The Chart System: A High-performance, Fair Transport Architecture Based On Explicit-rate Signaling

摘要

TCP/IP is known to have poor performance under conditions of moderate to high packet loss (5%-20%) and end-to-end latency (20-200 ms). The CHART system, under development by HP and its partners under contract to the US Defense Advanced Research Projects Agency, is a careful re-engineering of Internet Layer 3 and Layer 4 protocols to improve TCP/IP performance in these cases. The CHART system has just completed the second phase of a three-phase, 42-month development cycle. The goal for the 42-month program was a 10x improvement in the performance of TCP/IP under conditions of loss and delay. In independent tests for DARPA at Science Applications International Corporation, the CHART System demonstrated a 20x performance improvement over TCP/IP, exceeding the goals for the program by a factor of two. Fairness to legacy TCP and UDP flows was further demonstrated in DARPA testing. We describe the CHART System as a set of five interacting services and protocol improvements which act together to make TCP/IP robust under conditions of loss and latency, and we describe and detail the test regime and performance results.