mobile | classic
Dataweek Electronics & Communications Technology Magazine

Follow us on:
Follow us on Facebook Share via Twitter Share via LinkedIn


Electronics Buyers' Guide

Electronics Manufacturing & Production Handbook 2019


10 issues to consider before installing industrial Ethernet - Part V
25 September 2002, Computer/Embedded Technology

Transport layer protocols

Ethernet is termed a data link and physical layer technology and, therefore, occupies layers two and one of the OSI reference model. The original designers never intended the technology to guarantee end-to-end message delivery. This responsibility is given to the transport layer (layer four) of the OSI model in Figure 1.

Figure 1. Ethernet defines the lower two layers of the OSI reference model
Figure 1. Ethernet defines the lower two layers of the OSI reference model

Responsibility for internetworking (communication between two networks) is given to layer three - the network layer. The transport and internetworking layer functionality becomes part of the protocol stack and two protocols have found much use with Ethernet - TCP/IP and SPX/IPX. These two protocols will not directly interoperate so it is important that all Ethernet nodes on the network utilise compatible protocols. Since TCP/IP powers the Internet, this is the protocol that has won out and the one recommended for industrial Ethernet.

Actually, TCP/IP is a set of protocols defined by a series of RFCs (request for comments) that have evolved over the years. In Figure 2, one will notice how the TCP/IP stack of protocols relates to the OSI model. TCP/IP will work with other data link technologies besides Ethernet so it resides above the data link/physical layer. At the transport layer there are two important protocols. The transmission control protocol (TCP) acknowledges receipt of messages while the user datagram protocol (UDP) does not. Both are useful. At the very top of the protocol stack there are several useful application layer protocols that find use in industrial Ethernet. TCP/IP is a complex subject and it will not be addressed here. To the installer, the most important issue is the addressing of nodes, which is a network layer issue.

Figure 2. The TCP/IP stack is actually a set of protocols. IP resides at the network layer of the OSI reference model
Figure 2. The TCP/IP stack is actually a set of protocols. IP resides at the network layer of the OSI reference model

The Internet Protocol (IP) handles the routing of packets between stations that may reside on different networks. Each station must have a unique 32-bit address that not only identifies the host (station) but the network as well. Addresses are best shown as four bytes in a decimal-dot-decimal notation. A valid address would be but it is difficult to determine what part of the address is the host address and what part is the network address. Addresses are defined as residing in either one of five classes - A, B, C, D or E. Table 1 defines the classes by observing the value of the first byte of the address. It is the class that determines the <host><netid> split.

Table 1. The class of an IP address can be quickly identified by observing only the first byte
Table 1. The class of an IP address can be quickly identified by observing only the first byte

Assigning IP addresses is not simple and they are usually assigned by the network administrator. Once assigned they must be applied to each station in the network. Depending upon the system installed, IP addresses may be dynamically assigned or statically assigned. Dynamically assigned addresses come from a server, while statically assigned addresses must be entered for each station as part of the configuration. IP addresses are either public or private. A public address can usually be seen on the Internet. The following addresses are private and cannot be assessed through a router and, therefore, will not be seen on the Internet: to to to

IP addressing should not be confused with Ethernet MAC addresses. An Ethernet MAC address is assigned by the equipment vendor so as to be unique worldwide. IP addresses are assigned during installation and can be reassigned as necessary.

Application layer protocols

Now that we have determined our connector and cable needs, selected either hubs or switches and assigned the required IP addresses, we should be able to communicate between stations. This is not necessarily true. We still need compliance at the highest level of the OSI reference model. There are several industrial automation protocols that are being proposed such as EtherNet/IP, iDA, PROFInet and MODBUS/TCP. This does not include the traditional Internet applications such as FTP, SNMP, SMTP and TELNET. Your equipment may not support all these application protocols, so you must understand the capabilities of your system. It is also possible that your equipment can handle all these applications. This is another advantage for using a TCP/IP stack.

This is where our discussion stops. Industrial Ethernet offers many possibilities; however, because of this flexibility, the subject is somewhat complex. You may not have all the answers but you should have a better feeling about some of the questions that need to be asked.


We hope this series has been helpful. For a more in-depth analysis of industrial Ethernet, several articles can be downloaded from

For more information contact our representative in South Africa, Electronic Products Design, 012 665 9700.

