ICT

Domain Name System: How DNS works and Types of DNS Servers

len Alfred Ajibola - Tue, 11th June, 2019 @ 17:58

Topics in ICT

Routers, Types and Functions of Routers Computer scheme of work, SS1, First Term Computer scheme of work, SS1, Second Term Computer scheme of work, SS1, Third Term Computer Networks and Types of Computer Network Domain Name System: How DNS works and Types of DNS Servers Internet of Things (IoT), How IoT works, its advantages and challenges How to consume less data on your android phone Best Programming Languages to learn Internet and World Wide Web - Notable Dates and Events on Internet Evolution Computer Hardware, Parts and Functions of Computer Hardware


Academic Questions in ICT

Please check out our Test Your Knowledge page to see all Questions and Answers

The term SOHO is best represented as a _____.

  • A. LAN
  • B. WAN
  • C. CAN
  • D. PAN
  • E. MAN
  • F. SAN

Which of the following is NOT a function of the router?

  • A.To ensure that packets make it to their destination networks
  • B. To separate networks
  • C. To move traffic to the end devices within a LAN
  • D. To ensure some form of data security
  • E. To connect networks
  • F. To assist in connecting a home network to the internet

An example of a network that spans the entire globe is the _____.

  • A. LAN
  • B. PAN
  • C. MAN
  • D. CAN
  • E. NAN
  • F. INTERNET

A specialized router residing at the boundary of a company's network is called a/an _____.

  • A. Wired Router
  • B. Wireless Router
  • C. Core Router
  • D. Edge Router
  • E. Virtual Router
  • F. LAN Router
  • G. WAN Router

Which of the following is NOT a type of computer network?

  • A. NAN
  • B. MAN
  • C. CAN
  • D. LAN
  • E. WAN
  • F. PAN

The above diagram best illustrate a _____.

  • A. LAN
  • B. WAN
  • C. CAN
  • D. MAN
  • E. PAN
  • F. NAN

The layer 3 device that move packets between devices, allowing Network communication is called a _____.

  • A. Switch
  • B. Router
  • C. Firewall 
  • D. Computer
  • E. Smart phone
  • F. Central Procession Unit

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Domain Name System (DNS):

Let me begin by stating that there are at least two ways to get to this website (LEN ACADEMY @ len.com.ng).

Apparently, the first and recommended way is to enter len.com.ng on your web browser and you will be directed to this website (LEN ACADEMY). This is conventionally easy and apparently the normal route to follow.

A second way is by typing some four sets of numbers separated by dots (called IP address), for instance (10.102.18.11). This method is more technical and is generally not recommended for the average internet user.

The second way is actually the ideal way that the internet is meant to work because IP address is the protocol of the internet. This is what the founders of the internet used in designing the internet’s connectivity.

Note: IP Address means Internet Protocol Address.

Now, if we had gone with the second way from the above paragraph, the internet in itself will become quite difficult for almost everyone to use because it wouldn’t be fun memorizing the billions of available IP addresses. Some of the internet professionals knew this potential problem and thus decided to come up with the Domain Name System in 1983.

Please read the Notable Dates on Internet Evolution here.

Consider the followings:

  • This website on which you are on (Len.com.ng) is actually an IP address.

    The point is: You don’t need to know the IP address of LEN ACADEMY in order to get to it.

    All you need know is the domain name for LEN ACADEMY's IP Address; and that's "len.com.ng. All thanks to the Domain Name System for making this conversion possible.

    The DNS is a protocol that translates domain names to IP address. You may simply consider it as the phonebook of the internet.

    Think of the domain name as the name of a website, for instance, len.com.ng is a domain name, google.com is a domain name, yahoo.com is a domain name and so on.

Note: The DNS works at layer 7 or Application layer of the OSI Model and layer 4 of the TCP/IP Stack.

Please read on the OSI model here.

 

How DNS works

When you type in your destination website on your computer or phone's browser Uniform Resource Locator (URL); let’s say you entered example.com for instance, your browser will first attempt to resolve the entered address (example.com) to its specific IP address.

Note: Always understand that routing on the internet is a function of the IP addresses and technically NOT the domain name which you actually entered.

Please read on Routers and Routing here.

After your computer or phone does a successful domain lookup (that is; searches for the IP address that had been mapped to the domain name "example.com"), the IP address that matches "example.com" is henceforth used to get you the web page of example.com.

Note: Once the domain name (example.com in this instance) had been resolved to an IP address, DNS is done with its job because that’s specifically what it was created to do: “resolve domain namesIP address”.

Example.com could now be resolved to something like 192.168.0.100 (IP address) or the newer complex IPv6 Address that looks something like 1201:bca0:11aa:1992::1:100b.

