The Schedulability of Deadline - Ordered ServiceDisciplinesNorival

| In a deadline-ordered service discipline, packets are assigned transmission deadlines and are transmitted in increasing order of deadlines. Diierent deadline-ordered service disciplines are distinguished by how they deene deadlines. One of the more diicult analytical problems one faces when designing a new deadline-ordered service discipline is to prove that one can bound the end of transmission times of packets relative to their assigned deadlines, which we call schedulability. We show that, no matter how one deenes deadlines, there is a simple schedulability condition for deadline-ordered service disciplines. This schedu-lability condition is necessary and suucient for preemptive deadline-ordered service disciplines and, for a server that allows the presence of non real-time packets (i.e., packets with no deadlines), it is also necessary and suucient for non-preemptive deadline-ordered service disciplines. We also address the schedulability problem of arbitrary scheduling policies and show the optimality of deadline-ordered scheduling. To show how our results simplify schedulability determination, we use them to prove the known schedula-bility conditions of VirtualClock, PGPS, Stop-and-Go, and Delay-EDD, and to prove the necessary schedulability condition of VirtualClock.