Lecture Notes for Telecommunications

8 September 2004 - Introduction

ISO OSI Reference Architecture

• ISO: International Organization for Standards (in French).

• OSI: Open Systems Interconnection.

• Layered architectures reduce complexity.

• Each layer offers services to the layer immediately above it.

• Each layer shields the higher layer from the service implementation details.

• Layer n on one station communicates with layer n on another station.

The OSI Layers

• The OSI model defines seven layers.

Layer Services

1. Application: application-level data transfer.

2. Presentation: data representation.

3. Session: end-to-end communication.

4. Transport: host-to-host communication.

5. Network: addressing.

6. Data link: media access.

7. Physical: data transmission.

Layer Functions

Comments

• Internetworking evolved to support current and future applications.

• The OSI Reference model organizes network functions into seven layers.

• Data flows from upper-level user aplications to lower-level bits transmitted over network media.

• Peer-to-peer functions use encapsulation and de-encapsulation at layer inerfaces.

• most network manager tasks configure the lower three layers.

This page last modified on 14 November 2004.