Supplied By: Electronic Products Design
Tel: +27 12 661 4748
Fax: +27 12 661 6145
  Share on Facebook Share via Twitter Share via LinkedIn    

Further reading:

  • eSPI-to-LPC bridge
    26 June 2019, Avnet South Africa, Computer/Embedded Technology
    Microchip Technology’s new ECE1200 bridge allows developers to implement the eSPI standard in boards with legacy LPC connectors and peripherals. Product longevity is critical in industrial computing ...
  • Library of parts added to Proteus software
    26 June 2019, Dizzy Enterprises, Computer/Embedded Technology
    The version 8.9 update to the Proteus EDA software suite sees the integration of a growing online library – currently listing over 1,5 million parts – into its part selection dialog. This follows the ...
  • Industrial-grade graphics card in M.2 format
    29 May 2019, Vepac Electronics, Computer/Embedded Technology
    Innodisk is aiming at the industrial embedded sector with the addition of a new ultra-slim 4K M.2 graphics card to its portfolio of expansion cards. M.2 has become one of the dominant form factors in ...
  • SSDs for industrial computing
    30 April 2019, Vepac Electronics, Computer/Embedded Technology
    Innodisk has packaged Toshiba’s next-generation 3D NAND Flash technology into an industrial-grade solid state drive (SSD) designed to tackle the tough conditions seen in many embedded environments and ...
  • Raspberry Pi and Arduino not just for hobbyists
    27 February 2019, RS Components (SA), Computer/Embedded Technology
    It wouldn’t be an exaggeration to say that the Raspberry Pi single-board computer, and platforms like it, have sparked a revolution in the electronics hobbyist/maker community. We asked Brian Andrew, ...
  • Evaluation kit for Vishay sensors
    30 January 2019, RS Components (SA), Computer/Embedded Technology
    The Vishay SensorXplorer evaluation kit is based on a universal USB-to-I2C board for connecting individual sensor boards to a host PC. All software and connectors are included with the kit, which is backwards-compatible ...
  • Arduino shield for energy measurement
    30 January 2019, Altron Arrow, Computer/Embedded Technology
    Analog Devices’ EV-ADE9153ASHIELDZ is an Arduino shield compatible with Arduino Uno, Arduino Zero, or ESP8266. The shield has an on-board shunt resistor for line current measurement and enables quick ...
  • Development kit for IoT sensing
    30 January 2019, RS Components (SA), Computer/Embedded Technology
    RS Components is making IoT sensing projects even easier to start, and more affordable, with the latest UrsaLeo Pi development kit. By combining the Silicon Labs Thunderboard 2 sensor module with a Raspberry ...
  • Raspberry Pi 3 Model A+
    30 January 2019, Electrocomp Express, Computer/Embedded Technology
    The Raspberry Pi 3 Model A+ is the latest product in the Raspberry Pi 3 range. Like the Raspberry Pi 3 Model B+, it boasts a 64-bit quad-core processor running at 1,4 GHz, dual-band 2,4 GHz and 5 GHz ...
  • Dissipative bench mats
    EMP 2019 Electronics Manufacturing & Production Handbook, Altico Static Control Products, Computer/Embedded Technology
    Altico dissipative bench mats are made from durable vinyl and consist of two layers: a 2 mm dissipative top layer, and a 2 mm conductive bottom layer for optimal ESD protection. These mats are solder, ...
  • Development kits for students and hobbyists
    14 November 2018, RS Components (SA), Computer/Embedded Technology
    RS Components has introduced new ranges of tools from Seeed Studio, Arduino and Bare Conductive that target academic institutions, including educators and students of electronics, as well as inspiring ...
  • Accelerator cards for AI and data centres
    14 November 2018, Avnet South Africa, Computer/Embedded Technology
    At the recently held Xilinx Developer Forum (XDF), Xilinx launched the Alveo portfolio of powerful accelerator cards designed to increase performance in industry-standard servers across cloud and on-premise ...

Technews Publishing (Pty) Ltd
1st Floor, Stabilitas House
265 Kent Ave, Randburg, 2194
South Africa
Publications by Technews
Dataweek Electronics & Communications Technology
Electronics Buyers’ Guide (EBG)

Hi-Tech Security Solutions
Hi-Tech Security Business Directory

Motion Control in Southern Africa
Motion Control Buyers’ Guide (MCBG)

South African Instrumentation & Control
South African Instrumentation & Control Buyers’ Guide (IBG)
Terms & conditions of use, including privacy policy
PAIA Manual


    Classic | Mobile

Copyright © Technews Publishing (Pty) Ltd. All rights reserved.