IDENTIFYING A BOTTLENECK IN A DATA TRANSFER

A system, methods and apparatus are provided for determining the locus of a bottleneck in a data transfer between a data receiver (e.g., a client device) and a data sender (e.g., a computer server). The locus may be one of a receiver realm encompassing the data receiver (especially a receiver application that consumes the data), a sender realm encompassing the data sender (especially a sender application that produces the data), and a communication link realm that encompasses the communication link(s) over which the data are conveyed (and possibly network-layer protocols and lower that use the communication link(s)). A monitor entity may employ a state-machine model to represent and track progress of a given data transfer between states, using information collected from the data receiver and data sender to identify state transitions. Given a time at which a transfer was delayed or halted, the monitor outputs the locus of the problem.