The Financial Information eXchange ("FIX") Protocol is a series of messaging specifications for the electronic communication of trade-related messages.
It has been developed through the collaboration of banks, broker-dealers, exchanges, industry utilities and associations, institutional investors, and information technology providers from around the world. These market participants share a vision of a common, global language for the automated trading of financial instruments.
Nowadays, FIX is the industry-driven messaging standard that is changing the face of the global financial services sector, as firms use the protocol to transact in an electronic, transparent, cost efficient and timely manner. FIX is open and free, but it is not software. Rather, FIX is a specification around which software developers can create commercial or open-source software, as they see fit. As the market's leading trade-communications protocol, FIX is integral to many order management and trading systems. Yet, its power is unobtrusive, as users of these systems can benefit from FIX without knowing the language itself.
FIX 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 should be noted that if an "unreliable" or non-stream protocol is used, the Logon, Logout, and ResendRequest message processing is particularly susceptible to unordered delivery and/or message loss.
The protocol is defined at two levels: session and application. 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".
The FIX Protocol specifies in detail the format of messages that FIX applications will use to communicate and exchange data. FIX Message format is explained in detail in the FIX Messages topic.
FIX Sessions are bi-directional streams opened between 2 applications that send each other ordered FIX Messages. Sessions will be explained in the FIX Sessions topic.
The chapter About FIX 5.0 will explain the breaking changes in FIX 5.0 version and their influence on application design and development decisions.
The FAST protocol is a high-performance version of the FIX protocol and is an acronym for FIX Adapted for Streaming Information. Please see the About FAST link for further information about FAST.