This article relates to the Cisco TelePresence MCU 4203, Cisco TelePresence MCU MSE 8420, Cisco TelePresence MCU 4505 and Cisco TelePresence MCU MSE 8510 products.
Q. Why does the bandwidth sent from my endpoint to my Codian MCU drop?
A. In H.323 calls each end controls the bandwidth sent to it. So when the bandwidth to the Codian MCU drops, it is because the MCU has requested it.
There are two main reasons the MCU reduces the bandwidth being sent to it. First, if a participant is only being shown in a small screen, or is not being shown at all in the conference, then there is no need for a high bandwidth link. The MCU will reduce the bandwidth from that endpoint in order to stop the bandwidth being wasted. That behaviour can be turned off on the Settings > Conferences page using the Video receive bit rate optimization check box.
Secondly, the MCU will reduce the bandwidth if it detects packet loss from an endpoint. If there is packet loss it is possible the link cannot support such a high bandwidth, and reducing it could reach a bandwidth which is supported. Receiving all the data from a lower bandwidth link gives a much better picture than receiving some of the data from a high bandwidth link, so this can improve the picture quality. This behavior can be turned off on the Settings > Conferences page using the Flow control on video errors check box.