DNS - Domain Name System in Computer Networks

Summary

This educational video delves into the Domain Name System (DNS), explaining its fundamental role in translating domain names into IP addresses, which is essential for internet communication. The host illustrates DNS with practical examples using Wireshark, discusses the structure of domain names including generic and country domains, and clarifies hierarchical access. Further, the video explores DNS database organization and the two primary methods of address resolution: iterative and recursive, with an emphasis on the efficiency of the recursive method. The content is enriched with demonstrations of NS lookup commands and insights into DNS entries, TTL values, and the distributed database approach involving root, name, and host servers.

Takeaways

• 🌐 DNS (Domain Name System) is used to get IP addresses from domain names, facilitating communication between computers on a network.
• 🔍 The video demonstrates DNS in action using Wireshark software to show how a DNS query is sent and a response is received, retrieving an IP address from a domain name.
• 🏛️ Domain names are categorized into generic domains (like .com, .org, .edu) and country domains (like .in for India, .jp for Japan), each serving different purposes and regions.
• 📚 The hierarchical structure of domain names includes root domain, top-level domain (TLD), second-level domain, and subdomains, which are crucial for understanding how DNS organizes and resolves names.
• 📈 DNS uses a distributed database approach with three main levels: root DNS servers, name servers, and host servers. This structure helps manage and resolve domain names efficiently.
• 🔄 IP addresses are dynamic and can change over time, which is why DNS entries include a Time-To-Live (TTL) field to indicate how long the IP and domain name pairing remains valid.
• 🔎 The NSLOOKUP command is used to query DNS and retrieve IP addresses for a given domain name, demonstrating the practical application of DNS in accessing websites.
• 🔄 DNS resolution can occur through two methods: iterative, where the local server makes multiple requests to different servers to resolve the domain name, and recursive, where the local server delegates the resolution process to a DNS server that completes the task.
• 🕒 The time taken to resolve a domain name and retrieve an IP address depends on the method used, with recursive resolution generally being faster than iterative resolution.
• 💡 The video emphasizes the importance of understanding DNS, its structure, and resolution methods, especially for those preparing for competitive examinations or needing a deep dive into network communication.

Q & A

What is the primary function of DNS?

The primary function of DNS (Domain Name System) is to translate domain names, which are easy for humans to remember, into IP addresses that computers use to identify each other on the network.

What are the two types of IP addresses mentioned in the script?

The two types of IP addresses mentioned are IPv4 and IPv6.

How does the DNS protocol operate?

DNS protocol operates using a client-server model where the client sends a query to the DNS server, which then responds with the requested IP address associated with the domain name.

What is a practical example of using DNS mentioned in the script?

A practical example given in the script is using Wireshark software to observe DNS requests and responses, such as getting the IP address for 'grammarly.com'.

What are the two general categories of domain names discussed in the script?

The two general categories of domain names discussed are generic domain names (like .com, .org, .edu) and country domain names (like .in for India, .jp for Japan).

How does the script explain the hierarchical access to domain names?

The script explains hierarchical access to domain names through a practical example, showing how domain names are structured from the root domain to top-level domains, second-level domains, and subdomains.

What is the purpose of the TTL field in DNS entries?

The TTL (Time To Live) field in DNS entries specifies the duration for which the IP address and domain name are considered validly associated with each other before they become invalid and need to be refreshed.

What is the difference between iterative and recursive methods of address resolution in DNS?

In iterative address resolution, the client makes multiple requests to different DNS servers until it gets the IP address, while in recursive resolution, the local DNS server makes all the necessary requests on behalf of the client and provides the final IP address.

What does the script mean by 'root DNS server', 'name server', and 'host server' in the context of DNS database organization?

In the context of DNS database organization, 'root DNS server' refers to the top-level servers that manage the DNS hierarchy, 'name server' refers to the servers that handle specific top-level domains (like .com, .org), and 'host server' refers to the servers that host the actual websites or services associated with domain names.

