Congestion Control Thanks to Kai Shen ’ s Networking Course at the University of Rochester.

Two Senders, One Router, Two Receivers C (or capacity) is maximum transmission rate that router can sustain. Packets Backup In Network Host C Host D

Assume both HostA and HostB send packets at the same rate. As send rate aproaches half the router ’ s capacity, the receive rate is throttled by the router. The total receive rate can never exceed “ C ”, so the receive rate for HostC or HostD can never exceed “ C/2 ” The residence time (Service Time plus Wait Time) can be used to compute the delay caused by the router: Residence Time = Service Time / (1 – Utilization) As send rate approaches C/2, the router ’ s utilization approaches 100%. This creates the exponential rise in the curve above.

Data for Exponential Curve

Host D Host C Buffer Overflow In Network

ATN ABR Network-Assisted Congestion Control

TCP Congestion Control Example

TCP Congestion Control Example

TCP Efficiency: Large Congestion Window

TCP Efficiency: Small Congestion Window