Week #9

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Systems Analysis I
System Implementation
ISYS 200
Glenn Booker
ISYS 200
Week #9
1
System Implementation
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Now we get to actual creation of the system
we’ve designed
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Notice the text covers this fairly quickly,
since many other courses are needed to cover
the skills and concepts needed for implementation
Key aspects of implementation include
how the information is distributed,
providing user training, and choosing
a good conversion strategy
ISYS 200
Week #9
2
Implementing Distributed
Systems
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Variations of client/server (C/S) networks
have been widespread since the 1980’s,
and continue to evolve
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ISYS 200
In basic form, C/S refers to some system
processing being done by a PC-based client
application, while other parts are done on
the server
Now we tend to have many types of specialized
servers instead of just one
Week #9
3
Implementing Distributed
Systems
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Servers can include many varieties
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File servers, to hold shared files
Print servers, to manage print jobs
Database servers, to run a shared
database system
Now we might add web servers to control
access to our system, and various kinds
of application servers
ISYS 200
Week #9
4
Types of Networks
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The basic types of networks include
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ISYS 200
LAN – Local Area Network, a typical home
or office-sized network
WAN – Wide Area Network, a corporate
network which spans continents
WLAN – Wireless LAN, a LAN which uses
wireless (Wi-Fi) connections
Week #9
5
Network Connections
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Common network connections include
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ISYS 200
Ethernet cable, an 8-wire cable (RJ-45 plugs)
similar to 4-wire phone lines (RJ-11)
Fiber optic cable, for Gigabit and faster networks
“Thick” and “thin” Ethernet cables are
pretty obsolete
Week #9
6
Organizing Networks
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There are four major topologies (structures)
for a physical computer network
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Bus
Ring
Star
Hierarchical
They may be combined in some cases, such
as a hierarchical top level structure, and stars
used locally
ISYS 200
Week #9
7
Network Topology - Bus
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A key function to achieve connectivity
among computers is definition of the
network topology
The “bus” is the simplest topology - it
connects computers along a single line
A peer-to-peer (server-less) network uses the
bus topology, with AppleTalk or Ethernet
ISYS 200
Week #9
8
Ring Topology
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The ring topology connects computers in a
loop, and passes packets of data from one
computer to the next
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IBM’s Token Ring is the most famous example
Bad if a computer falls off the network – hard
to tell who “dropped” the packet
ISYS 200
Week #9
9
Star Network
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Many clients may be connected to each
server across a star network
The middle of each star is a server
Servers are connected to each other
Very common – think of using a server for
each department, and be able to control
which departments can see each other
ISYS 200
Week #9
10
Hierarchical Network
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This is a set of nested star networks, looks
kind of like an organization chart
Generally the servers get smaller the further
down the hierarchy
Sometimes used in very large corporations,
where the biggest servers store companywide or division-wide data
ISYS 200
Week #9
11
Network Modeling
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A network for a system or an organization is
developed to meet a need-to-know basis
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Ensure people who need to see data can get to it
And those who don’t need to, can’t
Networks are generally broken into portions
or segments which correspond to
organizational units
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ISYS 200
One segment is the Accounting dept., another
is the Human Resources dept., and so on
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12
Network Modeling
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Segments of the network are separated from
each other by network hardware
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Routers, switches, hubs, bridges, and other toys
are the hardware involved*
The type of hardware is chosen based on
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The protocols involved
The distances between segments
The amount of logic or processing needed
for isolation
* Cisco has some nice tutorials to help explain the hardware in more detail
ISYS 200
Week #9
13
Network Modeling
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Based on the type of network topology
chosen, a network decomposition diagram
(p. 628) can be developed to show the parts
of a network, and who they can talk to easily
Different symbols can be used to show hubs
at the center of each segment, key types of
users, groups of related workstations, and
external networks
ISYS 200
Week #9
14
Network Modeling
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In contrast, a hub connectivity diagram shows
the hubs of your network, and how far they
are from each other
A more detailed version is the workstation
connectivity diagram, which examines one
segment (hub) and looks at the distances
involved in its connections
ISYS 200
Week #9
15
Distribution
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Since computers were invented, the amount
of distribution of data and processing
functions has tended to go up without end
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The ultimate incarnation is web-based computing,
where both data storage and processing are
distributed across possibly hundreds of computers
While this allows more flexibility and often
better use of resources, it adds reliability
and security issues
ISYS 200
Week #9
16
Training Users
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As a system is being implemented, several
key aspects of training need to be managed
While end user training is often considered,
there may be other kinds of training needed
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ISYS 200
Training for other user roles, including managers
Training for support staff of the operational
system (help desk, and system maintainers)
Training for those who will train users (train-thetrainer), if there are many end users
Week #9
17
Training Users
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Training may also be needed on commercial
components of the system, so vendors may
need to provide training on how their OS or
bridge works
Training may be conducted by systems
analysts, consultant trainers, or training
staff within your organization
ISYS 200
Week #9
18
Conducting Training
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Training needs to be planned carefully
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Need to determine its objectives and methods
Need to determine where to conduct training
Need to develop training materials, and keep
them consistent with the actual system
User training needs to be done before the
system is implemented, but not so long that
they forget what they learned!
