Welcome to ITS323/CSS331
by Steven Gordon - Friday, 7 August 2015, 1:46 PM

To IT/CPE 3rd year students,

Welcome to ITS323 Introduction to Data Communications and CSS331 Fundamentals of Data Communications. A few notes before I see you in the first lecture.

1. ITS323 (for IT students) and CSS331 (for CPE students) will be managed by me as one course in many cases, e.g. same website, same lecture notes, some of the same assessment items. I will let you know of the differences during the lectures.

2. As Wednesday 12 August is a holiday (meaning no lecture for ITS323/IT students), I will also cancel the lecture for CSS331/CPE students on Tuesday 11 August. Therefore the first lecture for everyone will be morning of Thursday 13 August.

3. The course website is via my Moodle website:

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

Please visit and browse the course information and topics.

4. If you received this email then you already have an account on Moodle. Although you can view lecture notes without logging in, you will need to login to take online quizzes. Your login details are:

username: "u" followed by your ID, e.g. u5622123456

password: the first 4 characters of your email followed by the first 4 characters of your last name, e.g. stevGord

When you first login you will be asked to create a new password, at least 8 characters long. Choose a password that is reasonably secure (your friends cannot guess).

5. I don't have the email address of some students (or I have old addresses). If you know of someone who did not receive this email then tell them to send me an email with their full name and ID.

6. A booklet of handouts and lecture notes will be in the Copy Centre on Monday. Please get a copy before Thursdays lecture. Note that all lecture notes are also available as PDF on the website.

Finally your homework for week 1: Browse the course website and make sure you can do the following: login; know the assessment criteria and course text book; can find the PDF handouts and YouTube videos; take practice lesson 1 on Units and Prefixes (its not assessed); can find the exams from past years (hint: siit and ictcpeit).

See you Thursday 13 August.

Steve

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Re: Welcome to ITS323/CSS331
by Steven Gordon - Saturday, 15 August 2015, 1:19 PM
 
This is a reminder for you to check your logins on Moodle at:

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

The instructions were sent in the "Welcome to ITS323/CSS331" message last week, however some missing/wrong email addresses meant you may not have read it. Here is the welcome message:

http://ict.siit.tu.ac.th/moodle/mod/forum/discuss.php?d=160

In summary:

1. Login to Moodle

2. Explore the course website, reading the assessment criteria, etc.

3. Attempt Lesson 1 on Units and Prefixes (its not assessed). Optionally, you may also try Lesson 2 on Logarithms and Exponentiation (also not assessed, but useful refresher).

I will assume you have attempted Lesson 1 before the next lecture. If you have problems with Moodle, email me (steve@siit.tu.ac.th) or talk to me during the lecture.

Steve

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Cancel Lecture on Tue 18 August
by Steven Gordon - Monday, 17 August 2015, 4:12 PM

Unfortunately I am sick and cannot attend SIIT today (Monday) or tomorrow (Tuesday). Therefore the CSS331 lecture on Tuesday 10:40 is cancelled. I will consider a make-up at a later date. I hope to be back on Wednesday, but if not I will send another email tomorrow.

I suggest CPE students use the cancelled lecture time to complete Practice 1 (Units and Prefixes) and even try Practice 2 (Log and Exp) on Moodle. Even though they are unassessed, I highly recommend you complete the practice. Quizzes may have questions on the practice lessons.

Due to my illness, the 1st Quiz will not be released until after Thursday's lecture.

Steve 

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Re: Cancel Lecture on Tue 18 August
by Steven Gordon - Wednesday, 19 August 2015, 11:23 AM
 
Summary of schedule for ITS323/CSS331 this week:

- Tue 18 (yesterday): lecture cancelled for CPE (due to me being sick)

- Wed 19 (today): normal lecture for IT at 14:40 in BKD3506

- Thu 20 (tomorrow): normal lecture for CPE at 9:00 in BKD2501

- Thu 20 (tomorrow): lecture cancelled for IT (due to mandatory SIIT meeting I must attend)

I will see IT students this afternoon, and CPE tomorrow morning.

Steve

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Quiz 1
by Steven Gordon - Saturday, 22 August 2015, 3:23 PM
 
The first online quiz is now available on the course website. When you start the quiz you will have 10 minutes to complete it. There are 7 questions, some of them asking about basic information from the course syllabus and some simple questions on data communications and transmission. When the quiz is completed you can review your answers, seeing which are correct/incorrect. You may then re-attempt the quiz to try for a higher score. You are allowed a maximum of 3 attempts, so in this quiz I'd like to see all students score full marks.

