This article relates to the Cisco TelePresence MCU 4203, Cisco TelePresence MCU MSE 8420, Cisco TelePresence IP VCR 2210, Cisco TelePresence VCR MSE 8220, Cisco TelePresence ISDN GW 3241, Cisco TelePresence ISDN GW MSE 8321, Cisco TelePresence IP GW 3510, Cisco TelePresence MCU 4505, Cisco TelePresence Video Communication Server Expressway, Cisco TelePresence Server 7010 and Cisco TelePresence MCU MSE 8510 products.
Q. Why am I seeing a lot of packet loss in one direction with my TANDBERG network products and why is the audio/video quality poor in that direction?
A. If you are seeing a lot of packet loss in one direction, this could be caused by a duplex mismatch somewhere in your network.
A duplex mismatch occurs when a piece of equipment at one end of an ethernet cable has a different duplex setting from the equipment at the other end. Note: Often the duplex mode is auto-negotiated between the two pieces of equipment; however, auto-negotiation will only work if both devices are set to 'auto'. If one device is set to 'auto' and the other has any other setting, the 'auto' device will configure itself as 100/Half. The most common cause of mismatch issues is having one device set to 100/Full and the other to Auto.
If you are new to video conferencing over IP, you may have had a duplex mismatch in your network for some time: TCP traffic will be slowed down by it - and this may pass unnoticed - but UDP traffic will be lost.
There are a number of tools that can detect packet loss over a route by using a large number of pings to every device on the route. This information will help you locate the devices that have a duplex mismatch. Change the device settings so that the devices at each end of a cable have either the same speed/duplex settings or are both set to Auto.
On Codian devices this is set on the Network > Port A and Network > Port B pages. For more information, see the online help.
On the VCS this is set on the Ethernet page (System Configuration > Ethernet). We recommend that both the VCS and the ethernet switch are set to Auto, unless the switch is unable to auto-negotiate, in which case both should be set to 1000/Full.