Network Interview Questions & Answers

1.      What is the difference between TCP and UDP

TCP is a connection oriented protocol, which means that everytime a packet is sent say from host A to B, we will get an acknowledgement. Whereas UDP on the other hand, is a connection less protocol.

Where will it be used : TCP -> Say you have a file transfer and you need to ensure that the file reaches intact, and time is not a factor, in such a case we can use TCP.

UDP-> Media Streaming, question is say you are watching a movie…would you prefer that your movie comes..perfectly….but u need to wait a long time before you see the next frame ?..or would you prefer the movie to keep streaming…Yes…The second option is definely better….This is when we need UDP

2.      What is a MAC address?

MAC is a machines Physical address, The internet is addressed based on a logical addressing approach. Say, when the packet reaches say the bridge connection a LAN, the question is..how does it identify, which computer it needs to send the packet to. For this it uses the concept of ARP, Address Resolution Protocol, which it uses over time to build up a table mapping from the Logical addresses to the Physical addresses. Each computer is identified using its MAC/Physical address ( u can use the ipconfig -all option to get ur MAC address).

3.      What is MTU?

The MTU is the “Maximum Transmission Unit” used by the TCP protocol. TCP stands for Transmission Control Prototcol. The MTU determines the size of packets used by TCP for each transmission of data. Too large of an MTU size may mean retransmissions if the packet encounters a router along its route that can’t handle that large a packet. Too small of an MTU size means relatively more overhead and more acknowledgements that have to be sent and handled. The MTU is rated in “octets” or groups of 8 bits. The so-called “official” internet standard MTU is 576, but the standard rating for ethernet is an MTU of 1500.

4.      Difference Between. Switch , Hub, Router..

Hub: 1.it is a layer1 device..used to connect various machine on Lan.
2.It forwards broadcast by default.
3.It supports one collision domain and one broadcast domain.
4.it works on Bus topology resulting less speed.
Switch: 1. A layer2 device.
2. Forward broadcast first time only.
3. one broadcast domain & collision domains depends on no. of ports.
4.It is based on Star Topology giving 100mbps to every pc on Lan.
Router: 1. Does not Broadcast by default.
2. breaks up Broadcast domain.
3. Also called Layer3 switch.

5.      VPN.....
VPN(Virtual Private Network )… these are basically the logical networks on the physical line… you can have many VPN over same line..
Need of VPN arises when your company need to increase the network but don’t want to buy any more switches.. take an eg. your dept. your room is packed with employees and ur company need to add 4 more persons to ur deptt. what will they do.. the solution is to create VPN’s…you can configure the switch ports in other deptts. and create a specific VLAN of urdeptt. So that the persons can sit there and access to the required pcs.

6.      ARP & RARP.....

      Stands for Address Resolution Protocol…whenever a request is sent by a node on one network to the node on another network the Physical address(MAC) is required and for this the IP address need to be flow over the network..whenever a router with that network (IP) gets the msg. the required MAC address is sent through the network this process of converting the IP address to MAC address is Called ARP..and the reverse thats the convertion of the Mac address to the IP address is called RARP ( Reverse Address Resolution Protocol)

7.      What is the difference between layer 2 and layer 3 in the OSI model?

Layer 2 is responsible for switching data whereas Layer 3 is responsible for routing the data.

Layer3: With information gathered from user, Internet protocol make one IP packet with source IP and Destination IP and other relevant information. It can then route packet through router to the destination.

Layer2: Soon after it receives IP packet from layer 3, it encapsulate it with frame header (ATM header in case of ATM technology) and send it out for switching. In case of Ethernet it will send data to MAC address there by it can reach to exact destination. 

What is Windows Vista?

Operating systems control the functions performed by a computer. For example, the operating system on your computer controls the input from the keyboard and mouse to your computer, the opening and closing of programs, the transfer of information to a printer, the organization of the files on your computer, and the screen display. To function, every computer must have an operating system. Windows Vista is an operating system. It was released by the Microsoft Corporation in late 2006.

