| 6.033 - Computer System Engineering | Handout 8 - February 26, 2002 |
The medium access control protocol described in this paper has come to be referred to as CSMA/CD (Carrier Sense Multiple Access with Collision Detection ). Discuss one advantage and one disadvantage of this distributed control scheme compared to a centralized control scheme. The disadvantages of CSMA/CD can be addressed in a number of different ways, some of which are mentioned in the paper. Discuss a technique for addressing the problems of CSMA/CD. Does this technique for addressing the shortcomings of CSMA/CD introduce any new problems?The paper can be found in your reading packet, and is also available online.
Review session for the first quiz will be in Rm 34-101 from 7-9pm.
Design Project 1 is assigned today. Look for the Design Project on
the web.
No Reading or Hands-on assignments today. Study for Quiz 1.
Design Project 1 is due in two weeks: Thursday, March 21.
Quiz 1 will be held from 2-3pm on Friday, March 8, 2002. The quiz
will cover all the material up to and including the March 5th
recitation (R8). The quiz will be open book. That means you can bring
along any printed or written materials that you think might be useful.
Calculators are allowed, though not necessary. 6.033 quizzes typically
begin with half a dozen independent questions that focus on material
in the readings followed by one or two longer, multi-part questions
that deal with concepts of computer systems covered in lecture. The
quiz will be, at least in part, multiple choice. The quiz will be held
concurrently in three different rooms: 34-101, 4-270 and 4-370.
See the chart below to determine which location you should go to for the quiz.
You can find old quiz questions to practice on in the Problems
and Solutions section following chapter 9 of the class notes. Be
sure to check out both the independent problems and the problem
sets that pertain to the current topics. Note that each problem
in that section is followed by a code that tells what year it
was given and which quiz it appeared on. Although there has been
a little rearrangement of material over the years, you should be
able to answer most questions that came from an old quiz 1.
There will be a quiz review from 7-9pm, Wednesday, March 6th in room
34-101. During this time we will go over an outline of the covered
subjects and explain a few questions from the Problems and Solutions
section of the class notes.
The quiz is being held in a regularly scheduled class hour. The
date was announced at the beginning of the term, so you should not
have problems with scheduling conflicts. If, nevertheless, you have
managed to create a conflict, contact Prof. Kaashoek at
kaashoek@mit.edu as soon as possible to resolve the problem.
Read Hari Balakrishnan's "Wide-Area Unicast Routing." (Reading #10),
and do Hands-on #4 on Internet
Routes. The paper is in your reading package, and it is also available
online.
Yes, we will be having a lecture on Friday this week. A special lecture will be given by the writing program on the subject of writing up your design project. They will present the recommended format for the writeup and give you some tips about how to write a technical paper like the ones we have been reading in class. If you are planning on using your report to pass the Phase 2 requirement, you might find this lecture helpful.
For Quiz 1: Friday, March 8
Last Name Location A-F 4-270 G-L 4-370 M-Z 34-101 System aphorism of the week
"A complex system that works is invariably found to have evolved from a simple
system that works" (J. Gall, Systemantics).
For Lecture: Monday, March 11
Read Chapter 4, section D of the class notes.
For Recitation: Tuesday, March 12
For Lecture: Wednesday, March 13
Read Chapter 4, section E in the class notes.
For Recitation: Thursday, March 14
There are three separate tasks for today.
For fun, think about the following question while reading the paper
(You do not need to hand in an answer.):
A file transfer done using the EFTP protocol described in the
Ethernet paper will encounter two error-checking mechanisms. The first
is a CRC calculated on the data for purposes of catching errors in the
Ether (i.e., errors that occur in transit), and is performed in the
Ethernet hardware. The second is another checksum provided as a backup
to the (hardware) CRC, as well as for catching errors that occur at
the host or destination (but still within the network layer). This
check is done as part of the EFTP protocol. Note that the second
checksum does not have to be computed, though some value must always
be sent. What is the use of these error-checking mechanisms on the
basis of the End-to-End argument? Consider the usefulness of each
individual checksum as well as the combination of the two. Do you
need both checksums?
For Lecture: Friday, March 15
System aphorisms of the week
A system takes longer to debug than you expect, even when you take this
fact into account.
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