Pseudo-isochronous Cell Forwarding

Abstract This paper shows how to design a packet switched network, for real-time traffic, such that under full network load: (i) the end-to-end delay bound of a low-rate voice connection is minimized, (ii) the bound on the delay uncertainty or jitter is a fixed network parameter – independent of the network size and the connection rate, and (iii) the required buffer sizes (inside the network) to ensure congestion-free routing is minimized. In addition, this design can be generalized to accommodate either variable bit rate (VBR) traffic with statistical multiplexing or the integration of available bit rate (ABR) traffic 7 , 12 . The isochronous timing information (can be provided by the global positioning system (GPS) [1] ) is used for pacing the packet/cell forwarding inside the network. This means that a cell is forwarded from one switch to another not at a specific time but within a time frame of a relatively long duration as compared with the cell transmission time. This time frame is an independent network parameter, which determines the delay and jitter bounds inside the network. A study of the blocking probability of this approach is presented. (Blocking is defined as the impossibility of allocating bandwidth for a new connection while capacity is still available, but not in the proper time frames.) The study includes both analytical and simulation results, which demonstrate an important trade-off between the blocking probability and the end-to-end delay bound.