ISO 20022-6:2009 specifies the characteristics of the Message Transport System required for an ISO 20022 Business Transaction and Message Definition. Changes to the value of the Message Transport Characteristics can affect the Business Transaction and Message Definition. Each Business Transaction in the ISO 20022 Repository is associated with a Message Transport Mode. The Message Transport Mode specifies the values for the Message Transport Characteristics. ISO 20022-6:2009 specifically does not define the wire-level interoperability of message transports. The overall structure is of a layered specification, in order that ISO 20022 can be implemented over many message transports. ISO 20022-6:2009 defines only those characteristics required for interoperability at the business process and message level.