2013. június 17., hétfő

Where does the internet start?

It is so enjoyable that under Linux command line, you can use simple tool to find out where does the internet start! I mean, where does the DNS - domain name resolution - start. Without DNS, the Internet would halt and nobody would be able to browse. The following command will result in a simple answer to a name lookup of a SOA record. 

[qmi@localhost: ~]$ dig +short . SOA
a.root-servers.net. nstld.verisign-grs.com. 2013061701 1800 900 604800 86400
[qmi@localhost: ~]$ host a.root-servers.net
a.root-servers.net has address 198.41.0.4
a.root-servers.net has IPv6 address 2001:503:ba3e::2:30
[qmi@localhost: ~]$

 
The answer to the above lookup means that the SOA a.k.a. "start of authority" record starts at the a.root-servers.net computer which provides the domain zone for the "." domain. The "." (dot) is called the "root domain", which in the DNS hierarchy means the most top-level domain. The other result simply just an IP address entry to that highly important server (in fact, most probably it is a shared unicast load-balancer front-end that serves several back-end servers). Let's look at the top-level name servers as well by asking the NS records. This will show us the name servers responsible for the "." domain.  

[qmi@localhost: ~]$ dig +short . NS | sort
a.root-servers.net.
b.root-servers.net.

c.root-servers.net.
d.root-servers.net.
e.root-servers.net.
f.root-servers.net.
g.root-servers.net.
h.root-servers.net.
i.root-servers.net.
j.root-servers.net.
k.root-servers.net.
l.root-servers.net.
m.root-servers.net.
[qmi@localhost: ~]$



That's where it all starts :) 



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