Difference Between Wi-Fi and Wi-Max

Parameter	Wi-Fi	Wi-Max
Acronym for	Wireless Fidelity	World Interoperability for Microwave Access
Description	It is a wireless technology that allows any electronic device to exchange and transfer data wirelessly.	It a wireless technology which delivers carrier class, high speed wireless broadband at low cost and covering large distance than Wi-Fi.
IEEE Standard	IEEE 802.11	IEEE 802.16
Implementation	It is basically an implementation of wireless Local Area Connection within a small building, a college, or an institutional building.	It is a wireless broadband metropolitan technology whose objective is to interconnect houses, buildings, or even hot spots to allow communication between them or with other networks.
Cost	Can be implemented by using low cost access pints.	Wi-Max technology requires costly infrastructure.
Frequency band	2.4 GHz to 5 GHz	Licensed/Unlicensed 2 GHz to 11 GHz
Channel Bandwidth	Wi-Fi 802.11b= 25 MHz Wi-Fi 802.11 a/g=20 MHz	Adjustable 1.25 M to 20 MHz
Full/Half Duplex	Half Duplex	Full Duplex

Difference Between Cloud Computing and Grid Computing

Parameter	Grid Computing	Cloud Computing
Definition	It is a collection of heterogeneous Computers from different locations to achieve a common goal.	It is the delivery of computing as a service rather than a product, where resources, software, and information are provided to Computers and Other devices as a utility.
Platform	It makes use of heterogeneous Computers to run.	It makes use of Homogeneous computers to run.
Focused on	Intensive Calculus	Standard and intensive cloud.
Visualization	Not Much Reliable	Reliable
Performance	High	Less than Grid
Research Community	Grid is distributed and has multiple user communities and is grouped in virtual organization.	It has generally one research community and a common group of system administrators that take care of entire domain.

Difference Between MAC and IP address

Parameter	MAC Address	IP Address
Acronym for	media access control address	Internet Protocol Address
Used for	It is a unique identifier that is assigned to network interfaces for communicating on the physical network segments.	It is a numerical value that is assigned to all the participating devices in a network. i.e. Servers, Computers, Printers, WAP, Laptops etc.
Provided BY	It is generally provided by the manufacturer of the NIC cards and is stored in its hardware.	It is provided by the ISP (Internet Service Provider) or by the Network Administrator.

Difference Between OSI and TCP/IP Reference Models

Parameter	OSI Reference Model	TCP/IP Model
Clarification between Services, Interfaces and Protocols	OSI Model clearly distinguishes between Services, Interfaces and Protocols. Each layer performs some services to upper layers, layer interfaces tells the processes above it how to access it, and different protocols are used by different layers as per their needs until a job is not finished.	TCP/IP model does not clearly distinguish between Services, Interfaces and Protocols.
Protocol Biasing	This model is not biased for a particular set of protocols and was developed before corresponding protocols invention.	This Model was developed after inventing corresponding protocols and just was description of existing protocols.
Layers	It is a Seven Layered Model. Which are as follows : a)      Physical Layer b)      Data Link Layer c)       Network Layer d)      Transport Layer e)      Session Layer f)       Presentation Layer g)      Application Layer	It is a 4 Layered Model. Which are as follows: a)      Subnet Layer b)      Internet Layer c)       Transport layer d)      Application Layer

SPX (Sequential Packet Exchange) Protocols

It is the version of Novels’ Sequenced Packet Protocol (SPP). It is a transport layer protocol and is used by client server applications. This protocol provides a packet delivery system for third party applications.

Figure given below illustrate the structure of SPX packet.

Connection Control Flag	DataStream Type
Source Connection ID
Destination Connection ID
Sequence Number
Acknowledge Number
Allocation Number
0-534 bytes of data

Internetwork Packet Exchange (IPX)

Internetwork Packet Exchange (IPX) is a connectionless datagram protocol that is used by the Novell NetWare Operating System.  This protocol is the implementation of Xerox Network Systems’ IDP (Internet Datagram Protocols). It is Layer 3 protocol i.e. Network Layer Protocol.

IPX Protocol is very similar to the IP protocol. Some useful points about this protocol are as follows:

1)Unique 32 bit address is assigned to Logical Networks ranging from 0x1 to 0xFFFFFFFF (Hexadecimal).

2)48 bit node address is used by hosts, which is by default set to network card’s MAC address. Node address and network address are jointly used to identify the host on network.

3)00:00:00:00 means current network.

4)FF: FF: FF: FF is used as broadcast address.

Figure Given below Illustrates the IPX Packet.

Cryptography

It is the art or science to design ciphers, i.e. a message written in secret code. It is the key enabling technology that is used to protect distributed systems. The Process of breaking these secret codes is called cryptanalysis. Input text that is provided for encryption is called plaintext and the encrypted text so obtained as output is called cipher text.

