The article entitled “Lec-76: DNS Explained in Computer Networks” is a video by Gate Smashers, specifically created by Varun sir. In this video, Varun sir provides a comprehensive explanation of the Domain Name System (DNS) in computer networks. DNS serves as a naming database where internet domain names are located and translated into IP addresses. It is responsible for mapping the name people use to locate a website to the corresponding IP address used by computers. The article outlines the importance of DNS in simplifying website searching and highlights the dynamic nature of IP addresses. Additionally, it mentions the hierarchical architecture of DNS and the role of various servers, such as root servers, commercial servers, and authoritative servers.
DNS Explained in Computer Networks
Introduction to DNS
Domain Name System (DNS) is a critical component of computer networks. It serves as a naming database that translates internet domain names into Internet Protocol (IP) addresses. DNS maps the name that people use to locate a website to the IP address that a computer uses to locate that website. This article explores the purpose of DNS in computer networks, how it works, and its various components.
Why Use DNS?
Mapping Domain Names to IP Addresses
One of the primary reasons to use DNS is to map domain names to IP addresses. Domain names are human-readable names that are easier to remember and recognize compared to a string of numbers. When you enter a domain name in your browser, DNS resolves the name to its corresponding IP address, allowing your computer to connect to the website or service you requested.
Ease of Use and Memorability
DNS enables users to access websites and services using domain names instead of IP addresses. This makes it more convenient for users to navigate the internet and simplifies the process of recalling and communicating website addresses. Memorizing domain names is more natural and intuitive for humans compared to remembering long strings of numbers.
Dynamic IP Addresses
Another significant advantage of DNS is its ability to handle dynamic IP addresses. IP addresses assigned to websites and services can change over time, especially when hosting providers or applications are switched. DNS allows websites to keep the same domain name regardless of changes in IP addresses, ensuring seamless access for users.
How DNS Works
Mapping Domain Names to IP Addresses
When you enter a domain name in your browser, DNS performs the task of mapping that domain name to the desired IP address. This process starts with your browser sending a DNS query to a resolver, which is typically provided by your Internet Service Provider (ISP). The resolver forwards the query to a root server, which guides the resolver to the appropriate authoritative server for the domain name requested. The authoritative server contains the necessary information to resolve the domain name to its corresponding IP address.
Hierarchical Architecture
DNS employs a hierarchical architecture to efficiently handle the mapping of domain names to IP addresses. The architecture consists of multiple levels, including the root server, top-level domains, second-level domains, and subdomains. This hierarchy helps distribute the workload and prevent bottlenecks by dividing the mapping process into smaller, manageable segments.
Resolving DNS Requests
DNS requests can be resolved in two modes: recursive and iterative. In the recursive mode, the resolver sends requests to the DNS server, which then recursively queries other DNS servers until it obtains the final IP address. On the other hand, in the iterative mode, the resolver receives partial information from the DNS server and continues to send iterative requests until it obtains the complete IP address.
Components of DNS
DNS comprises several key components that work together to facilitate the mapping of domain names to IP addresses. These components include the root server, generic server level, authoritative server level, and resolver.
Root Server
The root server is the top-level server in the DNS hierarchy. There are 13 root servers distributed worldwide, and they are responsible for guiding resolvers to the appropriate authoritative server for a given domain name.
Generic Server Level
The generic server level consists of servers that handle specific domain extensions such as .com, .net, .org, and country-level domains. These servers provide the necessary mapping between domain names and IP addresses for their respective domain extensions.
Authoritative Server Level
Authoritative servers store the IP addresses and domain names for specific websites or services. They are responsible for responding to queries from resolvers with the correct IP address associated with a particular domain name. Authoritative servers can handle multiple IP addresses for a single domain, enabling load balancing and redundancy.
Resolver
The resolver is a crucial component that acts as an intermediary between the user’s device and the DNS servers. It receives the DNS query from the user’s device and sends the request to the appropriate DNS server based on the domain name requested. The resolver then receives the IP address from the DNS server and returns it to the user’s device to establish the desired network connection.
Hierarchy in DNS
Root Server
As mentioned earlier, the root server is the top-level server in the DNS hierarchy. Its primary function is to guide resolvers to the appropriate authoritative server for a given domain name. The root server infrastructure consists of 13 separate root servers distributed globally.
Top-Level Domains
Top-level domains (TLDs) are the next level in the DNS hierarchy. Examples of TLDs include .com, .net, .org, and country-level domains like .uk or .in. These domains are managed by specific organizations or registries responsible for maintaining the mapping between domain names and IP addresses.
Second-Level Domains
Second-level domains are the next level below TLDs and represent specific websites or services. For example, in the domain name “example.com,” “example” is the second-level domain. Second-level domains are managed by the organizations or individuals that own the corresponding websites or services.
Subdomains
Subdomains are extensions of the domain name hierarchy that allow further categorization and organization of websites or services. Subdomains are expressed by inserting a period before the domain name. For example, “blog.example.com” is a subdomain of “example.com.” Subdomains can have separate IP addresses and may be assigned to specific servers or hosting environments.
Root Server
The function of the Root Server
The root server plays a vital role in the DNS infrastructure. Its primary function is to act as a resolver, providing authoritative information to guide resolvers to the appropriate authoritative server for a given domain name. The root server infrastructure consists of 13 distinct root servers distributed worldwide.
13 Root Servers Worldwide
The 13 root servers are strategically located across the globe to ensure geographic redundancy and reduce latency. These servers are operated by independent organizations and share the responsibility of maintaining the stability and integrity of the DNS infrastructure. Each root server is assigned a unique IP address and domain name.
Generic Server Level
Resolving Specific Domain Extensions
The generic server level is responsible for handling specific domain extensions such as .com, .net, .org, and others. These servers hold the mapping information between domain names with the respective domain extensions and their IP addresses. They provide resolution services for all domain names falling under their assigned domain extensions.
Load Balancing
Many generic server-level infrastructures consist of multiple servers to handle the high volume of DNS queries efficiently. Load balancing techniques are implemented to distribute the requests evenly across these servers, ensuring optimal performance and preventing any single server from becoming overwhelmed with requests.
Authoritative Server Level
Storing IP Addresses and Domain Names
Authoritative servers store the IP addresses and associated domain names for specific websites or services. They serve as the ultimate source of truth for the IP address mapping of a domain name. When a resolver sends a query for a domain name, the authoritative server provides the corresponding IP address, enabling the resolver to establish the network connection.
Handling Multiple IP Addresses
In some cases, a domain name may have multiple IP addresses associated with it. This scenario often occurs with high-traffic websites or services that require load balancing or redundancy. Authoritative servers can handle these multiple IP addresses and return one of them to the resolver based on various factors such as geographical location, traffic conditions, or a round-robin method.
Conclusion
DNS is a crucial component of computer networks, facilitating the mapping of domain names to IP addresses. It provides multiple benefits, including ease of use and memorability, mapping domain names to dynamic IP addresses, and simplifying the navigation of the internet. DNS employs a hierarchical architecture with various components such as the root server, generic server level, authoritative server level, and resolver to ensure efficient and accurate resolution of domain names. Understanding DNS and its functionality is essential for anyone working with or using computer networks.
