EET: And though packets declared victory over circuits, there seems to be renewed interest in giving IP as many circuit-like characteristics as possible.
Jacobson: I hope that the circuit obsession is transitional. Anytime you try to apply scheduling to a problem to give latency strict bounds, the advantages are not worth the cost of implementation. Strict guarantees gain you at best a 100-microsecond gain in networks, where the intrinsic jitter in the thermal conditions of the planet is 300 microseconds.
EET: So all the late-1990s studies of QoS involved people speaking different languages, coming from different perspectives.
Jacobson: QoS has been an area of immense frustration for me. We’re suffering death by 10,000 theses. It seems to be a requirement of thesis committees that a proposal must be sufficiently complicated for a paper to be accepted. Look at Infocom, look at IEEE papers; it seems as though there are 100,000 complex solutions to simple priority-based QoS problems.
The result is vastly increased noise in the signal-to-noise ratio. The working assumption is that QoS must be hard, or there wouldn’t be 50,000 papers on the subject. The telephony journals assume this as a starting point, while the IP folks feel that progress in QoS comes from going out and doing something.