-8 .
INTERNATIONAL SOCIETY FOR PHOTOGRAMMETRY AND REMOTE SENSING
Commission VI
Symposium held in Mainz, FR Germany, 22 - 25 September 1982
DATA COMMUNICATION OVER
PUBLIC NETWORKS
Walter Tietz
Fernmeldetechnisches Zentralamt, Darmstadt, FR Germany
ABS TRACT
Data connection between interfaces and their compatibility is outlined. Open
communication systems are stressed. Access to telecommunication networks is
mentioned. Users rely on the performance capability and on the error control
system of countries being involved in the data transport. As an example for
international connections, the situation in the FR Germany is delineated.
1. Types of services and general aspects
All telecommunication services are used to transmit electric signals. The cha-
racteristic feature of data communication services is that they are based on
communication networks which use interfaces defined for the data signals and have
the task of transporting these signals between interfaces. The data sources and
sinks also termed data terminal equipment (DTE) operate over the communication
network, the inner structure of which may be technically different. Data con-
nections between the interfaces may be
- permanently dedicated or
- provided temporarily, that is switched
Figure 1 shows the interdependence of the system components in a data communication
system which , in general terms, is also called teleprocessing system.
All types of data communication performed over public telecommunication networks
in the Federal Republic of Germany are called Datel services whose function is the
transport of data. These data communication services differ in the various coun-
tries in their legal provisions, technical characteristics and certain facilities.
M — Data Network
| Fr DatacOMMuMENtION Net work
Ver ME Station messe un
| Reftected
Datostation \ image
OTE DCE
|
Switching Network
| Access Line
I fransms sion Nelwork - bam
I
|
i
Transport Network
digital _ann Loy - analogue o, d'a!
signais | signals signals
Interfuce between OTE and DCE
Packet - switched. Stations x 25
Circus - switched Stations X 20/X 20bıs
X 21/X 21bıs
DCE on Tetepnone Stations V - (mterfacen
DCE on Fixed Connections V-[nterfacon or X - [nterfaces
OTE: Dota Terminal Equipment
DCE. Data Circuit - terminating Equipment
Figure | Interface between OTE and OCE and essential network components
Bibliograpnic quotation :
Tietz, W. : Data communication over public networks. In: Int. Archive of Photo-
grammetry, 24 -VI, pp 78 - 81, Mainz 1982