3 Ethernet
3.1 System description
24
XI/ON: XNE-GWBR-2ETH-MB
10/2011 MN05002008Z-EN
www.eaton.com
3.1.3
Network classes
The available networks are divided into the different network classes A, B, and C.
According to their predefined address 192.168.1.××× the XI/ON gateways are thus nodes of
a Class C network.
3.1.4
Data transfer
The data are transferred from a transmitter to a receiver via the Ethernet. This data transfer
uses no acknowledgement of reception, which means data telegrams can get lost. Data
transfer via Ethernet without any protocol implementation can thus not be absolutely safe.
In order to assure a safe transmission of data, frame-protocols like TCP/IP are used.
IP (Internet Protocol)
The Internet Protocol is a connection-free transport protocol. The protocol does not use
acknowledgement messages, telegrams can get lost. It is thus not suitable for safe data
transfer. The main functions of the internet protocol are the addressing of hosts and the frag-
mentation of data packages.
TCP (Transmission Control Protocol)
The Transmission Control Protocol (TCP) is a connection-oriented transport protocol and is
based on the Internet Protocol. A safe and error-free data transport can be guaranteed by
means of certain error diagnostic mechanisms as for example acknowledgement and time
monitoring of telegrams.
Table 1:
Network class-
es
Class
Network addresses Bytes for net
address
Bytes for
host address
No. of the possible
networks/ hosts
A
1.×××.×××.×××-
126.×××.×××.×××
1
3
126/ 2
24
B
128.0.×××.××× -
191.255.×××.×××
2
2
2
14
/ 2
16
C
192.0.0.××× -
223.255.255.×××
3
1
2
21
/ 256
Figure 15:
Telegram
structure
Ethernet-
Header
EtherNet-DATA
IP-
Header
IP-DATA
IP-
Package
TCP-
Header
TCP-DATA
TCP-
Segment
EtherNet-
Package
LAYER 7
Modbus etc.
