Chapter 3. Ethernet Overview; Iso Reference Model - Control Technology Ethernet TCP/IP Adapter Module CTI 2572 Technical Overview

3.1 ISO Reference Model

Modern network implementations separate data communication functions into layers. Each layer
performs a specific set of services and interacts with layers above and below in a well defined
way.
In 1984 the International Standards Organization published the Open Systems Interconnection
(OSI) Reference model. Although there are few, if any, strict implementations of the entire
seven layer model, it is commonly used as a conceptual reference when discussing networking
software. The OSI model is briefly described below:
Layer
Layer 7
Application
Layer 6
Presentation
Layer 5
Session
Layer 4
Transport
Layer 3
Network
Layer 2
Data Link
Layer 1
Physical
The Ethernet specifications describe both the Physical layer (cabling, connectors, and
topology) as well as the Data Link (Medium Access) layer. As a result of this complete
specification, Ethernet equipment from various vendors can be used on the same network.
Ethernet is the most widely used local area network in the world and it is continuing to gain
market share due to its low cost and flexibility. One of the fastest growing areas in Ethernet
installations is the factory floor.
CTI 2572 Technical Overview Manual

CHAPTER 3. ETHERNET OVERVIEW

Function
Provides application services such as file transfer,
virtual terminal, and directory services.
Resolves differences in data representation between
the communicating applications
Synchronizes communications between applications
Provides reliable data transfer from end node to end
node.
Translates physical addresses into logical addresses
and routes packets to the destination node.
Places messages into data frames and manages access
to the media.
Defines the electrical and mechanical characteristics
of the transmission media .
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