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 -5
Reminder: DNS Resolving
Resolver
Question:
www.ripe.net A
www.ripe.net A ?
Caching
forwarder
(recursive)
root-server
www.ripe.net A ?
Ògo ask net server @ X.gtld-servers.netÓ
 (+ glue)
gtld-server
www.ripe.net A ?
Ògo ask ripe server @ ns.ripe.netÓ
 (+ glue)
ripe-server
www.ripe.net A ?
Ò192.168.5.10Ó
192.168.5.10
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4
5
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7
Add to cache
9
8
10
TTL
1. Resolver asks the question to the caching forwarder
2. Caching forwarded doesn not know the answer, and forwards the request to the root name server (Ò.Ó)
3. Root is answering with the name (and the address (glue)) of the gtld server
   (since itÕs not recursiveÉ)
4. Caching forwarder repeats the question (*)
5. É gets the next referral answer
6. É repeats the question (*)
É until it gets the (authorative) answer
7. Ns.ripe.net gives the IP address
8. Caching forwarded gives the answer to the resolver
9. Caching forwarded stores the answer in cache (* actually, after steps 4 and 6 it does the same!)
10. TTL determines how long is data going to stay (valid) in the cache