Indexing the archive…
Your Universe of Digital Possibilities
Sixteen senders share one wire and none of them is told its speed. Each obeys one line — halve on a loss, add one on an ack — and between them they find the capacity and split it fairly. Swap the rule and watch fairness fail; switch congestion control off and watch 1986 happen again.
A sender keeps W packets in flight and grows W by one packet each round trip until the network drops one, then halves it. Chiu & Jain proved it the one linear rule that converges to a share both efficient and fair; the sawtooth is what it looks like.
One number for how evenly n users share: 1 when all get the same, 1/n when one gets everything, and k/n when k share equally and the rest starve. It ignores how much there is — utilisation is a separate count.
Raise every flow’s rate together; freeze a flow when its demand is met and share what is left among the rest. No flow can gain without taking from one that has less. It needs every demand and the capacity in one place — an oracle, not a protocol.
A long-lived AIMD flow that loses a fraction p of its packets settles to this throughput: the window’s sawtooth between W/2 and W carries 1/p packets per cycle. Longer round trips and more loss both cost, whatever the wire’s speed.
The Packet kept a network connected with no centre; The Window keeps it usable. Every sender clocks itself by its own acks and reads one signal — a lost packet — and the one rule that converges (Chiu & Jain) turns sixteen strangers into a fair share of a wire none of them can see. It is the engineered twin of The Jam: there drivers who each keep a gap make a stop-and-go wave; here senders who each keep a window make a sawtooth — and Kelly (1998) showed the sawtooth is quietly solving an optimisation no one wrote down.