Computer:
Computer is an electronic device which performs all asthmatic and logical operations to get the required output.
COMPUTER stands for:-
Common-operating-memory-perfect-use in-tired less-education –result
Hardware:
All the physical components which are connected externally called as hardware.
EX:-Monitor, Keyboard, Speaker etc.
Software: Set of programmers called software. It internally connects different hardware components of computer.
Operating System:
Operating system is a collection of programs. It co-ordinate the operations of computer hardware and software.
In simple terms it’s an Interface between the computer h/w components and software applications.
Kernel:
Kernel is a central component of ever operating system.
Kernel responsibilities are managing the system's resources.
Such as,
Shell:
Shell is a program; it is an interface between the user and kernel.
In Linux shell act as command line Interface, so whenever user execute any commands the shell interprets all the commands to kernel, after processing the commands the kernel gives reply to shell.
Network: Network is a communication path.
Networking: It enables communication of all inter-connected network devices.
Example:Computer, switches, routers etc.
LAN - Local Area Network: a communication network path established within a single room or building called LAN
MAN - Metropolitan Area Network: acommunication network path established between different areas in a city called MAN.
WAN - Wide Area Network: acommunication network path established between different places in world called WAN.
Hub:Hub is network device; it allows communication between all inter-connected network devices. It always does broad-cast (one too many)
Switch:Switch is intelligent network device. It allows communications between all inter-connected network devices, but it does uni-cast (one to one).
Router: Router is agateway between different networks; it allows communication between more different networks.
IP-Address:IP-Addressing is numerical number to identify each computer on TCP/IP Networks.
There are 2 versions of I.P-Address:
IPv4 is a 32 bit Address & IPv6 is a 128 bit Address.
Note:IPv6 for Increase computer networks in Future.
There are 5 classes of I.P-Address in IPV4:
Class A 0 to 126
Loop back address 127 Networking purpose
Class B 128 to 191
Class C 192 to 223
Class D 224 to 239 Research purpose
Class E 240 to 255
Subnet mask:Subnet-mask also a numerical numbers to divide I.P-Address into the network portion and host portion.
Based on subnet mask only we can identify which computer belongs to witch network.
Subnet mask also 32 bits address.
Port Numbers: Port number is an entry and exit point of any network based service.
Each network application has default port number to send and receive the packets of network services over TCP/IP networks.
Around the world we have 65,534 port numbers.
From 0 to 1023 are reserved.
From 1024 to 65543 are un-reserved port numbers.
Ex:- HTTP - 80, FTP -20 & 21, DHCP – 68, DNS – 53, SMTP -25 etc.
Protocol:Set of rules and regulations in an order to manage for proper communication between different network services.
TCP /IP, UDP, HTTP, DHCP, FTP, LDAP etc.
Network Topologies:
Network topology, defines the structure of the network.
Physical topology, which is the actual layout of the media.
Logical topology, which defines how the media is accessed by the hosts for sending data.
Physical Topologies
Bus Topology:
Bus topology is a method of physical connectivity. Here all the hosts connect directly to single cable.
Media: BNC connector, Coaxial cable.
Ex: - Cable T.V Connections.
Ring Topology:
In Ring topology each host connects to the next host. Like all hosts connects each other.
Note: More cables and NIC card should use.
Ex:- usually this topology uses in Railways.
Star Topology:
In star topology all hosts connect to a central device is called as Hubs/ Switches.
Media: Hub, Switch, Cat cables, RJ45 Connectors.
Ex: - It common topology in LAN environment.
Extended Star Topology:
Extended star topology links individual stars together by connecting the hubs (or) switches.
Note: This topology can extend coverage of the network.
Hierarchical topology:
Hierarchical topology is combination of two/more topologies.
Ex: - star topology, ring topology etc.
Mesh topology:
Mesh topology each computer directly connects to other computer.
Mostly this topology uses in wireless communication.
Ex: - Telephone towers.
Firewall
Firewall is a gateway. It restricts and controls the network traffic, It monitors Incoming and outgoing traffic over networks.
As per firewall rule-sets it filters and redirects the packets based on source and destination IP-address, port-numbers and protocols.
It protects public access to private network resources such as production servers and It enables secure access of your servers and sensitive information over networks.
Types of firewalls:There are 4 categories of firewalls.
Packet Filter
Circuit level gateway
Application level gateway
State-full multilayer inspection firewall
UTM Firewall Features:
Packet Switching:
Packet switching is a technology of dividing data into packets and sends and receives the packets over a network.
Packet:
Each packet contains packet-header information, source and destination address, uniq sequence number to re- assemble the packet, error control data).
Duplex/ Full Duplex: Capability of transmitting the data in both directions over a communication channel called Full duplex.
Half-Duplex: Capability of transmitting the data in only one direction at a time called Half-duplex.
Session: A logical connection created between two hosts to exchange data and load balancing.
Handshaking: A series of signals acknowledging that communication can take place between computers.
Telnet: Telnet is a protocol allows remote logins with command base terminal access of servers.
It is Non-secure protocol, because it sends all information in clear text format, include users password also.
Telnet program available almost ever operating systems. It works on 23 port.
Secure Shell: SSH allows remote logins of server.
It provides strong authentication and secure communications over unsecure channels.
It provides facilities to remote logins in secure format manner. So the data travels in Encryption manner. It works on 22 port number.
NAT: Network Address Translation
It is mostly used for to share the internet with perfect bandwidth and advantage of NAT is the client doesn’t know I.S.P I.P-Address that will know only router I.P Address.
Band Width: Band width is a capacity for data transfer, in other words how much data can be moved from one point to another point in a given amount of Time.
INTERNET
The Internet has revolutionized many aspects of our daily lives, it has affected the way we do business as well as way we spend our leisure time.
Count the ways we used the Internet recently, we can sent E-mails to business associate , paid the utility bills, read the newspapers, read so many books, researched so many topic, train reservations, buses reservations and booked the hotel all by using the Internet, so that’s way Internet is a communication system.
A network is a group of connected communicating devices such as computer and printers. An Internet has composed of hundreds of thousands of interconnected networks.
Private organization as well as various government agencies, school, corporations and libraries in more than 100 countries using the Internet, millions of people are users, yet this extraordinary communication system only came into begin in 1969.
