- EP601 LOCAL AREA NETWORK

(LAN)
INTRODUCTION:
LOCAL AREA NETWORK (LAN)
LOGICAL & PHYSICAL TOPOLOGY
TOPOLOGY IN LAN:
BUS, RING, STAR,HYBRID & MESH
TRANSMISSION TECHNIQUES
BASEBAND & BROADBAND

DEFINITION OF LAN
1) A group of computers that shared hardware, software or data.
Widely used to link a personal computer (PC) or workstation
at homes, offices or plants to share sources and exchange
information.
2) Covers a small area for example, a computer laboratory,
school or a building.
Communication system which allows variety of devices to
communicate between each other in a limited geographic
area (in building or a nearby buildings).
3) Usually owned, used and organized by a private organization.

DEFINITION OF LAN
The following are configuration of Local Area Network (LAN):

Server
computer

NETWORK
A system that allows a group of users to communicate with each
other. The users can be referred to a computer or node that is
passing or using data.

Used for variety of applications; such as linking various PCs to

each other and to larger computer in office or building, industrial
plants, factories and scientific laboratories.
Each network application has different requirements in term of
message, speed, acceptable, cost and ability to add new users.

NETWORK
The following is computer network:

NETWORK
Terms use in computer network:

Server
Source sharing to
other network users
or computer that runs
network operational
system to handle
network
or
give
service
to
other
workstation users.

Network
Set of devices (node) which
relates by a media link to
establish a data path where
information can be shares.

NETWORK
Node
Communication channel.

Computer, printer or device

that can send or receive data
produce by other node.

Medium

Path

Method or way how the

computers are connected
(refers to interface card).

Channel where data moves.

Link

NETWORK
Client
Workstation or computer
that can reach source
sharing provides by server.

Protocol
Set of rules uses to manage
and handle network.

Terminal
Server computer that can
links to other terminal.

NETWORK
The following are terminology of computer network:

NETWORK TASK
Electronic communication
facilities - electronic mail,
teleconference, video, etc.

Shopping delivery
from
television or
radio and ecommerce

Network
Task

Internet facilities - email, chat,

downloading file, bulletin
board, online business

ATM card
usage draw cash,
fund
transfer

TOPOLOGY
1) Topology can state how computers communicate in network.
Most networks use cable as connection medium. We have
to consider combinational of cables with Network Interface
Card used, network operation system and other component.
2) The importance of topology is that it states how computer
communicate in network.
Different topology communicate in different ways.
3) Topology is an arrangement or physical layout of computer,
cable and other network components.
Network topology refers to basic design of network or
geometry representation of relations for all lines and
devices between one another.
4) Selection of a right topology must be done because it will
affect the entire network.

LOGICAL AND PHYSICAL TOPOLOGY

Generally, there are two types of topology:1) Logical: refers to how it operates (transmit data); or how the
media is accessed by the hosts.

2) Physical: real display of devices that connects in network,

including location and cable installation; or how
the nodes of the network are physically
connected.

TOPOLOGY in LAN
STAR Topology

BUS Topology

RING Topology

HYBRID Topology

MESH Topology

BUS TOPOLOGY
all stations
effectively share a
common bus cable
or the backbone

known as
linear bus
and simplest
topology
use single
cable known
as segment or
backbone
computers
communicate
base on data
addressing to
particular
computer

BUS
TOPOLOGY

communication
is bidirectional
to allow any
one station to
talk to another
station

communication is faster than

other topologies (sending
station effectively broadcasts its
message so all stations can
receive)

BUS TOPOLOGY
The following is configuration of bus topology:

BUS TOPOLOGY
Advantages
Cheapest topology

Disadvantages
Any problem at nodes will
interrupt the network

Easy to add station

Less cable usage

Well functioning for small

network

A beginner and closure is

required for backbone
Hard to handle problem
Response rate is low

BUS TOPOLOGY
TRANSMISSION SIGNAL
Data in network is in a form of electronic signal. The information
will be received only by computer that has address matched with
address coded by the original signal.
Only one computer can send signal or data in a period of time.
This condition will affect network performance when total of
connected computers is increasing.
The more computers connected to network, the longer time for
every computer has to wait turn to send data (network is slower).
Computer in bus topology only hear the network line to ensure
whether there is data to send. These computers do not response to
its next computer. If any of the computers failed, it does not affect
the whole network.

BUS TOPOLOGY
BOUNCE SIGNAL
Data in network will moves from starting to the end of network
cable. If the signal is not stopped, it will bounce in front or to the
back of network line, and causing another computer to be block
from sending signal or data. Thus the signal has to be stopped.

