TELE 201Introduction to

Telecommunications

Lecture 1: Introduction

Introduction

P Personnel:< Martin Purvis (Information Science Depart.)

– Email: mpurvis@infoscience.otago.ac.nz< Zhiyi Huang (Computer Science Dept.)

– Email: zhy@cs.otago.ac.nz< Supporting personnel:

– Brian Thompson– Reuben Elder– John Girgis

P TELE 201 web page< Check the Telecommunications Programme web

page at http://waitaki.otago.ac.nz/telecom/

Books

P Data & Computer Communications, SixthEdition, by William Stallings (Prentice Hall) – required

P Some other books of interest:< Computer Networks, by A. S. Tanenbaum

(Prentice Hall)< Introduction to Data Communications and

Networking, by B. Forouzan (McGraw-Hill)< Communication Systems, 4th ed., by S. Haykin

(Wiley)< The Essential Guide to Telecommunications, by

A. Z. Dodd (Prentice Hall)

Class Meetings

P Lectures: Monday, Tuesday < 8:00 am < 1W9, Burns

P Laboratory: Friday< 2:00 pm - 5:50pm< 121 Physics (Science III)

Outline

P A little historyP The nature of a communications systemP What is a protocol?P What is a protocol architecture?P Standards organisations in telecommunications

Some History

P 1800 - the electric battery invented by VoltaP 1831 - electromagnetic induction - FaradayP 1837 - telegraph (Morse, Henry, ...)P 1858 - transoceanic telegraph cable laidP 1876 - the telephone - BellP 1888 - electromagnetic waves - HertzP 1895 - wireless telegraph - MarconiP 1906 - the radioP 1939 - the electronic computer

History (continued)

P 1906 - the radioP 1939 - the electronic computerP 1948 - the transistorP 1961 - the integrated circuitP 1969 - the ARPANET (forerunner to the Internet)P 1971 - the microprocessorP 1978 - uucp (the Unix-to-Unix copy program)

The nature of acommunications system

A simple example

Networks

WAN: Wide Area Network

LAN: Local Area Network

Networks

P Wide Area Networks (WANs)< Circuit switching – a dedicated

communications path that lastsfor as long as the session.

< Packet switching - data sent in small chunks,each of which can take an independent path. These chunks may arrive out of sequence.

< Frame relay - a streamlined form of packetswitching

< ATM - a form of packet switching that ‘looks’ likecircuit switching to the end-user

Networks

P Local Area Networks (LANs)< Usually controlled and

managed by organisation thataccesses it.

< Usually employ a broadcastapproach (the “ether” isaccessed). One client getshold of the entire network forits uses at a time. Data isusually sent in packets.

What is a protocol?

P A protocol is a set of conventions (or rules) used tofacilitate an interaction.

P When a protocol is written down, it is necessary todefine < the terms< the control rules governing the use of those terms< other constraints involved

P Consider a protocol that you use when you order ameal at a restaurant....

What is a protocolarchitecture?

Suppose we want to carry out a file transfer. What are the steps involved in doing this over thenetwork?

A simple protocolarchitecture

P - a modular way to deal withthe business of exchanging data between thecomputer and the network.

P Transport layer - concerned with mechanisms forproviding reliable delivery across the network(independent of particular network used).

P Application layer - concerned with the sending andreceiving details associated with the particularapplication.

Protocol architectures

Protocols in architecture

Protocol Data Units (PDUs)

P At each layer, protocols are used to communicateP Control information is added to user data at each

layerP Transport layer may fragment user dataP Each fragment has a transport header added< Destination SAP< Sequence number< Error detection codeThis gives a transport protocol data unit

P Network PDU adds network header with networkaddress for destination computer

How it works

TCP/IP Protocols

P Developed by the US Defense Advanced ResearchProject Agency (DARPA) for the ARPANET

P It doesn’t have an official protocol architecture, buteffectively it has five layers:< Application layer - (as before)< Transport layer - (as before)< Internet layer - routing functions across

different networks< Network access layer - (as before)< Physical layer - physical interface to transmission

medium

TCP/IP protocol architecture

OSI protocol architecture

P The Open Systems Interconnection (OSI) protocolarchitecture is a seven-layer model developed byISO.

P It will be covered in greater detail later in the course

Standards

P Advantages< Ensure a large market for equipment and

software< Allow products from different vendors to

interoperateP Disadvantages< Can freeze technology< Multiple standards can interfere with each other

Standards OrganisationsP International< The Internet Society – includes the IETF< ISO – voluntary but made up of national

standards organisations< ITU (formerly CCIR and CCITT) – members are

governments< IEEE< ATM Forum – voluntary and made up mostly of

vendors (like OMG)P National< FCC< ANSI – a member of ISO< TIA – Telecommunications Industry Association