Transcript Systemic Semiotic Design Practice:

BUSS 909
Office Automation & Intranets
Lecture 2
Data Communication
Technologies
Clarke, R. J (2001) L909-02:
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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 Reserve
Pickup a copy of Learning Development
Student Services Brochure and Timetable
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Agenda L909-02
Data Communications Principles and
Technologies
in 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 Overview
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Office Automation
the greatest proportion of work
involves information in textual form:
procedures
reports
memoes
applies to:
service industries, bureaucracies,
public sector organisations, and smalllarge 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 meetings
brainstorming sessions
formal reviews
shareholders 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 Computers
by 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 marketplaceincluding 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 Processing &
Topologies
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Network Terms
topology = 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,
Planning & Control
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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 needs
Capacity 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 network
involves fault detection, fault
isolation, network restoration
firm needs standard procedures to
implement network control
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Network Architectures
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Network Architectures (1)
variety of hardware & software
products 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
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OSI Model (1)
OSI = Open Systems Interconnection
almost 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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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
Beginning
Flag
Address
Control
Message
Frame
Check
Ending
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)
USER
HOST
7: Application Layer
High
consists of application programs that use the network
High
6: Presentation Layer
standardises data presentation to applications
5: Session Layer
manages sessions between applications
4: Transport Layer
provides end-to-end error detection and correction
3: Network Layer
manages connections across the network for the upper layers
2: Data Link Layer
provides reliable data delivery across the physical link
Low 1: Physical Layer
Low
defines the physical characteristics of the network media
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OSI Model (9)
Intermediate Nodes
User Node
User
Actions
Terminal
Software
or ROM
Routines
Host User
Layer 7
AP
Layer 7
Layer 6
SP
Layer 6
Layer 5
SP
Layer 5
Layer 4
SP/P
Layer 4
Layer 3
Host
P
3
Layer 2
P
2
P
2
Layer 1
P
1
P
1
P
3
P
Layer 3
Protocols
Front-end processor
Front-end
or switching
Node
P
Layer 2
Front-end
Processor
P
Layer 1
Channel
Devices
Cluster Control Unit
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Web Clients & Servers
Source: Yeager & McGrath (1996, 11-16)
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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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Internet
Internet 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 packagesone packet at a time!
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Internet
Transmission 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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Internet
Other 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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Internet
Other Services & Protocols
Internet Protocol; Transmission Control Protocol; File Transfer Protocol
FTP
FTP
TCP
TCP
IP
IP
Physical Network
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Internet
Web 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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Internet
Web Services
works as a client-server- in terms of
services not necessarily hardware
differs from other network models
(terminal to mainframe; and peer-topeer) because client and server are
independent, fully functional
computer systems in their own right
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Internet
Web Services
Mainframe & Terminal
Typing
Printing
Client-server
Request
Reply
Peer-to-Peer
Send Message
email
Send Message
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Intranets & OA
Success 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 & OA
Success of WWW- Specific Issues
web protocols are general enough to
be implemented on any computer
web application are the ‘topmost’ layer
in the Internet protocol hierarchy
complex 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 & Clients
Source: Yeager & McGrath (1996, 11-16)
Web
Web
FTP
FTP
TCP
TCP
IP
IP
Physical Network
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Summary
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Intranets & OA
Failure of OA- Proprietary Technologies
OA did not become very important
because they were based on
proprietary technologies
implies ‘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 & OA
Failure of OA- Specific Issues
 data sometimes had to be re-enteredproprietary 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
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
4: 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
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Next Week
Lecture (L909-03):
Office Automation Systems Computer
supported Cooperative
Work/Groupware
Tutorial (T909-02):
Search Engines & Techniques (differs
from Tutorial Schedule)
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