1. LAN Cables: use high quality manufactured Category 5e or better LAN cabling, patch panels and patch cords
   1. If you are a large district or college, you may want to review the State of Wisconsin, Department of Administration, Division of Facilities Development's enterprise standards:
      • LAN/Voice Cable
      • LAN Cabling Termination using EIA/TIA 568A Color Scheme.
   2. Do NOT use home made cables, no matter how good you are at making cables.
   3. Keep cables away from electrical fields and outlets.
   4. Cable runs should be as short as possible. Don't exceed 100 meters (300 feet) on any Ethernet segment. If the segment is over 100 meters (300 feet), we recommend that you use a fiber connection between the switch and the codec.
2. Switched Hubs: use Switched Ethernet routers from the codec to the WA-K20 border router. A switch reduces the chance that packets carrying the transmission will collide with each other as they are sent and received. Hubs should be eliminated from the path.
3. Number of Switches: minimize the number of switches between the border router and your codec. Each switch adds more delay (latency), which is undesirable.
4. LAN Bandwidth: Minimum 10 Mbps, 100 Mbps is preferred on the transport path. Because some routers do not auto negotiate reliably, we recommend not using the AUTO setting, instead select 10 or 100 fixed. Codecs can also be fixed 10 or 100.
5. Duplex Settings: set duplexing to FULL on your Ethernet switch ports from the border router to the codec or any other paths the video signal will follow to other codecs on your LAN. Full Duplex is preferred to reduce jitter and latency. Continue Full Duplex from the codec to the border router and to other codecs resident on your LAN. K-20's T-1s and backbone are full duplex, minimizing the effects of latency and jitter. Codecs can also be fixed to Full Duplex.
   1. Do not select "Auto Negotiate" as this can cause jitter problems if one device keeps re-negotiating all the time. Some Cisco routers are known to do this, so make sure you have them set to FULL, not AUTO.
   2. Half Duplex should be used only when the codec will not support Full Duplex. Here's why:
      • On a half duplex circuit, the bandwidth required for a call is double your transmission speed. A calling speed of 384K requires 384K to send and 384K to receive; that is, 768k.
      • On a half duplex network, only one device may transmit at a time. If multiple devices attempt to transmit at the same time there is a collision. When this happens, both devices must back off momentarily and then attempt to retransmit. As the network becomes more congested collisions occur more frequently. This causes delay and jitter which in turn cause poor quality video.
6. Firewalls and Network Address Translation: videoconferencing and firewalls are like oil and water. At this time, they don't mix well. We recommend that you use a WA-K20 assigned IP address for your codec and connect the codec outside your firewall when possible. See Firewalls and NAT if you feel you must put your codec behind a firewall.
7. Codec Settings:
   1. Make sure that the NIC card or network paratmeters of the codec is fixed to 100 Mbps/Full Duplex.
   2. If the codec is an appliance (on a roll about monitor cart), make sure that the LAN jacks that it is plugged into are also set to 100 Mbps/Full Duplex. See Codec Recommendations for more details.
8. Bandwidth to WA-K20:
   Make sure you have ample bandwidth to handle most situations. Allow for the 384 Kbps bandwidth plus 20% overhead.
   

• Your H.323 video data should be less than 30% of the available bandwidth on your LAN and to WA-K20. Example: a full T1 to WA-K20 is 1.5Mbps. One H.323 connection at 384K + 20% overhead for call setup and signaling is 460K. One third of the T1 is 495K. So one T1 should never have more than one H.323 call across it.
• The total bandwidth, data and video, should be less than 75% of the available bandwidth. The remaining 25% is overhead used by routers and network devices that are the network.
• Check the current utilization of your WA-K20 bandwidth.

10. Technical Support:
    1. NCESD Videoconference Services:
       • Test and certify your new codec.
       • Learn more about what codecs to buy and which are supported.
       • Arrange a multipoint videoconference.
       • Help Desk phone number is 509-667-7108 or email debbyt@ncesd.org.
    2. It is very important to have your IT and Video staff communicate on a regular basis.
    3. Have on site support staff trained to operate equipment and troubleshoot problems, this is critical to success.