How Domain Name System (DNS) Works?

In the world of Internet and the area of computer networks, you will often come across the term Domain Name System or Domain Name Service which is simply referred to as DNS. The working of DNS forms one of the basic concepts of computer networks whose understanding is very much essential especially if you are planning to get into the field of ethical hacking or network security.

In this post, I will try to explain how Domain Name System works in a very simple and easy to follow manner so that even the readers who do not have any prior knowledge of computer networks should be able to understand the concept.

What is a Domain Name System?

A “Domain Name System” or “Domain Name Service” is a computer network protocol whose job is to map a user friendly domain name such as “Gohacking.com” to its corresponding IP address like “173.245.61.120″.

Every computer on the Internet, be it a web server, home computer or any other network device has a unique IP address allotted to it. This IP address is used to establish connections between the server and the client in order to initiate the transfer of data. Whether you are trying to access a website or sending an email, the DNS plays a very important role here.

For example, when you type “www.google.com” on your browser’s address bar, your computer will make use of the DNS server to fetch the IP address of Google’s server that is “74.125.236.37″. After obtaining the IP address, your computer will then establish a connection with the server only after which you see the Google’s home page loading on your browser. The whole process is called DNS Resolution.

With millions of websites on the Internet, it is impossible for people to remember the IP address of every website in order to access it. Therefore, the concept of domain name was introduced so that every website can be identified by its unique name which makes it easy for people to remember. However, the IP address is still used as the base for internal communication by network devices. This is where the DNS comes in to action that works by resolving the user friendly domain name to its corresponding machine friendly IP address.

In simple words, domain names are for humans while IP addresses are for network devices. The “Domain Name System” is a protocol to establish a link between the two. Hence, it is not a surprise that you can even load a website by directly typing its IP address instead of the domain name in the browser’s address bar (give it a try)!

Types of DNS Servers and their Role:

The Domain Name System (DNS) is a distributed database that resides on multiple computers on the Internet in a hierarchical manner. They include the following types:

Root Name Servers:

The root servers represent the top level of the DNS hierarchy. These are the DNS servers that contain the complete database of domain names and their corresponding IP addresses. Currently, there are 13 root servers distributed globally which are named using the letters A,B,C and so on up to M.

Local Name Servers:

Local servers represent the most lower level DNS servers that are owned and maintained by many business organizations and Internet Service providers (ISPs). These local servers are able to resolve frequently used domain names into their corresponding IP addresses by caching the recent information. This cache is updated and refreshed on a regular basis.

How DNS Server Works?

Whenever you type a URL such as “http://www.gohacking.com” on your browser’s address bar, your computer will send a request to the local name server to resolve the domain name into its corresponding IP address. This request is often referred to as a DNS query. The local name server will receive the query to find out whether it contains the matching name and IP address in its database. If found, the corresponding IP address (response) is returned. If not, the query is automatically passed on to another server that is in the next higher level of DNS hierarchy. This process continues until the query reaches the server that contains the matching name and IP address. The IP address (response) then flows back the chain in the reverse order to your computer.

In rare cases where none of the lower level DNS servers contain the record for a given domain name, the DNS query eventually reaches one of the root name server to obtain the response.

FAQs about Domain Name System:

Here is a list of some of the FAQs about DNS:

How does a “root name server” obtain the information about new domains?

Whenever a new domain name is created or an existing one is updated, it is the responsibility of the domain registrar to publish the details and register it with the root name server. Only after this, the information can move down the DNS hierarchy and get updated on the lower level DNS servers.

What is DNS propagation?

Whenever a new domain name is registered or an existing one is updated, the information about the domain must get updated on all the major DNS servers so that the domain can be reached from all parts of the globe. This is called DNS propagation and the whole process can take anywhere from 24 to 72 hours to get completed.

How often the DNS servers are updated to refresh the cache?

There is no specific rule that defines the rate at which DNS servers should be updated. It usually depends on the organization such as the ISP that maintains the server. Most DNS servers are updated on an hourly basis while some may update their databases on a daily basis.

I hope you have now understood the working of DNS in a very convincing manner. Pass your comments and share your opinion.

