Table of Contents
Objective
After you have completed this chapter you should:
Understand how the TCP/IP protocol stack compares to the OSI model
Understand the Internet Protocol and know how to configure an IP address
Know what ICMP is and how to use it to diagnose networking problems
Know what the ARP protocol is used for
Understand how TCP works and know what a TCP/IP socket is
Know what the important application layer protocols are and understand how they are deployed in a control system network
Understand the concept of encryption and the purpose of protocol encryption and know which encryption protocols to apply in a given scenario
Understand how the TCP/IP protocol communication stack is used in industrial communications protocols such as Modbus and DNP3 over TCP/IP
Understand how the TCP/IP protocol communication stack is used in DCOM and OPC applications
Understand the practical limitations of OPC on DCOM and how OPC on SOAP can overcome them
The TCP/IP communication stack (OSI levels 3 and 4) is at the heart of most modern industrial communication stacks and a solid understanding of the TCP/IP concept is also important for developing or configuring drivers and application layer software in SCADA systems.
Internet protocol suite is the set of communications protocols that implements the protocol stack on which the Internet and many commercial networks run. It is part of the TCP/IP protocol suite, which is named after two of the most important protocols in it: the Transmission Control Protocol (TCP) and the Internet Protocol (IP), which were also the first two networking protocols defined. Note that today's TCP/IP networking represents a synthesis of two developments that began in the 1970's, namely LAN (Local Area Networks) and the Internet, both of which have revolutionized computing.
The Internet protocol suite - like many protocol suites - can be viewed as a set of layers and can be compared to the OSI model. Each layer solves a set of problems involving the transmission of data, and provides a well-defined service to the upper layer protocols based on using services from some lower layers. Upper layers are logically closer to the user and deal with more abstract data, relying on lower layer protocols to translate data into forms that can eventually be physically transmitted. The original TCP/IP reference model consists (see Figure 5.1, “The TCP/IP protocol stack”) of 4 layers, but has evolved into a 5-layer model.
