Siemens Simantic Net NCM for Industrial Ethernet S7 - Manual (Page 205)

Glossary
205
SIMATIC NET NCM S7 for Industrial Ethernet
C79000-G8976-C129–06
Subnet
A subnet is part of a –> network whose parameters (for example –> PROFIBUS)
must be matched. The subnet includes bus components and all the attached
stations. Subnets can, for example, be connected together by –> gateways to
form a network.
A –> system consists of several subnets with unique –> subnet numbers. A
subnet consists of several –> stations with unique –> PROFIBUS or MAC
addresses (Industrial Ethernet).
System
This means all the electrical equipment within a system. A system includes,
among other things, programmable logic controllers, devices for operation and
monitoring, bus systems, field devices, actuators, supply lines.
Transmission rate
According to DIN 44302, this is the number of binary decisions transmitted per
time unit. The unit is bps. he set or selected transmission rate depends on va-
rious conditions, for example the distance across the network.
Transport layer
The transport layer is layer 4 of the ISO/OSI reference model for open system
interconnection. The purpose of the transport layer is to transfer data reliably
from device to device. Transport connections can be used for the transmission.
Transport interface
The transport interface of a SIMATIC S5 PLC is the access to the connection-
oriented services of the transport layer on the CP. The transport interface pre-
sents itself to the control program in the form of handling blocks (HDBs).
TSAP
Transport Service Access Point
Watchdog
Mechanism for monitoring operability.