Currently, FIX 5.0 is the latest version of FIX protocol specification that intoruced several breacking changes, comparing to FIX 4.X versions. FixAntenna.Net supports FIX 5.0 and all changes included into FIX 5.0 SP1, FIX 5.0 SP2 will be supported soon.
With the release of FIX 5.0 in October 2006, the FPL Global Technical Committee (GTC) introduced a new framework, the transport independence (TI) framework, which separated the FIX Session Protocol from the FIX Application Protocol. Under the TI framework the application protocol messages can be sent over any suitable session transport technology (e.g. WS-RX, MQ, publish/subscribe message bus), where the FIX Session Protocol is one of the available options as a session transport for FIX application messages. From this release forward the FIX Application layer and the FIX Session layer will have their own versioning moniker. The FIX Application layer will retain the traditional version moniker of "FIX x.y" while the FIX Session layer will utilize a new version moniker of "FIXT x.y" (note that the version numbers will be independent of each other). With the advent of Application Versioning and Transport Independence, the FIX Session and Application layers have been decoupled and are now independent.
The transport independence (TI) framework separates the previously coupled FIX Session layer from the FIX Application layer. Under this framework the FIX Application Protocol can use any transport technology in addition to the FIX Session Protocol. The diagram below illustrates how various transport mechanisms, including the FIX Session layer, can be used to carry the full suite of FIX Application versions.
To support this framework a key new field has been added called ApplVerID (application version ID, tag 1128). Depending on the use case ApplVerID may be optional or required. Additionally, the FIX field BeginString will no longer identify the FIX application version, but identifies the FIX Session Protocol version.
Application Versioning allows extensions to the current base application version to be applied using a formal release process. Extension Packs represent the individual gap analysis proposals submitted to the GTC for review and approval. Extension Packs are grouped into Service Packs and are applied to the base application version, usually the most current FIX application version. A new application version is formed when a new Service Pack is applied to a base version. In the diagram below, FIX 4.4 has been extended via Service Pack 0, forming a new application version called FIX 5.0. As new Extension Packs are approved they will be grouped into Service Pack 1 which is then released to form the next application version identified as FIX 5.0 SP1. These application versions are expressed using the new tag ApplVerID.