How does the script illustrate the dynamic nature of IP addresses?

The script illustrates the dynamic nature of IP addresses by explaining that IP addresses can change over time and that recently accessed domains are stored in cache entries for faster access, as they do not change immediately.

What command is used in the script to look up IP addresses associated with domain names?

The script uses the 'NS lookup' command to find the IP addresses associated with domain names.

Outlines

00:00

🌐 Understanding DNS and IP Address Resolution

This paragraph introduces the Domain Name System (DNS) and its role in resolving domain names to IP addresses. The speaker plans to cover the basics of DNS, demonstrate how DNS works using Wireshark software, discuss generic and country domain names, explain the hierarchical structure of domain names, describe the organization of the DNS database, and show how DNS entries are provided. The paragraph also mentions two methods of address resolution: iterative and recursive, which will be discussed with practical scenarios. The importance of IP addresses (both IPv4 and IPv6) in computer network communication is highlighted, emphasizing that communication is impossible without them.

05:01

🔍 DNS Query Process and Domain Name Classification

The speaker explains the process of how a DNS query works, using the example of accessing a website. They discuss the dynamic nature of IP addresses and how recently accessed domains are stored in cache for faster access. The TTL (Time To Live) field is introduced, which determines the validity period of the IP-address and domain name pairing. The paragraph also covers the use of the NS lookup command to retrieve IP addresses using DNS protocol. Additionally, domain names are classified into generic domains (like .com, .org, .edu) and country domains (like .in, .jp, .uk), with examples provided to illustrate the point.

10:04

📚 Hierarchical Structure of Domain Names

This paragraph delves into the hierarchical structure of domain names, explaining the concept of root domains, top-level domains (TLDs), second-level domains, and subdomains. Examples are given to illustrate how these levels are organized, such as 'engineeringfunder.co.in' and 'en.wikipedia.org'. The importance of understanding this hierarchy is emphasized, especially in the context of competitive examinations where questions might be asked about the different levels of a domain name.

15:04

🌐 DNS Database Organization and Address Resolution

The speaker discusses the organization of the DNS database, highlighting the three levels: root DNS servers, name servers, and host servers. The role of each level in the DNS hierarchy is explained, with an emphasis on the importance of having multiple root servers to avoid single points of failure. The paragraph also explains the process of address resolution, contrasting the iterative and recursive methods used by computers to obtain IP addresses through DNS. The iterative method involves multiple requests to different servers, while the recursive method involves a single request that follows the DNS hierarchy to retrieve the IP address.

20:07

⏱ Time Efficiency in DNS Resolution Methods

In the final paragraph, the speaker concludes by discussing the time efficiency of the DNS resolution methods. They note that the iterative method generally takes more time due to the multiple steps involved in querying different servers, while the recursive method is typically faster as it involves a single request that follows the DNS hierarchy. The speaker invites viewers to share their thoughts in the comments and thanks them for watching the video.

Keywords

💡DNS

DNS stands for Domain Name System, which is the phonebook of the internet. It translates human-friendly domain names into IP addresses that computers use to identify each other on the network. In the video, DNS is the central theme, as it is used to explain how to retrieve an IP address from a domain name, facilitating communication between devices.

💡Domain Name

A domain name is a human-readable address on the internet, like 'google.com'. It is used to access websites and services. The video script explains that domain names are crucial for identifying websites and that the DNS is used to find the corresponding IP address for a given domain name.

💡IP Address

An IP address is a unique numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication. The script mentions two types of IP addresses: IPv4 and IPv6. The video demonstrates how DNS is used to resolve domain names into IP addresses, which are necessary for network communication.

💡Wireshark

Wireshark is a network protocol analyzer used for network troubleshooting and analysis. In the context of the video, Wireshark software is used to demonstrate a practical example of how DNS queries and responses work to resolve domain names into IP addresses.

