‫The often used analogy to explain the domain name system is that it serves as the phonebook for the
‫internet by translating human friendly computer host names into IP addresses.
‫Simply, DNS is a directory of names that match with IP addresses.
‫As you may know, each device connected to the internet has a unique IP address, which other machines
‫use to find the device.
‫DNS servers eliminate the need for humans to memorize IP addresses, such as two one two eight eight
‫zero seven five one three four.
‫Think about the websites you visit every day.
‫Google and YouTube, Facebook, Twitter, etc. Without DNS, we would have to reach these sites by using
‫their IP addresses instead of their names.
‫I think remembering the names is so much easier than remembering the strange numbers, but it's still
‫possible to reach the computer with that strange number string as well.
‫Now, DNS deserves to have far more time spent on it.
‫It could be a whole course in and of itself.
‫But I just want to explain it simply without going to the.
‫So when you enter the URL, such as dub, dub, dub, dub, google.com, enter the web browser.
‫The request is not directly sent to the Google servers.
‫Instead, the request goes through the DNS server that uses a lookup table to determine the IP address
‫of the website that is being requested.
‫Then it forwards this information to the proper servers and returns, the information requested to your
‫specific browser.
‫DNS server is a computer server, which contains a database of public IP addresses and their associated
‫host names, it translates those common names to IP addresses as requested.
‫DNS servers run special software and communicate with each other using special protocols.
‫DNS is a client, server, network communication system.
‫DNS clients send their requests to and receive the responses from DNS servers.
‫The request containing the name and resulting in an IP address being returned from the server are called
‫forward DNS lookups.
‫The request containing IP addresses and resulting in the names are called the reverse DNS lookups.
‫The DNS directory that matches name two number isn't located all in one place.
‫Pretty much like the internet itself, the directory is distributed around the world, stored on domain
‫name servers that all communicate with each other on a very regular basis to provide updates as well
‫as redundancies.
‫There's more than 332 million domain names listed by the end of 2017, a single directory would be very
‫large indeed.
‫So when you type mailed out Google.com into your browser, your browser sends a query over the internet
‫to find the web site.
‫It's a query seeking to match the domain name with its corresponding IP address.
‫So let's follow the path of this question over the internet infrastructure.
‫The first server your query interacts with is the DNS Resolver, which can be operated by your ISP internet
‫service provider, a resolver is basically responsible for initiating and sequencing the queries that
‫ultimately lead to a full resolution.
‫Domain name resolvers determined the domain name servers responsible for the domain name in question
‫by a sequence of queries starting with the right most.
‫In other words, top level domain label.
‫Assuming the resolver has no cached records to accelerate the process, which is the worst case scenario,
‫the resolution process starts with a query to one of the root servers.
‫The root servers are running all over the world, and each one knows DNS information about top level
‫domains or TLD, such as dot com.
‫So to begin answering your query, the resolver asks a root server for DNS information about About.com.
‫So there are 13 sets of root servers in more than 300 locations around the world.
‫Each tailed DNS name, server stores, the address information for second level domains within the top
‫level domain.
‫Dot com.
‫In our example.
‫The second level domain is Google.com when your query reaches the TLD server.
‫The TLD server answers with the IP address of the domain name server, which will provide the next piece
‫of the puzzle.
‫So this is the final step of address resolution.
‫The recursive resolver sends the query to the domains named server.
‫This DNS server knows the IP address for the full domain mail that google.com and that answer is returned
‫to the recursive resolver.
‫Now that the recursive resolver knows the IP address for the domain name and your query, the recursive
‫resolver tells the browser what the IP address is.
‫So finally, your browser can send a request to the Web site to retrieve the website's content using
‫the IP address it just learned.
‫This whole process might seem, well, complicated, it certainly sounds it to talk it up, but really
‫takes very little time at all.