NETWORK IS A COLLECTION OR GROUP OF DEVICES THAT
CAN COMMUNICATE WITH EACH OTHER.

USING NETWORK WE CAN SHARE EXPENSIVE RESOURCES AND
ALLOW USERS IN THE NETWORK TO ACCESS THEM SIMULTANEOUSLY.

COMPUTER NETWORKS ENABLE DATA SHARING THAT IS FASTER
AND MORE EFFICIENT THAN USING DEVICES SUCH AS FLOOPIES
AND COMPACT DISC.

GIVES THE FACILITY OF SITTING IN A PLACE AND FLASHING MESSAGE
ON THE SCREEN OF OTHER COMPUTERS IN THE OFFICE.

A NETWORK IS VERY ACCOMODATING AND FLEXIBLE. NEW MACHINES CAN
BE ADDED AND EXISTING ONES REMOVED.

 DATA : IT REFERS TO THE INFORMATION
PRESENTED IN WHATEVER FORM IS AGREED
UPON BY THE PARTIES.

 DEPENDING UPON DIRECTION OF FLOW OF
DATA IT CAN BE :
A. SIMPLEX : COMMUNICATION IS UNIDIRECTIONAL.
B. HALF DUPLEX : EACH STATION CAN TRANSMIT AND
RECEIVE BUT NOT AT THE SAME TIME.
C. FULL DUPLEX : BOTH STATIONS CAN TRANSMIT AND
RECEIVE SIMULTANEOUSLY.

 COST: Indicates the general cost of
components, installation and maintenance of the network.

 SPEED: Is a measure of how fast a data can be transmitted
over a network, i.e. the data rate.

 SECURITY: Indicates how secure the network is including
the data that is transmitted.

 AVAILAIBILITY: Is a measure of the probability that the
network will be available for use when required.
PERCENTAGE AVAILABILITY=([NO OF MIN IN A YEAR-DOWNTIME]/[NO
OF MIN IN A YEAR]*100).

 SCALABILITY : Indicates how well a network can
accommodate new users an data transmission
requirements.

 RELIABILITY : Indicates the dependability of the
components that make up the network.

 TOPOLOGY : Are of two types – a. Physical b. Logical.

 PERSONAL COMPUTERS : The PCs serve as a end point in the
network, sending and receiving data.
 INTERCONNECTIONS: They provide a means for data to travel from
one point to another point in the network. They consists of
components like:
 NETWORK INTERFACE CARDS: That translates the data produced by
the computer into a format that can be transmitted over the local
network.
 NETWORK MEDIA: May be wired or wireless and provides a means by
which signals can be transmitted from on network device to another.
 CONNECTORS: It provides the connection points for the media.
 SWITCHES: Devices that provide attachment to the end systems and
intelligent switching of data within the local network.
 ROUTERS: They interconnect network and chooses the best path
between networks.

 UNICAST : ONE TO ONE COMMUNICATION.

 MULTICAST : ONE TO A GROUP
COMMUNICATION.

 BROADCAST : ONE TO ALL COMMUNICATION.

LOCAL AREA NETWORK (LAN).

METROPOLITIAN AREA NETWORK(MAN).

WIDE AREA NETWORK (WAN).

A LAN IS A GROUP OF COMPUTERS IN A LOCALIZED AREA. IT IS A
NETWORK CONFINED TO A SMALL ROOM, A BUILDING OR A CLUSTER
OF BUILDINGS AND IS INSTALLED FOR THE EXCLUSIVE USE OF A
PARTICULAR OFFICE OR A FACTORY OF AN ORGANISATION.

LAN COVERS AN AREA LARGER THAN LAN. IT COVERS AN AREA OF A STATE
OR A CITY AND INCLUDES TWO OR MORE LANS.

IN WAN, COMPUTER NETWORK LOCATED IN DIFFERENT COUNTRIES AND
CONTINENTS CAN BE CONNECTED TO SHARE INFORMATION. A WAN USES
TELEPHONE CABLES AND SATELLITES FOR COMMUNICATION. EG: INTERNET.

IN PHYSICAL BUS TOPOLOGY A SINGLE CABLE CONNECTS ALL DEVICES.

IN BUS TOPOLOGY ONLY ONE MACHINE IS ALLOWED TO TRANSMIT AT A TIME.

 IT USES THE CSMA/CD.

SPEED RATE IS 10 Mbps TO 10 Gbps.

HERE EACH HOST IS CONNECTED TO A CENTRAL DEVICE

ALL HOSTS ARE CONNECTED IN THE FORM OF A RING.

IT USES A SPECIAL FRAME CALLED TOKEN WHICH
ROTATES AROUND THE RING.

AND WHICHEVER DEVICE HAS THE TOKEN AT THAT TIME
WILL BE SENDER.

 EACH AND EVERY DEVICE IN THIS TOPOLOGY HAS A POINT TO POINT
CONNECTION WITH THE OTHER DEVICES.
THIS RESULTS IN A COSTLIEST DESIGN.

Computer Network

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