Remote estimation of round-trip delays in a data network

Abstract

Disclosed is a technique for data network congestion diagnosis using remote estimation of round-trip delays. A monitoring node transmits test messages between network nodes and measures the transit times between when the test messages are transmitted from, and when they return to, the monitoring node. A path delay between network nodes is determined based on the measured time delays. The techniques for determining network path delay are also utilized in conjunction with a three phase test procedure for diagnosing network congestion problems. Due to various network topologies and routing tables, certain confirmatory checks may be required to determine whether the procedures of the first or second phase test procedures are appropriate for particular path segments. Further, queuing delays may be determined by subtracting traffic independent delays from the measured transit times of the test messages, and such queuing delays may be used to determine the path delays. Such traffic independent delays may be determined during periods of low network traffic.