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Discussion on: Do I need to understand DNS as Web Developer?

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Kieran Pilkington

A nice top level overview. Well done. Just three minor things perhaps worth clarifying:

1) In your diagram, "Authoritative DNS Server" is often referred to as the "Nameserver". That is where the original A/CNAME/TXT records are stored when set by the user. The IP address of the nameservers is stored on the domain with the domain registrar. Request 4 asks for the nameserver IP from the domain registrar, request 5 returns the IP address to the nameserver, request 6 asks the nameserver for the A record for a specific domain, and request 7 returns that A record (a server IP address).

2) Step 8 does not actually return the webpage as indicated in the diagram. Now that the computer has the server IP, it needs to make a request to that server IP, hopping over the internet through various nodes known as the Border Gateway Protocol, which is an advanced topic outside the scope of this article. But in short, request 8 doesn't return the website.

3) You've mentioned if the ISP cache has the record, it stops there which is correct. Additionally, most computers/browsers have a DNS cache on the local machine, so often once a site is accessed, no further DNS requests for it are needed until that record expires (browser closes, DNS is cleared, or DNS record expires). Which means for sites you visit more than once, request 1 never needs to happen.