Deployment
Wieland Electric GmbH | BA001269 | 09/2021 (Rev. A)
36
MAC/DLL
While the Ethernet physics covers with its standard signal levels Layer 1, MAC/DLL covers the condi-
tions 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 commu-
nication participant has a MAC address that must be unique at the network. The deployment of MAC
addresses specifies source and destination unambiguously.
IP
The
I
nternet
P
rotocol covers the network layer (layer 3) of the ISO/OSI layer model. The main pur-
pose 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.
TCP
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 pro-
tocol 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 con-
tains, among others, the serial number for the according sequence. This causes that within a net-
work, the single datagrams may reach their destination on different ways.
API
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 cou-
pler uses the Modbus/TCP protocol, described further below.
