Task 3: Modification

Preparation

Let's start with our example files.

Create a directory named lab_1 in ~/switchyard. Your should start by copying the template files examples/start_mininet.py, examples/myhub.py and examples/hubtests.py into lab_1. And your project will look like

switchyard/
  ├─docs/
  ├─.../
+ ├─lab_1/
+ │ ├─hubtests.py
+ │ ├─myhub.py
+ │ └─start_mininet.py
  ├─.gitignore
  └─...

Play the Tutorial Again

You have done the tutorial. However it is necessary to work by yourself. So modify our examples files.

[!TIP] We suggest that you can commit in Git when you complete one step.

[!WARNING] All of your modifications should be done on the files under your directory lab_1. We will check and compare the git commits to judge the originality of your work. So remember to commit every time you complete one small task.

Step 1: Modify the Mininet topology

In the section Mininet, we introduced how to construct a topology. So here we have two options for you, choose one to implement. ✅ Then show the details of how you build the topology in your report.

Delete server2 in the topology,
Or create a different topology containing 6 nodes using hosts and hubs (don't use other kinds of devices).

The file you need to modify is lab_1/start_mininet.py.

Step 2: Modify the logic of a device

In the section Switchyard, we introduced how to program a device. Your task is to count how many packets pass through a hub in and out. You need to log the statistical result every time you receive one packet with the format of each line in:<ingress packet count> out:<egress packet count>. For example, if there is a packet that is not addressed to the hub itself, then the hub may log in:1 out:2. ✅ Then show the log of your hub when running it in Mininet and how you implement it in your report.

[!NOTE] In the old version we need you to print the timestamp then we remove it. So many students ask why because there is a function log_info which prints the time of log output. However we want you to log the packet arrival time which is different from output time.

Because our explanation is late, if you have implemented it in another way, you do not need to change.

The file you need to modify is lab_1/myhub.py.

Step 3: Modify the test scenario of a device

In the section Switchyard, we introduced how to write the test case. So here we have two options for you, choose one to implement. ✅ Then show the details of your test cases in your report.

Create one test case by using the given function mk_pkt with different arguments,
Or create one test case with your handmade packet.

The file you need to modify is lab_1/hubtests.py.

Step 4: Run your device in Mininet

In the section Switchyard, we introduced how to run Switchyard programs in Mininet. So run your new hub in your new topology and make sure it works. ✅ Show the procedure in your report.

Step 5: Capture using Wireshark

Both in section Wireshark and Switchyard, we introduced how to capture packets. In your own topology, capture packets on one host (no hub) while creating some traffic. Save your capture file and submit it with your report and code. ✅ Also you need to describe the details of your capture file.

Task 4: Modification