TELE 201Introduction to
Telecommunications
Lecture 1: Introduction
Introduction
P Personnel:< Martin Purvis (Information Science Depart.)
– Email: [email protected]< Zhiyi Huang (Computer Science Dept.)
– Email: [email protected]< 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