CSCI 3500: Studio 21

Intro to Networking

Networking concepts are important, but so are networking tools. Modern machines have a variety of useful utilities that help you to understand the networks that a machine is connected to, and how data flows to and from your machine. In this studio we will explore several of these command line utilities.

In this studio, you will:

1. Use a few basic command-line utilities related to networking
2. Analyze the TCP/IP and the OSI network model

Please complete the required exercises below, as well as any optional enrichment exercises that you wish to complete.

As you work through these exercises, please record your answers in a text file. When finished, submit your work via the git repository.

Make sure that the name of each person who worked on these exercises is listed in the first answer, and make sure you number each of your responses so it is easy to match your responses with each exercise.

Required Exercises

1. As the answer to the first exercise, list the names of the people who worked together on this studio.

2. In the TCP/IP model, layer two (the internet layer) handles the communication of data between different physical devices. To facilitate this all network-connected devices are assigned an internet protocol address, or IP address. The ifconfig command provides a variety of information, including this data. Issue the ifconfig command and copy/paste the entry under "br0".

3. What are the current IP addresses? These are given by the fields "inet" and "inet6"

4. On a computer with more than one physical network connection, it becomes important to distinguish these different physical devices. This is done through a hardware address, also known as a MAC address or ethernet address. What is the hardware address for this interface? It is given by the field called "ether".

5. One general concept in networking is that of hosts. Loosely, a host is any device that is capable of making or recieving network connections. You can find the current hostname of the machine you are currently using with the command hostname. What does this command give?

6. You can look up information about other machines, remote hosts, with the host command. Try using the host command with a website that you visit. What information is returned?

7. Try using the host command with slu.edu. This returns multiple IP addresses. Speculate a reason for why this one host maps to multiple IP addresses.

8. Wikipedia maintains a list of network protocols by their placement in the OSI model:

   https://en.wikipedia.org/wiki/List_of_network_protocols_(OSI_model)

   For this last exercise, pick out one protocol from each traditional layer. Briefly describe what it does and, if you can, give short justification for why you think it's been listed at that layer. Some layers, like layers 4, 5, and 6, you might have trouble justifying right now. Don't worry too hard about the justification!

Optional Enrichment Exercises

1. Two very useful programs are called ping and traceroute. These are unfortunately disabled on campus. The first times how long it takes to send a packet to a remote host (as well as other things). The second traces the path between all physical devices that are used to transmit information between your computer and a remote host. Try them at home!