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Welcome to ITS323
by Steven Gordon - Thursday, 6 June 2013, 5:12 PM
 
Welcome to ITS323 Introduction to Data Communications! The lectures start next week:

CS section: Monday 14:40 in BKD 2401
IT section: Tuesday 14:40 in BKD 2605

Printed handouts are available in the copy centre. The main course website is available via:
http://ict.siit.tu.ac.th/moodle/

We will use Moodle for course content and online quizzes. This will be explained in the first lecture. For now, make sure you have your username/password for the ICT server, received in an email to you around 5 June. Check your junk/trash mail for an email from:
root at ict.siit.tu.ac.th

That email contains your password. If you can't find the email let me know your name and ID and I will generate a new password. Without your password you will still be able to "Login as a guest", but you will not be able to take online quizzes or see your scores. For further instructions on ICT server and changing your password see: http://ict.siit.tu.ac.th/help/

Finally, I don't have the email address of the following students. If you know them, please tell them to contact me.

Watcharaporn Sitsawangsopon
Kittikhun Rujimongkon
Sutthiphat Ratanaphaisansri
Apichan Wimolthammawath
Thitirat Liaonoraset
Adiruj Siriban
Songpob Potisonothai
Varote Siriluesai

See you next week.

Steve

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Moodle Server Now Available
by Steven Gordon - Saturday, 8 June 2013, 4:00 PM
 
The course website is at:
http://ict.siit.tu.ac.th/moodle/

Last week there was a problem with SIIT Bangkadi gateway: it blocked outside access to port 443, disabling the login of Moodle. The problem has now been fixed.

You can now login and see the course information at:
http://ict.siit.tu.ac.th/moodle/

See you at the lectures on Monday (CS) and Tuesday (IT).

Steve

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Re: Moodle Server Now Available
by Steven Gordon - Sunday, 9 June 2013, 9:32 AM
 
Some students passwords were not working. That problem should be fixed now. Try to login again.

I'll explain how to change the password, and give you an opportunity to do so in the lecture this week.

Steve

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Change of Lectures on Tuesday 18 June
by Steven Gordon - Tuesday, 18 June 2013, 1:24 PM

Due to a cancelled lecture by another faculty member, I will start my lecture to IT section on Tuesday 18 June (today) early, at about 1:30pm.

If you are in IT section but cannot arrive until 14:40pm (normal lecture time), then please come then and we will discuss.

CS students: if you want to join the IT section at 14:20 or later, please do so. I may go through some new examples and demos.

Normal lectures on Wednesday morning.

Steve

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Moodle Unavailable Sunday 7 July
by Steven Gordon - Friday, 5 July 2013, 11:34 AM
 
On Sunday 7 July, electricity at SIIT Bangkadi will be cut at about 4pm. Since Moodle is hosted at Bangkadi, the server will be unavailable. Although electricity is planned to return at 6pm, its likely that Moodle will not be available until the morning of Monday 8 July (9am).

Please complete Quiz 4 before Sunday afternoon (or in the worst case, you could do it Monday between 9am and 1pm.

Steve

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Feedback on ITS323 so far
by Steven Gordon - Saturday, 13 July 2013, 9:45 AM

Firstly a reminder that Quiz 5 is available. To give you a chance to study more for this quiz I've extended the deadline to 9am Wednesday 17 July.

http://ict.siit.tu.ac.th/moodle/mod/quiz/view.php?id=368

Also I've created a short questionnaire of 10 questions to get your feedback on parts of the course so far. Please complete Feedback 1 before 9am Wednesday 17 July.

http://ict.siit.tu.ac.th/moodle/mod/feedback/view.php?id=367

The feedback is anonymous - I don't see who gave which answers (but I do see if you have completed it or not). So try to be honest in your answers.

Steve

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Access to past exams
by Steven Gordon - Sunday, 14 July 2013, 4:59 PM

The exams, assignments and other material from past years are available online. However they are on my old course website, not in Moodle. The best way to find them is go to:

http://ict.siit.tu.ac.th/~sgordon/

and then select the year (e.g. 2012) and follow the links to the "Assessment" page. There you will find past exams including answers. If prompted for a username/password, then use your Moodle username/password.

Please be aware that the material may be out of date (for example, different topics than the current course, errors in lecture notes and/or assessment items, broken links). If you use the material in this archive then it is your responsibility to deal with any differences from the current course.

