What is FIXP?

FIX Performance Session Layer (FIXP) is a lightweight protocol that describes how to establish and maintain a communication session between two endpoints. Its main goal is to provide a reliable and highly efficient exchange of financial messages over a variety of transports.

FIXP is developed by the High-Performance Working Group of the FIX Trading Community.


The main features of FIXP include
  • Low overhead session layer
  • No restriction on the application layer (no session-level fields are required in application messages)
  • Encoding independent, message binary wire format (for example, SBE, Google Protocol Buffer) is agreed between counterparties
  • Transport independent (both stream and datagram protocols are supported)
  • Negotiable message delivery guarantees

FIXP does not specify security features, counter-parties agree on user authentication techniques.

A message framing protocol (for example, “Simple Open Framing Header”) may be used to delimit messages by agreement between counter-parties.

FIXP technical standard features include

Session Identification

Each FIXP session must be identified by a unique Session ID encoded as a UUID version 4 (RFC 4122) assigned by the client (for example, f81d4fae-7dec-11d0-a765-00a0c91e6bf6).

A session identifier must be unique for all time.

Message Sequencing

Sequence numbering is used for ordered delivery and message recovery. Only application messages are sequenced. A session-level message is used to start a sequenced flow of application messages.

Session Lifetime

A FIXP session is established between counter-parties and lasts until message flows between them are complete.

Timing for session start and end are agreed between counter-party.

A logical FIXP session is identified by a Session ID and can span over several sequential transport connections. When an existing session is re-established, its original Session ID is used, and messages that were lost during the disconnect may be recovered.

Message Flow Types

A message flow is a stream of application messages in one direction.

FIXP supports configurable delivery guarantees for each flow:

  • Recoverable: exactly-once message delivery. If message gaps are detected, then missed messages may be recovered by retransmission.
  • Idempotent: at-most-once delivery. If message gaps are detected, the sender is notified, but recovery is under control of the application.
  • Unsequenced: no delivery guarantees (best-effort).
  • None: one-way flow of messages. All application messages should be sent in one direction of the session.

A bi-directional session may have asymmetrical message flows (e.g., the exchange flow could be Recoverable, and the client flow could be Idempotent).

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