Root DNS Servers

Root DNS (Domain Name System) Servers are a core & fundamental part of the Internet. These servers hold data about all existing domain names.

* In theory, there are 13 Root DNS Servers that hold data for gTLDs (generic Top Level Domains) like .com, .net, .org, .biz, etc. Root DNS Servers also know which servers hold data for ccTLD’s (country code Top Level Domains) like .co. uk, .us, etc.

For example, the domain name “cloudaccess.net” is a basically a subdomain “cloudaccess” under the generic Top Level Domain “net”. When we registered cloudaccess.net, we did so on a Root DNS Servers via a registrar like Verisign or ISC (Internet Systems Consortium). Eventually, the registrar provisions a domain name for us on the Root DNS Server. This process is controlled on paper by ICANN (the Internet Corporation for Assigned Names and Numbers) - they control the non-technical part. This means that they manage the policy and procedure for getting a domain name. Essentially, ICANN determines who gets what type of domain and so on. You can read more about ICANN at http://www.icann.org/.

Once a new domain is registered, and the registrar provides the Root DNS Servers the domain name, those Root DNS Servers update servers around the world. Whenever that domain is used by an end user (by simply visiting the website or sending a mail to a user on that domain name), the client actually connects to Root DNS Servers and passes through a DNS resolver (which is mostly run by the user’s ISP).

Visit this link to view all the root DNS servers located across world: http://www.root-servers.org/.

* In theory, there are 13 Root DNS Servers because there are 13 root servers given by name:

a - root server

b - root server

c - root server

(this list goes on until the m - root server)

We can quickly find this list by digging any gTLD root domain e.g com:

anurag@anurag-laptop:~$ dig +short com ns
f.gtld-servers.net.
h.gtld-servers.net.
j.gtld-servers.net.
l.gtld-servers.net.
g.gtld-servers.net.
d.gtld-servers.net.
b.gtld-servers.net.
a.gtld-servers.net.
c.gtld-servers.net.
i.gtld-servers.net.
m.gtld-servers.net.
k.gtld-servers.net.
e.gtld-servers.net.

These servers are “anycasting” - they have “real” physical nodes in multiple locations across the world, and they find the closest node to where the request was made. That is why the number 13 is just a virtual number. In reality, number is 259 (at the time when this document was written). This is how DNS resolution works!