There are three main techniques that are used to generate strong cipher:

FSK (Frequency Shift Keying)

It is the Modulation Technique in which Amplitude and Phase of Signal are kept Constant while frequency is varies to represent binary 1 or 0.One level of frequency represents binary 1 and other represents binary 0.The main advantage of using this technique is that it is less prone to noise and sender is only concerned about the frequency and not about the amplitude.

Amplitude Shift Keying (ASK)

Amplitude Shift Keying (ASK) is a Modulation technique that is used in Digital to analog Conversions. This technique uses strength of signal to represent binary 0 or 1 value.in this only amplitude changes while frequency and phase both are kept constant.it uses finite number of amplitudes, each assigned a unique pattern of binary digits that represents binary 1 or 0.

The main Disadvantage of this technique is that unwanted energy or noise from other sources may vary signal amplitude and can change original sent value. Another problem is that Transmission speed is dependent on the physical characteristics of the transmission media.

Network Protocols and Their Functions

Protocols

Whenever a person want to talk with another person then their communicating language should be same so that they can easily communicate with each other .If they will use different languages then they can not understand what the other is saying. Similarly in Computer Networks certain rules are defined so that computers can communicate with one another.These Pre defined rules are called Protocols and can be defined as "Protocols are the predefined rules between the communicating devices that govern the communication between them."

Functions Of Protocols

i)  Sequencing of Data:- Protocols split large size messages to equal size pieces called Packets which can be transmitted easily.each packet contains unique identification number and can be easily arranged at receiver end to create original message.

ii) Flow Control of Data:-This is another important function of protocols.if sender is sending continuously data and receiver is not in a condition to receive that data or having less receiving speed then their are the chances of data loss.This data loss is avoided by the use of Protocols.

Problems Associated with Wired Media

Attenuation

With The increase in the distance the energy of signal decreases.This energy loss is called Attenuation.This Energy loss is due to the Resistance of the Transmission wire which gets warm when signals are passed through them.This energy loss is Frequency Dependent.To re-boost these weak signals amplifiers are used and signal can travel long distance.

Difference Between LAN,MAN and WAN

Characteristics	LAN	MAN	WAN
Acronym	Local Area Network	Metropolitan Area Network	Wide Area Network
Cost	Less Costly	More Costly	Costliest
Speed	Up to 10-100Mbps	5-10Mbps	256Kbps to 2Mbps
Range	1Km	Up to 50 Kms.	Up to 10,000 Kms.
Topology	Bus and Ring	Distributed Queue Dual Bus [DQDB]	ATM, Frame Relay, Sonnet
Location of computers connected in the system	Computers are located within the same Building.	Computers are located in the city and are connected using modems or telephone lines so that they can be easily connected with Each other.	Computers are distributed all over the country or the Continent. The connection is made via satellite communication link Or via internet.

LAN,MAN and WAN

Local Area Network(LAN)

It is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building using network media.
ARCNET, Token Ring and other technology standards have been used in the past, but Ethernet over twisted pair cabling, and Wi-Fi are the two most common technologies currently used to build LANs.

LAN is generally limited to specific geographical area less than 2 K.M., supporting high speed networks. A wide variety of LANs have been built and installed, but a few types have more recently become dominant. The most widely used LAN system is the Ethernet system based on the bus topology.
Intermediate nodes (i.e., repeaters, bridges and switches) allow to be connected together to from larger LANs. A LAN may also be connected to another LAN or to WANs and MANs using a “router” device.

There are essentially five components of a LAN:
1) Network devices such as Workstations, printers, file servers which are
normally accessed by all other computers.
2) Network Communication Devices i.e., devices such as hubs, routers, switches etc. used for network connectivity.
3) Network Interface Cards (NICs) for each network device required to access the network. It is the interface between the machine and the physical network.
4) Cable as a physical transmission medium.
5) Network Operating System –software applications required to control the use of network operation and administration.

OSI Model

Open System Interconnection is a standard that describes how message  is transmitted and received between two points in telecommunication.It is developed by ISO( International Organization for Standardization ). It is a seven layer model and are labeled 1 to 7 with layer 1 at bottom(as per X.200 Recommendations).This concept of a seven-layer model was provided by the work of Charles Bachman, Honeywell Information Services.Idea behind this model was that the telecommunication between two points can be divided into layers with each layer adding its own set of special, related functions. The seven Layers are: 1)Physical Layer 2)Data Link Layer 3)Network Layer 4)Transport Layer 5)Session Layer 6)Presentation Layer 7)Application Layer. these seven layers are divided into two groups. The upper four layers are used whenever a message passes from or to a user(known as Host Layers). The lower three layers (up to the network layer) are used when any message passes through the host computer(known as Media Layers) . Messages intended for this computer pass to the upper layers. Messages destined for some other host are not passed up to the upper layers but are forwarded to another host.