Before you take the quiz you may refresh your knowledge from:

Videos and notes from last lecture: http://ict.siit.tu.ac.th/moodle/mod/page/view.php?id=893

Hints on taking quizzes in Moodle: http://ict.siit.tu.ac.th/moodle/mod/page/view.php?id=905

and also read the course information on the website.

The quiz closes on Wednesday afternoon, so you may ask me questions either via email or in the next lecture.

Steve

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Makeup Lecture on Monday 31 Aug
by Steven Gordon - Friday, 28 August 2015, 11:09 AM

Due to cancelled lectures in the first 2 weeks, we will have a makeup lecture on Monday 31 August. There are two time slots - you only need to attend one of them:

Either Monday 31 Aug, 10:40-12:00 in BKD3207

Or Monday 31 Aug, 13:00-14:20 in BKD2601

The lecture will be joint between CPE (CSS331) and IT (ITS323). Since BKD3207 is the biggest room, I suggest if you don't have a class at 10:40, to attend in the morning. But if you have a class at 10:40, attend in the afternoon.

If you cannot attend either of the slots, then you have two options:

- View the lecture on YouTube to catch up

- Talk to me and I can schedule a time slot when I can go through the lecture with you

Hope to see you all on Monday.

Steve

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Quiz 2 and Practice on Signals
by Steven Gordon - Saturday, 29 August 2015, 8:32 AM
 
The last lectures we have covered many details of communication signals. To check your understanding you must complete Quiz 2 and should also attempt Practice 3.

Quiz 2 is assessed and includes questions like "what is the bandwidth of this plot" and about the tradeoffs of accuracy, bandwidth and data rate.

Practice 3 in not assessed. It aims to explain the relationship between signal frequency, bandwidth, data rate and accuracy using simple signal equations. It takes up to 1 hour and you must read the information carefully and complete the questions in order. You should "Check" your answers as you go, as each new page of questions depends on the previous pages. You should complete the lesson in one attempt (don't start it today and then complete it tomorrow).

You can complete Quiz 2 without doing Practice 3, but if you really want to understand WHY increasing the bandwidth increases the data rate, you should also try Practice 3.

See you at the makeup lecture on Monday.

Steve

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Quiz 3
by Steven Gordon - Thursday, 3 September 2015, 2:04 PM
 
Quiz 3 is now available. It has 3 questions on Nyquist and Shannon capacity, and 3 questions on dB, gain and loss. The questions involves doing several calculations and since you only have 20 minutes I recommend you have a calculator, pen/paper and the equations (Nyquist, Shannon, dB) in front of you when you start the quiz.

Also, some questions mention "receiver sensitivity". In brief, it is the minimum receive power that a receiver can understand. For a detailed explanation, here the text taken directly from one of the quiz questions:

In wireless systems, a characteristic of a receiver is the minimum power of a signal that it can receive and successfully understand. This is often called the receive sensitivity (or receive threshold). Ignoring noise, if the receiver receives a signal with power larger than the sensitivity, then it can successfully receive; but if the signal received has a power smaller than the sensitivity then the receiver cannot receive any data (it treats it as noise).

Receive sensitivity of a device often differs depending on the data rate, technology and frequency. For example, the TP-Link AC1750 WiFi router has receive sensitivity of:

    5GHz, 802.11a, 6Mb/s: -96 dBm
    5GHz, 802.11ac, 80 MHz bandwidth: -63 dBm
    2.4GHz, 802.11g, 54Mb/s: -77 dBm

Read and understand this before starting the quiz.

Steve

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Quiz 4
by Steven Gordon - Friday, 11 September 2015, 6:18 PM

Quiz 4 is available and has 2 questions on path loss, antennas etc., and 5 questions on encoding digital data as digital signals. We only briefly covered some of the encoding schemes in the lecture - you should look at the examples in the lecture notes before the quiz to understand the encoding schemes: NRZL, NRZL, Bipolar AMI, Pseudoternary, Manchester, Differential Manchester.

Steve

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Quiz 5
by Steven Gordon - Thursday, 17 September 2015, 7:42 PM
 
Quiz 5 is now available. Since many people are finding the quizzes easy and getting full marks, this quiz is limited to just 2 attempts.

Also I suggest you try the Packets lesson available on the website to enhance your knowledge packet (frame) formats.

Steve

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Re: Quiz 5
by Steven Gordon - Wednesday, 23 September 2015, 7:16 AM
 

Quiz 5 closes TODAY (Wednesday 23 Sep) at 5pm.

Steve

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Re: Quiz 5
by Steven Gordon - Wednesday, 23 September 2015, 4:10 PM
 
Final change due to some requests: Quiz 5 deadline is extended to 9am tomorrow (Thu 24 Sep) and you now have 3 attempts.

