Service Differentiation: Congestion Pricing, Brokers and Bandwidth Futures
Peter B. Key · 1999
In most Networks or Systems, users compete for a set of limited resources. Resources might be point-to-point bandwidth, buffer space, memory, CPU cycles etc. and users can be humans, applications or processes. Connection-oriented Telecoms services use either reservation, where resources are booked in advanced or Admission Control — think of telephony or ATM for example. Packet-based services and Operating Systems rely mainly on either priority schemes, for instance using simple priority queues, or flow-control feedback mechanisms such as TCP. The current Internet uses flow-control with an admit-all policy that relies on secondary measures, such as users’ willingness to tolerate current service, to throttle excess load. Within the IETF, IntServ is attempting to define connection-oriented admission control schemes whilst DiffServ is based on connectionless ideas, attempting to use priorities and complex queuing disciplines to provide QoS classes. But if we step outside the Computer Science or Telecommunication mindset, we see the same problem occurring in other areas, but solved using resource pricing as a fundamental ingredient. For example, think of resources as airline seats, units of (electrical) power or economic wealth. Prices or taxes are used to control the load, or to maximise the return by offering differential services at different prices — think for instance of power companies who use price incentives and penalties, or airlines. We claim not only that it is impossible to separate service differentiation from pricing, but also that some use of resource pricing is the only sensible way to proceed. The first point is clear: if there are two qualities which both cost the same, any rational person will chose the higher quality! As an example, most current DiffServ proposals are interesting but fundamentally flawed, caused by attempting to define technologies independently of economics or implementation. They attempt to define local priority schemes and scheduling policies, whereas an application/user is interested in