HTML tutorials:Chapter 1 includes-HTML basics,History,hello world program,and running procedure[VIDEO]

HTML tutorials :How to make a simple webpage on notepad(free)[Video]

HTML tutorials :How to make a simple webpage on notepad(free)[Video]

What is Firewall?How its help in network security?

Firewall is a device or a server which helps to protect our network nodes from unauthorised user's.

In simple words,

Firewall is a technique which is used to protect our private network from a public network i.e. Internet.

It is generally divided into 2 parts:-

• Network firewall:-This firewall is used to check source and destination address of the network.
• Application firewall:-It is also  used to check source and destination address of the network after network firewall.

Some attributes which are used by network firewall are service control,direction control,behaviour control and user control.Now I discuss some different-2 types of firewall.

Firewall is generally divided into 5 parts that are:-

1)Packet Filtering Router:-It is used to validates the source address of data and allows only authorised user's.

Some information used by Packet Filtering Router are:-

• Source IP Address.
• Destination IP Address.
• Protocols etc.

Advantages and disadvantages of Packet Filtering Router:-

1. It provide good security.
2. It is cheap technique as compared to other types of firewall.
3. It is very complex.
4. Difficult to manage.

2)Stateful Inspection Firewall or Stateful Packet Inspection Firewall(SPI):-This firewall is use to protect our network from unauthorised user's.It is also provide Synchronisation,Acknowledgement etc.

3)Circuit Level Gateway:-It is used to validates the data packets  from a malicious code.It does not contain any specific proxy server.

4,5)Application Gateway and Guard Firewall:-

Application gateway firewall is also called as proxy server or proxy gateway.It is used to controls most of the protocols like http,ftp,mail protocol etc. from network.It provide good security as compared to SPI but it is very complex.

Guard firewall is the most complex firewall of all time.It is used to audit different-2 activities.

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What is Router?

Router is a networking device that send group of messages(packets) to different-2 networks(It will send packets only on those networks which have same protocols).Example Internet or Intranet.

In simple words,

Router is a device which connect two or more networks.

Router chooses the shortest route for data communication.It is used to determine the next network point in which we sends packets.Routing feature is also used in OSI model in network layer.

Type of router:-

1)Wired Router:-Those routers which uses wired medium for data communication.

2)Wireless Router:-Those routers which uses wireless medium for data communication.

Routing methods:-Routing method are of two types-

1)Static routing:-It conclude that how packet will send or received from one network to another.

2)Dynamic routing:-It is much advance than static routing.

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What is Open System Interconnection Model(OSI Model) and its 7 layers?

OSI stands for Open System Interconnection as I mention in the title of the post.This model is develop by ISO company in 1978.This model allow communication between multiple networks.This model tells how data is travel  from one node to another node in a network.This model represent different-2 layers/levels that tells how our data are transfer from one computer to another.This model overcomes all the limitations of TCP/IP model.
TCP/IP contains only 4 layers i.e. Application layer,transport layer,Internet layer and host to network layer but OSI model contains 7 layers i.e. application layer,presentation layer,session layer,transport layer,network layer,data link layer and physical layer.

In OSI model transmission is done from application to physical layer and receiving is done from physical to application layer.Now I draw the diagram of OSI model that tells how data flow from one layer to other on the basis of transmission as well as receiving.

On the basis of transmission 

On the basis of receiving 

Different-2 layers of Open System Interconnection Model with functions:-

1)Application Layer:-Application layer is the seventh layer of OSI model.It contains applications,protocols etc.Applications like file transfer,email and protocols like FTP,HTTP etc.It is also called as data unit.

2)Presentation Layer:-Presentation layer is the sixth layer of OSI model.This layer is used for encryption of data and this layer is also used for compressing of data for fast transmission.It is also called as syntax layer.

3)Session Layer:-Session layer is the fifth layer of OSI model.This layer is used to manage the dialogue session between the application of data.Session layer also uses different-2 duplex method like simple duplex,half duplex and full duplex.

4)Transport Layer:-Transport layer is the fourth layer of OSI model.This layer is used for transfer data between network.This layer used two protocols namely TCP(Transmission Control Protocol) and UDP(User Data gram Protocol).TCP is the connection oriented protocol as well as it provide more reliable connection as compared to UDP.UDP is connection less protocol and it only receive or transmit data but not manage it as like TCP.It is also called as segment unit.

5)Network Layer:-Network layer is the third layer of OSI model.Network layer uses switches,routers.This layer is also called as packet unit.It represent how packets(group of data) are travels from one node to another.

6)Data Link Layer:-Data link layer is the second layer of OSI model.Those packets which are send from network layer are decode and encode in this layer.Data link layer is also called as frame unit.It has two sub layers i.e. MAC(Media Access Control) and LLC(Logic Link Control).

7)Physical Layer:-Physical layer is the first layer of OSI model.This layer receive data in the form of bit stream(0 or 1).It is also responsible for physical devices like Ethernet,cables,HUB etc.This layer is also called as bit unit.

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Computer Architecture:What is Data Bus?

Data Bus is the bus which carries data and transfer machine instructions(which are given by us)from one place to another,but don't be confused with Address bus(Address bus carries the address not data but it carries the information of data).

Accumulator Data(AC):-AC is also called as Processor Register.The main purpose of AC is to store and accumulate data.

Status Register:-Status register is also called as flag register.Its generally in 1 bit.Some important consideration of flag register are carry,zero,sign,parity.

Program Counter Register(PC):-The main purpose of Program counter register is to execute instruction.

Instruction Register(IR):-The main purpose of Instruction register is to execute and store machine instruction.

Address Register(AR):-The main aim of Address register is to holds the memory address.

Temporary Register(TR):-The purpose of this register is to holds the data temporarily.

Input Register(INPR):-INPR is used to hold the incoming data which are coming from input devices like keyboard etc.

Output Register(OUTR):-OUTR is used to hold the output data.

Data Register:-It is called as DR.It is used to holds the data.  

Now I draw the flow chart/diagram of data bus and its bits table.

Register	Number of bits
DR	16
IR	16
AR	12
TR	16
AC	16
PC	12l
INPR	8
OUTR	8

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