Abstract: An Open SIP Protocol Stack provides a variety of functions within a SIP-based telecommunications network. A set of cooperating layers including a transport layer, a transaction layer and a transaction user core layer. Various processes in these layers index into an associated configuration database designed in accordance with the present invention. The configuration database includes plurality of “mini-stacks.” When a particular transaction is being processed by one of the layers of the Open SIP Protocol Stack, PPL state machines that are to be utilized for that process are “loaded” with the appropriate information from the mini-stack for that attribute. Techniques for transaction processing and editing state machines are also provided by the Open SIP Protocol Stack of the present invention. The Open SIP Protocol Stack may be deployed in a SIP/PSTN gateway, a SIP Application Server, a SIP Media Server, a SIP Redirect Server and a SIP Registrar.