Real-Time Communication in an Internetwork

Can end-to-end communication performance be guaranteed by a packet-switching internetwork? This paper addresses the question by examining the feasibility of extending to an internetwork the Tenet approach to real-time communication service design. The conditions to be satisfied by an internetwork so that the approach can be extended to it are investigated. These include conditions for the scheduling discipline to be used in the nodes of the internetwork. The original Tenet approach to real-time communication applies to a network consisting of hosts, homogeneous nodes (or switches), and physical links connecting nodes and hosts in an arbitrary topology. The nodes are store-and-forward, and are scheduled by a multi-class version of the Earliest Due Date deadline-based policy. The discussion presented in this paper results in extendibility conditions that are quite broad; hence, the Tenet approach may be used to establish and run real-time channels in a vast class of internetworks. A case study is also discussed, involving a simple network, whose nodes are scheduled by FCFS-based disciplines, and the connection of such a network to an internetwork with deadline-based and hierarchical round robin scheduling. hhhhhhhhhhhhhhhhhh This research was supported by the National Science Foundation and the Defense Advanced Research Projects Agency (DARPA) under Cooperative Agreement NCR-8919038 with the Corporation for National Research Initiatives, by AT&T Bell Laboratories, Hitachi, Ltd., Hitachi America, Ltd., Pacific Bell, the University of California under a MICRO grant, and the International Computer Science Institute. The views and conclusions contained in this document are those of the author, and should not be interpreted as representing official policies, either expressed or implied, of the U.S. Government or any of the sponsoring organizations.