Clarke, R. J (2001) L909-02: 1 Office Automation & Intranets BUSS 909 Lecture 2 Data Communication Technologies
Clarke, R. J (2001) L909-02: 1
Office Automation & Intranets
BUSS 909
Lecture 2Data Communication
Technologies
Clarke, R. J (2001) L909-02: 2
Notices
Assignment 1:Pickup Assignment 1 Handout now
Assistance with Assignment 1:Buy a copy of Woodward-Kron’s book from
UniCentre Bookshop (if available)Also refer to Academic Essay Writing Notes in
Closed ReservePickup a copy of Learning Development
Student Services Brochure and Timetable
Clarke, R. J (2001) L909-02: 3
Agenda L909-02
Data Communications Principles and Technologiesin this lecture we consider only the Data
Communications technologies relevant to Office Automation
we will revisit this topic in subsequent lectures
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Agenda T909-01
Writing for Commerce: Essays and Case Studies (differs from the published schedule)
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Office Automation
the greatest proportion of work involves information in textual form:proceduresreportsmemoes
applies to:service industries, bureaucracies, public
sector organisations, and small-large private sector organisations
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Office Automation
additionally, decision making (work about work) in any organisation is conducted in groups
these groups almost always are involved in language activities (reading, writing etc)board room meetingsbrainstorming sessionsformal reviewsshareholders meetings
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Office Automation
technologies called OA systems have been developed since the mid-1970s to cope with these kinds of work
generally these systems are based on networks of various kinds (we review the various types and some standard terminology used to describe them this lecture)
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Office Automation
these technologies at that time were very expensive (special hardware and software)
the leader was Wang Computersby the mid 80s experimental systems
were being researched to support group-based activities- this research is still ongoing (Nunamaker et al 1991 40-61)
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Office Automation
OA systems were augmented with systems that had similar functionality
other names that can be found include: OIS- Office Information Systems; EMS- Electronic Meeting Systems; Collaborative Management Systems
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Office Automation
much of this has been superceded by developments in the marketplace- including proprietary integrated software eg. Lotus Notes; Microsoft Office97
also the WWW and graphical browsers provide a way for organisations to transform desktop computing to webtop computing
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Office Automation
but the research that led to these systems is still relevant as we try to implement the same functionality in the form of intranets and extranets (private networks based on Internet technology)
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Office Automation
an additional trend is to create the virtual organisation, which again is based on theory and principles established and developed during the mid-1970s
telework, remote work, mobile data systems etc
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Network Termstopology = pattern of a network
circuit transmission facility provides =>1
channels of communication eg/ phone line, microwave signal, optical cable
node point in a network where circuits are
interconnected by one or more units may be other computers
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Network Processing (1)
Timesharing Networks oldest approach introduced in 3rd generation consists of a single computer performance limited to the computer
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Network Processing (2)
Distributed Processing when minicomputers became popular companies started distributing minis
and micros throughout the organisation when interconnected the technique is
called distributed computing or distributed data processing (DDP)
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Network Processing (3)
Client/Server Computing some functions are best handled locally and some
are best handled centrally blend of timesharing approach (central use) and
distributed processing (local) usually LANs but can be WANs client: user has access to network by means of
desktop computer server: computer of any size which provides
control of network function
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Network Topologies (1)
describes how multiple computers are connected together (eg/ distributed processing, client/server computing) on a network
several different topologies are available
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Network Topologies (2)
Star Network central computer called the central node guarentees centralised control failure on central node causes failure
over entire network
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Network Topologies (3)
Ring Network does not include a central node control is distributed throughout network failure in any link causes problem for
network
Hybrid Network star & rings can be used together when this occurs the topology is referred to
as a Hybrid Topology
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Network Management (1)
often critical to firms network failures can be catastropic require planning and control need to be managed
What would happen if a your banks ATM data comms network fails ?
