Lab1 PDF

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Lab1...

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Exercise 1: nslookup 1. IP address of google.com:

Reason: Google uses Round Robin DNS, meaning it balances the load of page requests across all their servers. Each server has its own IP address to bring up the page faster for each user based on their location. 2. Name of 127.0.0.1: localhost What is special about 127.0.0.1: localhost is the default name describing the local computer. Exercise 2: Use ping to test host reachability Host

Reachable?

If not, why?

www.cse.unsw.edu.au

Yes

N/A

www.getfittest.com.au

No

Unknown Host, Server Not Found

www.mit.edu

Yes

N/A

www.intel.com.au

Yes

N/A

www.tpg.com.au

Yes

N/A

www.hola.hp

No

Unknown Host, Server Not Found

www.amazon.com

Yes

N/A

www.tsinghua.edu.cn

Yes

N/A

www.kremlin.ru

Yes

N/A

8.8.8.8

Yes

N/A

The addresses unreachable by ping were also not reachable by Web Browser thus indicating that that url does not exist. Exercise 3: Use traceroute to understand network topology 1.

There are 21 routers between my workstation and w  ww.columbia.edu. There are 4 routers that are part of the unsw network. Between router 9 (Australia) and router 10 (Los Angeles), the packets cross the pacific ocean 2.

The paths split at after route 6 (138.44.5.0) Further details about 138.44.5.0 using whois:

The number of hops is not proportional to the physical distance as going to the ucla website (America) takes 14 hops while the japan website takes 15 hops, which is interesting as japan is closer to australia than America. 3. Traceroute from h  ttp://www.speedtest.com.sg/tr.php:

Traceroute to h  ttp://www.speedtest.com.sg/tr.php:

Traceroute from https://www.telstra.net/cgi-bin/trace:

Traceroute to h  ttps://www.telstra.net/cgi-bin/trace:

We can notice by comparing the outputs that the forward and the reverse paths are different. The IP address of h  ttps://www.telstra.net/cgi-bin/trace: 203.50.5.178 The IP address of http://www.speedtest.com.sg/tr.php: 202.150.221.70

Exercise 4: Use ping to gain insights into network performance 1.

2. Based on the delay.pdf plot, it is clear that the delay varies over time and is not constant. This is because it depends on the other traffic in the network. 3. Delays that depend on packet size: ● Transmission Delay ● Processing Delay Delays that do not depend on packet size: ● Processing Delay ● Queueing Delay...