Steve

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Comments on Quiz 5
by Steven Gordon - Monday, 15 July 2013, 5:09 PM

Several students have asked me about Quiz 5: they thought there answer was correct, but it was marked incorrect. Here is my response:

- Question 3: my answer is correct, but there is a mistake in my explanation. I give the free space path loss equation to use 4 pi d^2 but I am missing brackets. It should read (4 pi d)^2. The correct equation is in the lecture notes.

- Question 4: the answer is marked correct if using dBm as units, but not if using mW as units. This is because of a limitation of Moodle. If you give your answer in mW, then it still may be correct. I will manually check these answers and update your grade when the quiz closes.

I have changed the quiz to allow students to take 4 attempts (instead of the normal 3). Please complete your attempts before the deadline Wednesday.

Steve

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Midterm Exam Hints
by Steven Gordon - Friday, 19 July 2013, 2:44 PM
 
A few updates about ITS323:

- Hints for the upcoming Midterm Exam are now available on the course website.

- I have manually checked Question 4 of Quiz 5 and changed the score for several students. Please look at your score again and let me know if there are any problems (e.g. you want me to re-check your quiz).

- Less than half of students have responded to the Feedback. It will be open until 1pm Wednesday 24 July. If you haven't already done so, please offer some feedback.

- Practice 3 is a set of 32 questions on all topics. It does not count as a quiz (you will not be penalised for not attempting it). You can use it as practice for the midterm exam. Midterms from past years are also good practice.

http://ict.siit.tu.ac.th/moodle/

See you at the lecture on Wednesday morning. Have a happy and safe looooong weekend!

Steve

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Re: Midterm Exam Hints
by Steven Gordon - Thursday, 25 July 2013, 8:57 AM

Thanks to the students that provided feedback. Those students can view responses at:

http://ict.siit.tu.ac.th/moodle/mod/feedback/view.php?id=367

I will analyse your responses in the coming days and discuss some outcomes of the feedback after the midterm. One suggestion was to allow the practice lessons to be taken anytime. So I have opened Practice 1 and 2 again - you may take them to practice about units and logarithms.

Units and Prefixes: http://ict.siit.tu.ac.th/moodle/mod/lesson/view.php?id=351

Logarithms: http://ict.siit.tu.ac.th/moodle/mod/lesson/view.php?id=352

Steve

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Midterm Exam Scores
by Steven Gordon - Friday, 9 August 2013, 10:57 AM
 
Dear ITS323 students,

Scores for the midterm exam are now available on Moodle. You can also view a scanned PDF of your marked exam and my answers. I recommend you do the following:

    Compare your exam against the answers - see where you went wrong. Discuss with me if you still don't understand my answers.
    Check that I have correctly added up the scores for each question to arrive at your total score.
    Check that the score on the front page of your exam is the same as you see online in Moodle.
    Compare you score against the class statistics (including your rank which is available on the course grades page). See how you are progressing.

If there are any problems or questions about the exam and marking, please let me know.

Have a good long weekend and see you refreshed in the lecture next week.

Steve

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Lecture Next Tuesday and Assignment
by Steven Gordon - Friday, 9 August 2013, 4:29 PM
 
Monday 12 August is a public holiday and therefore no lecture for CS section.

On Tuesday 13 August there WILL be a lecture for IT section (and any CS students that are free to attend). However I will not start the new topic. Instead I will use the Tuesday lecture to give a response to your feedback about the online quizzes, and answer any of your questions about the midterm exam. If you miss the Tuesday lecture, you will be able to catch up via the video or talking to me individually.

On Wednesday 14 August the normal lectures will be held. I will start on the new topic for both CS and IT sections. The handouts are in the Copy Centre.

The assignment is now available on Moodle. Please read the instructions and form a group of 3 students (Dana and Thiri can form a group of 2). I will explain the assignment tasks further during Wednesdays lecture.

Steve

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Quiz This Week
by Steven Gordon - Wednesday, 14 August 2013, 2:10 PM

Your homework tasks for this week are:

- Let me know the 3 people in your assignment group before 12noon Monday 19 August (e.g. by email)

- Start your assignment by reading the instructions carefully and starting the first task by recording some audio.

