What is VLan ?

VLan (Virtual Local Area Network) :

A virtual local area network is a logical group of work stations and

 network devices that appear to be on the same LAN despite their 

geographical distribution. A VLan allows a network of computer and 

users to communicate in a simulated environment as if they exist in

 a single LAN and are sharing a single broad cast and multicast 

domain. 

Vlan are used for security and scalability.

A VLan allows several networks to work virtually as a Lan. One of the benefit of vlan is it removes latency in the network. Traffic issue could easily be controlled by vlan. 

Advantages of Vlan:  

   

    Allow administrator to secure network communication.

    It provide flexibility 

    It does decrease latency and traffic load on the 

       network and its devices  

Disadvantages :    

    Virus issue : An infected system may spread the virus in

        the entire logical network      

   

 Equipment Limitation could be occure in a large network.Because

         it might need additional routers.

       More effective at controlling latency than a wan but less 

           efficient than a Lan.   

What is Active Directory ?

 Active Directory:

 

Introduced first by Microsoft in window 2000 (operating System) . It is a centralized database which has information about all the     object. ie  users, computer resources like printer etc. in an organization      network  

Today most window server (OS) include active directory.  

Domain Controller: 

If an active directory domain service (ADDS)  is running in a server is called domain controller . It authenticates and authorizes all users and computer in a window domain type network assigning and enforcing security policies for all computer and installing or updating software.  

Example of AD: 

When a user want to login to a computer which is part of window domain. Active directory check first whether the email and password match with the active directory server email and password or not. If it does match access provided. Other wise login avoided by an error, or warning. 

What is voip?

 Voice over Internet Protocol

       

       definition:

(VoIP) is a technology that enables you to make and receive phone calls through  the Internet instead of using  the traditional analogy  PSTN (Public Switched  Telephone Network) lines.

            In Voice over ip   the classic public switch telephone system 

        audio is converted to packets and it passes along the network. It

        is a full duplex(two way)  voice transmission over broadband. It is also

        called IP telephony, internet telephony ,voice over broadband, 

        broadband telephony.   

How it works.

         When we call on the internet . The voice change to digital signal 

       and from analogue and compressed

        

     ( compress mean’s to make the data size smaller) , 

      And afterward  this data is encapsulated and is  move

      

      (Moving is done by routing,  data is rout from one router to another 

     

      and finally reach its destination )

.    

     (Encapsulation : change data to packet  is called encapsulation )

    

     And as it reach's  it’s destination it changes back to analogue signal

     and produce the voice you sent

   Advantages :

·                       According to public switch telephone network call as your call

          destination    and time increased cast increases.

      This is one of the best major advantage of VoIP .. you can call anywhere        in the world for a very long time absolutely free. Using Skype,

      IMO or Facebook , only internet cast..

·       

           It doesn’t need dedicated path between caller and called party.

  Disadvantage:

      Security Risk:

   

      Data could be hacked because as we know   that we are communicating        on the world wide  internet

WHAT IS HUB, SWITCH AND ROUTER DIFFINITIONS, EXPLANAITIONS AND DIFFERENCES

HUB:

Definition:

Hub is a device that connects Pc’s together.

Installation:

In a hub there are ports with which pc’s (devices) are connected.

How hub works :

 In a hub when one pc send the data in a wire to the hub, the hub simply forward the data to all the pc’s(devices) connected to it . Afterward devices deside that which data Is for which device.So in other  a hub doesn’t send the data to it’s exact destination . Infact it send the to all the devices.

Switch:

Definition:

               

                            Switch is a device that take a data and send it to its exact destination.

How switch works:

A switch records the ip and mac addresses in a table of all the devices connected to it.

 When a packet arrive to the switch, The switch reads the destination address of the packet and send it to it’s exact destination, if the destination address is found.

If the destination isn’t found so the switch send the packet to all the devices connected to it. So in this case a device decide whether or not the device is the destination .

In other words a device decide that am I the distination or not.

Router:

Definition:

A router is a hardware device that receive , analyze and move/forward incoming packets to another network or device, It may also decode and encode packets.

How router works:

A router also records the address information of everything’s (devices) connected to it .

But it also records the next router address .

A router reads more efficient information and then make decision .

A router recognized a packet to send where ie..

If a router received a packet but the packet address isn’t in its table it then send the packet along and it to another router close to it. And in this process the data send to it’s destination.

Types of router:

1 Broad band Router

2 wireless Router

3 Core Router

4 Edge router

4 Brouter