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Midterm Exam
by Steven Gordon - Saturday, 26 September 2015, 12:38 PM

Hints on the midterm exam are available via:

http://ict.siit.tu.ac.th/moodle/mod/page/view.php?id=942

I have created some unassessed practice questions on error detection and FEC:

http://ict.siit.tu.ac.th/moodle/mod/quiz/view.php?id=941

You can also try the other practice lessons on the website.

Most of the handwritten notes that I make during the lecture (e.g. the examples) can be downloaded via the topic website or as PDFs directly from:

https://ict.siit.tu.ac.th/~sgordon/its323y15s1/notes/

I am available in my office to answer questions most of next week, except: Monday morning, Tuesday afternoon, Thursday morning.

Good luck,

Steve

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Re: Midterm Exam
by Steven Gordon - Sunday, 4 October 2015, 5:58 PM
 
ICT webserver has been unavailable for most of this afternoon (Sunday 4 Oct). The ICT technician and I have been at Bangkadi trying to fix the problem, and now (6pm) Moodle is back working again. 

If there is another problem between now and the exam, you can at least access past exams at:

http://sandilands.info/siit/

Sorry for any inconveniences.

Steve

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Re: Midterm Exam
by Steven Gordon - Friday, 9 October 2015, 7:04 PM
 
Midterm exam scores and answers are available on Moodle:

http://ict.siit.tu.ac.th/moodle/mod/page/view.php?id=942

To see your score, look in the Grades menu on Moodle.

Note that the total scores for the course on Moodle are not yet correct (the weightings for the individual quizzes and exam are wrong). I will fix that next week.

Steve

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New Lecture Notes
by Admin User - Tuesday, 13 October 2015, 2:09 PM
 
I just put the new lecture notes for ITS323/CSS331 in the copy centre. So there should be copies available this afternoon or tomorrow morning. I will upload the lecture notes to the course website later this week.
Steve

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Assignment
by Steven Gordon - Sunday, 18 October 2015, 1:12 PM
 
The instructions for the assignment are now on Moodle. To get started:

1. Form a group of 3 and let me know by 5pm Wed 21 Oct of the students in your group (email or give me a piece of paper with the name list in the lecture)

2. Read the instructions at:

http://ict.siit.tu.ac.th/moodle/mod/page/view.php?id=958

3. Each group needs access to at least 2 computers (e.g. laptops) and a WiFi access point with in-built switch. If you don't then you can use the Network lab (ground floor of IT/MT building).

4. Try "ping" and "iperf" (or jperf) to test delay and throughput.

You should do the above 4 steps within the next week, to give you enough time to complete the tasks.

I may add more information to the instructions as questions arise, and give a demo during the lecture next week.

Steve

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Mistake in Quiz 6
by Steven Gordon - Wednesday, 28 October 2015, 7:43 AM
 
As several people informed me, there is a mistake in my answer for a question in Quiz 6 that involves calculating the efficiency of sliding window (I think many people noticed because my answer gave an efficiency about 100%). If you gave the correct answer but it was marked wrong, I have manually changed your score to 2 out of 2. I will manually check the remaining answers today.

Steve

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Practice on Packets
by Steven Gordon - Friday, 30 October 2015, 3:17 PM
 
There is no quiz this week, but instead you have two tasks that you MUST do:

1. Make sure ping and iperf work on your computers for the assignment. You should be collecting some results from your experiments.

2. Complete practice 4 on packets. You know you have completed when you get to the last page which says:

"Well done! You now have a good understanding of packets in computer networks."

http://ict.siit.tu.ac.th/moodle/mod/lesson/view.php?id=908

Although you get no score for practice 4, I will give a penalty for the next quiz for anyone who has NOT completed practice 4 by 5pm Wednesday 4 Nov. You can re-attempt as often as you like. Some people have already completed the practice before the midterm, so there is no need for them to do it again.

Steve

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Quiz 7 and Cancelled Lecture
by Steven Gordon - Monday, 9 November 2015, 10:42 AM
 
This week we have normal lectures. But I will be away 16 to 18 November, so lectures on Tuesday 17th (CPE) and Wednesday 18th (IT) are cancelled. Instead of a makeup lecture, later this week I will assign you a task you can complete online.

Also, don't forget Quiz 7.

