1. Architecture of DNS CS 718 Activity 4 Submitted by Parag Abhyankar 08305017 Anup S. Kunte 08305302

2. 2 The Domain Name System The domain name system is usually used to translate a host name into an IP address. Domain names comprise a hierarchy so that names are unique, yet easy to remember.

3. 3 DNS Servers Servers handle requests for their domain directly. Servers handle requests for other domains by contacting remote DNS server(s).  The server finds a nameserver for the target domain.  The server asks the nameserver to provide the host name to IP translation. Servers cache external mappings.

4. 4 DNS Infrastructure Host at cis.poly.edu wants IP address for gaia.cs.umass.edu Infrastructure:  Client resolver  Local DNS server  Authoritative DNS Server  Root DNS Server  Top-Level Domain DNS Server

5. 5 Iterated query iterated query:  contacted server replies with name of server to contact  “I don’t know this name, but ask this server” requesting host cis.poly.edu gaia.cs.umass.edu local DNS server dns.poly.edu 1 2 3 4 5 6 authoritative DNS server dns.cs.umass.edu 7 8 TLD DNS server root DNS server

6. 6 requesting host cis.poly.edu gaia.cs.umass.edu root DNS server local DNS server dns.poly.edu 1 2 4 5 6 authoritative DNS server dns.cs.umass.edu 7 8 TLD DNS server 3 Recursive queries recursive query:  puts burden of name resolution on contacted name server  heavy load?

7. 7 requesting host cis.poly.edu gaia.cs.umass.edu root DNS server local DNS server dns.poly.edu 1 2 authoritative DNS server dns.cs.umass.edu 4 TLD DNS server Subsequent Lookup Operations 3 DNS responses are cached : Quick response for repeated translations DNS negative queries are cached Don’t have to repeat past mistakes

8. 8 Comment on DNS Architecture Architecture of DNS can be considered as a mix of client-server and peer-peer. Interaction between DNS server and client requesting name resolution is clearly client- server architecture. Interaction between any two DNS servers is p2p architecture.