Practical_modern_SCADA_protocols_-_dnp3,_60870-5_and_Related_Systems

12
Ethernet and TCP/IP networks
Objectives
When you have completed study of this chapter you should be able to:
• Describe the major hardware components of an IEEE 802.3 CSMA/CD
network;
• Explain the method of connection of 10Base5, 10Base2 and 10BaseT networks;
• Explain the operation of the CSMA/CD protocol;
• List the fields in the Ethernet data frame;
• Describe the causes of Ethernet collisions and how to reduce them;
• Demonstrate how to apply the Ethernet design rules;
• Describe how the TCP/IP protocols fit into an Ethernet frame;
• Describe the structure and operation of the Internet protocol (IP);
• Describe the structure and operation of the transmission control protocol
(TCP);
• Describe the structure and operation of the user datagram protocol (UDP);
• Describe the TCP/IP application level protocols
12.1 IEEE 802.3 CSMA/CD (‘Ethernet’)
The Ethernet network concept was developed by Xerox Corporation at its Palo Alto
Research Center (PARC) in the mid-seventies. It was based on the work done by
researchers at the University of Hawaii where there were campus sites on the various
islands. Its ALOHA network was set up using radio broadcasts to connect the various sites.
This was colloquially known as their ‘Ethernet’ since it used the ‘ether’ as the transmission
medium and created a network ‘net’ between the sites. The philosophy was quite straightforward.
Any station that wanted to broadcast to another station would do so immediately.
The receiving stations then had a responsibility to acknowledge the message; thus
advising the original transmitting station of a successful reception of the original message.
This primitive system did not rely on any detection of collisions (two radio stations