How a DNS Server (Domain Name System) works.

Summary

This script explains the fundamental role of DNS in bridging the communication gap between humans and computers. DNS, or Domain Name System, translates human-friendly domain names into IP addresses that computers use for internet navigation. The process involves a sequence of queries from the user's browser to the resolver, then to the root, TLD, and finally the authoritative name servers, which provide the IP address. This system ensures a seamless user experience by caching IP addresses to speed up future requests.

Takeaways

• 🔢 Computers use IP addresses to identify each other over a network, while humans prefer using names.
• 🌐 DNS, or Domain Name System, was developed to bridge the communication gap between computers and humans by resolving domain names to IP addresses.
• 🌐️ When you type a web address, DNS converts the domain name into an IP address that computers understand.
• 📚 DNS functions like a phone book, providing a way to look up a number by name, in this case, an IP address by domain name.
• 🔍 If a web browser or operating system can't find an IP address in its cache, it sends a query to the resolver server, typically your ISP.
• 🔄 The resolver server checks its cache first; if the IP address is not found, it escalates the query to the root server.
• 🌐️ Root servers are at the top of the DNS hierarchy and there are 13 sets of them, operated by 12 different organizations worldwide.
• 🔑 The root server directs the resolver to the appropriate TLD (Top Level Domain) server, which manages domains like .com, .net, .org, etc.
• 🏢 The TLD server then directs the resolver to the authoritative name servers, which are the final authority on domain information, including IP addresses.
• 🔒 Authoritative name servers hold all the information about a domain and provide the IP address when queried by the resolver.
• 💾 Once the resolver receives the IP address, it caches it for quicker access in case of future queries for the same domain.

Q & A

What is the primary purpose of DNS?

DNS, or Domain Name System, is designed to resolve domain names to IP addresses, making it easier for humans to communicate with computers by using names instead of numbers.

How do computers identify each other over a network?

Computers identify each other over a network using numerical IP addresses, as they communicate and interact through numbers.

Why was the DNS developed?

DNS was developed to bridge the communication gap between computers and humans, allowing for the use of domain names instead of memorizing IP addresses.

What happens when you type a web address in your browser?

When you type a web address, DNS resolves the domain name to an IP address, enabling your computer to communicate with the web server and retrieve the webpage.

Can you access a website by typing its IP address directly?

Yes, you can access a website by typing its IP address directly into your browser if you know it, although DNS makes this process easier by using domain names.

What is the role of the resolver server in DNS queries?

The resolver server is typically provided by your ISP and checks its cache memory for an IP address associated with the domain name. If not found, it forwards the query to the next level in the DNS hierarchy.

What are the root servers in the context of DNS?

Root servers are at the top of the DNS hierarchy and are strategically placed around the world. They direct the resolver to the appropriate top-level domain (TLD) server when a query is received.

How many sets of root servers are there, and who operates them?

There are 13 sets of root servers, operated by 12 different organizations, each with a unique IP address.

What is the function of the top-level domain (TLD) server in DNS?

The TLD server stores address information for top-level domains such as .com, .net, .org, and directs the resolver to the authoritative name servers for a specific domain.

What are authoritative name servers, and what is their role in DNS?

Authoritative name servers are the final authority on domain information, including IP addresses. They respond to resolver queries with the correct IP address for a domain.

Why is caching important in the DNS process?

Caching is important because it stores the IP address of a domain once resolved, reducing the need to repeat the resolution process for subsequent queries, thus speeding up access to websites.

Outlines

00:00

🌐 Understanding DNS: Domain Names to IP Addresses

This paragraph introduces the concept of DNS (Domain Name System), which serves as a crucial intermediary between human-readable domain names and the numerical IP addresses that computers use to communicate over a network. It explains that humans prefer using names over numbers, but computers require numerical IP addresses to identify and communicate with each other. DNS bridges this gap by translating domain names into IP addresses, making it easier for users to access websites by typing in a domain name rather than memorizing an IP address. The example of accessing yahoo.com is used to illustrate how DNS works, starting from the user's web browser, through the resolver server (often the ISP), to the root server, and finally to the authoritative name servers that provide the actual IP address.

