Universal Timestamp-Scheduling for real-time networks

Consider a network of computers interconnected by point-to-point communication channels. Before generating network packets, each source in the network reserves a fraction of the packet rate of each output channel in the path to its destination. We define a family of scheduling protocols, called Universal Timestamp-Scheduling, to forward packets in this network such that all members of the protocol family provide the same upper bound on packet delay as Virtual Clock scheduling. That is, the packets from a source will exit the output channel of a computer no later than the time they would exit an output channel whose rate equals the source's reserved rate and whose input is exclusively the packets from this source. The protocol family is called universal because it encompasses a wide variety of protocols. To show this, we prove that many scheduling protocols in the literature are members of the protocol family, and thus provide the above guarantee. In addition, we show that the protocols in the literature have only considered one side of the spectrum of possible scheduling protocols, and that there is another side of the spectrum that deserves attention and remains to be investigated.