Ethernet X001 Interface; Ethernet; Fig. 12 Structure Of The Ethernet Protocol - Beckhoff CX8180 Manual

Ethernet X001 Interface

8 Ethernet X001 Interface
8.1

Ethernet

Ethernet was originally developed by DEC, Intel and XEROX (as the "DIX" standard) for passing data
between office devices. The term nowadays generally refers to the IEEE 802.3 CSMA/CD specification,
published in 1985. Because of the high acceptance around the world this technology is available everywhere
and is very economical. This means that it is easy to make connections to existing networks.
There are now a wide variety of transmission media: coaxial cable (10Base5), fiber optic (10BaseF) or
twisted pair cable (10BaseT) with shielding (STP) or without shielding (UTP). Using Ethernet, different
topologies can be built such as ring, line or star.
Ethernet transmits Ethernet packets from a sender to one or more receivers. This transmission takes place
without acknowledgement, and without the repetition of lost packets. To achieve reliable data
communication, there are protocols, such as TCP/IP, that can run on top of Ethernet.
MAC-ID
The sender and receiver of Ethernet packets are addressed by means of the MAC-ID. The MAC-ID is a 6-
byte identification code unique to every Ethernet device in the world. The MAC-ID consists of two parts. The
first part (i.e. the first 3 bytes) is a manufacturer identifier. The identifier for Beckhoff is 00 01 05. The next
3 bytes are assigned by the vendor and implement a unique serial number. The MAC-ID can, for example,
be used for the BootP protocol in order to set the TCP/IP number. This involves sending a telegram
containing the information such as the name or the TCP/IP number to the corresponding node. You can read
the MAC-ID with the KS2000 configuration software.
The Internet Protocol (IP)
The internet protocol (IP) forms the basis of this data communication. IP transports data packets from one
device to another; the devices can be in the same network, or in different networks. IP here looks after the
address management (finding and assigning MAC-IDs), segmentation and routing. Like the Ethernet
protocol, IP does not guarantee that the data is transported - data packets can be lost, or their sequence can
be changed.
TCP/IP was developed to provide standardized, reliable data exchange between any numbers of different
networks. TCP/IP is largely independent of the hardware and software used. Although the term is often used
as a single concept, a number of protocols are layered together here: e.g. IP, TCP, UDP, ARP and ICMP.
Fig. 12: Structure of the Ethernet protocol.
Transmission Control Protocol (TCP)
The Transmission Control Protocol (TCP) which runs on top of IP is a connection-oriented transport protocol.
It includes error detection and handling mechanisms. Lost telegrams are repeated.
52 Version: 1.5 CX8180