Steve

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Quiz 8 and Makeup Lecture
by Steven Gordon - Thursday, 12 November 2015, 4:30 PM
 
As previously stated, the lecture for Tuesday 17 (CPE) and Wednesday 18 (IT) is cancelled. Rather than having a makeup, you should view the lecture on Ethernet from last year on YouTube:

https://www.youtube.com/watch?v=Qtn7-1_2v60

You only need to watch the first 40 minutes (it changes topics after that). If you are too lazy to watch the 40 minutes of video, then at least read the lecture slides on the Ethernet topic (there are only 13 slides).

Quiz 8 is now available, but note it contains questions on Ethernet. So you should watch the video before taking the quiz.

As I will be away Mon-Wed next week, I have extended the assignment deadline until 10am Tuesday 24 November. That gives you a chance to get some feedback later next week if you need.

Steve

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iperf in Assignment
by Steven Gordon - Friday, 13 November 2015, 12:32 PM
 
iperf3 or iperf2?

I have always used iperf version 2, but in the past year or so, iperf version 3 was released. Although it is a complete re-write (essentially a different application) I expected both versions would give about the same results for the assignment.

However some students have reported strange results with iperf3, especially with UDP tests. I just performed some tests myself using both iperf2 and iperf3 and discovered the following:

    For Ethernet, with both TCP and UDP, iperf2 and iperf3 are about the same. So you can use either.
    For WiFi, with TCP, iperf2 and iperf3 are about the same. So you can use either.
    For WiFi, with UDP, iperf2 looks to be ok, but iperf3 returns strange results (e.g. throughput higher than data rate). I think this is because of packet drops, but it needs further investigation. I recommend you only use iperf2 for WiFi/UDP experiments (or don't perform WiFi/UDP experiments).

What should you do?

    If you are using iperf2 already, no problem.
    If you haven't performed many experiments yet, I suggest using only iperf2.
    If you have already run many experiments with iperf3, then your results with Ethernet (TCP/UDP) as well as WiFi (TCP) can be used - you don't have to run them again. But you should ignore any results you obtained for WiFi with UDP. You can either run those again with iperf2 or don't use UDP as a parameter.

The results of my tests are at:

http://ict.siit.tu.ac.th/moodle/mod/page/view.php?id=971

Sorry for this late information, but I don't think it will extra work from many of you, since you can keep using most of your iperf3 results. Thanks to the students that pointed out strange iperf3 results.

Steve

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Assignment Submission
by Steven Gordon - Friday, 20 November 2015, 10:24 AM

The assignment is due 10am Tuesday 24 November. You should now be preparing your report. Now is a good time to read ALL the assignment instructions again:

http://ict.siit.tu.ac.th/moodle/mod/page/view.php?id=958

At the bottom of that page is the submission instructions - follow them carefully.

There is no quiz this week.

Steve

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Steven Gordon
Re: Assignment Submission
by Steven Gordon - Saturday, 21 November 2015, 7:48 PM
 
Several people have asked about the data rate. For the assignment you must report three values:

delay (measured using ping)

throughput (measured using iperf)

efficiency (calculated as throughput / data rate)

Therefore you need to know the data rate of the link when using iperf to measure throughput.

The data rate is a characteristic of the link. You do NOT measure it or calculate; you just observe it.

With Ethernet, the data rate is either 10, 100 or 1000 Mb/s. In some cases, you can probably guess which one based on your throughput measurements. E.g. if your throughput is above 100, then data rate is 1000. But to be precise you should check the value from your network settings. See attached for my view of "Connection Information" in Ubuntu. It says the speed (data rate) is 1000 Mb/s. In Windows, if you view information about the Network Settings, you should be able to find the data rate or speed.

Be careful that if you are using two links, e.g.: A --- switch --- B, then you need to check the data rate for both A and B. If A --- switch is 1000 Mb/s, but B --- switch is 100 Mb/s, then effectively the data rate is 100 Mb/s.

The same applies for Wifi (check your network settings to see the current value), but the added problem that the data rate often changes automatically based on the signal strength. If the signal is strong, the data rate will be high; if the signal is weak, the data will be low. And there are many more possible values, depending on the Wifi chip in your laptop and access point (e.g. 11g, 11n, 11ac).

In summary, to know the data rate, you must look at the value from your network settings or connection information when running the iperf test. For Ethernet, it will be fixed. For wifi, it may change. If it does change a lot during a test, then maybe move your laptop closer to the AP until it is stable data rate.

Steve

PS if using Ubuntu command line (or possible even on OSX - I haven't tested) then you can see your Ethernet data rate with

ethtool eth0

You can change it to 100 Mb/s with:

sudo ethtool -s eth0 speed 100 duplex full

You can even view/set the WiFi data rate, but if you haven't done that by now, then its probably too late to try.

