CHAPTER Requirements of network systems 3 INTRODUCTION Network systems are embedded, special-purpose computational systems that imple- ment one or more protocol stacks. The set of network systems in a network con- figuration constitutes the infrastructure over which end systems communicate to implement distributed applications. Thus, network systems need to meet the require- ments set by these applications. Similarly, network systems may need to meet requirements set forth by network operators. Due to the diverse needs of emerging network applications and services and operational concerns, requirements for network systems span a range of issues and parameters from performance to cost