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Lab 10: Measuring DNS

In this lab you will monitor and measure DNS packets.

Introduction
DNS performance has a huge impact on web browsing. Each time your browser encounters a new hostname it must lookup the IP address of that hostname. Because most web pages have a complicated mix of elements (including ads) you may rack up 1,000 DNS lookups or more every minute of heavy browsing. In this lab you will capture and analyze the performance of DNS.

Gather a Baseline
Start a live capture on your computer. While capturing browse the web. Where you go doesn't matter, but be sure to go to a few sites, preferably complicated ones with ads. Once you're done browsing stop your capture and save only the DNS packets. Once you have the DNS packets isolated answer the following questions: 
  1. How many DNS lookups were done? 
  2. How many lookup errors were there?
  3. What was the worst lookup time? 
  4. What was the average lookup time? 
Submit your capture (with ONLY DNS packets) with the answers to your questions.

Use a Public DNS (Extra Credit)
Google's public DNS boasts very high performance, supposedly better than the one provided by your ISP. For extra credit switch your computer to using Google's public DNS servers then redo part 1. Google's public DNS servers have the IP addresses: 
  • 8.8.8.8 
  • 8.8.4.4
If you are already using Google's DNS servers then switch to the ones provided by your ISP for this part instead. 

Turn In
  1. Answers to the questions in part 1 
  2. Your packets from part 1
  3. (Optional) Answer to the questions in part 2
  4. (Optional) Your packets from part 2
Submit your homework on blackboard.

Grading
  • 20 points for part 1
  • 10 points extra credit for part 2 
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