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Homework

There are four homework assignments, each homework assignment is worth 100 points. The homework assignments are part of your preparation for the exam, therefore you have to collect at least 300 points for the four assignments in order to be able to sit for the exam. Individual homework assignments can be graded with any integer number between 0 and 100.

The homework solutions should be submitted individually (not in groups). You are not allowed to copy your assignment from another student or from another source. See code of honour regulation 3. Violation of this rule will be considered as cheating.

There is a submission deadline for every homework assignment (see below). You will have to submit your solution on the web using the homework submission system. You will be asked the course username/password to access the front page. From the front page there is a link to the KTH authentication system, through which you can authenticate yourself using your KTH username/password. Help is available on the front page via a link before login, and in the status bar after login.

Please report problems to György Dán via e-mail.

After the submission deadline we publish the solutions of the assignment on the course home page (below), and you will be able to see the solution submitted by a fellow student in the homework submission system, which you will have to grade within 48 hours. You will have to submit your evaluation of your fellow student's homework through the homework submission system. You will only obtain points for your submitted assignment if you submit the evaluation for your fellow student.

In order to ensure that everyone can read the submitted documents, we ask you to use PDF format and to write your solutions and review in English. To keep the server load managable, the file size is limited to 500KB.
Please name your documents "lastname_firstname_hwX.pdf", where X is the homework number. Please avoid using accented letters in the file name.
(Hint: OpenOffice exports to PDF, an add-in is available for newer versions of MS Office (Microsoft Save as PDF or XPS), but there is also a freeware converter (doPDF). There are also other freeware converters available on the web, e.g., Text2PDF for text to PDF conversion.)

  • Homework 1 IP [assignment]
    - submission deadline 17:00 CET on 2015.Sept.09.
    - review deadline 17:00 CET on 2015.Sept.11.
  • Homework 2 IP, ARP, Routing, ICMP, TCP [assignment]
    - submission deadline 17:00 CET on 2015.Sept.23.
    - review deadline 17:00 CET on 2015.Sept.25.
  • Homework 3 Application layer and autoconfiguration [assignment]
    - submission deadline 17:00 CET on 2015.Sep. 30.
    - review deadline 17:00 CET on 2015.Oct. 2.
  • Homework 4 Autoconfiguration, network address translation, etc [assignment]
  • - submission deadline 17:00 CET on 2015.Oct. 8.
    - review deadline 17:00 CET on 2015.Oct. 12.
  • Homework 5 (make-up) All topics [assignment]
    - submission deadline 17:00 CET on 2015.Oct. 14.
    - review deadline 17:00 CET on 2015.Oct. 16.

György Dán skapade sidan 30 juni 2015

kommenterade 31 augusti 2015

When will the homework be available?

Anmäl missbruk
Lärare kommenterade 31 augusti 2015

It should be available 1 week before the submission deadline.

Anmäl missbruk
kommenterade 2 september 2015

Hej, 

Where can we find the subject for Homework 1?
Thanks !

Anmäl missbruk
Lärare kommenterade 2 september 2015

You can now find a link to the assignment above.

Anmäl missbruk
kommenterade 7 september 2015

Are we supposed to put our name in the submitted solution as well (that is, apart from the name of the document), or keep it hidden to avoid bias for the student grading the solution?

Anmäl missbruk
Lärare kommenterade 8 september 2015

Yes, please put your name in the solution. The grader will be able to see your name, nonetheless, you will not be able to see in the system the name of the one who graded your solution.

Anmäl missbruk
kommenterade 8 september 2015

I'm having trouble logging in to the homework submission system. The above link immediately prompts a username/password popup dialog. There is no front page, and especially no link to a KTH login page. Please advise.

Anmäl missbruk
Lärare kommenterade 8 september 2015

Please use the username/password provided at the first lecture in the popup. You will then be able to see the front page.

Anmäl missbruk
kommenterade 8 september 2015

I was unable to make the first lecture due to scheduling issues. The slides from said lecture are also locked behind (presumably) the same login wall. How should I gain access?

A side note - surely I can't be the only participant who missed the first lecture. Is there a system in place to make sure these people get the access they need?

Anmäl missbruk
Lärare kommenterade 8 september 2015

Of course, send me an email.

Anmäl missbruk
kommenterade 9 september 2015

Regarding

MS Office can export to PDF using the freeware doPDF PDF converter.