The analogy of the above process indicates how all websites are accessed including len.com.ng.

The point is; with DNS, you are more likely to remember len.com.ng or google.com or yahoo.com rather than some sets of numbers separated by dots (IP Address or IPv6 Address).

Again, think of it this way: You make use of names to save phone numbers so that you can easily recognize the owners of such numbers right? The same goes for DNS in mapping domain names to IP address; since you can easily remember domain names compared to IP addresses.

Another question is; what if the domain name that was entered is incorrect; let’s say "len.cm.ng" was entered by a user instead of "len.com.ng".

Since "len.cm.ng" isn't matched to any IP Address, that will imply that "len.cm.ng" cannot be resolved to any IP address.

Well, the browser will respond with an error message while also giving you some suggestions on how to go about the issue.

See the error message below from an internet explorer browser

Browser Error Message - Len Academy

Note: We have got millions of DNS servers around the world. If one of the servers does not know how to translate a specific domain name, it will question the next server until the appropriate IP address for such domain name is returned.

Please read on the Internet of Things (IoT) here.


Types of DNS Server

DNS servers are classified into 4 types. These are:

1. DNS Recursor: The function of the recursive DNS server is to receive DNS queries directly from your computer or phone or any other client machine that has a browser.

The DNS recursor then makes additional request so that the correct IP address can be given back to the client machine.

  • If the recursive DNS server had already cached the correct IP address for the domain name (probably from an initial request), there will be no need for it to send an additional request to another DNS server (termed the Root Nameserver); rather it directly sends the correct IP address to the client machine.

2. Root Nameserver: This is the first DNS server that translates domain names to IP address. It does not contain a list of all the IP addresses for every domain name.

The root Nameserver only serves the domain name for specific locations.


3. Top Level Domain (TLD) Nameserver: This name server hosts the last segment of a domain name.

For instance, in the example.com domain, the TLD server hosts the “.com” portion of such name.


4. Authoritative Nameserver: Think of it as an encyclopedia that contains all domain names with each name mapped specifically to its correct IP address.

The authoritative name server returns the IP address to a specific domain name if it has the records, else the intended website (domain name) will be unreachable.

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len

Alfred Ajibola is a Medical Biochemist, a passionate Academician with over 7 years of experience, a Versatile Writer, a Web Developer, a Cisco Certified Network Associate and a Cisco CyberOps Associate.


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Amazing facts in ICT

Image Credit: Neowin

Smoking near an Apple (Mac) computer voids the warranty.

When you add /4 to the end of Facebook's URL, it will take you to Mark Zuckerberg.

You can try it on you own; or better still, try the link below:

facebook.com/4

Image Credit: Apple Insider

Apple iPad retina display is actually manufactured by Samsung

The big five tech companies are GOOGLE, AMAZON, FACEBOOK, APPLE and MICROSOFT

Please read on Notable dates on internet evolution here.


NOTABLE POINTS IN ICT

Computer Network is a group of computers that are linked to each other such that they can share resources.

Generally, these groups of computers that form a network are called nodes.

Some of these nodes will function to store information which will be served to other computers. The nodes that function to store and serve such information are known as servers.

Some of the computers (nodes) will request information from the server. The computers that functions to request information from the server are known as clients.

Please read on Computer Networks here

The internet and the World Wide Web (www) IS NOT the same thing. 

The internet is formed from the joining or linking of different networks. 

For instance, Google's network, Facebook's network and Yahoo's network are among the many other networks that make up the internet.

World Wide Web on the other hand is a collection of linked pages (for instance, this page you're on).

There are actually billions of linked pages in various servers around the world.

You require the internet and a web browser to get to the World Wide Web

Please read more on the internet here

Types of Networks Based on Geographical size

  1. Personal Area Network (PAN): An instance is a Bluetooth connection between two devices.

  2. Local Area Network (LAN): This is the network under a single administrative control and usually within a building.

  3. Campus Area Network (CAN): This network connects various devices within a campus or college

  4. Metropolitan Area Network (MAN): This network connects two offices/companies within a city

  5. Wide Area Network (WAN): This network connects devices throughout the globe. The internet is a typical example of a WAN.

You can read more on the types of network based on Geographical Size here

Functions of a Router

  1. They ensure that data (preferably called packets) make it to their intended destination.
  2. They ensure the security of data to some extent.
  3. When a network becomes too big within a LAN, routers are used to separate such networks.
  4. They connect different networks. This is the very reason why you are able to access the internet. (The internet's network and your service provider's network are different; but thanks to the router for connecting them).
  5. Multiple devices in the home or office can access the internet through the internet (and with a single IP Address). The term associated with this process is referred to a Network Address Translation (NAT)

Please read on Types and Functions of Router here