Overview
ISO 20022-6:2013 - "Financial services - Universal financial industry message scheme - Part 6: Message transport characteristics" defines the transport-level characteristics required to support ISO 20022 business transactions and message definitions. It specifies the MessageTransportSystem behaviour and the MessageTransportMode concept that assigns values for the MessageTransportCharacteristics. ISO 20022-6 focuses on business‑level interoperability (Layer 8/9 in the ISO 20022 layering model) and deliberately does not define wire‑level or protocol‑specific formats.
Key topics and technical requirements
- Layered protocol model: distinguishes the Business Layer (MessageInstances, MessageChoreography, MessageDefinition) from the MessageTransport Layer (TransportMessages). The Messaging Application Layer (examples: AMQP, FTP, HTTP/SOAP, WebsphereMQ) sits beneath.
- MessageInstance vs TransportMessage:
- MessageInstance contains business payload and must be independent of transport mechanics and addresses.
- TransportMessage carries the MessageInstance and may include transport-specific headers/envelopes (not registered in the repository).
- MessageTransportCharacteristics:
- Defined in the ISO 20022 metamodel; values are a closed set and typically mutually exclusive.
- Each BusinessTransaction is associated with a single MessageTransportMode which sets these characteristics.
- Example modes registered in the Repository include Reliable Mode, Quick Mode, and Bulk Transfer Mode. (Reliable Mode sample values: DeliveryAssurance = AtLeastOnce; Sender/Receiver Asynchronicity = Asynchronous; MessageDeliveryOrder = Unordered.)
- Idempotency rules:
- MessageInstance Republication Idempotency: endpoints must behave as if a MessageInstance received multiple times was received once.
- Transport Message Republication Idempotency: same principle for republished TransportMessages.
- Operational assumptions:
- Bandwidth Assumption: layer‑8 bandwidth is assumed unconstrained for business choreography (implementers remain responsible for meeting requirements).
- Security Assumption: transports are assumed to provide secure, unmodified delivery between named endpoints (basic confidentiality/integrity assumed; not a substitute for added security measures).
- Time and clocks: no single global clock assumed; endpoints may have clock variance bounded by the MessageTransportMode (Maximum Clock Variation concept).
Practical applications & users
- Who uses it: banks, payment systems, securities infrastructures, fintechs, middleware vendors, system architects, integration teams, and Registration Authority/operators of the ISO 20022 Repository.
- Practical value: guides selection and configuration of messaging transports to meet business choreography needs; ensures predictable delivery semantics (reliability, ordering, asynchronicity); informs middleware, message gateways, and operational requirements for interoperability testing and deployment.
Related standards
- ISO 20022 series (Parts 1–8): metamodel, UML profile, modelling, XML/ASN.1 generation, registration.
- ISO 7498-1 (OSI model) referenced for layering terminology.
Keywords: ISO 20022, message transport characteristics, MessageTransportMode, MessageInstance, TransportMessage, MessageChoreography, DeliveryAssurance, idempotency, messaging interoperability.
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