TERMINATOR
To stop signal from bouncing, terminator is required at each end of
cable. Terminator will functioned to absorb signal sent so that it will
not bounce and disturb another computer who waits for its turn to
send data.

STAR TOPOLOGY
star network is
used mostly in
Ethernet and
LAN
star topology
reduces
chance of
network
failure by
connecting all
of the systems
to a central
node

computers and devices in

the network are connected
to a central master
computer known as hub

STAR
TOPOLOGY
?
central hub rebroadcasts all
transmissions received from
any peripheral node to all
peripheral nodes on network,
sometimes including the
originating node

communication
must take place
through the hub
that allows any
user to be linked
up with any
other user

STAR TOPOLOGY
The following are configuration of star topology:

Server

iBook

HUB

Computer

Printer

Tower PC

STAR TOPOLOGY
Advantages
Connection process is easy
Installation and elimination
process will not interrupt
network system

Any damages to network

system can be detected

Disadvantages
Requires longer cable than
bus topology

If hub break downs, all

nodes cannot functioned
in the network
Cost is higher compares to
bus topology

RING TOPOLOGY

if only one unit

of MSAU is
used, then
physically it is
same as
connection of
star topology

known as token
ring (connects all
nodes into a circle
of chain /ring)

RING
TOPOLOGY
addition device is
required in ring
topology, known
as Multi Station
Access Unit
(MSAU)

message or data
will be transferred
by sequence
through a same
route and ring
every data that
pass through the
node will have
to check its
delivery location
if the node does not
match, then it has to be
passed to the next node
until it finds the
matching node
(destination address)

RING TOPOLOGY
The following is configuration of ring topology:

Ring Topology

RING TOPOLOGY
Advantages

Disadvantages

No collision

Only one device can

transmit data on the
network at a time

Data transferring using high

speed
Easy to detect problem

Any damages on connection

will interrupts the whole
system
Seldom used
Required many cables

HYBRID TOPOLOGY
active hub will
regenerate
electrical signal
received before it
send the signal to
all computers
connected in
topology

passive hub
will only acts
as source of
connection
that does not
strengthen or
regenerate any
signal

combination of any two or more

topologies, resulting network does
not exhibit one of the standard
topology

HYBRID
TOPOLOGY

two common
examples for
hybrid network
are: star-ring
network and
star bus
network.

star-ring network consists of two or more

star topologies is connected using a MSAU
as a centralized hub while a star-bus
network consists of two or more star
topologies connected using a bus trunk (the
bus trunk serves as the network's
backbone).

HYBRID TOPOLOGY
The following is configuration of hybrid topology:

HYBRID TOPOLOGY
Advantages

Disadvantages

Reliable and scalable

Complexity of design

Flexible (design for

different network
environment)

Highly cost of hub and

infrastructure

Effective in combination
and the speed is consistent

Installation and
configuration is difficult

MESH TOPOLOGY
refers to a Wide
Area Network
(WAN)
router is used
to search
multiple paths
and determine
the best path
for data

connecting multiple sites;

and reliability is important
as number of sites being
connected together.

MESH
TOPOLOGY

three or four sites mesh

network is relatively
easy to create, whereas
it is impractical to set
up a mesh network of
100 sites or nodes

a mesh is best
suited for
situations where
it will not need to
be moved or
expanded beyond
five sites or
nodes

MESH TOPOLOGY
The following is configuration of mesh topology:

MESH TOPOLOGY
FULL MESH
Occurs when every node has a circuit connecting it to every
other nodes in network.
Very expensive to implement and yields the great amount of
redundancy (if one node fails, network traffic can be directed to
other nodes).

Usually reserved for backbone networks.

MESH TOPOLOGY
PARTIAL MESH
Some nodes are organized in a full mesh scheme, but others only
connected to one or two in network.
Less expensive to implement and yields less redundancy
compares to full mesh topology.
Commonly found in peripheral networks connected to a full
meshed backbone.

MESH TOPOLOGY
Advantages

Disadvantages

Data can be transmitted

from different devices
simultaneously

High chances of
redundancy in many
network connections

If one components fails

there is always alternative

Overall cost of this

network is way too high

Expansion and modification

in topology can be done
easily

Setup and maintenance of

network is difficult

TRANSMISSION TECHNIQUES

BASEBAND

BROADBAND

BASEBAND
Means no carrier is modulated,
which refers to data or
information signal whether it is
binary, analog voice or video.
Such systems are
simple,
inexpensive and
easy to work with,
but
only
one
signal can be
carried on the
medium at a time.