05:07

🔍 DNS Query Process: From Browser to Authoritative Name Servers

This paragraph delves deeper into the DNS query process, explaining how it unfolds when a user types a domain name into their web browser. Initially, the browser or operating system checks its cache for the IP address associated with the domain name. If not found, the query is passed to the resolver server, typically the ISP. The resolver then checks its cache, and if the IP address is still not found, the query escalates to the root servers. These root servers, of which there are 13 sets operated by 12 organizations, direct the resolver to the appropriate top-level domain (TLD) server, such as .com, .net, or .org. The TLD server, in turn, directs the query to the authoritative name servers, which hold the final authority on the domain's IP address. Once the authoritative name server provides the IP address, the resolver communicates it back to the user's computer, allowing access to the website. The paragraph also highlights the caching mechanism, where the resolver stores the IP address to expedite future queries for the same domain.

Keywords

💡Networking

Networking refers to the practice of connecting multiple computers or devices together to share resources and communicate with one another. In the context of the video, it highlights the foundation upon which computers and devices interact, emphasizing the importance of using numbers, such as IP addresses, for communication.

💡IP Address

An IP address is a numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication. The video script uses the term to illustrate how computers identify each other and communicate over a network, as opposed to human preference for names.

💡Domain Name System (DNS)

DNS is a system that translates human-friendly domain names, such as 'yahoo.com', into IP addresses that computers use to identify each other on the internet. The video explains that DNS is crucial for bridging the communication gap between human-readable names and computer-readable numbers.

💡Domain Name

A domain name is the human-readable address of a website, like 'yahoo.com'. The video script mentions domain names to demonstrate how users can access websites by typing in names instead of memorizing numerical IP addresses, with DNS resolving these to the corresponding IP addresses.

💡Human-readable

The term 'human-readable' refers to information that is easily understandable by humans, as opposed to machines. In the video, it is used to contrast the way humans prefer names over numbers when identifying things, in contrast to computers which use numbers.

💡Computer-readable

Computer-readable information is data formatted in a way that computers can easily process. The video script mentions that computers communicate using numbers, such as IP addresses, which are computer-readable formats.

💡Resolver Server

A resolver server is the first point of contact for a user's device when trying to resolve a domain name into an IP address. The video script describes how the resolver server checks its cache or queries further if the IP address is not found locally.

💡ISP (Internet Service Provider)

An Internet Service Provider is a company that provides customers with access to the internet. In the context of the video, the ISP operates the resolver server that helps in the DNS resolution process when a user types a domain name into their browser.

💡Root Server

Root servers are the highest level of the DNS hierarchy and are responsible for directing resolvers to the appropriate Top-Level Domain (TLD) servers. The video script explains that there are 13 sets of root servers globally, operated by different organizations, which play a pivotal role in the DNS resolution process.

💡Top-Level Domain (TLD) Server

A TLD server manages the domain names that share the same suffix, such as .com, .net, or .org. The video script mentions that after the root server directs the resolver, it is the TLD server's role to guide the resolver to the authoritative name server for a specific domain.

💡Authoritative Name Server

Authoritative name servers are the final point of authority for a domain's DNS information, including its IP address. The video script describes how once the resolver reaches this level, it retrieves the IP address for the domain name from the authoritative name server.

💡Cache Memory

Cache memory is a component that stores frequently accessed data temporarily for quicker access. The video script explains the importance of cache in the DNS process, where once an IP address is resolved, it is stored in the resolver's cache to avoid repeating the resolution process for subsequent requests.

Highlights

Computers use IP addresses to communicate over a network, while humans use names.

DNS (Domain Name System) was developed to bridge the communication gap between computers and humans.

DNS resolves domain names to IP addresses, making it easier for humans to access websites.

You can access a website by typing its domain name or IP address in the browser.

DNS converts domain names to IP addresses so computers can retrieve web pages.

When you type a domain name, your browser's DNS server searches for the corresponding IP address.

DNS works like a phone book, mapping names to numbers for easy lookup.