- Complete the stop-and-wait flow control example from the lecture today, making sure you can calculate the total time (25023 us) and understand how to determine the throughput (959,118 b/s). To check your answers, I've created a simple online flow control calculator at:

http://sandilands.info/sgordon/flow-control-efficiency-calculator

There is no online quiz this week.

Steve

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Rearrange Lectures This Week
by Steven Gordon - Monday, 19 August 2013, 6:02 PM
 
As several of your other lectures have been cancelled this week, I will use your "spare time" to hold a tutorial. The schedule for this week is:

- Tuesday 20 Aug, 13:00-14:20, BKD2605: Lecture for IT Section

- Tuesday 20 Aug, 14:40-16:00 BKD2605: Repeat for students that missed 1pm lecture (e.g. Tanabordi, Suchatit; anyone else may join if they wish)

- Wednesday 21 Aug, 9:00-10:20 BKD2605: Lecture for BOTH IT and CS sections

- Wednesday 21 Aug, 10:40-12:00 BKD2605: Tutorial on flow control for BOTH IT and CS sections

That is, IT lecture for tomorrow is moved to 1pm. Then on Wednesday it will be joint with CS section in 2605. At 10:40 on Wed I provide some exercises for you to do in class and will be available to answer questions.

If these changes cause you problems, then let me know and I'll make specific arrangements with you.

Also, assignment groups are allocated - the list is on the website. Discuss with me in the lecture if any problems.

Steve

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Solar Eclipse Photos from Mars Curiosity Rover
by Steven Gordon - Friday, 6 September 2013, 1:46 PM
 
Recently photos and a video of a solar eclipse on Mars were recorded by the NASA Mars Curiosity rover.

http://www.youtube.com/watch?v=OyZoD7BRTtg

http://www.nasa.gov/mission_pages/msl/index.html

The Curiosity rover landed on Mars about one year ago and has been conducting experiments about the surface and atmosphere of Mars.

One of the challenges of this project is communications between the rover on Mars and NASA headquarters on Earth, e.g. downloading the photos and uploading commands. For example, the path loss is such that the received signal is about 1,000,000,000,000,000,000,000,000,000 times weaker than the transmitted signal. Big antennas and powerful transmitters are needed.

Also the round-trip-time is about 28 minutes! Imagine browsing the web when it takes 28 minutes from when you click on a link until when the page is displayed.

Last year I wrote about some of these communication challenges from the perspective of ITS323. I discussed path loss, antenna gain, frequencies, bandwidth and spectrum, data rates and transmission and propagation delays. Feel free to read at:

http://sandilands.info/sgordon/communications-with-mars-curiosity

Another topic: a reminder that this week there is no quiz, however I suggest you try Practice 4 - Packets and also try to finish your assignment.

Steve

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IP Addressing
by Steven Gordon - Wednesday, 18 September 2013, 1:43 PM

In the lecture today, the last part about IP addressing was a bit rushed. I'll summarize again next week. However Quiz 9 asks some questions about IP addresses. Therefore I recommend that BEFORE you take Quiz 9 you:

1. Read the slides about IP addressing, including special addresses

2. Read the "IP Addressing Summary" handout in your lecture notes (and online)

3. Attempt the "Internetworking Practice" questions in your lecture notes (and online). Note that you can skip section 1.1 classful addressing - start at section 1.2 classless addressing. Answers are also online.

Then Quiz 9 should be very easy.

Steve

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Re: IP Addressing
by Steven Gordon - Thursday, 19 September 2013, 9:46 AM

There are two problems in Quiz 9, specifically on the question(s) that require you to input an IP address in dotted decimal notation as an answer. First, when you type in an IP address like 1.1.1.1 you will see a warning like:

Please enter a valid number and nothing else.

This is just a warning and can be ignored - your answer of 1.1.1.1 is still recorded and you can submit the quiz.Second, there is a bug in marking answers of this kind. This bugs means that your incorrect answer may mistakenly marked correct. I don't think it will cause your correct answer to be mistakenly marked incorrect though. I will try to fix this bug. In the meantime, please attempt the quiz and just be aware of these issues.

If you think these issues have caused you problems, then contact me and I will manually mark your quiz.
Steve

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Re: IP Addressing
by Steven Gordon - Friday, 20 September 2013, 8:07 AM
 
Due to the bugs in the IP addressing questions, Quiz 9 has been changed to Practice 5. It will not be counted as a quiz (that is, it does not impact on your grade whether you do it or not). You can also make unlimited attempts.

