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Web Science/Part1: Foundations of the web/Domain Name System/Delegating DNS queries

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Delegating DNS queries

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Video

Quiz

1 How can the lookup of IP addresses in the DNS be sped up?

You can edit your local host file
Browsers can implement a DNS cache
Internet hot spots and local routers can provide a DNS cache
Internet service provider can provide a DNS cache

2 There is some domain X

  • your host file resolves it to address A
  • your ISP's name server resolves it to address B
  • the authoritative name server for X resolves it to address C

Which of the following statements is true

when typing X into your browser it will be resolved to A
when typing X into your browser it will be resolved to B
when typing X into your browser it will be resolved to C
A = B = C
most likely B = C

3 How can you find the authoritative name server for some domain?

You start with a root server and use the zone files and delegation until you find the name server for a domain
You trust your internet service provider
The ICANN provides an official version of the complete DNS tree on their website

4 How can the DNS system be manipulated (e.g. by governments) to block (censor) web sites?

IP traffic to root name servers and name servers for the Top level domains has to be prohibited. ISPs have to exclude the domains that shall be blocked from their zone files of their name servers
ISPs have to exclude the domains that shall be blocked from their zone files of their name servers.
IP traffic to root name servers and name servers for the Top level domains has to be prohibited.
This is no real censorship since the websites can still be accessed via their IP addresses.

Further reading

  1. Record caching

Discussion

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