Windows Vista comes in several versions: Home Basic, Home Premium, Business, Ultimate, and Enterprise. The features available to you depend on the version of Windows Vista you have.

Windows Vista Enterprise is for large global organizations and is only available to organizations with desktops covered by Software Assurance agreements or organizations with a Microsoft Enterprise Agreement that includes the Windows desktop component.

Windows Vista Home Basic is the entry-level edition. Geared toward home computer users, Home Basic has features that allow you to search your computer, search the Web, browse the Internet, view photos, send and retrieve e-mail, and set parental controls. Windows Defender and Windows Firewall are included with Windows Vista Home Basic. Windows Defender helps protect your computer from spyware. Spyware is malicious software you install on your computer inadvertently or is put on your computer without your consent. Windows Firewall helps protect your computer from malicious software and unauthorized access to your computer.

Windows Vista Home Premium has most of the features found in Windows Vista Home Basic plus additional features such as Aero, Windows Media Center, Windows Meeting Space, Windows Mobility Center, Windows SideShow, and Tablet PC support. Windows Aero features translucent windows and smooth animations, including the capability to do three-dimensional flips through open windows. It also provides a thumbnail preview of the contents of open windows when you pause your mouse pointer over the window’s identifier on the taskbar or Alt-Tab through windows. With Windows Media Center, you can record and watch TV shows, listen to Internet and FM radio, view home movies, create slide shows, and burn CDs or DVDs. You can use Windows Meeting Space to set up meetings in which you can share documents, programs, or your desktop with others. Windows Mobility Center provides a convenient location for you to adjust the settings for your mobile PC. With Windows SideShow, you can send information from your computer to other devices such as mobile phones, hand-held computers, and TVs. A tablet PC is a mobile computer that you can interact with by writing on the screen or by using your finger or a pen. You can use Windows Vista Premium with a tablet PC.

Windows Vista Business is designed for small businesses. It is simple to use and has mechanisms that protect your information from unauthorized viewing.

Windows Ultimate includes all the features of Windows Vista Home Premium and Windows Vista Business and has extra features such as DreamScene, Language Packs, and BitLocker Drive Encryption. With DreamScene, you can use full-motion video as your wallpaper. Language packs allow you to install multiple languages on a single PC. BitLocker Drive Encryption encrypts your data to protect it from unauthorized viewing.

How & Why You Should Backup Registry Files

If you ever come across Windows boot error when it fails to load one or more (corrupted) registry hives, you can follow the steps explained in MS KB307545 to recover from corrupted registry. Having said that, lets understand few non-obvious facts.

When Windows is installed, it creates a backup of all the registry files in \%SYSTEMROOT%\repair\, whereas all the active registry files that Windows uses during run time are stored in \%SYSTEMROOT%\System32\Config. If any of the registry files inside \Config folder is corrupted, you can use Recovery Console to recover registry files from \repair folder to \config folder. There is however one significant consequence - the system will lose all the softare installation settings and system configuration done since Windows installation because registry files inside \repair folder are never updated after Windows installation, so after recovering those files the system essentially goes back to the same state when it was first installed (KB307545: "...This registry was created and saved during the initial setup of Windows XP. Therefore any changes and settings that occurred after the Setup program was finished are lost...").

To avoid this consequence, you can periodically update \repair folder using NTBACKUP tool. NTBACKUP doesn't have any specific option to update registry files, but all you need to do is take a System State backup, which will create a flat .BKF file, but will also update the \repair folder with copies of all registry files from \config folder. You can later delete that .BKF files because all we want to accomplish here is to update \repair folder with the most recent copy of registry files. It is also very easy to automate this entire process by creating a scheduled backup job which runs once a week (or depending on how frequently you change system settings or install/uninstall softwares) and overwrites the same BKF file. Here is a related article which addresses similar requirement

What’s the difference between symmetric and asymmetric encryption?

