This International Standard specifies a) five classes of procedures :
1) dass 0 : simple dass;
2) dass 1 : basic error recovery dass;
3) dass 2 : multiplexing dass;
4) dass 3 : error recovery and multiplexing dass;
5) dass 4 : error detection and recovery dass;
for the connection oriented transfer of data and control information from one transport entity to a peer transport entity;
b) the means of negotiating the dass of procedures to be used by the transport entities;
c) the structure and encoding of the transport protocol data units used for the transfer of data and control infor-mation.
The procedures are defined in terms of
a) the interactions between peer transport entities through the exchange of transport protocol data units;
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 net-work service provider through the exchange of network ser-vice primitives.
These procedures are defined in the main text of this Inter-national Standard supplemented by state tables in annex A.
These procedures are applicable to instances of communication between systems which support the Transport Layer of the OSI Reference Model and which wish to interconnect in an open systems environment.
This International Standard also specifies conformance re-quirements for systems implementing these procedures. It does not contain tests which can be used to demonstrate this conformance.