DNS Client Server Model on OPNET

1
DNS Client Server Model on OPNET
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????????? ?- DNS ??? client-server ??? ?????
?????? OPNET .
2
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• ????? ???????? ?- DNS ?? ???????.
• ????? use-cases ??????????.
• ???? ?- OPNET.
• ????? ???? ?????? ????????? ?"? ?-OPNET .
• ???? ???????? (debugging ).
• ????? ??? ?'.
• ????? ?? ???????? Linux.
• ????? ??????.

3
DNS- background

• DNS- Domain Name System
• The system is used over the internet to map names
  to IP addresses and addresses to names.
• The DNS is a hierarchical name space designed in
  a tree structure with the root at the top.
• The tree can have up to 128 levels

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DNS- background (cont).Hierarchy overview
Root
Country domains
Inverse domain
Generic domains
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DNS- the Protocol

• The two resolution options of mapping requests
• Recursive resolution.
• The server acts as resolver querying another
  server and so on recursively, until it receives
  final answer, and sends it to client.

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Simulation- Recursive resolusion.
Root server
if cached
if cached
10
9
4
il
3
if cached
8
com
if cached
5
11
ac.il
2
7
if cached
12
6
dns.yahoo.com
technion.ac.il
1
comnet.technion.ac.il
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DNS- the Protocol (cont.)

• Iterative resolution.
• The server repeats the same query to multiple
  servers until receives answer, which is sent back
  to the client

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Simulation- Iterative resolusion.
ac.il
com (has ac.il IP)
comnet.technion.ac.il
if cached
3
4
if cached
5
comnet.technion.ac.il
2
technion.ac.il
7
if cached
8
6
1
comnet.technion.ac.il
comnet.technion.ac.il
dns.yahoo.com
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DNS MESSAGES
DNS has two types of messagesquery and response,
both have the same format.
Header question section
Header question section Answer section Authoritati
ve section Additional section
Identical
Response
Query
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OPNET model simulator

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  ?????.
• ?????? ????? ????? ????? ??????? ????? ?"? ????
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  ??????? ????.
• ????? ????? ?????? ?????????? ??????? ???? (????
  TCP/IP ) ??? ?????? ????? ?????????? ????? ?"?
  ????? ???? ???????.

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OPNET general node model
Client
Server
12
Server process model
13
Server query resolve process
14
Client process model
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Server DataBase- Resource Record example-

• netvision.net.il MX 1
  mx20.netvision.net.il
• netvision.net.il A 194.90.1.6
• netvision.net.il NS
  dns.netvision.net.il
• netvision.net.il SOA
  dns.netvision.net.il
• hostmaster.netvision.net.il (
• 2001121604 serial (version)
• 28800 refresh period (8
  hours)
• 7200 retry interval (2 hours)
• 604800 expire time (1 week)
• 86400 default ttl (1 day)
• )

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DNS Experiment
The DNS experiment was designated to give us real
system delays
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DNS Experiment - characterizations

• Server file size (s-50 m-500 l-5000)
• Client domain names (good bad).
• repetition (1,2.. 1,1,2,2.. 1,2..1,2).
• delay (non 0.1 sec).
• Sniffer collect all DNS traffic.

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DNS Experiment query format

• To allow easy monitoring of charecteristics.
• DomainQuery_K_WXY.cn10w02.comnet.technion.ac.il
• K query num (from 1 to NUM_OF_QUERIES).
• W delay mode (1no delay 2with delay).
• X query repetition group (1/2/3 group)
• Y - server file size (1small 2medium
  3large).

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DNS Experiment - utilities

• Use of scripts
• Server
• create DNS db file (size, XYZ).
• Client
• create query list in file.
• make DNS queries (from list).

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DNS Experiment result example (File size)
Small file avarage 0.233ms
Large file avarage 0.277ms
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DNS Experiment result example (Delay)
Medium file (no) avarage 0.237ms
Medium file (delay) avarage 0.310ms
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DNS Client Server Model on OPNET - summary

• DNS protocol
• OPNET simulation platform
• Built-in models (code debug)
• Experiment (plan, install and analyze)
• Future
• More complex simulation topology.