💡Generic Domain

A generic domain, as explained in the script, refers to a top-level domain (TLD) that is not specific to any country, such as .com, .org, .edu, and .net. These are used for various purposes, including commercial, organizational, and educational entities.

💡Country Domain

Country domains are top-level domains that represent specific countries, such as .in for India, .jp for Japan, and .uk for the United Kingdom. The video script discusses how these domains are used to signify the geographical or national affiliation of a website or service.

💡Hierarchical Access

Hierarchical access in the context of DNS refers to the structured way domain names are organized and resolved. The script uses a practical example to illustrate how domain names are broken down from the root domain to the top-level domain, second-level domain, and subdomains.

💡DNS Database Organization

The DNS database organization is a distributed system that involves root DNS servers, name servers, and host servers. The video script explains that this hierarchical structure is essential for the efficient resolution of domain names to IP addresses across the globe.

💡TTL

TTL stands for Time To Live, which is a field in DNS records that indicates the duration for which a record is valid. The script mentions TTL to explain how recently accessed domains are stored with a validity period, allowing for faster access before they become invalid.

💡NS Lookup

NS Lookup is a command used to obtain the IP address associated with a domain name using the DNS protocol. The video script provides examples of using NS Lookup to query for the IP addresses of google.com and yahoo.com, demonstrating how DNS is used in practice.

💡Iterative Method

The iterative method is one of the two methods for address resolution explained in the script. It involves a series of requests from a local server to various levels of DNS servers until the correct IP address is obtained. The video illustrates this process with a practical example, showing how multiple iterations may be required.

💡Recursive Method

The recursive method is an alternative approach to address resolution where a local server makes a single request to a root DNS server, which then handles all further queries and responses to ultimately provide the IP address. The script contrasts this method with the iterative method, noting that it may be faster due to fewer interactions required.

Highlights

Introduction to DNS (Domain Name System) and its purpose in translating domain names to IP addresses.

Explanation of the basics of DNS with a practical example using Wireshark software.

Discussion on the two types of IP addresses: IPv4 and IPv6.

Demonstration of how DNS is used to communicate with websites like Google.

Description of DNS using the UDP protocol in a practical scenario.

Introduction to the concept of domain names and their importance in internet communication.

Explanation of generic and country domain names and their classifications.

Practical example illustrating the hierarchical access to domain names.

Discussion on DNS database organization and how DNS entries are provided.

Introduction to address resolution methods: iterative and recursive.

Practical scenario demonstrating DNS protocol frames for IP address retrieval.

Explanation of how IP addresses are dynamic and change over time.

Description of how recently accessed domains are stored for faster access.

Introduction to the NS lookup command and its use in DNS protocol.

Practical demonstration of NS lookup for domain names like Google and Yahoo.

Explanation of the hierarchical structure of domain names with examples.

Discussion on the three levels of DNS database organization: root DNS server, name server, and host server.

Practical example of how DNS entries are stored with TTL values.

Detailed explanation of the iterative method in DNS address resolution.

Detailed explanation of the recursive method in DNS address resolution.

Conclusion on the importance of understanding DNS for internet communication.