I'm using Word 11 for Mac and there is a built-in option to save to PDF from the print window. Maybe there's a similar option for the windows version? Would mean one less installed program. :)

Anmäl missbruk
Lärare kommenterade 9 september 2015

Thanks for the hint.

Anmäl missbruk
kommenterade 9 september 2015

Hej

Jag har försökt i en halv timme att skicka in min homework men det går inte att logga in.Jag skickar den via mejlet till dig.

MVH Sara

Anmäl missbruk
Lärare kommenterade 9 september 2015

Hi, I cannot upload the file for you, but I can provide you the username/password.

Anmäl missbruk
kommenterade 9 september 2015

Hej,

What is the process of evaluation of peer's solution?

For example if somebody put 262 144 hosts instead of 262 142 hosts, shall I give him some points or go straight to zero? Feels very subjective for me, because he has some knowledge, but forgot to subtract 2 addresses...

Sounds very subjective to me. Thanks for some recommendations

Anmäl missbruk
Lärare kommenterade 9 september 2015

Grading is not easy...you should try to judge what fraction of the question was answered correctly, and if there is some fundamental error. If there is some explanation, it can help in case the numerical result is bogus or inaccurate. I do not think this should be worth zero.

Anmäl missbruk
kommenterade 9 september 2015

Hey,

Should we add sticky notes onto the fellow student's solution (of .pdf format) in order to comment on how much points he/she gets and why it worths the given points for each question? Or what would be the preferred way to correct/grade the fellow student's solution? Thanks in advance.

Anmäl missbruk
Lärare kommenterade 10 september 2015

Hi, yes, adding notes to the PDF is a good solution. Creating a new file is good too.

Anmäl missbruk
kommenterade 10 september 2015

I'm concerned about this grading system - like previous writers, I think it seems fuzzy how a partially incorrect answer should be scored, bordering on completely arbitrary.

For a fictional but plausible example: A largely correct solution to task 2 which does not assign a specific subnet to the H network, in which it might be assumed that the lower-tier routers can handle those routing rules. Would that remove 1 point, or 5 points, or 15? What if this assumption is instead explicitly stated - should that give a full score, since all units are known to be connectable, or still lose some points as a (potentially) sub-optimal solution? 

The complete lack of scoring guidance makes it very difficult to confidently assign a score to my partner's essay, and likewise reduces my confidence in that my own will be graded fairly. Would it be possible to get some guidance on this matter?

Anmäl missbruk
kommenterade 10 september 2015

Especially since, in Sean's example above, one could also consider it not to be an error.

The task explicitly states that you're supposed to assign a sub-block of the network to networks A-E. It doesn't say that you have to specify the blocks for F-H. As long as they aggregate properly, I think it should give full points, but since the solutions mention the blocks for F-H, I think people might subtract points for not mentioning them.

Anmäl missbruk
kommenterade 10 september 2015

Hej,

I just tried to add my review in the homework submission system and I can't upload it " No documents checked out to you ". Is there a problem or something with the submission system? 

Anmäl missbruk
kommenterade 10 september 2015

I've just uploaded  my review in the homework submission  but the problem is that when I open it I can not see my comment !!!!!!!!!!! What should I do?

Anmäl missbruk
Lärare kommenterade 10 september 2015

@Pierre: Please "check out" the original file, then you can "check in" the reviewed file.

Anmäl missbruk
Lärare kommenterade 10 september 2015

@Maliheh: "check out" the file again, and verify that you can see the comments. Then "check in" a version on which you can see the comments.

Anmäl missbruk
kommenterade 10 september 2015

Perfect working fine now! Tack !

Anmäl missbruk
kommenterade 10 september 2015

Tack.

Anmäl missbruk
Lärare kommenterade 10 september 2015

@Erik & Sean: Grading is indeed not an easy task, one needs to carefully assess what fraction of the answer is correct, whether there is some fundamental mistake, etc. We do not provide detailed instructions on how to grade, but hope that you can make an informed judgement based on your understanding of the problem and of the solutions. This is an important part of the learning process, as you will have to understand the material fairly well to be able to assess the value of a partially correct solution.

Anmäl missbruk
Lärare kommenterade 11 september 2015

About grading: with peer reviewing there will always be differences in the grading, we are fully aware of that. Should you end up in the situation that you don't have enough points to take the exam, and you feel that you haven't received a fair grading, you should contact the teachers and we will review the grading. We will only do it in those cases, though. Keep in mind that the purpose of the home assignments is that you should learn, not to prevent students from taking the exam.

