EP016 – ServicePacks and Versioning

Defines the service-pack and application-versioning model introduced with FIX 5.0. It separates the FIX application layer from the FIX session layer, identifies the session using FIXT.1.1, and introduces ApplVerID, DefaultApplVerID, RefApplVerID and custom-version identifiers. It describes per-message, per-session and per-message-type version selection, cumulative service packs, pre-service-pack Extension Packs, use of application messages over non-FIX transports, and corresponding FIXML version identification.