G52CCN Computer Communications and Networks Milena Radenkovic Room: B47

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

Lectures Monday,11:00 Monday,11:00 Tuesday 12:00 Tuesday 12:00

Related modules G53ACC - Advanced Computer Communications G53ACC - Advanced Computer Communications G5BIAW - The Internet and the World Wide Web G5BIAW - The Internet and the World Wide Web

Objectives To understand the basic principles of data communications and computer networks. 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 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 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. To learn about current networking technologies, especially Internet protocols.

Assessment Two hour written examination Two hour written examination The style of question will be based upon those from previous years. Their content will of course be different. 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. Last year’s exam paper is on sale in the bookshop and previous papers are in the library. No coursework No coursework

Text books and notes My notes are available at: My notes are available at:  The core recommended course text is: The core recommended course text is:  Computer Networks and Internets, Douglas E. Comer, Prentice Hall Supplementary texts are: 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) 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 Access to remote resources Human communication Human communication Mobile computing Mobile computing Computing power through parallelism Computing power through parallelism Optimising resources - load balancing Optimising resources - load balancing Incremental growth of computer systems (reduced cost and risk) Incremental growth of computer systems (reduced cost and risk) Increased robustness through graceful degradation Increased robustness through graceful degradation

Uses of computer networks , 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 , 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 By size  Local area networks (LANs) versus Wide area networks (WANs) By connectivity By connectivity  Point to point versus broadcast networks By communication medium By communication medium By mobility By mobility  Fixed versus mobile

Size - differences between local and wide area networks ‘Speed’ - bandwidth and latency ‘Speed’ - bandwidth and latency Management Management Security Security Reliability Reliability Billing Billing Heterogeneity (and standards) Heterogeneity (and standards)

Connectivity - point to point networks star tree irregular mesh

Connectivity - broadcast networks satellite/radio wire

Medium - differences between communication media ‘Speed’ - bandwidth and latency ‘Speed’ - bandwidth and latency Range Range Sharing Sharing Topology Topology Installation and maintenance costs Installation and maintenance costs Reliability Reliability

Mobility - issues arising in mobile networks Mobile networking has emerged in the last decade. Introduces new issues of: 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 Addressing Routing Routing Framing and encoding Framing and encoding Error detection and correction Error detection and correction Flow and congestion 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  Client-server interaction  The socket interface  Example applications

Next Lecture: Transmission media Transmission media