ICT

Understanding Domain Name System, DNS

Olawunmi Omosanya - Tue, 11th June, 2019 @ 17:58: PM

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 Understanding Domain Name System, DNS Introduction to the Internet of Things How to consume less data on your android phone Best programming languages to learn Notable dates on Internet evolution



Academic Questions in ICT

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

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

Domain Name System (DNS):

Let me begin by saying that there are at least two ways to get to this website (len.com.ng). Apparently, one of the ways is to enter len.com.ng on your web browser and you will be directed to this website (Len Academy). A second way to is by typing some four sets of numbers separated by dots (called IP address), for instance 10.102.18.11. The second way is actually the ideal way that the internet is supposed 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. You don’t need to know the IP address of LEN ACADEMY in order to get to it; all thanks to the Domain Name System.

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 URL, let’s say example.com for instance, your browser will first attempt to resolve the entered address (example.com) to its specific IP address. Always remember that routing on the internet is a function of the IP addresses and technically NOT the domain name which you actually entered. 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 IP address, DNS is done with its job because that’s specifically what it was created to do “resolve domain names to IP address.” Example.com could now be resolved to something like 192.168.0.100 (IP address) or the newer complex address that looks something like 1201:bca0:11aa:1992::1:100b (called IPv6 address). This is how every other website would work 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).

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". That will mean 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:

Image Credit: Social Technet

 

We have got millions of DNS servers around the world such that 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.

DNS servers are of four types:

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 it 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; 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. It 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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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


NOTABLE POINTS IN ICT

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

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