outside can’t call them.
  • Most videoconferences are at 384K. Compare that to the amount of available bandwidth on a typical day to know if you’ll be able to sustain a “good enough” videoconference.
  • Packets are little pieces of info sent over the network. In email the packets eventually get there, get together, and give you an email. But in VC, if the packets don’t show up in time, they get thrown away. Hence, packet loss. Usually 2% packet loss or higher becomes intolerable.
  • A NAT is network address translation, and both the codec/endpoint and the firewall/router need matching settings for NAT to work. This is because the endpoint/codec needs that info to set up the packets properly.
  • An IP videoconference call is set up on port 1720. After that the two codecs negotiate which ports to use for the audio and video streaming. This is what’s going on when it rings & rings.
  • If you’re using a gatekeeper, ports 1718 and 1719 are used to find and register with the gatekeeper. More on ports here.
  • Two great resources to learn more about H323 and your network are: H323 and Firewalls from MOREnet in MO; and UKERNA/Janet Security Guide for H323 from the UK.

Working with District Tech Coordinators

  • It’s important that they understand the impact of VC on their network. See the notes above. Even if you don’t understand how it all works, it helps to know a bit of “techie language”, enough to explain what VC does. I’ve found VTC Talk a useful site to learn to talk to the technicians. It’s desirable to be able to point themĀ  in the right direction of what to do to make it work, and where to find answers.
  • It’s also important that those of us in VC realize that network technicians have legitimate concerns about the health of their network. Listen. Realize also that they are busy and usually overworked. Hear their side. Send them to third party resources (such as those above) to explain the issues in their language.
  • We try to do summer installations and upgrades if at all possible. During the school year, there are so many problems to fix, it’s hard to find time to learn new things or change network policies to make VC work. It can take 3-6 months to get VC working on your network during the school year. Better to do it in the summer.
  • Know your audience. Some tech coordinators in our districts came from the education side, and others came from business/technology. Some of them are interested and want to know a lot about how to use VC in the curriculum. Others know that the teachers want and use it, and all they want to know is what needs to be done on the network. Tailor your message accordingly!

Your Turn
What do you think? Do you use any of these strategies? Do you have any other tips? Please comment!