ISYS 200
Week #9
19
System Conversion Strategies
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To implement a new information system, you
are presumably replacing whatever existing
system (if any) and processes (whether
manual and/or automated) that are currently
performing the system’s functions
Need to choose a conversion strategy
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ISYS 200
How to convert from doing things the old way
to using the new system
Week #9
20
System Conversion Strategies
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There are about five types of conversion
strategies to choose from (p. 636)
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ISYS 200
Direct changeover means the old system is used
until a stated date and time, after that, the new
system is used
Parallel conversion means that the old and new
systems are used together for some period of
time, until you’re okay to shut off the old system
Week #9
21
System Conversion Strategies
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ISYS 200
Gradual conversion tries to slowly phase in the
percent of transactions handled by the new
system, until it does everything
Modular prototype conversion means that the new
system is developed in chunks of functionality;
when a set of functions are ready to be released,
it becomes operational and that part of the old
system is shut down
The distributed conversion strategy works
geographically – convert sites one group at
a time until they are all done
Week #9
22
Security Concerns
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Both traditional and web-based systems
have security and privacy issues
Security concerns can be divided into
physical, logical, and behavioral
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ISYS 200
Physical security is making sure the computer
facilities aren’t broken into, the computers don’t
get stolen, backup tapes don’t grow legs, etc.
Week #9
23
Security Concerns
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Logical security is within the system software
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ISYS 200
To ensure that users are validated,
Passwords expire and don’t get reused,
Passwords are sufficiently complex
User access to system functions really is controlled by
their security profiles
Firewalls on public Internet access points also fit into
this category
Week #9
24
Security Concerns
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Behavioral security is avoiding compromise of
your system from inside – by its users
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ISYS 200
Screening potential employees
Making security policies clear
Monitor behavior which may compromise the system
Limit number of incorrect sign-on attempts
Monitor your own software activity and look for
suspicious activities
Control distribution and/or encrypt system outputs
Shred discarded system outputs
Week #9
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Internet Security
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Basic aspects of Internet security include
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Use and maintain virus protection software
Filter email from spam
Restrict Internet access by employees
Monitor network connections to the public
Encrypt anything passing through the Internet
The Rainbow Series of reports by the
NIST is a widely used set of computer
security standards
ISYS 200
Week #9
26
Privacy Concerns
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Privacy has become a key public issue
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ISYS 200
Establish clear privacy policies, and follow them
Only get required information
Make personal information optional, if you
must ask for it
Use anonymous sources about clients
where possible
Be ethical
Week #9
27
System Evaluation
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Once the new system is fully operational,
it is important to evaluate its success
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Go back to the system objectives developed
from the problems and opportunities analysis
Measure the quantities described in the objectives
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ISYS 200
Customer satisfaction, system throughput, number
of transactions, number of bad transactions, …
Compare the measurements to the predicted
values, and analyze differences between them
Week #9
28
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