Network Topology

Network Topology is the arrangement of computers or nodes in the network.it describes how nodes are connected to each other in a network.There are two basic categories of network topologies:
i)Physical topologies
ii)Logical topologies
Physical Topologies:-The shape of the cabling layout used to link devices  in any network is referred to as physical topology of the network. This refers to the layout of cabling, the locations of nodes, and the interconnections between the nodes and the cabling.
Logical Topologies:-It is the way by which signals act on the network media, or  data passes through the network from one device to the next without regard to the physical interconnection of the devices.
Various Physical Topologies are:

Simplex, Half Duplex,Full Duplex

Simplex
It is the mode of transmission in which data is transmitted in one way only.The transmitter will always transmit signal and receiver will always work as receiver and can’t be used as transmitter.This method is not often used because it is not possible to send back error or control signals to the transmit end.
Best example of Simplex mode of transmission is,data transmission from keyboard to mouse.

Peer to Peer and Client Server Model

Client Server Model
Client Server model is a Networking Technique in which one of two roles are assigned  to the computers in a network: Client or server.server is a computer system that selectively shares its resources and provide services to its clients; client is a computer that make use of a resources with the help of server. Some features of this model are:
1)There will be atleast one Server and any no. of clients.
2)Server Provides services to clients.eg. if client 1 wants to access internet,then it will make request to server.server will check its rights and will provide access to internet as per rights assigned.Similarly if anybody wants to communicate with client 1 ,then it will authorized by server to gain access.
3)There is centralized controlling hub hence more security and rights assignment can be implemented.
4)Failure of Server will fail the entire network.
5)Clients and servers exchange messages in a request-response messaging pattern: The client sends a request, and the server returns a response.

below given image demonstrates the complete Client server model.

Telnet

Telnet is a networking protocol that is used on the Internet or LAN  to provide a bidirectional interactive Command line  communication facility using a virtual terminal connection.Telnet was originally designed for the small institutions and security was not the concern.Telnet, by default, does not encrypt any data sent over the connection including passwords.The Telnet protocol uses various commands to control the client-server connection. These commands are transmitted within the data stream. The commands are distinguished from the data by setting the most significant bit to 1. (Remember that data is transmitted as 7-bits with the eighth bit set to 0) Commands are always introduced by the Interpret as command (IAC) character.
Communication is established using TCP/IP and is based on a Network Virtual Terminal (NVT). On the client, the Telnet program is responsible for translating incoming NVT codes to codes understood by the client’s display device as well as for translating client-generated keyboard codes into outgoing NVT codes.
The NVT uses 7-bit codes for characters. The display device, referred to as a printer in the RFC, is only required to display the standard printing ASCII characters represented by 7-bit codes and to recognize and process certain control codes. The 7-bit characters are transmitted as 8-bit bytes with the most significant bit set to zero. An end-of-line is transmitted as a carriage return (CR) followed by a line feed (LF). If you want to transmit an actual carriage return, this is transmitted as a carriage return followed by a NUL (all bits zero) character.

Proxy Server

In Computer Networks,Proxy Server is a Server that acts as intermediary for requests from clients seeking resources from other servers.A client connects to the proxy server, requesting some service, such as a file, connection, web page, or other resource available from a different server and the proxy server evaluates the request as a way to simplify and control its complexity.
Uses of Proxy Server
1)High Security because each client is provided access according to rights assigned to him.
2)To Speed up access to resources.these are used to cache web pages from web servers which makes fast access.
3)To create Web logs for the audit usage.
4)To scan transmitted content for malware before delivery
5)Access enhancement/restriction
6)Filtering of data means which contents can be accessed or not.
7)Translation
Types of Proxy

Difference Between Hub Switch and Router

Hub	Switch	Router
In Hub signal introduced at the input of any port appears at the output of every port except the original  incoming. The device is a form of multiport repeater.	Network switch is a telecommunication device which receives a  message from any device connected to it and then transmits the message only to the device for which the message was meant. This makes the switch a more intelligent device than a hub	A router looks at packet headers to determine which port it needs to forward a packet through, and also will translate packets between different protocols if needed. A router can also define subnets and will filter traffic as needed. Routers usually include DHCP, port forwarding capabilities and a whole host of other things usually controlled by software and therefore user customizable.
A Hub is, in its simplest form, just like a mains multi plug unit. There is no intelligence or circuitry in it. More complex units may incorporate an amplifier or repeater. The network signal goes into one port and out of all the others.	A Switch has a small level of intelligence, in that it can open a message, check the IP address, and direct the message packets to the port on which the device with that IP address resides. It cannot modify IP addresses or see addresses outside of the range of the ‘home’ network	A Router can read IP addresses, and direct the messages to another network with different IP addresses to the originating network. The Router software can build up an address table, so that it ‘knows’ where other devices are.