BASEBAND

Digital data is
applied directly
to medium and
the
entire
bandwidth of
medium
is
used by signal.

Cable attenuation and distortion greatly limit

the transmission distance, up to 1 mile with
twisted pair and 5 mile with coaxial cable.

BASEBAND
BASEBAND CHARACTERISTICS
Baseband provides single channel for the whole bandwidth
where it is not divided into channels.
It carries different kind of information using Time Division
Multiplexing (TDM) where the time slot is use by turns.
Baseband also use digital transmission which does not required
modem, however for voice, modem is required.
Bandwidth is not necessarily huge if using baseband cable
between PC.
Maximum baseband transmission is 10Mbps or high.

BASEBAND ADVANTAGES
Baseband technique is less expensive and easier to install.

BASEBAND
The following are configuration of baseband:
Point to point

Multidrop

Coaxial cable signal

BROADBAND

An enormous
number of high
speed channels
can be created.
In addition,
transmission
over longer
distances (up to
10 mile) on
coaxial cable
can be
achieved.

Means data signals

modulate a higher-frequency
carrier (analog methods are
used to transmit digital data).

BROADBAND

This system is more complex

and expensive because
modems are required at each
node.

Data signals
can be
translated up
in frequency
to specific
channels.
Broadband
has
bandwidth of
up to 300 to
450 MHz.

BROADBAND
BROADBAND CHARACTERISTICS
Broadband bandwidth is divided into channels to provide sub
channels for communication and enables information
transferring in parallel.
It use Frequency Division Multiplexing (FDM) because each
channel carries different frequency.
FDM devices usually called as modem RF. FDM also allows
several conversations to coexist on the LAN simultaneously.
Broadband techniques involved modulation and demodulation
process, and frequency filtering.

BROADBAND ADVANTAGES
Broadband technique can accommodate many channels, for
example 20 to 30 channels per cable.

BROADBAND
The following are configuration of broadband:
Bandwidth

Schematic RF

Schematic cable

Baseband vs. Broadband

Baseband communication is bi-directional, which same channel
can be used to send and receive signals. However, the sending and
receiving cannot occur on the same wire at the same time.

Broadband communication is unidirectional, so in order to send

and receive, two pathways are needed.
Using Baseband transmissions, it is possible to transmit multiple
signals on a single cable by using a process known as multiplexing.
Baseband uses Time-Division Multiplexing (TDM), which divides a
single channel into time slots.
Multiple channels are created in a broadband system by using a
multiplexing technique known as Frequency-Division Multiplexing
(FDM). FDM allows broadband media to accommodate traffic
going in different directions on a single media at the same time.

Baseband vs. Broadband

Data signals can be sent over a network cable in one of two ways:
broadband or baseband.

Baseband, data is sent as digital signals through the media as a

single channel that uses the entire bandwidth of the themselves
take the form of either electrical pulses or light.
Broadband uses analog signals in the form of optical or
electromagnetic waves over multiple transmission frequencies.
Each transmission is assigned to a portion of the bandwidth,
hence multiple transmissions are possible at the same time.

BASEBAND AND BROADBAND

COMPARISON OF BASEBAND AND BROADBAND
No Characteristics

Baseband

Main channel single channel systems that

use the entire bandwidth
division

Bandwidth
length

Multiplexing
technique

Broadband

divided into several subchannels

greater bandwidth to
accommodate many
not necessarily wide
subchannels, up to 20-30
subchannels
use time-division multiplexing use frequency division
(TDM) which divides a single multiplexing (FDM) to create
channel into time slots to
multiple broadband channels,
allow multiple channels over thus parallel transmission
a single baseband
(multiple transmissions are
transmission line, thus serial possible at the same time)
transmission

BASEBAND AND BROADBAND

COMPARISON OF BASEBAND AND BROADBAND
No Characteristics

Baseband

Broadband

analog or digital signal onto RF

carrier (Analog),
use modem
up to 180 Mbps

Signal type

digital (unmodulated) ,
no need of modems

Speed

up to 10 Mbps

Distance

short distances up to a
few kilometres

Direction

unidirectionaltraveling in only
bidirectional so that a
one direction at a timeso a
baseband system can
broadband system can generally
both transmit and receive
either transmit or receive but
signals simultaneously
cannot do both simultaneously

long distances up to tens of

kilometres