Queueing and Framing Disciplines for a Mixture of Data Traffic Types
Alistair Fraser, S. Philip Morgan · AT&T Bell Laboratories Technical Journal · 1984
Packet-switched data networks are constructed from switching nodes interconnected by trunks. Trunk queueing delays for short messages can be reduced at the expense of long messages by having the trunk server take no more than a fixed number of bytes from each message before going on to the next message. We report analysis and simulations of two partial-service disciplines, namely Round Robin (RR) and Priority first-in first-out followed by Round Robin (PR + RR), for a mixture of traffic types. The PR + RR discipline permits short messages to experience finite mean delay at traffic levels where longer messages see infinite mean delay. Information is transmitted over the trunk in frames, where a frame may contain parts of several messages. At the far end of the trunk, the contents of a frame are not transmitted further until the end of the frame has arrived. We simulate two framing algorithms that work effectively with the PR + RR queueing discipline to achieve acceptably low frame overhead together with short delays for short messages. In addition, queueing plus framing delays for longer messages are substantially reduced, at a given overall traffic intensity if the access lines run more slowly than the trunk.