FIX Session Protocol was written to be independent of any specific communications protocol (X.25, asynch, TCP/IP, etc.) or physical medium (copper, fiber, satellite, etc.) chosen for electronic data delivery. It offers a reliable stream where a message is delivered once and in order. Up until October 2006, the FIX Session Protocol was coupled with the FIX Application Protocol to provide a reliable transport mechanism for the FIX application messages that did not really exist at the inception of FIX in 1994.

The session level is concerned with the delivery of data while the application level defines business-related data content. This section focuses on the delivery of data using the FIX Session Protocol. For details on the FIX Application Protocol please refer to the appropriate version of the FIX Protocol Specification documentation.

In October 2006, FPL's Global Technical Committee introduced a new framework which separated the FIX Session Protocol from the FIX Application Protocol. This allowed the application protocol messages to use any suitable session transport technology, where the FIX Session Protocol became one of the available options as a session transport for FIX application messages. With this new framework, the GTC has introduced a new moniker associated with the FIX Session Protocol. Going forward the moniker to identifier the session protocol and the version is FIXT.x.y, with the first version being FIXT 1.1.