1. A method of analyzing a network data stream comprising: capturing frames from a network data stream; parsing said captured frames using a protocol parser having a data structure, stored on a computer-readable medium, that includes a data type that identifies the protocol to generate parsed frames, wherein the protocol parser is created by interpreting a script that describes the format of the protocol and that is written in a language describing network protocols; organizing said parsed frames into conversations; and substituting a data structure size in said protocol parser for a selected data structure.