Symmetric cryptography uses the same secret (private) key to encrypt and decrypt its data whereas asymmetric uses both a public and private key. Symmetric requires that the secret key be known by the party encrypting the data and the party decrypting the data. Asymmetric allows for distribution of your public key to anyone with which they can encrypt the data they want to send securely and then it can only be decoded by the person having the private key. This eliminates the need of having to give someone the secret key (as with symmetric encryption) and risk having it compromised. 

The issue with asymmetric is that it is about 1000 times slower than symmetric encryption which makes it impractical when trying to encrypt large amounts of data. Also to get the same security strength as symmetric, asymmetric must use strong a stronger key than symmetric. 

If you do a quick search on the differences between symmetric and asymmetric you can find many more explanations. This just a quick overview.

What’s the difference between encryption and hashing?

Encryption is a scheme where an intelligible text (plain text in crypto terms) is made unintelligible (cipher text in crypto terms) using a secure key. Block and stream ciphers and public key systems do this work. The security of the ciphers reside in the key length and decryption process is a difficult without proper knowledge of the key. 

Coming to hashing, they are one-way functions that compress arbitrary length strings into fixed short strings (message digests). Hash Functions can be designed using block ciphers using a secret key as a parameter along with the message that has to be hashed or with out them (dedicated hash functions MD4,MD5, SHA-1 etc..). 

How to Download Facebook Album Photos ?

Facebook is the most popular social media network and now become the most popular service for Photo sharing. As you know Facebook allowing users to download photos hosted to their or friends facebook profile but they not allowing users to download the facebook album photos as a whole. Today we come up with a simple extension to solve this problem.

To download facebook album photos as a whole you need two things.

1. Google Chrome Browser. if you don’t have Google Chrome Internet browser just get thelatest version from here.
2. Facebook Album extension for Google Chrome. You can download it from here.

Once you installed Google Chrome browser now your turn to install facebook album extension.

Once the installation finish, you will see a Facebook icon coming on the top right corner of your Google Chrome window. You are now ready to download your friend’s facebook album photos as a whole.

Step 1 :  Log in to your facebook account  and visit your friend’s or your own facebook album.

Step 2:  click on the facebook icon on top right corner of your Google Chrome browser.

Step 3:   Now click Ctrl +S button from your keyboard to download all facebook album photos  of your friend’s or your own.

The Facebook album extension creates an HTML page with all the photos from the album and then saves it to your PC by saving the page.Let me know you have any difficulties in downloading facebook album photos as a whole.

Trick To Make Free Call to Any Number In World with movibox

Well this is not any hack of mobile services but instead a legitimate way of making a free call to any number in world.This can be a real helpful if you do not have any account balance in your mobile and you need to make a urgent call.This is the right time movibox can help you out.

So  what you will get with this service.

You will get free calling time of 5 minutes and you can call with it  anywhere in world to any mobile number.To make a call click on Direct call Button after you register a account with them.

Can you Make unlimited calls?

One of my friends suggested me a trick to make unlimited calls using this service.

What’s the Trick?

Well the trick is quite simple one..He suggested me to make multiple email accounts so that I can register on movibox multiple times.This trick worked for me around 5 to 6 times and I think they have figured out this method and Now my account gets automatically blocked when I create a new account.

BTW, I was not creating multiple email accounts instead I was using my gmail trick of multiple account.It worked like charm for 5-6 times and I guess they have figured this out.

What are the Mistakes That I could have made?

Well If you want to try the above trick..Please donot make following mistakes

1. Donot make multiple movibox accounts quikly because then you can be easily figured out!
2. Clear your cache and cookies before registering new Account.
3. Donot use same mobile number everytime..use fake one at the time of registertion and change it later after succesful login into your account.
4. Disconnect and reconnect your internet before registering new account as it will change your Ip address if you have dyanmic Ip address.