I should add that in practice, this has rarely been a problem.

Anmäl missbruk
kommenterade 17 september 2015

In homework two, question three, part c, we are asked to name the interfaces on which messages are sent. But the topographical sketch doesn't seem to supply these. Are we supposed to make up interfaces or can we just use the IP-addresses?

Furthermore, when building routing tables, are we to use made up interfaces or can we use IP-adresses here as well?

Anmäl missbruk
Lärare kommenterade 17 september 2015

You can make up interface names, just make sure you give a definition. You can also use North, South, East, West.

Anmäl missbruk
Lärare kommenterade 17 september 2015

Re 2nd part of your question: the figure contains the IP addresses (.1, .2,...).

Anmäl missbruk
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kommenterade 24 september 2015

In the solutions for homework two it says for the very last exercise that "Missing the transmission time (2 ms) is a mistake." What does the transmission time refer to?

Also, in my hand-in I used an MSS of 536 since that's the default TCP value - is it always assumed that the path MTU is used for MSS? I don't think that's obvious at all. The problem is that it propagates to the rest of the TCP questions and I, although I'm biased, don't think that it should result in a total deduction of all points in the follow-up questions, even if the answers are essentially wrong. What's your stand on this? 

Anmäl missbruk
kommenterade 24 september 2015

There is a problem with the submission system, when somebody used accented letters in the name of the file. After the check-in of review in the system there follows the error message

"Error: wrong file! Please check in the right file."

This happens even when the correct (the same) name is used as in the original name of the pdf. How can I fix this in order to being able to upload the review?

Anmäl missbruk
kommenterade 24 september 2015

I have a question about the grading on the solution for question 3c, Routing. If the student has written that A send one message each to the neighbours B, D and E and in that case sent the same vectors to both B and D, and another one to E (with the infinity number). According to the solution the same message with the infinity number is sent to D and E. I have a hard time grading this solution since I am not sure how "big" this mistake is.

Anmäl missbruk
kommenterade 24 september 2015

And also, when will the next homework be out? It is due next wednesday.

Anmäl missbruk
Lärare kommenterade 24 september 2015

@Matej: Yes, accented letters are complicated, as they may have different codes on different systems. This is why we asked "Please avoid using accented letters in the file name.". pls send me a mail.

Anmäl missbruk
Lärare kommenterade 24 september 2015

@Erika: According to RFC 2453 routers would use multicast on multicast/broadcast capable networks, like Ethernet, but you can configure most RIPv2 routers to use unicast.

Anmäl missbruk
Lärare kommenterade 24 september 2015

@Fredrik: Transmission time is the time need to transmit a packet (send the bits).

If the path MTU is known then you would set the MSS based on that, as it allows higher throughput.

Anmäl missbruk
kommenterade 24 september 2015

Is the transmission time something that should've been defined in the question or something that we were to figure out by ourselves somehow (e.g. by calculating it from the given data)?

Sure, that makes a lot of sense. Is it the de jure way, i.e. is it always done like that? Can I read up on it in the course book or somewhere online?  Sorry for being so inquisitive. :)

Anmäl missbruk
kommenterade 24 september 2015

Hello.

I was wondering when the next homework will be uploaded. I was planning on doing it today or at the latest tomorrow as I have problems finding time for it afterwards. So I was hoping you would upload it soon.

Can you tell me when it will be uploaded so that I can plan better?

Thanks!

Anmäl missbruk
Lärare kommenterade 24 september 2015

You could calculate the transmission time based on the given data.

The book does not say much about setting the MSS, other than based on the IPv4 reqs. There is quite some info available online though (e.g., Cisco has many pages dealing with MSS and PMTUD).

Anmäl missbruk
Lärare kommenterade 24 september 2015

We plan to open homework number three in an hour or two. Sorry for the delay.

Anmäl missbruk
Lärare kommenterade 24 september 2015

Homework 3 is now available.

