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What is the Domain Name System (DNS)? How does it Work

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The domain name server or DNS is a naming database. Internet domain names are located within a DNS. They then translate into Internet Protocol (IP) addresses.

People use a name to locate a website, which is the URL. DNS maps this name to an IP address. As an example, suppose an internet user types in computer.com over a browser’s search bar. The server operating behind the scenes maps this name to a corresponding IP address. This is something like 121.12.12.121 in structure.

DNS quickly provides the information to connect users and remote hosts. This information helps with web browsing and other internet activities.

DNS mapping is spread hierarchically across the internet. Governments, universities, enterprises, access providers, and other organizations use this information. In most cases, they are assigned a domain name and a range of IP addresses. They may run DNS servers as well to map their domain names to the addresses. URLs are frequently built around the domain name of the webserver, which takes client requests.

Operation of DNS

DNS servers respond to queries, both within and outside their domains. It provides an authoritative response when the server gets a request from outside the domain for an address or a name within the domain.

Similarly, the DNS server passes the request on to another server, when it gets a request from within the domain for a name or address located outside the domain.

In most cases, an Internet Service Provider (ISP) manages the DNS server. If the server is unsure about the answer, or the authoritative source for the answer, it accesses the DNS Server for the top-level domain. This may be in the format of all of .org or .edu.

Following this, the server passes the request on to the server which is authoritative for a specific domain. This may be in the form of stanforduniversity.edu or projecttiger.org. The answer comes through the same path.

DNS Structure

Labels or multiple parts make a domain name. Reading of domain hierarchy starts towards the right and proceeds towards the left. Following the dot (.) in the domain name, the top-level domain appears. .edu, .org, and .uk are a few examples of top-level domains. But there is a range of others that can be used as well.

All labels towards the left stand for another subdomain, which is towards the right. As an example, in stanforduniversity.edu, “stanforduniversity” is the subdomain of “.edu.” Similarly, “www” is the subdomain of stanforduniversity.edu. It is possible to have 127 levels of subdomains. Each level may have up to 63 characters.

DNS enhances web performance

Servers cache answers that they receive for a set amount of time. This, in turn, promotes efficiency. When the following request for the same lookup comes in, they can respond quicker.

Just as an example, let us suppose that in a corporate scenario, a number of employees need to see the same video on the same day, over a corporate website. DNS resolves the name only once. The cache serves the requests that follow.

One can also configure the duration for which the record stays. Short values keep responses accurate, while longer values decrease the load over the server.

DNS Security

DNS does have some vulnerabilities that were discovered over time. Cache poisoning of DNS is one such vulnerability. Caching resolvers pose as authoritative origin servers in cache poisoning, and gain access to the data. Correspondingly, the information represented by the data may be false or lagging in credibility. This may render an influence over time to live as well.

In the same way, it is possible that actual application requests are redirected to a host network that is corrupt.