Do comment and tell me whether this trick is working or not for you people..In the meantime I will try to figure another way out.

Note:-If after you enter your details and click on register button and it takes too long to load then just go to homepage again and click on  Register for free..You will automatically get confermation code at your earlier entered email address

Note:-The purpose of this article is to make companies and developers aware about these type of loopholes.This is purely for educational purpose.

Trick To Use Multiple Email ID’s From Single Gmail Account

You may call this as a hack or a trick or a bug in gmail.If you have a gmail ID then you can create and use multiple email ID’s with the single gmail ID .So, there is no need to create different email accounts for registering multiple times on a single website.Suppose ,I want to create two accounts on abc.com then I have to use different email id’s for each account but with this method I will be able to register on any site multiple times with single email account.I have tested this trick on gmail account but have not tried it on Yahoo orHotmail.So the Requirement for this trick to work is

• You should have a gmail account

Here is the step by step tutorial on Trick To Use Multiple Email ID’s From Single Gmail Account

The basic idea behind this trick is that websites treat email Id with .(dots) or +(Plus) to different whereas gmail considers them same.

If I have an email id abctips@gmail.com then all the messages delivered to the email addresses such as abc.tips@gmail.com or abc+tips@gmail.com will be delivered to inbox of abctips@gmail.com whereas the websites treat these email id’s as a different email id’s.So by varying the postion of .(dots) or +(plus) sign you can create multiple accounts on any website.

So, there is no need to manage multiple email accounts for multiple  website accounts .

How to Delete or protect Important Data From Lost (Stolen) Laptop | Notebook

If you loose your laptop then the first thing that comes in your mind is the amount of money lost you. Later you will realize that the amount of data you lost was priceless and was as precious as your lost money. It becomes impossible to retrieve of all of your data, but then the problem become worse if any confidential data from your laptop gets into wrong hands.

LaptopLock protects the data and aids in the recovery process of a computer if it's stolen. The LaptopLock can:
Delete files (secure data wiping now available)
Encrypt files
Show a message to the user
Execute a program
Play a sound
Visible or hidden from user

How do I setup The LaptopLock?Sign up for a free account to register the computer(s). Install the LaptopLock agent for Windows 2000/XP/Vista. Complete the setup wizard.
How does The LaptopLock work?

If the computer is stolen, login into your account, mark the computer status as stolen. As soon as that machine connects to the Internet, the actions you set during setup will execute. The LaptopLock will also try to find out as much as possible about the connection to help in recovery of the machine.

"THE LAPTOPLOCK DOES NOT MONITOR OR RECORD USER ACTIONS. THE LAPTOPLOCK DOES NOT ALLOW ANYONE ACCESS TO YOUR COMPUTER OR DATA. THE LAPTOPLOCK CAN ONLY EXECUTE ACTIONS THE USER HAS PRE-PROGRAMMED IT WITH."

What if there is no internet connection?

If after a while LaptopLock has been unable to connect to the Internet, it could ask the user to verify their identity by asking for a password. This option is set during installation and depends on how visible LaptopLock's presence should be.

Whenever you feel unsatisfied with the working of this tool you can remove your system’s ID from your account and then uninstall it from your system. The best feature about this tool is that besides giving all these important facilities or services it is a freeware.

This freeware is compatible with all the versions of Windows as it has been checked on Windows 7 Ultimate 32-bit edition.

Download Laptoplock

How to know Who Used my PC in my Absence

Just go to Start > run >eventvwr.msc

Events are stored in three log files: Application, Security, and System. These logs can be reviewed and archived.

For our purposes we want the System log. Click on "System" in the left-hand column for a list of events.

Look for a date and time when you weren't home and your computer should have been off.

Double click on the e.g.: info and it will show you the detail.

You can also use this log to see how long someone was on the computer. Just look at the time the computer was turned on and off for that day.