Anmäl missbruk
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kommenterade 28 september 2015 
(Homework 3) 
Exactly why do we need to study header fields not discussed in the
textbook for question 3f? Do you seek any specific header
fields attached in the reply/request, or whats the deal here? :)

2. (minor question). In question 3.e, shall we assume that the
tcp connection must be terminated properly using 3/4 way terminating
handshakes before the page is fully loaded?
Anmäl missbruk
Lärare kommenterade 28 september 2015

Jack,

Question 3f: Yes, there are header fields that are relevant for the proxy. They shouldn't be too hard to spot. The book's coverage of proxy servers is a bit simplistic, so we want you to first study the basics of a proxy in the book, and then use the Internet to learn a little more about about proxies in practice. 

Question 3e: You can ignore the time it takes to terminate the connection. The grading guidelines (which you of course haven't seen yet) say that either way is fine. 

Anmäl missbruk
kommenterade 28 september 2015

I thought those fields are related to client-side caching by the browser rather than by the proxy server. Is that a misunderstanding?

Anmäl missbruk
Lärare kommenterade 28 september 2015

Fredrik,

Without being too specific, I wouldn't say that cache-related fields concern the client only. On the contrary, cache directives are intended for controlling intermediate caches between client and server. 

Anmäl missbruk
kommenterade 28 september 2015

Peter,

Okay, thanks! I will re-evaluate my answers and try to be more thorough.

Anmäl missbruk
kommenterade 29 september 2015

Regarding question 3(d) in Homework 3 - Should we solve it using the sequential approach or the parallel approach ?

Anmäl missbruk
Lärare kommenterade 29 september 2015

Surya,

For 3d in homework 3, any legal behavior is fine. As long as you can argue that your solution is valid according to HTTP, given the information in the problem, the solution is acceptable.

Anmäl missbruk
Lärare kommenterade 30 september 2015

There was a question for clarification of 1b in homework 3. The question is straight-forward: you should describe the communication in the problem using the vocabulary "connection-oriented", "concurrent", "connectionless", and "iterative".

 

Anmäl missbruk
kommenterade 30 september 2015

Is the solution for homework 3 incorrect for question 3a? It says the answer is https:/www.opera.org:9821/claypool . I'm not sure where that port number comes from.

Anmäl missbruk
Lärare kommenterade 30 september 2015

Erik,

The correct port number for hw 3, question 3a, should be 1935. I have updated the solutions. 

Anmäl missbruk
kommenterade 1 oktober 2015

Hej!

I'm grading my partner's homework number 3 and I seek consultation regarding question 3.a

The student answered shortly, http://www.opera.org/claypool. Since the student missed the port in the URL, any points should be deducted for this? 

Anmäl missbruk
kommenterade 1 oktober 2015

In addition to Ahmad's question, should you deduct points for a missing "http://" ? Since both http and https are accepted answers and http is usually implied when writing urls.

Anmäl missbruk
Lärare kommenterade 1 oktober 2015

About grading for hw3, question 3a: Deduct one point for every missing or incorrect component of the URL. 

Anmäl missbruk
kommenterade 1 oktober 2015

It seems that the person grading my submission of HW3 skipped the second half and by doing so he/she gives me (probably) fewer points than what I should have been given.

Will I have to do the make-up assignment because of this?

Anmäl missbruk
Lärare kommenterade 1 oktober 2015

Fabin, 

Too bad that your entire submission wasn't graded.

The usual policy applies: After the 4th homework, if you don't have enough points and feel that you haven't received a fair grading, you can contact the teachers and we will look into it.

Anmäl missbruk
kommenterade 2 oktober 2015

I seem to be unable to download the solution pdf. I get the error message ERR_TOO_MANY_REDIRECTS.

Anmäl missbruk
Lärare kommenterade 2 oktober 2015

Martin,

By mistake I responded as a new post, it should have been as a comment to the Homework page. I submit it again, so it ends up in the right place.

If you get too many redirects, there are a few things you could try:

- Clear the cache in the browser

- Open a private or incognito browser window

- Erase your browser cookies (or install a fresh copy of some other browser)

Anmäl missbruk
kommenterade 2 oktober 2015

Thank you for the response.

Anmäl missbruk
kommenterade 2 oktober 2015

About solution for question 3d, The client would know about the 5 images only after it receives the main page. So would it be possible to send requests for the images along with the request for the main page when requesting in parallel (as in the solution)? Shouldn't the requests for the images be send only after the main page is received?

Anmäl missbruk
kommenterade 2 oktober 2015

Quarter past 5 and still no grade for my homework, what's the procedure about that?

