VIPA System 200V IM Series, Руководство пользователя

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Manual VIPA System 200V
Chapter 8 Ethernet coupler
HB97E - IM - Rev. 06/29 8-5
MAC/DLL IP TCP API
Layer 2 Layer 3 Layer 4 Layer 7
14 Byte 20 Byte 20 Byte Length depends on protocol
...
While the Ethernet physics covers with its normed signal levels Layer 1,
MAC/DLL covers the conditions of the security layer (Layer 2). With MAC
(
M
edium
A
ccess
C
ontrol) / DLL (
D
ata
L
ink
L
ayer) the communication
happens at the lowest Ethernet level using MAC addresses. Every Ethernet
communication participant has a MAC address that must be unique at the
network.
The deployment of MAC addresses specifies source and destination
unambiguously.
The Internet Protocol covers the network layer (layer 3) of the ISO/OSI
layer model.
The main purpose of IP is to send data packages from one station to
another, passing several other stations. This data packages are referred to
as datagrams. The IP does neither serve the according sequence nor the
deliverance at the receiver.
For the unambiguous distinction between sender and receiver, 32Bit
addresses are used (IP addresses) that are normally written in four octets
of each 8Bit, e.g. 172.16.192.11. One octet may represent numbers
between 0 and 255.
A part of the address specifies the network, the rest identifies the single
stations in the network. The proportions of network part and station part is
floating and depends on the network size.
The TCP (
T ransmission C ontrol P rotocol) puts directly upon the
IP and
covers therefore the transport layer (layer 4) of the ISO/OSI layer model.
TCP is a connection orientated end-to-end protocol and serves the logical
connection between two partners.
TCP ensures the sequential correct and reliable data transfer.
Every datagram is preceded by a header of at least 20 octets that contains,
among others, the serial number for the according sequence. This causes
that within a network, the single datagrams may reach their destination on
different ways.
API means
A
pplication
P
rogramming
I
nterface. API covers the conditions
of the Application Layer (Layer 7).
Here, the header and user data of the according protocols are stored.
The Ethernet coupler IM 253NET from VIPA uses the following protocols,
described further below:
•
ModbusTCP
•
Siemens S5 Header
Telegram
structure
MAC/DLL
IP
TCP
API