INTRODUCTION:

LOCAL AREA NETWORK (LAN)

LOGICAL & PHYSICAL TOPOLOGY

TOPOLOGY IN LAN:

BUS, RING, STAR,HYBRID & MESH

TRANSMISSION TECHNIQUES BASEBAND & BROADBAND

- EP601 - LOCAL AREA NETWORK

(LAN)

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

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

Terms use in computer network:

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

Node

Computer, printer or device that can send or receive data produce by other node.

Link

Communication channel.

Path

Channel where data moves.

Medium

Method or way how the computers are connected (refers to interface card).

NETWORK

Protocol

Set of rules uses to manage and handle network.

Terminal Server computer that can links to other terminal.

Client

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

NETWORK

The following are terminology of computer network:

NETWORK TASK

Network

Task

Electronic communication

facilities - electronic mail,

teleconference, video, etc.

Internet facilities - email, chat,

downloading file, bulletin

board, online business

Shopping -

delivery

from

television or

radio and e-

commerce

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

BUS Topology

STAR Topology

RING Topology

HYBRID Topology

MESH Topology

BUS TOPOLOGY

use single cable known

as segment or backbone

BUS TOPOLOGY

known as linear bus

and simplest topology

computers communicate base on data addressing to

particular computer

all stations effectively share a common bus cable

or the backbone

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)

The following is configuration of bus topology:

BUS TOPOLOGY

BUS TOPOLOGY

Cheapest topology

Advantages

Any problem at nodes will interrupt the network

Disadvantages

Easy to add station

Less cable usage

Well functioning for small network

Hard to handle problem

A beginner and closure is required for backbone

Response rate is low

TRANSMISSION 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).

BUS TOPOLOGY

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.

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.

BOUNCE SIGNAL

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.

BUS TOPOLOGY

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

STAR TOPOLOGY

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

communication must take place through the hub that allows any

user to be linked up with any other user

central hub rebroadcasts all transmissions received from

any peripheral node to all peripheral nodes on network,

sometimes including the originating node

The following are configuration of star topology:

STAR TOPOLOGY

Server

Computer

Printer

iBook Tower PC

HUB

STAR TOPOLOGY

Connection process is easy

Advantages

Requires longer cable than bus topology

Disadvantages

Installation and elimination process will not interrupt

network system

Any damages to network system can be detected

Cost is higher compares to bus topology

If hub break downs, all nodes cannot functioned

in the network

RING TOPOLOGY

if only one unit of MSAU is used, then

physically it is same as

connection of star topology

RING TOPOLOGY

known as token ring (connects all nodes into a circle

of chain /ring)

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)

The following is configuration of ring topology:

RING TOPOLOGY

Ring Topology

RING TOPOLOGY

No collision

Advantages

Only one device can transmit data on the

network at a time

Disadvantages

Data transferring using high speed

Seldom used

Any damages on connection will interrupts the whole

system Easy to detect problem

Required many cables

HYBRID TOPOLOGY

HYBRID TOPOLOGY

combination of any two or more topologies, resulting network does

not exhibit one of the standard topology

passive hub will only acts as source of connection

that does not strengthen or

regenerate any signal

two common examples for

hybrid network are: star-ring network and

star bus network.

active hub will regenerate

electrical signal received before it send the signal to

all computers connected in

topology

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).

The following is configuration of hybrid topology:

HYBRID TOPOLOGY

HYBRID TOPOLOGY

Reliable and scalable

Advantages

Complexity of design

Disadvantages

Flexible (design for different network

environment)

Effective in combination and the speed is consistent

Installation and configuration is difficult

Highly cost of hub and infrastructure

MESH TOPOLOGY

router is used to search

multiple paths and determine the best path

for data

MESH TOPOLOGY

refers to a Wide Area Network

(WAN)

connecting multiple sites; and reliability is important as number of sites being

connected together.

a mesh is best suited for

situations where it will not need to

be moved or expanded beyond

five sites or nodes

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

The following is configuration of mesh topology:

MESH TOPOLOGY

FULL MESH

MESH TOPOLOGY

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.

PARTIAL MESH

MESH TOPOLOGY

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

Data can be transmitted from different devices

simultaneously

Advantages

High chances of redundancy in many network connections

Disadvantages

If one components fails there is always alternative

Expansion and modification in topology can be done

easily

Setup and maintenance of network is difficult

Overall cost of this network is way too high

TRANSMISSION TECHNIQUES

BASEBAND

BROADBAND

BASEBAND

BASEBAND

Digital data is

applied directly

to medium and

the entire

bandwidth of

medium is

used by signal.

Means no carrier is modulated,

which refers to data or

information signal whether it is

binary, analog voice or video.

Cable attenuation and distortion greatly limit

the transmission distance, up to 1 mile with

twisted pair and 5 mile with coaxial cable.

Such systems are

simple,

inexpensive and

easy to work with,

but only one

signal can be

carried on the

medium at a time.

BASEBAND CHARACTERISTICS

BASEBAND

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.

The following are configuration of baseband:

BASEBAND

Coaxial cable signal

Point to point

Multidrop

BROADBAND

BROADBAND

Data signals

can be

translated up

in frequency

to specific

channels.

Broadband

has

bandwidth of

up to 300 to

450 MHz.

Means data signals

modulate a higher-frequency

carrier (analog methods are

used to transmit digital data).

This system is more complex

and expensive because

modems are required at each

node.

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.

BROADBAND CHARACTERISTICS

BROADBAND

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.

The following are configuration of broadband:

BROADBAND

Schematic cable

Bandwidth

Schematic RF

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.

COMPARISON OF BASEBAND AND BROADBAND

BASEBAND AND BROADBAND

No Characteristics Baseband Broadband

1 Main channel division

single channel systems that use the entire bandwidth divided into several subchannels

2 Bandwidth length

not necessarily wide

greater bandwidth to accommodate many subchannels, up to 20-30 subchannels

3 Multiplexing technique

use time-division multiplexing (TDM) which divides a single channel into time slots to allow multiple channels over a single baseband transmission line, thus serial transmission

use frequency division multiplexing (FDM) to create multiple broadband channels, thus parallel transmission (multiple transmissions are possible at the same time)

COMPARISON OF BASEBAND AND BROADBAND

BASEBAND AND BROADBAND

No Characteristics Baseband Broadband

4 Signal type digital (unmodulated) , no need of modems

analog or digital signal onto RF carrier (Analog), use modem

5 Speed up to 10 Mbps up to 180 Mbps

6 Distance short distances up to a few kilometres

long distances up to tens of kilometres

7 Direction

bidirectional so that a baseband system can both transmit and receive signals simultaneously

unidirectionaltraveling in only one direction at a timeso a broadband system can generally either transmit or receive but cannot do both simultaneously