Anmäl missbruk
Lärare kommenterade 2 oktober 2015

If your fellow student fails to grade your submission then we do it instead. You will see your points as soon as it is done.

Anmäl missbruk
Lärare kommenterade 2 oktober 2015

Vishnu,

You are absolutely right! Getting the main page takes an RTT, so 5 RTTs total. Solutions updated.

As a side note, HTTP/2 introduces "Server Push" to avoid this extra RTT.

Anmäl missbruk
kommenterade 2 oktober 2015

Hai 

Are we able to claim for the points for 3d if our solution is correct according to updated solutions.

Thank you.

Lakshmi.

Anmäl missbruk
kommenterade 5 oktober 2015

Is the 4th homework submission 8th of October or is it a misprint? Usually it has been every Wednesday.

Anmäl missbruk
kommenterade 5 oktober 2015

No. They added an extra day since the lecture on Wednesday is related to the homework, so we will get an extra day to hand it in. 

Anmäl missbruk
kommenterade 6 oktober 2015

The last lecture is actually on Thursday 13-15 according to schedule. So it seems rather unrealistic to have the homework deadline two hours later. Are we supposed to only have these two hours for doing the part of the homework related to the last lecture (Firewalls and NAT)? Surely something must be wrong?

Anmäl missbruk
Lärare kommenterade 7 oktober 2015

Daniel, 

We explained at the introduction that it might happen at a few occasions that there is little time between a lecture and the homework deadline.

The slides from the lecture will be available very soon, so you can study them in advance. They should give some guidance for solving the home assignment.

Anmäl missbruk
Lärare kommenterade 7 oktober 2015

Hi,

the lecture notes for tomorrow's lecture on IP gateways are now available.

Best regards,
Markus

Anmäl missbruk
kommenterade 7 oktober 2015

Hi,

I am just wondering when will the Make-up Homework be posted since it is already due (a little) less than a week from now.

Thanks,

Sharbel

Anmäl missbruk
Lärare kommenterade 8 oktober 2015

Homework 5 is now available. It is an opportunity to make up if you did not get sufficiently many points on the first four homeworks.  

Anmäl missbruk
kommenterade 8 oktober 2015

Are the points on homework 5 added to the total score, or is it judged independently?

Anmäl missbruk
Lärare kommenterade 8 oktober 2015

They are added to the total.

Anmäl missbruk
kommenterade 9 oktober 2015

Why the score of my 4th homework bocame 77, it's wrong.

Some guy's all four homeworks score bocame 77. What's going on?

Anmäl missbruk
Lärare kommenterade 9 oktober 2015

It should be correct now, please let me know if not. All others' have been restored to the original values as well.

Anmäl missbruk
kommenterade 10 oktober 2015

Solution for homework 4 contains the answer for a question 2d) while the homework doesn't even have a d) question on 2. In addition, the "solution" for 2d) is literally the same as 2b). Is this just a mistake that we should ignore?

Anmäl missbruk
Lärare kommenterade 11 oktober 2015

Hi,

solution 2b) was duplicated by mistake and ended up also as solution 2d) (so you can just ignore it). I have uploaded a new version without the duplicate now.

Regards,
Markus

Anmäl missbruk
kommenterade 11 oktober 2015

The make-up lab task 4 starts at c) and ends at e), I guess that's an error?

Anmäl missbruk
kommenterade 12 oktober 2015

In Homework 5, Question 2)a

The datagram is delivered to Host H3 or H4 ? as it's mentioned before that it should be to host H4 

Anmäl missbruk
Lärare kommenterade 12 oktober 2015

Unfortunately there were some small errors in homework 5. We have uploaded a corrected version. 

The errors were in questions 2 and 4. The corrections are clearly marked so you can easily see what has changed.

Anmäl missbruk
kommenterade 13 oktober 2015

As Ehab points out question 2a) still claims that a datagram is delivered to H3, even though you switch the recipient to H4 in 2b), is it an error?

Anmäl missbruk
Lärare kommenterade 13 oktober 2015

It should be H4 in 2a as well. There is only 1 datagram being delivered (from H5 to H4).

Anmäl missbruk
kommenterade 13 oktober 2015

If we already have 300 points, the 5th one is optional right ? 

Anmäl missbruk
Lärare kommenterade 13 oktober 2015

Yes.

Anmäl missbruk
kommenterade 13 oktober 2015

thank you 

Anmäl missbruk
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