Chapter 11: LAN / WAN And Open System Interconnection In MIS

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MANAGEMENT INFORMATION SYSTEMS


C
hapter

11


LAN / WAN AND OPEN SYSTEM INTERCONNECTION

IN MIS


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C
hapter
11
:

LAN / WAN
A
nd Open System Interconnection

In MIS



1
1
.1 Learning O
utcomes

After complete this lesson, you would
be
able to:



Know the various categories of Networks have been used in
Management Information Systems.



Identify the various
types of topology have been used in Local Area
Networks (LAN).



Discus
s

the advantages and disadvantages of various types of
topology.



Explain
about OSI model and
the
seven layers of OSI model.



11.
2

Line Configuration



Line configuration refers to the way

two or more communication
devices attach to a link.



A link is the physical communication pathway.



There are two possible line configurations: point
-
to
-
point and
multipoint.


11.
2
.1 Point
-
T
o
-
P
oint



P
rovides a dedicated link between two devices
.



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11.
2
.2 Mu
ltipoint (
M
ultidrop)



M
ore than two devices share a single link.




11.
3

Categories
O
f Networks



There are 3 primary categories of networks: LAN, MAN, and WAN
.


11.
3
.1 Local Area Network (LAN)





LAN is usually privately owned and linked the devices in a si
ngle
office, building, or campus.



LAN can be extend throughout a company and include voice, sound,
and video peripherals.

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It is designed to allow resources (h/w, s/w, or data) to be shared
between personal computers / workstations.



Beside size, LANs are di
stinguished from other types of networks by
their transmission media and topology such as bus, ring and star.



Traditionally, LANs have data rates in the 4


16 Mbps range.
However its speed is increasing today and can reach 100 Mbps with
gigabit system.


1
1.
3
.2 Metropolitan Area Network (MAN)



It is designed to extend over an entire city. I.e. it can be a single
network (cable television network) or connecting a number of LANs
into a larger network.



A MAN may be wholly owned and operated by a private company

or
be a service provided by a public company.





11.
3
.3 Wide Area Network (WAN)



It provides long
-
distance transmission of data, voice, image and video
information over large geographical areas that may comprise a
country, or even the whole world.



WANs m
ay utilize public, leased, or private communication devices,
usually in combinations, therefore span an unlimited number of miles.

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A WAN that is wholly owned and used by a single company is often
referred to as an enterprise network.





11.4 Internetwork
s






Internetwork / internet is refer as when two or more networks are
connected.



Individual networks are joined into internetworks by the use of
internetworking devices (such as routers, gateways).



Intranet
: a generic term used to mean an interconnection

of networks.



Internet: the name of a specific worldwide network.


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11.
5

Topology



Topology of a network is the geometric representation of the
relationship (peer
-
to
-
peer or primary
-
secondary) of all the links as
linking devices. It refers to the way a netwo
rk is laid out, either
physically or logically



Basic topologies: star, bus, and ring



Peer
-
to
-
peer: all the devices share the link equally. E.g. ring, bus



Primary
-
secondary: one device controls traffic and other must
transmit through it. E.g. star, bus.


11
.
5
.1 Star



Each device has a dedicated point
-
to
-
point link only to a central
controller (hub), which act as an exchange.



Advantage: Easy to install and reconfigure; robustness and easy fault
identification and fault isolation
.



Disadvantage: Whole network do
wn when hub is not working














11.
5.
2 Bus



It is a multipoint line configuration, where one long cable acts as a
backbone to link all the devices in the network.



Nodes are connected to the bus cable by drop line (a connection
running between the d
evice and main cable) and taps (a connector).



Advantage: easy of installation; less cable than, star topology
.



Disadvantage: there is a limit on the number of taps a bus can support
and on the distance between those taps


cause by heat (signal
reflection)

and losing of energy during transmission; difficult
reconfiguration and fault isolation

HUB

Node

Node

Node

Node

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11.
5
.3 Ring



Each device has a dedicated point
-
to
-
point line configuration only
with the two devices on either side of it. Each device in the ring
incorporates a rep
eater.



Signal is passed along the ring in 1 direction.



Advantage: Easy to install and reconfigure, Simplified fault isolation.



Disadvantage: Media and traffic consideration


maximum length and
number of devices); A break in the ring can disable the entire

network
.















11.
6

The OSI (Open System Interconnection) Model



International Standards Organization (ISO
)

is a multinational
body dedicated to worldwide agreement on international standards.



An ISO standard that covers all aspects of network com
munication is
the
Open System Interconnection (OSI) model
.


Node

Node

Node

N
o
de

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11.
6
.1 Layered Architecture



A typical computer networking within a business contains the
following components: Computers, centrally located wiring
concentrators, wires and its connectors and jacks
, disk drivers,
computer applications (e
-
mails, word etc), computer programs and
etc).



To keep the pieces mentions above working together harmoniously
and to allow modularity between them,
network architecture model

is
necessary where it places the appropr
iate network pieces in layers.



The model consists of 7 separate but related layers, each of which
defines a segment of the process of moving information across a
network. Each layer in the model defines what services either
hardware or software or both pr
ovide.



The scheme shown below basically the architecture model adopted by
the ISO when its members created the
open system interconnection
(OSI)

reference model.



Open system: a model that allows any two different systems to
communicate regardless of their

underlying architecture.



7

Application

6

Presentation

5

Session

4

Transport

3

Network

2

Data link

1

Physical


The 7
-
layers of OSI model




A mnemonic for remembering the layer of the OSI model is:


P
lease
D
o
N
ot
T
ouch
S
teve’s
P
et
A
lligator

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Differen
t layers perform different tasks, and the whole would not
function without the proper operation of each of its parts.
Communications s/w is no exception.



As the message travels from A to B, it may pass through many
intermediate nodes


which usually involv
e only the 1
st

three layers
(physical, data link and network later) of the OSI model.



The network workers performing their job duties at each layer in the model


11.
6
.2 Organization
O
f
T
he Layers

The 7
-
layers can be categories into 3 subgroups:



Network
support layers
: physical, data link and network layer.



Transport layer



User support layers
: session, presentation, and application



Network support layers
: deal with the physical aspects of moving
data from one device to another. I.e. electrical specificati
ons, physical
connections and addressing, transport timing and reliability.



Transport layer
: to ensure and
-
to
-
end reliable data transmission.



User support layers
: to allow interoperability among unrelated s/w
system.


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11.6.3
Summary
O
f
OSI L
ayer functions


Application

To allow access to the network resources

Presentation

To translate, encrypt, and compress data

Session

To establish, manage, and terminate sessions

Transport

To provide end
-
to
-
end message delivery and error recovery

Network

To move packets

from source to destination; to provide
internetworking

Data link

Organize bit into frames; to provide node
-
to
-
node delivery

Physical

To transmit bits over a medium; to provide mechanical and
electrical specification


Review Questions

1.

List and explain t
he
categories of Networks

use
d in Management
Information Systems.

2.

Identify the various types of topology have been used in Local Area
Networks (LAN).

3.

Discuss the advantages of various types of topology.

4.

Explain about OSI model and the seven layers of OSI
model.