Transcript Transmission media

G52CCN
Computer Communications
and Networks
Milena Radenkovic
Room: B47
Email: [email protected]
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
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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
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‘Speed’ - bandwidth and latency
Management
Security
Reliability
Billing
Heterogeneity (and standards)
Connectivity - point to point
networks
tree
star
irregular
mesh
Connectivity - broadcast
networks
satellite/radio
wire
Medium - differences between
communication media
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‘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
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Addressing
Routing
Framing and encoding
Error detection and correction
Flow and congestion
Module contents and structure
Part 4: applications
Part 3: internetworking
Part 2: packet transmission
Part 1: data transmission
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 RS232