networking

Chapter 1
1. Computer Network:-A computer network is a group of computer systems
and other computing hardware devices that are linked together through
communication channels to facilitate communication and resource-sharing
among a wide range of users. Networks are commonly categorized based
on their characteristics.

Networks are used to:

 Facilitate communication via email, video conferencing, instant messaging,
etc.

 Enable multiple users to share a single hardware device like a printer or
scanner.

 Enable file sharing across the network.

 Allow for the sharing of software or operating programs on remote
systems.

 Make information easier to access and maintain among network users.

2. Functionality of computer network:- Computer network has two type of
functionality:
 Mandatory function.
 Optional function.

,(A). Mandatory function:
Some function is mandatory in computer network and when mandatory function
include in computer network, then perform operation in computer network.
Some mandatory functions are given below:

Error control:The computer network has some responsibility like transmission of
data from one device to another device and end to end transfer of data from a
transmitting application to a receiving application involves many steps, each
subject to error.

 (a). Single bit error:
The terms single bit error means that only one bit of the data unit was
changed from 1 to 0 and 0 to 1.

 (b). Burst Error:
The term burst error means that two or more bits in the data unit were
changed. A burst error is also called packet-level error, where errors like
packet loss, duplication, reordering.

Flow control:When a packet (Layer-2 data) is sent from one host to another over a
single medium, it is required that the sender and receiver should work at the
same speed. That is, the sender sends at a speed on which the receiver can
process and accept the data. If the sender is sending too fast the receiver may be
overloaded, (swamped) and data may be lost.

Access control:
Network access control is a method of enhancing the security of a private
organizational network by restricting the availability of network resources to
endpoint devices that comply with the organization’s security policy. The network
access control scheme comprises of two major components such as Restricted
Access and Network Boundary Protection.

Multiplexing and Demultiplexing:
A multiplexing is a technique by which different analog and digital streams of
transmission can be simultaneously processed over a shared link. Multiplexing
divides the high capacity medium into low capacity logical medium which is then
shared by different streams.

, (B) Optional function:-Some function is optional in computer network and
optional function do not need always in computer network. Some optional
functions are given below:

1. Encryption and decryption:Decryption and Encryption is a security method in
which information is encoded in such a way that only authorized user can
read it. Some network uses encryption algorithm to generate cipher text that
can only be read if decrypted.
Types of encryption-
(a). Symmetric Key encryption.
(b). Public Key encryption.

2. Direction of data flow:-There are many transmission mode which is used
to flow of data.
 SIMPLEX:-In this type of transmission mode, data can be sent only in
one direction i.e. communication is unidirectional. We cannot send a
message back to the sender. Unidirectional communication is done in
Simplex Systems where we just need to send a command/signal, and
do not expect any response back.
Examples of simplex Mode are loudspeakers, television broadcasting,
television and remote, keyboard and monitor etc.




 HALF-DUPLEX: - Half-duplex data transmission means that data can
be transmitted in both directions on a signal carrier, but not at the
same time.
 Example of half duplex is a walkie- talkie in which message is sent
one at a time but messages are sent in both the directions.