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:

1. Facilitate communication via email, video conferencing, instant messaging, etc.
2. Enable multiple users to share a single hardware device like a printer or scanner
3. Enable file sharing across the network
4. Allow for the sharing of software or operating programs on remote systems
5. Make information easier to access and maintain among network users

Pros and cons of computer network

Pros

1. It enhances communication and availability of information.
2. It allows for more convenient resource sharing.
3. It makes file sharing easier.
4. It is highly flexible.
5. It is an inexpensive system.
6. It increases cost efficiency.
7. It boosts storage capacity.

Cons

1. It lacks independence.
2. It poses security difficulties.
3. It lacks robustness.
4. It allows for more presence of computer viruses and malware.
5. Its light policing usage promotes negative acts.
6. It requires an efficient handler.
7. It requires an expensive set-up.

Types of computer network

Local Area Network (LAN)

Networks used to interconnect computers in a single room, rooms within a building or buildings on one site are called Local Area Network (LAN). LAN transmits data with a speed of several megabits  per second (106 bits per second). The transmission medium is normally coaxial cables.

The various devices in LAN are connected to central devices called Hub or Switch using a cable.

Now-a-days LANs are being installed using wireless technologies.

Metropolitan Area Network (MAN)

 A MAN is a relatively new class of network. MAN is larger than a local area network and as its name implies, covers the area of a single city. MANs rarely extend beyond 100 KM and frequently comprise a combination of different hardware and transmission media. It can be single network such as a cable TV network, or it is a means of connecting a number of LANs into a larger network so that resources can be shared LAN to LAN as well as device to device.

Wide Area Network (WAN)

WAN is a computer network which spans over a large geographical area such as state, region, country etc. WANs are typically used to connect two or more LANs or MANs which are located relatively very far from each other. To provide connectivity, this network uses special devices, cables and technologies.

Personal Area Network (PAN)

A personal area network is a computer network organized around an individual person. Personal area networks typically involve a mobile computer, Personal area networks can be constructed with cables or wirelessly. Personal area networks generally cover a Network range of less than 10 meters (about 30 feet).

PAN (Personal Area Network) first was developed by Thomas Zimmerman and other researchers at M.I.T.'s Media Lab and later supported by IBM's Almaden research lab.

Introduction to IP addresses

IP address is short for Internet Protocol (IP) address. An IP address is an identifier for a computer or device on a TCP/IP network. Networks using the TCP/IP protocol route messages based on the IP address of the destination. Contrast with IP, which specifies the format of packets, also called datagrams, and the addressing scheme.

The format of an IP address is a 32-bit numeric address written as four numbers separated by periods. Each number can be zero to 255. For example, 1.160.10.240 could be an IP address.

IPV4

IPv4 (Internet Protocol Version 4) is the fourth revision of the Internet Protocol (IP) used to to identify devices on a network through an addressing system. The Internet Protocol is designed for use in interconnected systems of packet-switched computer communication networks.

IPv4 is the most widely deployed Internet protocol used to connect devices to the Internet. IPv4 uses a 32-bit address scheme allowing for a total of 2^32 addresses (just over 4 billion addresses).  With the growth of the Internet it is expected that the number of unused IPv4 addresses will eventually run out because every device -- including computers, smartphones and game consoles -- that connects to the Internet requires an address.

IPV6

A new Internet addressing system Internet Protocol version 6 (IPv6) is being deployed to fulfill the need for more Internet addresses.

IPv6 (Internet Protocol Version 6) is also called IPng (Internet Protocol next generation) and it is the newest version of the Internet Protocol (IP) reviewed in the IETF standards committees to replace the current version of IPv4 (Internet Protocol Version 4).

IPv6 is the successor to Internet Protocol Version 4 (IPv4).

Difference between IPV4 and IPV6

Basis of Comparision	IPV4	IPV6
Address Configuration	Supports Manual and DHCP configuration	Supports Auto-configuration and renumbering
End-to-end connection integrity	Unachievable	Achievable
Address Space	It can generate 4.29 x 109 addresses	It can produce quite a large number of addresses, i.e., 3.4 x 1038
Security features	Security is dependent on application	IPSEC is inbuilt in the IPv6 protocol
Address length	32 bits (4 bytes)	128 bits (16 bytes)
Address Representation	In decimal	In hexadecimal
Fragmentation performed by	Sender and forwarding routers	Only by the sender
Packet flow identification	Not available	Available and uses flow label field in the header
Checksum Field	Available	Not Available
Message Transmission Scheme	Broadcasting	Multicasting and Any casting
Encryption and Authentication	Not Provided	Provided