CONGESTION CONTROL FOR HIGH SPEED PACKET NETWORKS

摘要

Congestion in a high speed connection oriented packet is avoided by an in-call negotiation scheme for reserving bandwidth for real time calls and reserving buffer capacity for bursty calls. For a real time call, a centralized call controller in each switch in the network determines which of its outgoing trunkshas available the peak bandwidth needed to accommodate the call. If so, the callrouting is set up so that the call is directed through that trunk. Calls involving bursty data cause the call controllers in the switches to set up the routing of the call and allocate some minimum bandwidth on selected output trunks. A special packet which contains an indication of a requested buffer capacity is produced by the call transmitter and sent to all the switches along the route. At each switch along the route, a check is made to see if there is sufficient unallocated buffer capacity on associated trunks equal to the requested capacity. If so, that amount of buffer capacity is allocated to the call and the special packet is passed unchanged to the next switch. If that amount of buffer capacity is not available, then the switch may refuse the call by placing an indication of such refusal in the special packet and which is passed to the next switch. When the special packet has reached the intended destination of the call, an acknowledgment packet is produced and sent back to the origin. If the request for buffer capacity has been completely denied by one of the switches or if a smaller amount of requested buffer capacity has been written into the special packet by one of the switches,the acknowledgment packet deallocates the excess previously allocated buffer capacity on its trip back to the origin and notifies the transmitter of the buffer capacity which has been allocated along the route of the call, if any. If the call has not been completely denied, the data making up the call is then sent along the prescribed route at a rate which will not cause an overflow of the buffers allocated to the call.