This post is originally posted on GoHacking.com.

By: Unknown On 4:03 pm

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How to make Solar Water Geyser at Home?

You Will Need :

•  2L plastic bottles (60),
• Cartons (50)
• 100mm PVC pipe (70 cm)
• 20mm PVC pipe (11.7m)
• 90-degree 20 mm PVC elbows (4)
• 20mm PVC T-connectors (20)
• 20 mm PVC end caps (2)
• PVC glue
• Black matt paint
• Paint Roller
• Sand paper
• Self-amalgamating tape
• Tools – Rubber hammer, saw, wood or other material for the support

Process :

Use the 100mm PVC pipe as a mold and cut off the bottom of the bottles. Cut the 20mm PVC pipes into 10 x 1m and 20 x 8.5 cm pieces, and assemble with the T-connectors. Cut and paint the cartons, as well as the one-meter long pipes. Assemble according to figure B.

The panels must be placed at least 30 cm below the tank and be sited on a south facing wall or roof. To optimize heat absorption, the panels must be mounted at the angle of your latitude, plus 10°. In London, for instance, the panel’s inclination should be 61°. We recommends that the plastic bottles in the panels should be swapped for new ones every 5 years: ‘Over time, the plastic becomes opaque, which reduces the heat caption, while the black cartons can be repainted.’ So once the bottles become opaque it is time to replace the bottles and send the used ones to the recycle dump.

By: Unknown On 11:07 am

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How to make Hot Ice?

All you need are two common kitchen ingredients to make hot ice - a non-toxic chemical that crystallizes when you touch it into a material that looks like ice except it gives off heat. See how to make hot ice and get ideas for fun hot ice activities.

You Will Need :

• White Vinegar
• Backing Soda

Process :

          Mix one liter of vinegar with 4 tablespoons of baking soda. These chemicals react to form nontoxic sodium acetate or hot ice in water. You need to boil off most of the water, so heat the solution until it is boiling and keep applying low heat until you see a crystal skin start to form on the surface of the liquid. Remove the hot ice solution from heat, pour it into a new container and refrigerate the solution until it is chilled.

          When the hot ice has cooled, you can get it to instantly crystallize simply by touching it. You can try crystallizing the hot ice as you pour it, too. Either way, the solution will give off heat as it crystallizes.

          You can re-dissolve and reheat the hot ice to play with it again or you can throw it away when you are finished. 

          I hope you've enjoyed making hot ice.

By: Unknown On 10:44 am

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How to make Fake Fingerprints?

Courtesy: Gujranwala Science Club

NOTE : The post is only for educational purpose. I'm not responsible for ANY misuse of this post.

In order to fake a fingerprint, one needs an original first. Latent fingerprints are nothing but fat and sweat on touched items. Thus to retrieve someone else's fingerprint (in this case the fingerprint you want to forge) one should rely on well tested forensic research methods. Which is what's to be explained here.

Process :

Find some good counterfeits. A good source of originals for our counterfeits are glasses, doorknobs and glossy paper. The standard method of forensic research makes them visible: Sprinkling it with colored powder, which sticks to the fat.

Try something related to superglue. Another solution involves Cyanoacrylate, the main ingredient of superglue. A small amount thereof is poured into a bottlecap, which is then turned upside down and put over the fingerprint. The Cyanoacrylate gasses out and reacts with the fat residue to a solid, white substance.

Get a digital reproduction. The further treatment involves scanning/photographing (Figure 5) and a bit of graphical refurbishment. The goal is to get an exact image of the fingerprint, for further use as mold, out of which the dummy is made. The easiest way is to print the image on a transparency slide (the ones normally used for an overhead projector) with a laser printer. The toner forms a relief, which is later used similar to letter press printing. Wood glue is suitable for producing the dummy.

Use a small dash of glycerin to optimize humidity and workability. After thorough mixing, the dummy gets coated with a thin layer of the compound.

After the glue has dried (Figure 10), pull off the foil (Figure 11) and cut it to finger size.

Glue the counterfeit to your own finger. Theatrical glue is used to glue the dummy onto the own finger. The new identity is ready!

By: Unknown On 10:22 am

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