This Recommendation | International Standard specifies: a) Two modes of procedures when operating over the connection oriented network service: 1) mode 0: acts on network signalled errors; 2) mode 4: ignores network signalled errors, for the connection oriented transfer of data and control information from one transport entity to a peer transport entity. b) The means of selecting the mode of procedures to be used by the transport entities. c) The structure and encoding of the TPDUs used for the transfer of data and control information. The procedures are defined in terms of: a) the interactions between peer transport entities through the exchange of TPDUs; b) the interactions between a transport entity and the transport service user in the same system through the exchange of transport service primitives; c) the interactions between a transport entity and the network service provider through the exchange of network service primitives. These procedures are applicable to instances of communication between systems which support the Transport Layer of the OSI Reference Model and wish to interconnect in the open systems environment using the Transport Fast Byte Protocol. This Recommendation | International Standard specifies, in clause 8, conformance requirements for systems implementing these procedures and provides the PICS proforma in compliance with the relevant requirements, and in accordance with the relevant guidance, given in ITU-T Rec. X.296 and ISO/IEC 9646-7. It does not contain tests which can be used to demonstrate this conformance.