Quality of service

Applications and users of IP networks have different requirements for the service they receive from those networks. A network that treats all traffic as best effort does not meet the needs of such users. Service differentiation is a mechanism to provide different service levels to different traffic types based on their requirements and importance in an enterprise network. For example, it might be critical to provide Enterprise Resource Planning (ERP) traffic better service during peak hours than that of FTP or web traffic. The overall service provided to applications or users, in terms of elements such as throughput and delay, is termed Quality of service (QoS). Network service providers that need to provide different QoS levels express their business goals in Service Level Agreements (SLAs). There are two types of service in IP networks that relate to QoS. The first is Differentiated Services, which provides QoS to broad classes of traffic or users, for example all outbound web traffic accessed by a particular subnet. The second is Integrated Services, which provides end-to-end QoS to an application, by reserving resources along a data path. For z/OS® Communications Server, Integrated Services is largely provided by the RSVP Agent, which implements the Resource ReserVation Protocol.

Workload distribution also relates to QoS, in terms of the throughput and delay characteristics of a given server in a sysplex. The ability to dynamically monitor server performance and affect sysplex workload distribution is an important part of the overall QoS of a sysplex. Also important is the ability to limit the set of target systems considered for sysplex routing based on network selection criteria, such as source subnet.