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Quiz 9 and Homework
by Steven Gordon - Thursday, 26 November 2015, 6:49 PM

Your homework, which you must do before the next lecture, is to complete the routing tables for R3, R4, R5, H1 and H2. If you want to check the routing table for R2 and see the IP addresses I used in class, see:

http://ict.siit.tu.ac.th/~sgordon/reports/ip-networking-example-partialanswers.pdf

Quiz 9 is available. It has 2 questions on internetworking concepts, and 7 questions on IP addresses. Have your brain ready for binary/decimal conversions so you can do the questions within 15 minutes.

We have two lectures remaining next week. We will talk about some other special case IP addresses (0.0.0.0, 255.255.255.255, 127.0.0.1), cover basics of transport protocols, and complete our IP networking example.

Videos for this weeks lectures will be uploaded tomorrow (Friday).

Steve

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Final Exam Preparation
by Steven Gordon - Saturday, 5 December 2015, 11:01 AM
 
Hints for the final exam are available on the course website. Also, there is a practice quiz that you can use to study for the exam.

There is no actual Quiz 10. Instead, if you make at least one attempt at all questions in the exam practice, and also have made an attempt at the Packet practice (which was required beforehand - it is no longer available), then I will give you full marks for Quiz 10.

Remember from the course website you can also see Youtube screencasts of all lectures, as well as download a PDF or image of the handwritten notes I make in class. Also, answers for the addressing and routing table example we used in the last few lectures are on the website.

A reminder: siit and ictcpeit for accessing some files.

Steve

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Assignment Marks
by Steven Gordon - Saturday, 12 December 2015, 1:16 PM
 

Assignment marks are now on Moodle (look in the 'Grades'). You can see some comments on your assignment in:

http://ict.siit.tu.ac.th/moodle/mod/resource/view.php?id=980

You can see examples of excellent reports at:

http://ict.siit.tu.ac.th/~sgordon/its323y15s1/reports/

Some general comments:

- Most groups conducted some good experiments, learning about Ethernet, Wifi and testing software like iperf and ping

- Despite the good experiments, some groups got lower scores because they did not report the results well. In particular, some groups did not give clear (or any) plots, instead including many screenshots/tables from iperf etc. The assignment instructions required you to include plots in your reports (not just in the spreadsheet) and discuss those plots.

- Some groups did not think enough about which parameter values to use, and hence the results did not clearly show the trends. (The trends should be seen in the plots, e.g. increasing the packet size shows the throughput going up).

After the midterm exam I gave some feedback on avoiding 'insane' answers. Again, in the assignment I see some answers that students did not think about, including:

- 300% efficiency (e.g. throughput much higher than data rate)

- packet size of 0.00009465 Bytes. How many bits is that?

- Listing DOS as the operating system. As much as I like to use different operating systems, I doubt anyone is using MSDOS.

- Submitting an 80 page report, where 75 of the pages are results copied from iperf

- Submitting a 140MB spreadsheet.

If you have any queries about your assignment score, I recommend you look at the example reports to see where you may have went wrong.

A final reminder that you must make a 'reasonable' attempt at the Practice 6 before the final exam. If you leave an answer blank or complete the practice in 30 seconds, then it will NOT be counted as a reasonable attempt. You must attempt all questions.

Steve

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Final Exam Results
by Steven Gordon - Friday, 18 December 2015, 1:17 PM

Final exam answers and results are on Moodle. You will also see your total score for quizzes, assignment and exams, giving the course total out of 100. However I have not yet checked the calculations are correct (especially some bonuses). I will do a final check over the weekend and then confirm the totals.

If you notice any problems or have questions about the exam let me know. I will be available in my office Monday and Tuesday.

Well done, and hope to see you all in the lab next semester.

Have a safe and happy new year!

Steve

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Steven Gordon
Re: Final Exam Results
by Steven Gordon - Friday, 18 December 2015, 3:57 PM
 
I have checked the scores in Moodle closer and I think they are correct. You should see your quiz score out of 15, assignment out of 20, and the exams out of 65. Please check the scores closely and let me know if there are concerns BEFORE Tuesday 22 Dec.

Your total score out of 100 will be used to determine your grade. I use a variety of factors to determine the grade cutoffs, e.g. class mean and average, distribution of scores, expected distribution of grades, difficulty of assessment items compared to past years. I cannot tell you your grade or the cutoffs for this year - you must wait for it to be officially announced by SIIT. However the APPROXIMATE cutoffs from the past few years were:

A 85

B+ 70

B 60

C+ 50

C 40

D+ 30

D 25

This year the cutoffs may be different.

Steve

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