Transcripts

Hello friends welcome to engineering

Wonder family in this video I am going

to explain you DNS domain name system

and to understand DNS let me show you

how many things that I'm going to cover

in this video see first I'll be

discussing about basics of DNS here I'll

give you one practical example in which

I'll show you in my computer with the

use of Wireshark software in which I'll

show you how DNS that is used to get IP

address from domain names right after

that I'll explain you how domain names

are there like generic domain and

Country domains that is how two general

categories are there then I'll be

discussing about hierarchical access to

domain name that I'll explain You by One

practical example like how hierarchical

approach is there with domain name then

I'll be showing you how DNS database

organization is there and how DNS

entries are provided so both of these

things that I'll be showing you by one

practical scenario and at last I'll be

showing you two methods for address

resolution so address resolutions using

iterative method and address resolution

using recursive method that I am going

to discuss that in this video along with

one practical scenario so let us try to

understand first how Basics are there

with domain name

system

so domain name system that we use it to

get IP address from domain names so

first of all you should know what is IP

address there are two types of IP

address ipv4 and IPv6 right and with the

use of IP address only one can

communicate with another computer

without IP address we cannot communicate

on computer network right so to get IP

from domain name

we will be using DNS so what is doing

name means google.com that is one domain

name so to have a communication with

Google you should be having IP of Google

to get IP of Google we will be using DNS

right so when you write

www.google.com you are writing domain

name over here on web browser right you

don't have IP of Google but to get IP of

Google first DNS frame that is getting

forwarded and then DNS reply will come

by which user will get to know IP of

Google and now user can communicate with

Google so before communication user

should be having IP address to get IP

address DNS is used right

DNS is using UDP protocol so let me show

you that by one practical scenario so

that will give you more clarity so let

me take you to my computer screen here

on my computer screen you see here I'll

be showing you DNS protocol frame you

see this is first one and this is second

one first one is request and second one

is reply right first one is request you

can say query and second one is reply

now see what I was been doing I was

trying to search something on grammarly

now I I was not having I was not having

IP of grammarly right so you see

to access grammarly I just need to have

IP

to get IP I am forwarding query

so this is my IP and this is IP of my

router

right so I'm sending frame to my router

obviously I can communicate with router

only right my router is communicating to

the internet now see this my IP is

sending request to my router regarding

IP of grammarly that is BNS query you

see here domain name system query that

is written over here

right and see this domain name system

that is implemented over

UDP

and UDP is implemented here over ipv4

and that is implemented over ethernet

over here right and then we are having

frame

so this is my request you see here query

or request that you can say that is

first frame

after that you see this IP which is my

IP that is destination IP means now my

router's IP which is Source IP now that

is forwarding frame to me that is DMS

that is DMS response so by this dmse

response now I am getting IP of

grammarly right now I am getting IP of

grammarly now once I am having IP of

grammarly I can communicate with

grammarly right so see to get IP of

grammarly I am sending frame that is DNS

frame that is implemented over udb

protocol remember this right

so now I think you are having idea about

what what is that which we are doing

right

so practically DNS protocol that we use

it to get IP address from domain name

right from domain name you will be

trying to get IP address right

once you have IP address you can

communicate so you can have your own

domain name as my website is there you

should know that website name is

available.engineeringfunder.co.in so

this is my domain name right now as if

you want to access this website first

you will be forwarding DNS free

along with DNS protocol so that will be

request then you will get reply in that

reply you will be getting IP of my

website once you have IP of my website

you can communicate on my website means

you can access my website right see IP

addresses are Dynamic you should know

that dynamic means with respect to time

IP will change before two days when I

was watching my IP of my computer that

was different compared to today right

so IP address will change with respect

to time right IP addresses are Dynamic

that will change with respect to time

recently access the domain are stored in

entries for faster access

to The Domain so recently accessed

domains are stored on your system right

and based on that you can have faster

access the reason is every time you

cannot ask for domain name and all those

things right do me name that you are

having but every time you cannot ask for

IP address

one time you can ask IB address once you

have it you just store it in the entries

it will not change immediately right it

will take some time so how entries are

stored let me show you that over here

see first there will be domain name

domain name means you can have Google

Amazon or my website that is domain name

