Domain Name System (DNS)
The Domain Name System (DNS) is a crucial component of the Internet that translates human-readable domain names, like www.example.com, into numeric Internet Protocol (IP) addresses that computers use to identify each other. This system simplifies the process of navigating the Internet, allowing users to remember names rather than complex strings of numbers. As the Internet expanded from a few hundred devices in its early days, the need for a structured naming system led to the creation of DNS and its hierarchical organization, which categorizes domain names by their suffixes, such as .com and .org.
When a user types a domain name into their web browser, the computer queries a nearby DNS server, which may resolve the query using cached information or by communicating with other DNS servers if the information is not readily available. This process, known as recursive querying, helps maintain efficient access to the vast array of domain names on the Internet. Additionally, DNS supports reverse lookups, allowing users to find domain names associated with specific IP addresses. Security is also a significant concern, leading to the development of Domain Name System Security Extensions (DNSSEC) to help protect against malicious activities and ensure the integrity of DNS data.
Domain Name System (DNS)
The domain name system (DNS) is the system that converts alphabetic Internet domain names into numeric Internet Protocol (IP) addresses. Domain names are easy for people to remember because they are mostly made up of words and letters. Internet sites are actually made up of numeric IP addresses, but the DNS allows people to easily remember domain names rather than memorizing long strings of numbers. A DNS can also be used in networks other than the Internet (e.g., a company’s intranet network) to give specific locations easy-to-remember names instead of numeric addresses.
Using the DNS System
The Internet is a global system that is made up of computers, servers, and networks that are all connected. The Internet allows all of these devices and networks to communicate with each other. In the early days of the Internet, only a few hundred devices were connected to create a network. Each device on the network had its own numeric address. Soon, people noticed that it was difficult to remember these numeric addresses; therefore, host names, or domain names, were created to make remembering a specific device’s "address" easier. Since the domain names needed to be decoded into the numeric addresses, DNS servers were created and installed.
People who use the Internet often access specific websites. To access a website, people commonly type domain names into Internet browser software. When a person enters a domain name into the software, the computer sends a query (using query language) to a nearby DNS server. (A DNS server is a server that holds the information that will decode the domain name into the IP address.)
The computer sends the server three things in the query: the fully qualified domain name (FQDN), the specific query type, and the class of the domain name. The DNS sever then reads the query. The server can answer the query with the information it has in its local database or with information it has cached from previous queries. If the server can locate the information it needs to answer the query, the server sends that information to the computer and the query is resolved.
If a server does not have the information needed to answer the query, it can query other DNS servers to find the information. The server needs to break down the computer's query to find the correct server. First the original server identifies the type of domain being queried (e.g., .com, .org, .edu) and the specific name of the domain (e.g., example.com). Then the original DNS server queries another server and accesses the correct information. This process is called the recursive query process. Although it takes multiple steps, this process helps the DNS server "learn" about the domain name being queried. The original DNS server will cache information about the queried domain name so it has the information for future queries.
When the DNS server locates the information the original computer needed, it sends the IP address to the computer. This resolves the computer's query. Most of the time, the query is resolved and the Internet browser opens the webpage from the IP address. Sometimes, however, a query is answered with a negative response. This can happen either because the domain name that the computer queried does not exist in the DNS namespace or because the name exists but no records exist for it.
Hierarchy of the DNS
The Internet originated from ARPANET, which was a network created by the US government. During the late 1960s and early 1970s, only a few hundred devices were connected through this network. At that time, all of the domain names were stored in a .txt file that was managed by Stanford Research Institute (SRI). Since that time, the number of devices making up the Internet has grown exponentially. Since so many devices require domain names and IP addresses, the DNS system was created and spread out over many different servers.
Since many different DNS servers exist, the servers had to have some type of recognizable order. To make DNS queries simpler, the servers have a hierarchy. This makes it easier for the servers to query each other when looking for DNS information. One of the simplest ways to establish this organization was to separate the domain names by their domain suffixes. Some of the most common domain suffixes include .com (used for commercial organizations and businesses); .gov (used by the government); .org (used by noncommercial organizations); .mil (used by the military); and .int (used by international organizations).
Many other domain suffixes exist, and more are being created. Since the DNS servers are organized by the domain suffix, queries from computers take much less time than they would in a disorganized DNS.
Reverse Lookup
The DNS is most commonly used for forward lookup, which is the process of searching for an IP address to match a queried domain name. However, the DNS can also be used in a process called reverse lookup, which allows a user to search for a domain name that is associated with a particular IP address. This process is similar to forward lookup, but it does not use the same information that is stored for forward lookup. Since the domain names for forward lookup are stored according to their domain suffix (e.g., .com, .edu), the IP addresses in this system are not organized in a particular way. Searching through this unorganized cluster of IP addresses would be very inefficient. Therefore, the DNS servers also include information reserved for lookup queries, and this information is organized by the first new numbers in the IP address.
Security
Security of websites and systems has become an increasing concern. Hackers have exploited systems to steal, hold information hostage, and disrupt companies and organizations. Domain Name System Security Extentions (DNSSEC) check server signatures to authenticate them to protect DNS.
Bibliography
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