Lab#3 and other stuff

Reading from the book sections 3.1, 3.2 & 3.3 is recommended for next lecture.

Third lab sketch is available for download.

From now on, we have a series of labs that will require you to create small programs in Java. You may use your favorite editor (if installed) and command line or you can use BlueJ if you prefer.

Lab#2

You can get the second lab handout from our site.

Solved exam

click on the image to get a larger version

Next class reading is Section 2.5 about DNS.

Reminder

Next Friday Oct 18th a short test of Chapter 1 questions will be held in the classroom. Those arriving late will have no extra time, so be on time or be quick.

Next lecture reading is section 2.4 about electronic mail.

What should I have learned from Lab#1?

I am not sure all of you got it it right, but the expected outcomes for this lab were:

1. To understand the usage of netcat command for creating TCP connections both as a client or as a server (-l) and how it can be used for accesing a certain server from the command line.
2. To capture network traffic using Wireshark and how to interpret HTTP traffic.
3. To understand the function of "conditional GET" in HTTP.
4. To see the traffic caused by HTTP persistent connections.

Please remember that labs are just 90 minutes long and that requires you to have read the lab exercises in advance.

I realized that some of you had not much familiarity with Wireshark program, though you were asked to do a lab#0 just about that. Try to review what capture filters are, what visualization filters are and what Follow TCP stream is for. These are basic concepts that will make your life easier when working with Wireshark software.

Moved class and test

I am scheduling both activities for next Monday morning, October 14th, from 10:00 to 12:00. Besides the lecture, a short written test about Chapter 1 will take place too.

We will have written tests of all chapters during the course. Not to be confused with the written exams that we will have at the end of each term. These classroom tests are mostly for you to know your level of understanding of chapter's contents. A small fraction of them will contribute to the 20% of your mark that measures your classroom performance.

Please note this same week signals the beginning of Lab sessions. There is an exercise for you to do at home to get familiar with some of the tools we will later use in the lab. The main purpose is for you to learn how to use Wireshark software, for which you have plenty of information here. And you may want to start by watching this video.

Lab#1 is already available here.

I wanted to remind you that we use a blog format so you can be a part of it too. That is why anyone can post a comment to any entry. Of course I receive an email every time a comment is made so I have a chance to provide an answer right away, or make note so I can address that in the next lecture. Sending me an email works too, but it deprives others of your comment or question and that may not be as efficient (i.e. repeated question) as a shared question posted as a comment.

Notice A change of hour has been requested by some students. Class will then be held same Monday 14th from 17-19h. In order to make it possible for you all not to miss the test, test has been rescheduled to the next class on Friday, October 18th.

File Transfer Protocol

It is an old protocol designed to provide a way for sending a file from a client to a server and backwards. It allows clients to download files without proper authentication, but it is not a very secure protocol (to say the least).  You can read about it in Section 2.3 and it will be covered in one Lab too.

You can have a look to RFC1945 and RFC2616 though I do not expect you to actually read it. A quick look may be not so hard for you to get familiar with how protocols are detailed.

October 11th class is moved to a yet to be defined date as I will be out of town. Please let me know what date may suit you better to recover that class as soon as possible.

Remember you can check on-line both attendance and marks. Let me know any mistake that could have been made.

Homework

1. Please research by yourself what persistent connections are (in the context of HTTP protocol)? 
2. What are persistent connections for?
3. Show with an example how persistent connections may improve HTTP client-server interaction.