During the lecture on Wednesday 25 Sep I will give you Quiz 9 (on IP and addressing) in class, i.e. a paper quiz.

You should use "Internetworking Practice" and "Practice 5" as preparation for your in-class quiz on Wednesday.

Steve

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Assignment Marks
by Steven Gordon - Friday, 27 September 2013, 2:24 PM

Assignment marks are available on Moodle. The feedback files contains my short notes on your report. Some general comments, and explanation of my feedback notes follows.

General:

In my feedback I generally include a + for good things and - for bad things or problems in your report. A = means its just a note (normal). I also give a score for each section based upon how I consider you performed with respect to the requirements and with respect to other groups.

I marked parts A, B and C (and also gave a score for presentation). Below are some comments on what I expected to see in each part (=), what would have been good to see (+), and some common mistakes people made (-).

Part A (Audio):

= 3 or more different samples (i.e. WAV files). You should have indicated what you recorded and the duration of that recording.

= 3 or more codecs. You should have tried different codecs, e.g. a lossless vs lossy compression codec.

= A comparison of the WAV and codecs for your samples should have included: file size, perceived quality and some of the following: licensing, cost, OS support, time to encode (not compression time).

+ It would have been nice to see some comparison for codecs using different parameters, e.g. 32 kb/s MP3 vs 160 kb/s MP3. I don't think any group did this.

+ A comparison of the quality via listening tests and/or analysing the spectrum of the file would be good. 2 or 3 groups did this.

Part B (Capture)

= Description of the experiment setup and instructions of what you did (including how you performed the capture)

= Specifications of the computers used, especially the manufacturer, OS and wireless chip details, e.g. IEEE 802.11 a/b/g

= A time sequence diagram showing packet type. Many people didn't identify the types of packets (e.g. DATA, ACK) and simply copied down times from Wireshark (not very useful).

= Brief discussion of the protocol used for data transfer (e.g. SMB, AFP, HTTP, ...)

+ A discussion of how the file transfer protocol works, and analysis of the number of packets and overhead, was performed by several groups.

Part C (Throughput)

= Description of experiment setup.

= Results of throughput.

- Many people did not state the data rate used, e.g. 54 Mb/s or 11 Mb/s. It is very important to know this so you can evaluate how good the throughput is. For example, if you measure a throughput of 5.5 Mb/s, then that is 50% efficiency if using 11 Mb/s, but only 10% efficiency if using 54 Mb/s.

- Few people discussed the detailed reasons why the efficiency for WLAN is usually less than 50%. Hint: the data link layer protocol is stop and wait (Data, Ack, Data, Ack) and there are overheads of frame headers, waiting times and retransmissions.

Finally, a number of groups copied results from other groups (especially in part B). When I saw any clear evidence of copying, the entire group received 0 for the entire assignment.

Talk to me if you have questions about your assignment.

Steve

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Final Exam Hints
by Steven Gordon - Monday, 7 October 2013, 2:28 PM

Hints for the final exam can be found at:

http://ict.siit.tu.ac.th/moodle/mod/assign/view.php?id=394

I will be available in my office for consultation most of today through to Thursday 3pm this week (except Wed 9am-12noon).

I've also written some notes on the assignment, in particular why groups were penalised for copying. Although too late for this course, most of you will take courses with me next semester so it is worth reading:

http://ict.siit.tu.ac.th/~sgordon/its323y13s1/unprotected/ITS323Y13S1A01-Assignment-Copying.pdf

I hope those that were penalised will work extra hard to improve their score in the final exam.

Good luck in the exam.

Steve

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Final Exam Results
by Steven Gordon - Monday, 21 October 2013, 9:28 AM
 
Results and answers for the final exam are now available. You can see me in my office this week if you want to view your exam.

http://ict.siit.tu.ac.th/moodle/mod/assign/view.php?id=394

You can see your total score for the course, i.e. sum of quiz, assignment and two exams:

http://ict.siit.tu.ac.th/moodle/grade/report/index.php?id=9

Please check and let me know if you have any queries. However I will ignore any queries about grades - you have to wait for official announcement on Oct 31 to learn your grade. If there are students deciding whether to re-enter, then they must see me in my office this week.

Well done, and see most of you next semester in ITS335, CSS322 and ITS332 Lab.

Steve

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