Tutorial introduction to layered modeling of software performance

We consider layered systems (software systems, and other kinds of systems too) that are made up of servers (and other resources which we will model as servers); the generic term we will use for these entities is “task”. A server is either a pure server, which executes operations on command (for instance a processor), or a more complex logical bundle of operations, which include the use of lower layer services. Such a bundle of operations may be implemented as a software server.