What is Quality? Service? Why Integrated?
Quality encompasses data loss, induced delay or latency, consistency in delays (jitter), efficient use of network resources, …
Service means end-to-end communication between applications (e.g., audio, video, Web browsing), a protocol type (e.g., TCP, UDP), …
A single network is better --- unused capacity is available to others, one network to manage
Better to give each user/traffic what it wants
QoS mechanisms for unfairness: managing queuing behavior, shaping traffic, control admission, routing, …
Engineering the network is hard, and over-engineering it is expensive (especially for long-distance links)