Architecture of DNS

CS 718 Activity 4

Submitted byParag Abhyankar 08305017

Anup S. Kunte 08305302

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

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

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

Iterated query

iterated query: contacted server replies with

name of server to contact

“I don’t know this name, but ask this server”

requesting hostcis.poly.edu

gaia.cs.umass.edu

local DNS serverdns.poly.edu

1

23

4

5

6

authoritative DNS serverdns.cs.umass.edu

78

TLD DNS server

root DNS server

6

requesting hostcis.poly.edu

gaia.cs.umass.edu

root DNS server

local DNS serverdns.poly.edu

1

2

45

6

authoritative DNS serverdns.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

requesting hostcis.poly.edu

gaia.cs.umass.edu

root DNS server

local DNS serverdns.poly.edu

1

2

authoritative DNS serverdns.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

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.