Hugo Gallagher

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Building Services Engineering Design 1 Module
BNEE378

• Hugo Gallagher
• Room M709
• h.gallagher_at_gcal.ac.uk
• hugo_at_logis-tech.co.uk
• Tel [phone]
• Lecture 1

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BNEE378 Recommended Text

• Data Computer Communications 7th Edition by
  William Stallings, Prentice Hall (2003)
• Distributed Systems and Networks by William
  Buchanan, McGraw-Hill (2000)
• Electronic Communication Systems, 2nd Edition by
  Roy Blake

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BNEE378 Teaching Syllabus

• Data and Computer Communications by William
  Stallings, 7th edition
• Ch. 1 Data Communications Networks Overview
• Ch. 2 Protocols Architecture
• Ch. 3 Data Transmission
• Ch. 4 Transmission Media
• Ch.15 Local Area Network Overview

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William StallingsData and Computer
Communications7th Edition

• Chapter 1Data Communications and Networks
  Overview

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A Communications Model

• Source
• generates data to be transmitted
• Transmitter
• Converts data into transmittable signals
• Transmission System
• Carries data
• Receiver
• Converts received signal into data
• Destination
• Takes incoming data

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Communications Tasks
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Simplified Communications Model - Diagram
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Simplified Data Communications Model
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Networking

• Point to point communication not usually
  practical
• Devices are too far apart
• Large set of devices would need impractical
  number of connections
• Solution is a communications network
• Wide Area Network (WAN)
• Local Area Network (LAN)

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Wide Area Networks

• Large geographical area
• Crossing public rights of way
• Rely in part on common carrier circuits
• Alternative technologies
• Circuit switching
• Packet switching
• Frame relay
• Asynchronous Transfer Mode (ATM)

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Circuit Switching

• Dedicated communications path established for the
  duration of the conversation
• e.g. telephone network

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Packet Switching

• Data sent out of sequence
• Small chunks (packets) of data at a time
• Packets passed from node to node between source
  and destination
• Used for terminal to computer and computer to
  computer communications

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Frame Relay

• Packet switching systems have large overheads to
  compensate for errors
• Modern systems are more reliable
• Errors can be caught in end system
• Most overhead for error control is stripped out

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Asynchronous Transfer Mode

• ATM
• Evolution of frame relay
• Little overhead for error control
• Fixed packet (called cell) length
• Anything from 10Mbps to Gbps
• Constant data rate using packet switching
  technique

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Local Area Networks

• Smaller scope
• Building or small campus
• Usually owned by same organization as attached
  devices
• Data rates much higher
• Usually broadcast systems
• Now some switched systems and ATM are being
  introduced

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LAN Configurations

• Switched
• Switched Ethernet
• May be single or multiple switches
• ATM LAN
• Fibre Channel
• Wireless
• Mobility
• Ease of installation

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Metropolitan Area Networks

• MAN
• Middle ground between LAN and WAN
• Private or public network
• High speed
• Large area

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NetworkingConfiguration
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Communications Networks

• LANs, MANs, WANs
• A Comms. Network is a facility that interconnects
  a number of devices and provides a means for
  transmitting data from one attached device to
  another

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Classification

• In terms of topology and transmission medium
  most common geographical scope
• Traditionally, networks have been classified as
  either local area networks (LANs) or wide-area
  networks (WANs)
• MAN, which occupies a middle ground between LANs
  and WANs.

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LAN Local Area Network

• Covers a limited area
• Generally provides a high data rate capability
• Confined to a single site and provides for the
  exchange of info. and efficient use of shared
  resources within the site.

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LAN

• Conform to a defined international standard
• Support a high data rate typically 1 to 10 Mbps
• Max. range of typically at least 500m, (10km)
• Supports a variety of hardware independent
  devices
• High standards of reliability and data integrity
• Minimal reliance on centralised components and
  controlling elements
• Maintain performance under conditions of high
  loading
• Allow easy installation and expansion
• permit maintenance, reconfiguration, expansion

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ORIGIN of LANs

• IBM introduced a series of terminal devices
  (1974) for transaction-processing applications
• Uniqueness - method of connection a common cable
  that formed a loop provided a comms. path within
  a localised geographical area.
• limitations - data transfer rate and
  incompatibility between individual IBM loop
  systems
• Key advantages - media-sharing common access to
  a centralised resource.
• In 1977, Datapoint Corporation began selling its
  Attached Resource Computer Network (Arcnet) first
  commercial LAN product.

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Comparison with WANs

• Geographical area
• Data transmission and error rates
• Ownership
• Regulation
• Data routing
• Topology
• Type of info. carried

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Geographical Area

• LAN - localised to a building, group of
  buildings, campus
• WAN - can span an area ranging in size from a
  city to the globe

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Data Transmission and Error Rates

• LAN - 4Mbps to 16Mbps, some metallic and fibre
  optic based operating at 100Mbps, Error rate 1 in
  107 to 1 in 108
• WAN - normally operate at or below T1 and E1
  translation rates of 1.544 Mbps and 2.048 Mbps
• Error rate 1 in 106 to 1 in 107

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Ownership

• LAN - usually with the implementor
• WAN comms. carrier retains ownership of line
  facilities

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Regulation

• LAN - building codes
• WAN - governmental regulation at local, state and
  national levels

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Data Routing

• LAN - normally flows fixed route
• WAN - switching capability of network allows
  dynamic alteration of data flow

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Topology

• LAN - usually limited to bus, ring, tree and star
• WAN - virtually unlimited design capability

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Type of info. carried

• LAN - primarily data
• WAN - voice, data and video commonly integrated