Computer Network Overview

Computer network is a group of computers connected to each other electronically. That means the computer can talk to each other, every computer in the network send and receive information. There are many type of computer network exit in the world such as

ü  LAN (Local area Network)

ü  MAN (Metropolitan Area Network)

ü  CAN (Campus Area Network)

ü  WAN (Wide Area Network)

OSI (Open System Interconnection) Model: OSI is a seven layer model define by ISO(International Organization for standardization) and it is widely used around the world.

07	Application Layer	Network Service, User Authentication.
06	Presentation Layer	Data Packet  Translation, Encryption etc
05	Sessions	Connection establishment, Sessions maintenance
04	Transport Layer	Data fragmentation ,D-fragmentation, Reliable Data transmission, Error correction, Data segmentation, TCP/UDP etc
03	Network Layer	Logical Addressing, Path Selection, Routing
02	Data-Link Layer	Frame making, CRC checking, Network access.
01	Physical  Layer	Media, Connector, Electrical signal etc.

Network Device:

·         Bridge: A network bridge connected to multiple network segments at the Layer 2 of OSI model to from a single network. Bridges broadcast all ports.

·         Switch: Switch operate Data link layer of OSI model. Switch brake up collision domain by default, but have a large broadcast domain.

·         Router: A router is a very intelligent device in a network, router operates is Network Layer of OSI model. Router perform shortest path selection, packet inspect, packet filtering etc.

·         Firewall: A firewall is a network device for controlling network security and access control.

Internet Protocol (IP): IP address is numerical label, it participate in computer network device and printers. IP address serve two major portion Host and Network identification. IP are 32-bit numeric value.

Actually IP address is binary number, it represent to numeric number because human can easy to understand. Today two version Ip address are exit in the world IPv4 and IPv6.

Private IP address: Private IP address reserved in personally or private used, the range of private IP address is shown below

Class	Start	End	No. of Address
A	10.0.0.0	10.255.255.255	16777216
B	172.16.0.0	172.31.255.255	1048576
C	192.168.0.0	192.168.255.255	65536