The efforts to transmit video traffic by ABR service in ATM environment have been made recent years. In the efforts to transmit the interactive real-time video traffic by ABR, we should consider the characteristics of video traffic which are different from data traffic and not considered in the existing congestion control schemes.
First, the interactive real-time video traffic is very sensitive to delay. So we should observe end-to-end time delay of video traffic. Over delay may be dominantly caused by congestion in the switch queues. Existing ABR congestion control algorithms are developed for the non-real time data traffic which is robust to delay and suitable for avoiding overflow. So we are required to design a new congestion control scheme which is apt for avoiding over-delay.
In existing congestion control schemes, a switch detects only its own congestion status. Even if overflow may not happen in each switch queue, over-delay might happen by the sum of the queuing delay of these switches in existing congestion control schemes. So I suggest a method to detect the congestion status in a virtual connection and I suggest a scheme to control congestion using this status information, in order to avoid not only overflow but also over delay.
Second, the interactive real-time video traffic source is assumed to declare its demand, which is the amount of bits which should be sent at given time, to network. If network can't afford to accept the source demand, the source should diminish its sending rate to the allowed rate by network. In this case, the larger source demand is, the more quality degradation happens. As a result, quality fluctuation might be. So, I suggest a method to diminish quality fluctuation by the congestion control scheme in ABR switch.