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Network Management (2)
in large companies network manager network analysts software analysts datacom technicians
in small companies LAN manager
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Network Management (3)
Network Manager:responsible for
planning implementing operating controlling
responsible to CIO
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Network Management (4)
Network Analyst perform same function as systems
analysts restricted to communication-oriented
systems
Software Analysts program & maintain datacom
software
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Network Management (5)
Datacom technicians concerned with hardware and operations
LAN Manager found in smaller organisations members of information services generally a member of using organisation may perform all of the duties of network
manager
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Network Planning
all activities that aim to anticipate firms networking needsCapacity planning analyses & plans for traffic volumes
Staff planning people to manage network & skills
Performance monitoring analyse response times and potential
changes
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Network Control
day-to-day monitoring of the networkinvolves fault detection, fault
isolation, network restorationfirm needs standard procedures to
implement network control
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Network Architectures (1)
variety of hardware & softwareproducts available from:
computer manufacturers common carriers data coms specialist companies
many suppliers & standards is a ‘mixed blessing’
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Network Architectures (2)
network architectures specify protocols rule for interfacing (interconnecting)
various units all data coms devices will follow
specific protocols variety of units led to a small number of
‘industry’ standards
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Network Architectures (3)
Industry standards include:SNA (IBM)BNA (Burroughs)DSE (Honeywell)
One of the most common data coms standards is called OSI
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Network Architectures (4)
SNA Systems Network Architecture developed by IBM because it
marketed 200 different data coms products
one of the first standards developed a proprietary standard
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Network Architectures (5)
SNA: defines all activities involved in
transmitting data through a network transmitted from a user node transmitted to a host node transmitted through one or more
intermediate nodes
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Network Architectures (6)
separates physical activities that transmit data
and logical activities that control transmission
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Network Architectures (7)
SNA classifies logical activities into layers layers insulate users from changes in
the datacom hardware and software layers have become a common strategy
in other datacoms standards
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OSI Model (1)
OSI = Open Systems Interconnectionalmost all Network rely upon this
Model to organise communications between Clients and Servers
uses layers like SNA to define physical and logical layers
7 layers are used; all nodes have them
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OSI Model (2)
A layer at one node (user) ‘talks’ to its corresponding layer at the other (host) end
Layers 1-3 needed at every node; Layers 4-7 at host & user nodes only
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Frame Check
OSI Model (3)
1: Physical Layer Transmits the data from one node to
another eg./ RS232c
2: Data Link Layer Formats the data into a record called a
frame Performs error detection
Address Control MessageEnding
FlagBeginning
Flag
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OSI Model (4)
3: Network Layer causes the physical layer to transfer the
frames from node to node
4: Transport Layer enables user and host nodes to
communicate with each other synchronizes fast- and slow- speed
equipment as well as overburdened and idle units
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OSI Model (5)
5: Session Layer initiates, maintains and terminates each
session sessions consist of all frames that
comprise an activity, and all signals that identify beginning and end
eg./ log-on and user id routines to initiate sessions
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OSI Model (6)6: Presentation Layer
formats data for presenting to user or host
eg./ information to be displayed on users screen is formatted into proper number of screen lines and characters per line
7: Application Layer controls user input from the terminaland
executes the user’s application program
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OSI Model (7)
Eg./ User needs host software L7 (application) takes request L6 (presentation) changes input data to
correct format for transmission L5 (session) starts the session on the host
machines L4 (transport) selects route from user to host L3 & 2 (network & data link) cause data to be
transmitted through L1 (physical)
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OSI Model (8)7: Application Layer
consists of application programs that use the network
6: Presentation Layerstandardises data presentation to applications
5: Session Layermanages sessions between applications
4: Transport Layerprovides end-to-end error detection and correction
3: Network Layermanages connections across the network for the upper layers
2: Data Link Layerprovides reliable data delivery across the physical link
1: Physical Layerdefines the physical characteristics of the network media
Low
High
USER HOST
Low
High
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Layer 7
Layer 6
Layer 5
Layer 4
Layer 3
Layer 2
Layer 1
Protocols
Layer 7
Layer 6
Layer 5
Layer 4
Layer 3
Layer 2
Layer 1
2
1
2
1
33
Front-end processor Cluster Control Unit
P
P
P
P
P
P
P
P
P
AP
SP
SP
SP/P
User Node Host UserIntermediate Nodes
TerminalSoftwareor ROMRoutines
UserActions
Host
ChannelDevices
Front-endProcessor
Front-endor switching Node
OSI Model (9)
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Internet
Internet (=Internetworking) collection of computer networks and to allow interoperability between them
networks can consist of many types of network technologies, protocols, and computers
Several protocols are required for transmitting data across the Internet (TCP/IP)
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InternetInternet Protocol
IP manages the transfer of data across physically distinct networks
transfers data into packets within an ‘envelope’ that describing its source and destination
a message is in effect shattered into pieces, packaged as packets in envelopes, and burst transmitted to the destination
IP looks after delivering these packages- one packet at a time!