The DNS resolution process involves multiple steps, starting with the browser's cache.

If the IP address is not in the cache, the query goes to the resolver server, typically your ISP.

The resolver server checks its cache before forwarding the query to the root server if needed.

There are 13 sets of root servers worldwide, operated by 12 organizations, forming the top of the DNS hierarchy.

The root server directs the resolver to the appropriate Top Level Domain (TLD) server.

TLD servers store address information for domains like .com, .net, and .org.

The TLD server directs the resolver to the authoritative name servers for the specific domain.

Authoritative name servers are the final authority, knowing all details about a domain, including its IP address.

Once the resolver receives the IP address, it caches it for quicker access in future queries.

The DNS resolution process ensures efficient and user-friendly access to websites.

Transcripts

In the world of networking, computers don't go by names like humans do, they go

by numbers, because that's how computers and other similar devices talk and

identify with each other over a network, which is by using numbers such as IP

addresses. Humans on the other hand are accustomed to using names instead of

numbers,

whether is talking directly to another person or identifying a country,

place, or thing, humans identify with names instead of numbers. So in order to

bridge the communication gap between computers and humans and make the

communication of a lot easier,

networking engineers developed DNS, and DNS stands for a domain name system. And DNS

resolves names to numbers, to be more specific

it resolves domain names to IP addresses. So if you type in a web address in your

web browser, DNS will resolve the name to a number because the only thing

computers know are numbers. So for example if you wanted to go to a certain

website you would open up your web browser and type in the domain name of

that website, so for example let's use yahoo.com. Now technically you really

don't have to type in yahoo.com to retrieve the Yahoo web page, you can just

type in the IP address instead if you already knew what the IP address was, but

since we are not accustomed to memorizing and dealing with numbers,

especially when there are millions of websites on the internet, we can just

type in the domain name instead and let DNS convert it to an IP address for us.

So back to our example, when you type in yahoo.com your web browser

the DNS server with search through its database to find a matching IP address

for that domain name, and when it finds it it will resolve that domain name to

the IP address of the Yahoo web site, and once that is done then your computer is

able to communicate with a Yahoo web server and retrieve the webpage. So DNS

basically works like a phone book, when you want to find a number, you don't look

up the number first, you look up the name first, then it will give you the number.

So to break this down into further detail let's examine the steps that DNS

takes.

So when you type in yahoo.com in your web browser and if your web browser

or operating system can't find the IP address in its own cache memory, it will

send the query to the next level to what is called the resolver server. The resolver

server is basically your ISP or Internet service provider, so when the resolver

receives the query, it will check its own cache memory to find an IP

address for yahoo.com, and if it can't find it it will send the query to the

next level which is the root server.

The root servers are the top or the root of a DNS hierarchy. There are 13 sets of

these root servers and they are strategically placed around the world,

and they are operated by 12 different organizations and each set of these root

servers has their own unique IP address. So when the root server receives the

query for the IP address for yahoo.com, the root server is not going to know

what the IP address is, but the root server does know where to send the

resolver to help it find the IP address. So the root server will direct the

resolver to the TLD or top level domain server for the dot com domain. So the

resolver will now ask the TLD server for the IP address for yahoo.com.

The top level domain server stores the address information for a top level

domains, such as .com, .net, .org and so on. This particular TLD server manages

the dot-com domain which yahoo.com is a part of.

So when a TLD server receives the query for the IP address for yahoo.com, the

TLD server is not going to know what the IP addresses for yahoo.com. So

the TLD will direct the resolver to the next and final level, which are the

authoritative name servers.

So once again the resolver will now ask the authoritative name server for the IP

address for yahoo.com.

The authoritative name server or servers are responsible for knowing everything

about the domain which includes the IP address. They are the final authority. So

when the authoritative name server receives the query from the resolver, the

name server will respond with the IP address for yahoo.com. And finally the

resolver will tell your computer the IP address for yahoo.com and then your

computer can now retrieve the Yahoo web page.

It's important to note that once the resolver receives the IP address, it will

store it in its cache memory in case it receives another query for yahoo.com so

it doesn't have to go through all those steps again.