Introduction to Network Communications G64INC Dr. Gail Hopkins Introduction Practical matters Module goals, structure and contents Initial introduction to some key ideas and issues Lectures Two lectures per week All slides available online: http://www.cs.nott.ac.uk/~gtr/inc/ Related Modules G52CCN Introduction to Computer Networks G53ACC Advanced Computer Communication Spring semester, INC is prerequisite 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 questions will be based upon those from the previous years. Past exam papers from G52CCN are also useful for exam preparation. No coursework 1
Text Books and Notes The notes are available at: http://www.cs.nott.ac.uk/~gtr/inc The core recommended course text is: Computer Networks and Internets, Douglas E. Comer, Prentice Hall Supplementary texts are: Tanenbaum, Computer Networks, Prentice Hall Halsall, Data communications, computer networks and open systems, Addison Wesley http://computer.howstuffworks.com/ Module Contents and Structure Part 1: Introduction and Internet Applications Part 2: Data Communications Part3: Packet Switching and Network Technologies Part 4: Internetworking using TCP/IP Part 1: Introduction and Network Applications Introduction and overview Internet Applications Part 2: Data Communications Information Sources and Signals Analogue/digital, bandwidth, bits, baud rates, Nyquist theorem, Manchester encoding Transmission media Reliability and Channel Coding Error detection mechanisms Transmission modes RS232, bytes, blocks, frames, simplex and half/full duplex communication Modulation and Modems FM, AM, PSK, Modems Multiplexing and Demultiplexing FDM, TDM, WDM Part 3: Packet Switching and Network Technologies LANS packets, frames and topologies IEEE Mac Sub-layer FDMA, CDMA, TDMA, CSMA (/CD,/CA) Wired LAN Technologies Ethernet, 802.3 Wireless Networking Technologies Wifi, bluetooth, WiMax, PAN, VSAT, GPS LAN Extensions Fibre modems, repeaters, bridges, switches WAN Technologies and Dynamic Routing Part 4: Internetworking using TCP/IP Internetworking IP Concepts, architecture and protocols Internet addressing, dotted decimal notation, classless addressing Datagram Forwarding Datagrams, encapsulation, MTU Support Protocols and Technologies ARP, ICMP, DHCP, NAT IPv6 UDP/TCP 2
The Growth of the Internet Introduction and Overview History of Communications What is a Computer Network? Telephone Electric Telegraph Television Radio Ethernet ARPANET The World Wide Web The Internet Worm Neuromancer MUDs You can order pizza online Social networking Mobile web > 600 M computers Mobile users > desktop users An interconnection of autonomous computers (as opposed to communication between separate but interdependent parts of a single computer) 1837 1906 1876 1926 1969 1973 1979 1984 1988 1991 1999 2008 1994 2002 2010 Uses of Computer Networks Email, World Wide Web, Video Conferencing, File Transfer, Collaborative Virtual Environments, Remote control of robots and machines, Online databases, Webcasting, Distributed Programs, Hacking, Banking, Internet telephone, e-learning, social networking 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 3
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 Common Issues in Networking Addressing Routing Framing and encoding Error detection and correction Flow and congestion Mobility - Issues Arising in Mobile Networks Mobile networking has emerged in the last decade. Introduces new issues of: location and tracking semi-persistent connections complex administration and billing as devices and users move around the network energy efficiency Public and Private Parts of the Internet Public network Service available to subscribers E.g. ISPs Private network Controlled by one particular group Not necessarily owned by them! E.g. a leased data circuit used as part of a company s private network Four categories: Consumer, Small office/home Office (SOHO), Small- To-Medium Business (SMB), Large Enterprise Networks, Interoperability and Standards Communication involves at least two entities sender and receiver Most packet switching communication systems contain intermediate entities (e.g. routers) Therefore, must agree on how information will be represented and communicated! Interoperability Need rules for this - protocols Protocol Suites and Layering Models Each protocol handles part of the communication not handled by another To achieve interoperability, protocols are constructed in suites Application Transport Internet Network Interface Physical Layer 5 Layer 4 Layer 3 Layer 2 Layer 1 4
How Data Passes Through Layers Headers and Layers Each layer on the sending computer adds its own information in a header on the front of the packet The equivalent layer on the receiving end removes it and uses it This header information is for the protocol software at each end to use Physical header (sometimes) Network Interface header Internet header Transport header Message sent by application (payload) ISO OSI Seven Layer Reference Model Questions? Module web page: http://www.cs.nott.ac.uk/~gtr/inc/ Reading: Chapter 1, Computer Networks and Internets, Douglas Comer, 5 th Edition 5