Cyber Journal

What are Networks?

Computer network are group of computers connected together.They have the ability to share information,content,media,displays.They can communicate to any corners of the networks and to any device connected to networks.

They can be

• LAN -> Loca Area Networks (offices,Institutions)
• WAN -> Wide Area  Networks (University,Industries,Big  Institutions)
• MAN ->Metropolitan Area Network(Applicable for Bigger and wide area like Small towns and even cities)

BASIC  TERMINOLOGIES IN NETWORKING

• DHCP : Dynamic Host Configuration Protocol; OKAY…. no too technical as it seems ,
  This is nothing but the part of router that allocates IP address,Subnet Mask,Default Gateways to every device connected to the router.
• Subnet Mask -> It’s just estimate how many computers are connected to the network the user connected to.These are in the form of 255.255.255.255 -> Zero computer.
  255.255.255.0 -> 255 computers are connected to the network
• Default Gateway : actually its just the IP Address of the router through which all the traffic goes through.It also acts access point by which the router of one network is connected to another network.
• ISP -> Internet Service Provider is a company or organisation which provides the internet services like Virgin,Airtel, Vodafone.
• DNS :Domain Name System.These ar names associated to the ip address where a website is hosted.
• PORTS :Are the end points of the network that through which information or data is transferred. Few ports one should always  keep in mind:
  Port 80 :Http(Hyper Text Transfer Protocol)  port this tells that website is hosted
  Port 443: http with secured socket layer(SSL)  (https)
  Port 25 : SMTP :Simple Mail TRansfer Protocol
  Port 23: Telenet.
  Port 20 :FTP (File Transfer Protocol)
  Port 8080: HTTP Proxy
  Port 8200:VMWare Server
  Port 9988:Spybot/Rbot
  Port 67,68:DHCP
  Port 465 : SMTP over SSL
• HOSTING SERVERS:It provides base for the website to be hosted on the internet.these are divided into two types :
  Free Hosting server: these are free of cost. These actually add their name after the web address eg: ripway provides free hosting so the websites hosted on this server will have the url www. xyzurl.ripway.com
  Dedicated Hosting Server:These are paid hosting server and provide user required space on payment .
• IP ADDRESS: Internet Protocol Address.These are address (identifier) specified to every device that are connected to network.These are categorised into two types :
  1). Public IP address: these ip’s are connected to internet and are visible t the whole world anybody who soever checks the ip outside the network can trace us
  2).Private IP: these are ip’s that are assigned to different devices and are assigned by the router inside the network and helps router to respond to the various the requests by different devices in network.These are recorded in NAT table of router.
  Another category in which ip’s are categorised on the basis of their length:
  1).IPv4:Internet Protocol Version 4 (IPv4) is 32 bit ip address.which limits the address space to 4294967296.It has 4 octects. AAA:BBB:CCC:DDD
  2) IPv6:Internet Protocol Version 6 (IPv6) i.The address size was increased from 32 to 128 bits (16 octets), thus providing up to 2¹²⁸ (approximately 3.403×10³⁸) addresses. This is deemed sufficient for the future.A:B:C:D:E:F:G:H
• ROUTER: This is one of the  most important device of networks as it is the junction where the network is connected to the external network (like internet) and this is connected  to isp which provides the internet to it and  has a public ip which communicates to the whole world.The communication through the device(user)
  and the internet is done in packets as the
•  NAT: Network Address Translation is a method of remapping  Private IP address into router for the comnvenience. packets delivering to specific devices.
• NETWORK PROTOCOLS:Is the set of rules according to TCP/IP model.
• PROXIES AND VPN:These are services which helps us to hide ur identity by changing the public ip that is assigned t mac adress of the particular device which makes difficult to forensics and other people which wants to trace that ip.
• FIREWALL:It acts as a security channel gate (barrier)  for the network.It is used to prevent the un-authorised access to the network.Every requests whether incoming or outgoing passes through it.

TCP/IP MODEL

Transmission Control Protocol / Internet Protocol : that defines the set of rules by which a successful network is established.TCP/IP protocols map to a four-layer conceptual model known as the DARPA model, named after the U.S. government agency that initially developed TCP/IP.TCP breaks down the request into small packets and IP helps to transport the packets to designated address and at the receiver side TCP reassembles those packets and serves as request sent by the sender. The four layers of the TCP/IP model are:

1. Application
2. Transport
3. Internet
4. Network Interface.