ppt

wartrashyNetworking and Communications

Oct 26, 2013 (3 years and 7 months ago)

82 views

1


RAJESH KATRAGADDA


BHARATH NADELLA


SHIVANANDAN GOUD KOMMURI


SRIDHARA PRUDHVI DUTH POTLURI


COMPUTER NETWORKS


LAB 3: HUBS AND SWITCHES

2

3


A

switch

is

a

multi
-
input,

multi
-
output

device

which

transfers

packets

from

an

input

to

one

or

more

outputs
.


Switch

is

basically

a

star

topology

having

features

like

a.
Large

networks

can

be

built

by

interconnecting

a

number

of

switches

b.
Adding

new

host

to

network

by

connecting

it

to

a

switch

does

not

necessarily

reduce

the

performance

of

the

network

for

other

hosts

already

connected
.

SWITCHES:

4


Switch

makes

use

of

header

of

the

packet

for

an

identifier

to

trace

the

destination
.


Basically

three

approaches

used

are

a.
Datagram

or

connectionless

(data

transfer

only)

b.
Virtual

circuit

or

connection
-
oriented

(connection

setup

and

data

transfer)

c.
Source

routing

APPROACH:

5


A

hub

joins

multiple

computers

(or

other

network

devices)

together

to

form

a

single

network

segment
.

On

this

network

segment,

all

computers

can

communicate

directly

with

each

other
.


Hubs

do

not

read

any

of

the

data

passing

through

them

and

are

not

aware

of

their

source

or

destination
.

It

just

broadcasts

the

packets

out

to

all

devices

on

the

network

-

including

the

one

that

originally

sent

the

packet
.

HUBS:

6


Three

different

types

of

hubs

exist

a.
Passive

:

do

not

amplify

the

electrical

signal

of

incoming

packets

before

broadcasting

them

out

to

the

network
.

b.
Active

:

amplify

the

electrical

signal

of

incoming

packets

before

broadcasting

them

out

to

the

network
.

c.
Intelligent

:

add

extra

features

to

an

active

hub

that

are

of

particular

importance

to

businesses
.

TYPES OF HUBS:

7

AIM:


This lab demonstrates the implementation of
switched local area networks.


The

simulation

in

this

lab

will

help

us

to

examine

the

performance

of

different

implementations

of

local

area

networks

connected

by

switches

and

hubs
.

8

Only HUB Scenario:

9

10

Hub and Switch Scenario:

11

Manage Scenarios:

12

Compare Results:

13

Graph for TRAFFIC SENT:

14

Graphs for PACKETS RECEIVED:

15

Graph for DELAY:

16

Graph for COLLISION COUNT:

17

18


Explain

why

adding

a

switch

makes

the

network

perform

better

in

terms

of

throughput

and

delay



ANS
:

Unlike

hubs,

Switches

Buffer

the

frames

reaching

it
.

So

Switches

share

the

bandwidth

equally

among

all

the

nodes

and

maintains

address

tables

to

forward

frames
.

Hence

it

leads

to

better

performance

in

terms

of

throughput

and

delay
.


POSSIBLE QUESTIONS:

19


We

analyzed

the

collision

counts

of

the

hubs
.

Can

you

analyze

the

collision

count

of

the

switch?


ANS
:

As

hubs

don’t

look

at

the

destination

address

of

the

frames

reaching

it

and

just

forwards

them

to

all

other

nodes,

there

is

collision

count

for

Hubs
.

But

in

case

of

Switches,

it

look

at

the

destination

address

and

buffer

the

frames

and

send

them

according

to

the

address

table
.

So

Switches

have

no

Collisions,

so

no

Collision

Count
.

POSSIBLE QUESTIONS:

20

21

Only SWITCHES Scenario:

22

Graph for DELAY:

23

Graph for TRAFFIC RECEIVED:

24

Graph for TRAFFIC SENT:

25

CONCLUSION:


From

above

Graph

for

DELAY,

its

clear

that

delay

for

Only

Hub

Scenario

(Blue)

is

pretty

high

and

for

Hub

and

Switch

Scenario

(Red)

it

is

significantly

low

compared

with

Only

Hub

Scenario
.

But

the

Delay

for

Hub

and

Switch

Scenario

and

Only

Switches

Scenario

(Green)

is

not

that

significantly

different,

as

in

the

earlier

case
.



More

over

as

Switches

cost

more

than

hubs,

Its

better

to

use

a

Hub

and

Switch

combination

in

the

network

than

only

Switch

or

only

Hub

combination
.

26