IPv6 Essentials

Chapter 6. Quality of Service in IPv6

The basic Internet design handles traffic in a manner close to George Orwell’s Animal Farm paradigm in which all animals are alike. Like the pigs in Orwell’s gloomy vision, only a very few packet types, under special circumstances, are treated differently—in most cases only by end systems, not by intermediate routers during transport. This flat paradigm was well suited for uniform, best-effort services as provided by the original Internet. Today’s applications are more differentiated and require different classes of service for real- or near-time traffic, e.g., for multimedia data that needs to be captured, transmitted, and played back with sufficient, homogeneous, consistent quality regarding throughput, delay, or jitter. As the Internet grows into the consumer market, expectation levels are high with respect to these services because users are already experiencing such real-time services from telephony and cable television services.

Changing the Internet to handle real-time as well as traditional traffic requires changes at the very root of the Internet: the IP packet design and the routing and forwarding functions. Routes in IP are determined by the IP destination address and the state of routing tables in each router on the path to the destination. Thus, all IP packets follow the same route until the route changes due to congestion, topology updates, etc.; thus, there is no implicit route per service possible. An attempt in IPv4 to classify ...