that we are storing with respect to IP

address and that IP address that we get

it with the use of DNS protocol

and along with IB there will be validity

or you can say TTL field so that TTL

field that will show you for how much

time this IP and domain name are

validated with each other

after this time both of these entries

that will get invalid remember this

right

see one more command is there that is NS

lookup by which you can get to know like

how we can get IP address and see this

NS lookup that is inherently using DNS

protocol right let me show you that on

my computer screen so that will gives

you more regularity

so Here If You observe this is command

prompt in which I have written NS lookup

space google.com

so see this server means my Wi-Fi is my

WiFi is initiating that communication

which is asking for IP address of Google

so you see now name that is google.com

that is having IP address that is this

this is IPv6 address and this is ipv4

address let me show you one more example

NS

look up

space if I write yahoo.com

now you see how many how many IPS are

available with this so that many IPv6

addresses are available with Yahoo and

these are ipv4 addresses are available

with Yahoo with which my computer can

communicate to yahoo.com and to get this

IB DNS protocol that we are using right

so this is how things are there so I

think now you are having idea about how

NS lookup is there and how DNS that is

working right now let me give bit

clarity about how domain names are

classified

see in general you can say generic

domain and Country domain that is how it

is classified these are main domain that

you can see right generic means.com dot

org.edu.net dot mil that is how generic

domains are there.com that is used for

commercial

domains.org is used for organizations

dot edu that is used for educational

institutions dot net initially that was

used for Internet service provider only

but nowadays some companies are even

using this dot mil that is used for

military organizations nowadays probably

with rare use that is there right

country domains are there country

domains like with India dot in is there

like my website dot Co dot in So Last At

Last dot in is there that belongs to

country India at last if dot JP is there

that belongs to Japan at last if dot UK

is there that belongs to United Kingdom

at last if dot d e is there that belongs

to Germany right so that is how country

domains are there generic domains are

there right now let me explain you how

hierarchical axis that is there with

domain

so first thing that you need to

understand that is this dot this dot

explains root domain this dot that

explains root domain then top level

domain will be there at second level

means after root domain there will be

top level domain top level domains are

like dot in dot org dot

edu.com.net.uk right so those are top

level domains

right after that there will be second

level domains second level do beans are

like dot Co dot AC you might have seen

that even right like my website that is

dot Co dot in

there can be dot AC dot in so these are

second level domain Wikipedia is also

second level domain

and then there will be Sub doming sub

domain could be like

en example let me show you one practical

example so that will give you more

clarity right

like you see

if I write

engineering Funda if I write engineering

panda

so that is my that that is my sub domain

the reason is I I am taking it from

GoDaddy right so GoDaddy have provided

this sub domain to me

and then there is dot o

so dot Co that is second level domain

and then there is dot in right

so see this is my

in total

domain name

where this dot this first Dot that is

domain root

then dot in is there that is top level

domain then dot Co is there that is

second level domain and then sub domain

that is engineering conduct let me give

you one another example

see in another example what I'll be

doing is I'll be writing

e n

dot Wikipedia

Dot

org

right so now if You observe here this

first Dot this first dot that is root

domain then dot org

that is top level domain and then see

Wikipedia that is second level domain

and then e n en stands for English so

that is my sub Domi with Wikipedia and

then one can communicate with host

system right so see this is how this is

how two examples that I have converted

to you so you should know how

hierarchical axis that is happening

right

so root domain is there after that top

level domain that is how this top level

domains are there then second level

domain like dot Co dot AC those are

second level domain and then e an

example that is how some sub domains are

there right sometimes like my website is

sub domain so sometimes what happens you

know like in competitive examination

they may give you uh that domain name

and in domain name there can be equation

like what is sub domain with that domain

name what is second level do mean with

that domain name what is top level

domain with that domain name see that

kind of questions may come in

competitive examination so for that you

should be ready right I think now these

two examples are sufficient to

understand that

now let me explain you how DNS database

organization is there

see there are three levels of

organization that is distributed

database approach that you should know

right first of all you need to remember

these three names that is quite easy one

see root DNS server after that the name

server and after that host server that

is how it is there right root DNS server

then name server and then host server

there are 13 root servers that is

available in the world

and why there are 13 root servers the

