Requirements of network applications and services 27 Qualitative requirements Qualitative parameters capture the characteristics of the network overall rather than the network systems themselves, as they include clients, servers, switches, and other network systems as well as links. Thus, they are considered as network characteristics overall. Characteristic qualitative parameters include correct oper- ation, work conservation, in-order packet delivery, graceful degradation, etc. Cor- rect operation implies that the network behaves as expected and as specified by the protocol of the application/service it executes; furthermore, it implies that the network can handle any type of valid traffic data. The network needs to be work conserving, avoiding loss of data or augmentation of work in the network. In terms of human users, as well as applications, data packets may need to be delivered to the receiver in order (i.e., without reordering the packet sequence sent by the sender); this property is a critical characteristic of the vast majority of applications and services. Finally, graceful degradation is an important requirement that leads to systems and users perceiving gradual degradation of net- work performance under load. That is, the network exhibits a gradual "slow down," as traffic increases or system components fail, but avoids a collapse of services and systems; graceful degradation is an important characteristic to ensure