RFC - 892

ISO Transport Protocol Specification

Original:	ftp://ftp.isi.edu/in-notes/rfc892.txt
Authors:	ISO []
Date:	December 1983
Category:	Informational
This specification has been !!! obsoleted !!!

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Obsoleted by:
RFC-905	ISO Transport Protocol specification ISO DP 8073

Referred by:	6 RFC
Refers to:	0 RFC

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Status

This document is distributed as an RFC for information only. It does not specify a standard for the ARPA Internet.

Abstract

Note:  This document appeared in:

ISO/TC97/SC16/WG6.  Information Processing Systems - Open Systems
    Interconnection - Transport Protocol Specification.  Computer
    Communication Review 12, 3-4 (July/October 1982), pp.  24-67.

and differs from it only in format.

        The Transport Protocol Standard is one of a set of International
Standards produced to facilitate the interconection of computer
systems.  The set of standards covers the services and protocols
required to achieve such interconnection.

        The Transport Protocol Standard is positioned with respect to
other related standards by the layers defined in the Reference Model
for Open Systems Interconnection (ISO 7498).  It is most closely
related to, and lies within the field of application of the Transport

Service Standard (DP aaaa).  It also uses and makes reference to the
Network Service Standard (DP bbbb), whose provisions it assumes in
order to accomplish the transport protocol's aims.  The
interrelationship of these standards is depicted in Figure 1.

-----------------------------------TRANSPORT SERVICE DEFINITION-----

 Transport                --Reference to aims---------------
 Protocol
 Specification            --Reference to assumptions--------

------------------------------------NETWORK SERVICE DEFINITION------

Figure 1  -  Relationship between the transport protocol and adjacent
             services

        The standard specifies a common encoding and a number of 
classes of transport protocol procedures to be used with different 
network qualities of service.

        It is intended that the Transport Protocol should be simple 
but general enough to cater for the total range of Network Service
qualities possible, without restricting future extensions.

        The protocol is structured to give rise to classes of protocol 
which are designed to minimize possible incompatibilities and 
implementation costs.

        The classes are selectable with respect to the Transport and 
Network Services in providing the required quality of service for the
interconnection of two session entities (note that each class provides
a different set of functions for enhancement of service qualities).

        This protocol standard is concerned with optimisation of network
tariffs and the following qualities of service:

     a)  different throughput rates;
     b)  different error rates;
     c)  integrity of data requirements;
     d)  reliability requirements.

        The aim of this standard is primarily to provide a definition 
for implementors.  Since the protocol is complex, the document contains
much material which is advisory or descriptive, but mandatory
requirements on implementations are clearly identified. 

        It should be noted that, as the number of valid protocol sequences 
is very large, it is not possible with current technology to verify that an
implementation will operate the protocol defined in this document
correctly under all circumstances.  It is possible by means of testing
to establish confidence that an implementation correctly operates the
protocol in a representative sample of circumstances.  It is, however,
intended that this standard can be used in circumstances where two
implementations fail to communicate in order to determine whether one
or both have failed to operate the protocol correctly.

        The variations and options available within this standard are
essential to enable a Transport Service to be provided for a wide
variety of applications over a variety of network qualities.  Thus, a
minimally conforming implementation will not be suitable for use in
all possible circumstances.  It is important therefore to qualify all
references to this standard with statements of the options provided or
required or with statements of the intended purpose of provision or
use.

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