In this lab exercise, you will learn how to use ping and traceroute to measure round trip times and find network routes.

Learning Objectives:

• Understand how the ping and traceroute utilities work.
• Use the ping utility to measure network round trip times.
• Use the traceroute utility to find network routes.
• Observe and understand the effects of varying packet sizes on delays experienced.

You will need ping and traceroute to be installed on your OS. Most Ubuntu or macOS installations should already include ping by default. You can install traceroute by running sudo apt install traceroute from the command line.

RTT Measurement using ping

The ping utility is one of the most widely-used network utilities. It enables you to measure the time that it takes for a packet to travel through the Internet to a remote host and back.

The ping utility works by sending a short message, known as an echo request to a remote host using the Internet Control Message Protocol (ICMP).

When a host that supports ICMP receives an echo-request message, it replies by sending an echo-response message back to the originating host.

In this first part of this lab exercise, you will use the ping utility to send echo requests to a number of different hosts. In many of the exercises, you will be referring to hosts using their domain name rather than their IP addresses¹. For more information about ping, you can look up its manual page by running man ping from the command line.

The following info is relevant for the next few tasks:

• ping netflix.com is the easiest and simplest way to ping a server. It will continuously send packets and print out the response (if any). You may press ctrl+c to terminate it.
• It supports several options:
  • -c [no_of_packets]: specify the number of packets that should be sent by ping before terminating (otherwise it will continue forever until SIGINT² is sent by ctrl+c).
  • -s [packet_size]: set packet size. The default is 56.
  • -i [seconds_interval]: interval of ping packets sent to the destination

Round-Trip Time

The ping utility can be used to measure the round-trip time (RTT).

Round-trip time (RTT) is the duration, measured in milliseconds, from when a browser sends a request to when it receives a response from a server.

RTT is one of the key performance metric for web applications.

Task 1

TASK 1: Use ping to send 10 packets (56 bytes each) to each of the following hosts, and there should be an interval of 5 seconds between each packet sent:

• www.csail.mit.edu
• www.berkeley.edu
• www.usyd.edu.au
• www.kyoto-u.ac.jp

Note: The size of each packet is 56 bytes by default, but you may observe that the actual size of the packet is larger than 56 bytes. You can look up the manual for ping to understand why such a discrepancy exists.

Fill up the table below, and head to edimension to key in your answer.

Website	Successfull %	Min RTT	Ave RTT	Max RTT
www.csail.mit.edu
www.berkeley.edu
www.usyd.edu.au
www.kyoto-u.ac.jp

Also, go to this online ping test site and ping www.csail.mit.edu

From whom do you receive replies? You can get the IP address and use the command whois [ip_address]

Task 2

TASK 2: Repeat the exercise from Task 1 using packet sizes of 512 and 1024 bytes. Record the minimum, average, and maximum round trip times for each of the packet sizes with a table like the previous task, and head to edimension to key in your answer.

Why are the minimum round-trip times to the same hosts different when using 56, 512, and 1024–byte packets?

Unanswered pings

Task 3

TASK 3: Use ping to send 100 packets to the following host: www.wits.ac.za

Each packet should have a size of 56 bytes, and there should be an interval of 5 seconds between each packet sent.

Record the percentage of the packets sent that resulted in a successful response for each host.

What are some possible reasons why you may not have received a response? (Be sure to check the host in a web browser).