G52CCNComputer Communications

and Networks

Milena RadenkovicRoom: B47

Email: mvr@cs.nott.ac.uk

Introduction

• Practical matters• Module goals, structure and contents• Initial introduction to some key ideas and

issues

Lectures

• Thursday 15:00 – 16:00– Jubilee Campus, Exchange Building, LT2

• Friday 09:00 – 10:00– Jubilee Campus, Exchange Building, LT2

Related modules

• G53ACC - Advanced Computer Communications

• G5BIAW - The Internet and the World Wide Web

Objectives• To understand the basic principles of data

communications and computer networks.• To appreciate the complex trade-offs that are

inherent in the design of networks.• To provide a guided tour of network technologies

from the lowest levels of data transmission up to network applications.

• To learn about current networking technologies, especially Internet protocols.

Assessment

• Two hour written examination

• The style of question will be based upon those from previous years. Their content will of course be different.

• Last year’s exam paper is on sale in the bookshop and previous papers are in the library.

• No coursework

Text books and notes• My notes are available at:

– http://www.cs.nott.ac.uk/~mvr/ccn

• The core recommended course text is:

– Computer Networks and Internets, Douglas E. Comer, Prentice Hall

• Supplementary texts are:– Tannenbaum, Computer Networks, Prentice Hall– Halsall, Data and Computer Communications,

Macmillan

What is a computer network?

• An interconnection of autonomous computers (as opposed to communication between separate but interdependent parts of a single computer)

Some goals of computer networks• Access to remote resources• Human communication• Mobile computing• Computing power through parallelism• Optimising resources - load balancing• Incremental growth of computer systems (reduced

cost and risk)• Increased robustness through graceful degradation

Uses of computer networks

• Email, World Wide Web, Video Conferencing, File Transfer, Collaborative Virtual Environments, Remote control of robots and machines, Dial up databases, Webcasting, Distributed Programs, Hacking, Banking, Internet telephone

Classifying networks

• By size– Local area networks (LANs) versus Wide area

networks (WANs)• By connectivity– Point to point versus broadcast networks

• By communication medium• By mobility– Fixed versus mobile

Size - differences between local and wide area networks

• ‘Speed’ - bandwidth and latency• Management• Security• Reliability• Billing• Heterogeneity (and standards)

Connectivity - point to point networks

startree

irregular

mesh

Connectivity - broadcast networks

satellite/radio wire

Medium - differences between communication media

• ‘Speed’ - bandwidth and latency• Range• Sharing• Topology• Installation and maintenance costs• Reliability

Mobility - issues arising in mobile networks

• Mobile networking has emerged in the last decade. Introduces new issues of:– energy efficiency– location and tracking– semi-persistent connections– complex administration and billing as devices

and users move around the network

Common issues in networking

• Addressing• Routing• Framing and encoding• Error detection and correction• Flow and congestion

Module contents and structure

Part 1: data transmission

Part 2: packet transmission

Part 3: internetworking

Part 4: applications

Part 1: data transmission

– Transmission media;

– Local asynchronous communication (RS-232);

– Long distance communication (modems and carriers)

Part 2: packet transmission

– Packets, frames and error detection– Local area networks (LANs)– Hardware addressing– LAN wiring and physical topology– Extending LANS: Fiber Modems, repeaters,

bridges and switches; – WAN Technologies and routing– Network ownership and service paradigm – Protocols and layering

Part 3: internetworking

– Concepts, architecture and protocols– IP addresses– Binding protocol addresses (ARP)– IP Datagrams and datagram forwarding– IP encapsulations, fragmentation and

reassembly– The future of IP– An error reporting mechanism (ICMP)– TCP (reliable transport service)

Part 4: Applications and Security

– Client-server interaction

– The socket interface

– Example applications

Next Lecture:

• Local Ansynchronous Communication and RS-232