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InternetTransmission Control Protocol
networks are unreliable and IP does not guarantee that all pieces arrive (no notion of a connection)
TCP defines conventions that make sure the pieces arrive in the correct order- by specifying another envelope around the data packets
IP layer moves packets, TCP manages the connection
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InternetOther Services & Protocols
the layering or encapsulation which is a characteristic of OSI also works in much the same way with other services supported by the Internet (TCP/IP)
File Transfer Protocol defines the conventions which describe how computers can cooperate in order to copy files from one computer to another on the Internet- it uses TCP/IP to do this
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InternetOther Services & Protocols
TCP
IP
FTP
TCP
FTP
IP
Physical Network
Internet Protocol; Transmission Control Protocol; File Transfer Protocol
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InternetWeb Services & Protocols
the web is just another internet service!Hypertext Transfer Protocol (HTTP) is the
set of rules for making and fulfilling web requests
however, the web is also designed to encapsulate other protocols including FTP, Gopher, WAIS, telnet and NNTP- we will talk about these services latter
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InternetWeb Services
works as a client-server- in terms of services not necessarily hardware
differs from other network models (terminal to mainframe; and peer-to-peer) because client and server are independent, fully functional computer systems in their own right
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InternetWeb Services
Mainframe & Terminal
Client-server
Peer-to-Peer
Typing
Printing
Request
Reply
Send Message
Send Messageemail
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Intranets & OASuccess of WWW- Open Standards
machines on the Internet are effectively decentralised
an important aspect of the web is that it is a set of open (not proprietary) protocols:Uniform Resource Locators URLs Hypertext Transfer Protocol (HTTP) Hypertext Markup Language (HTML)
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Intranets & OASuccess of WWW- Specific Issues
web protocols are general enough to be implemented on any computerweb application are the ‘topmost’ layer in
the Internet protocol hierarchycomplex processes of transfer of data are
‘hidden’ from the web application developer and user
as a consequence there is a great variety of web applications available
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Web Servers & ClientsSource: Yeager & McGrath (1996, 11-16)
Web
TCP
Web
IP
FTP
TCP
FTP
IP
Physical Network
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Intranets & OAFailure of OA- Proprietary Technologies
OA did not become very important because they were based on proprietary technologiesimplies ‘closed’ technologies and
markets- ultimately counter-productive!slow development time, large market lags,
small client bases, under utilised technology, increased expense in setup, use, maintenance, upgrade
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Intranets & OAFailure of OA- Specific Issues
data sometimes had to be re-entered- proprietary technologies mean that other vendors don’t have the technical information needed to write transfer routines
had to rely on the vendor to keep the technology current- there development team is the only one available to service your needs
incompatibilities- can’t supplement the OA vendors equipment with other vendors products
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From OSI to TCP/IP
OSI
7: Application Layer
6: Presentation Layer
5: Session Layer
4: Transport Layer
3: Network Layer
2: Data Link Layer
1: Physical Layer
TCP/IP4: Application Layer
consists of applications and processes that use the network
3: Host-to-Host Transport Layer
provides end-to-end data delivery services
2: Internet Layer
defines the datagram and handles the
routing of data
1: Network Access Layer
consists of routines for accessing physical networks