Here are some notes and ramblings from the Internet2 Commons Site Coordinator On-line Workshop today. If you want to attend future sessions, sign up for the email list.
H.239 is NOT there yet. While the tool has potential, I have yet to see it work well in a conference with multiple kinds of units & MCUs. Maybe I’m old fashioned, but give me the old S-Video connection into the codec anytime. It just seems to work consistently across any kind of unit or MCU. To the receiving sites it’s just another camera input.
VC is the canary on your network. It’s always good to have a reminder that while things might work “fine” on a network, videoconferencing may not. VC shows the potential problems and issues on your network.
Get rid of hubs! I know in our elementary schools we still have some hubs in the network path of the videoconference. Something to work on upgrading as time and money allow.
Ethernet duplex mismatch between device and switch. There is a need for collaboration between videoconferencing and networking people to work to solve these types of issues. See this Cisco page and Hostingtech page. It’s best to talk to your networking people and check the duplex settings. If at all possible, stick with auto negotiate.
UDP. The majority of H323 videoconference content is UDP because if packets don’t get there in time they are discarded (vs. TCP where the packet is sent again).
An interesting thought about packet shaping tools. If the system doing the packet shaping is overloaded it can introduce jitter and packet loss because it can’t keep up. So it may not always be a quick fix tool for bandwidth and traffic problems.
Firewalls. An interesting thing about H323 and firewalls is the UDP ports. Usually the devices negotiate with each other which UDP ports to use for video and audio. So think about those calls that start, ring & ring, but never finish negotiating and you know that at least one firewall is involved in the call. The two devices probably can’t negotiate the UDP ports to use. This also explains why if you set your codec to fixed ports for UDP, then sometimes you can’t connect to other sites because their codec might be locked down to different UDP ports.
It’s interesting also that this workshop suggests that using a firewall that “snoops the H323 call set up channels and opens ports for the audio/video as needed.” With my limited experience with firewall traversal systems, I think I agree.
NAT. If you ever see a 10.* or 192.168.* you can know for sure that it’s an internal NAT address that you cannot call from outside the network. If you’re talking to people outside your network, make sure you know how to give them the external address.
Latency (the transmission delay) can be introduced with an overloaded network. There’s the “store-and-forward” delay which is the time it takes the networking devices to receive, process, and resend the packets. It varies based on the network load. Jitter is the variation in latency over time. Someone shared that anything over 50ms becomes a problem.
Packet loss. Numbers to pay attention to. 1% is noticable. 5% is intolerable. How high have you seen? Me – 80%. Pretty bad!!
As participants shared, I thought about all the different network names out there. How many videoconference networks can you name off the top of your head? CANET, MOREnet were two mentioned. Others I can think of are TETN, JANET, K12HSN, to name a few. Leave a comment if you know where those are! Pop quiz!
H323 is “network sensitive.” Ever heard that phrase? It’s an apt description of what we deal with on a regular basis.
Chuckles. They suggested that you shouldn’t make changes to the network without letting everyone know. Yes, wouldn’t it be nice if in little K12 schools we could know when someone changes something on the network!! Usually the techs are so busy that they forget videoconferencing until a problem comes up.
GDS has redundant gatekeepers with geographically dispersed gatekeepers to take over in case of a disaster. So in theory if GDS doesn’t work, it’s probably at your endpoint.
They say that if you want to be a citizen of the world you should join the GDS dialing plan. I tend to agree with this but haven’t been able to implement it successfully yet. But I really want to so that my schools can call JANET schools without going through an MCU. Did you figure out where JANET is yet?
The whole gatekeeper section of this workshop was very helpful. While we’re not really into gatekeepers so much in K12, I do think it’s one potential solution to many of the dialing problems we have.
The workshop also covered MCUs, gateways, etiquette and Internet2 Commons procedures. If you look at the procedures implemented in the Internet2 Commons, they are a great model for any K12 educational service agency.
This was a great workshop and one I recommend for anyone getting started with supporting videoconferences.