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Probing TCP Implementations

Douglas E. Comer and John C. Lin
Department of Computer Sciences
Purdue University
West Lafayette, Indiana 47907


In this paper, we demonstrate a technique called active probing used to study TCP implementations. Active probing treats a TCP implementation as a black box, and uses a set of procedures to probe the black box. By studying the way TCP responds to the probes, one can deduce several characteristics of the implementation. The technique is particularly useful if TCP source code is unavailable.

To demonstrate the technique, the paper shows example probe procedures that examine three aspects of TCP. The results are informative: they reveal implementation flaws, protocol violations, and the details of design decisions in five vendor-supported TCP implementations. The results of our experiment suggest that active probing can be used to test TCP implementations.

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