reason is single point failure is not

allowed right like you might have seen

tsunami have came to Japan now if root

DNS server that is there in Japan and if

single point failure is happening then

entire world's internet will go down

So to avoid those situations right now

there are 13 root level servers that is

available in the globe so single point

failure will not happen right now root

DNS server

after that there will be name server

name server is like.com dot in dot org

dot net right so those are name servers

after that there will be host servers

post servers are like YouTube servers

maybe their Google server maybe their

Yahoo server may be their Amazon server

may be there so those are host servers

right so DNS database organization that

is happening like this root DNS server

name server and host server always

remember this sequence the reason is

always DNS is DNS is patching IP in this

hierarchy only right I'll show you that

by one practical example but right now

consider this hierarchy

see DNS entry that I have already told

you once you take IP address from DNS

there will be entry that entry will be

asked for a domain name then IP address

and then validity value it remains TTL

that explains you for this much duration

only this IP and this domain name those

are actively attached to each other

after that that will get invalid right

so that is how DNS entries that is

getting stored and based on that only we

are communicating on computer network

now very interesting part that I am

going to explain is that is address

resolution means how

computer is taking IP address with the

use of DNS you see here one computer

that I have shown now this computer is

requesting for let us say any website

right so obviously to access website

with the use of DNS first what we will

be taking IP address of that website

right but how there are two ways one is

iterative and second is recursive

let me explain you first iterative

method see what we do is this computer

is requesting for website that will go

to this router like I am having my

computer in front of me that is

connected with my router so obviously I

can request to my router only now my

router will request it to uh exterior

environment right so this is local

server which is my router which is

connected to root DNS server

now you see this router will be

requesting root DNS server regarding

regarding IP so this root DNS server is

saying what root DNS server is saying

you should go to name server how this

root DNS server that will give this IP

this IP in feedback you see this IP in

feedback so now this IP that is there

with this local server so it will send

request to this name server now this

name server will give this ipe to this

local router so now this IP now that

came to this local router now it will

request to host server now host server

will say okay this is my IP only you can

communicate with me over here right so

if You observe here we are having

iteration three iterations are there

first iteration that have happened with

root DNS server root DNS server have

given address of name server like see

root DNS server that is having that is

having database of everything right like

root DNS server is saying you should go

to.com so.com that is there with name

server I have told you see

this name server that is that could

be.com dot in dot org.net right

so root DNS server that is giving

approach to name server so name server

again is giving approach to host server

so in iterations that is happening that

is one way by which this DNS will give

IP of website to host right now second

approach is quite interesting you see

what is happening when this host is

requesting for websites IP with the use

of DNS at the time this local server is

requesting this DNS server now this DNS

server is not having idea about what is

the IP so what it does is now it will

not give feedback directly over here

what it does is it will ask to name

server then name server will ask you to

it to host a server now host server will

deliver exact IP to name server now name

server will deliver that IP to root DNS

now that IP will come over here

so here local server is not doing

iterations like this local server is

just asking it to root DNS server root

DNS server is approaching in this

hierarchy and it is taking that IP from

host server and it is giving it to this

local server now this local server will

give it to this host right so this is

recursive method right so in recursive

method local server that will approach

once only while in in iterative method

local server will approaches

many times that depends on how many

iterations are happening here I have

shown you pre-level hierarchy right

there can be five level hierarchy

obviously that is always possible right

so that is that that is possible over

here in iterative method

so this is our address resolution that

is happening in short you just need to

understand one thing as if this computer

is writing Google

dot com then this is domain now this

computer wants IP so this request will

be given to local server now it will

request like this or it may request like

this right that depends on the approach

there can be iterative method or there

can be recursive method right at last

this computer will get what it will get

this IP right at last

but how much time how long it will take

that depends on which method that we use

in iterative method it will take bit

more time in the recursive method it

will take bit less time that is how

things are there if anything that you

would like to share please note it down

in comment section I'll be happy to help

you thank you so much for watching this

video