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Kuhn-Tucker sufficiency

We would like to know if we have tu understand the Kuhn-Tucker in exercise 4.2.

Thank you
Posted by Andréa Buttu at 13:28
Comments (2)
Section 5, Routing

In some exercises of section 5, routing, it is often spoken about CBR. I looked in my slides but I didn't manage to find it. Could you please explain me what it is?


Posted by Céline Di Venuto at 9:53
Comments (1)
Application Layer

There is something I don't understand in exercise 3.5

Question 3)Assume one cache is removed, but the cached objects remains where they are and the configured cache update the request. What is the fraction of cached object that are in the wrong cache? What if you add one cache? The solution is 1/2-1/N and 1/2 but I don't understand how this is computed.

Question 4) If we use robust hash routing, I understand that if we remove one cache there is no objects that are in the wrong cache. But I don't understand how do you compute the number of objects that are in the wrong cache if you add one cache.

Thanks a lot for your answers

Posted by Céline Di Venuto at 8:59
Comments (5)
Duration of final exam
for your information: the final exam of saturday 11/03/06 will last 3 hours.
Posted by Gianluca Rizzo at 10:42
Course Material for the final

Are all the lecture slides available on the web-page of the course, included in the course material for the final exam? For example, mixed.pdf ? mpls.pdf? security.pdf? mcast.pdf? all slides of ls.pdf?

Thanks a bunch!

Posted by Muhammad Shuaib Siddiqui at 16:58
Comments (2)
Midterm & TPs grades

Would it be possible for you to put the resume of all the Midterm & TPs grades on the website (as I lost some of them, shame on me...)?

Thank you
Posted by Baptiste Dubuis at 11:39
Comments (1)
A (useless?) advice for final exam
Hi everibody,
I would like to say something about "assumptions" on your exam (even from what I saw on the midterm):

It is true that you can make some assumptions while trying to answer to the questions in the exam,
but this should be done when there is actually the necessity to do it,
that is when the formulation of the problem really leaves free space for making some assumptions (e.g.: missing values of some parameters, some unspecified features...).

So it can happen to you to assume something only because you did not understand well the problem, or you simply did not read it attentively, or because you did not find the reasoning that can provide you with the missing information (the most frequent situation).
In these cases, making assumptions can cost you many points...

To sum up, make a careful use of assumptions!
Posted by Gianluca Rizzo at 11:14
Old exams

I have some questions regarding the old exams that are on the web site

For exam 2002-2003:
Question 3, proportional fairness.
We are supposed to maximize the function f(x1) =ln(x1)+2ln(x2)+4ln(x3).
Furthermore we know that x2=(c-x1)/2 and x3=(c-x1)/4, because the channels should be full. So f(x1)=ln(x1)+2ln((c-x1)/2)+4ln((c-x1)/4).
If I take the derivative and equals to 0 I got :
<=> 1/x1-20/(c-x1)=0
<=> x1=c/21
In the solution it is x1=c/7. I don't see my mistake

For exam 2003-2004
For problem 1 proportional fairness, I understand how to solve it graphically but I'm not sure about the analytical solution.
I have to maximize f(x1)=ln(x1)+ln(x2) and I know x1+x2=7, x1<=2, x2<=6 then
f(x1) = ln(x1)+ln(7-x1). I take the derivative and equals to 0.
<=>1/X1=1/(7-X1) <=> 7-x1=x1 <=> 2x1 = 7 <=> x1=3.5 => x2=3.5.
As x2 should not be more than 2 I put x2=2 then by "water filling" 7=x1+x2 => x1 = 5
Is this solution correct?


Posted by Céline Di Venuto at 15:21
Comments (1)
Some questions regarding midterm exam

I have questions regarding the mid-term exam solution

Problem 1: Why does pc33 do a dns request? Doesn't it know that batz is the server for daytime?

Problem 2:
Point 2) for destination why is next hop, for destination why is next hop, for all destinations that are not on-link, why is there no next hop?

Point 3) Why is it only possible that R2 and R3 are default routers for M and not all the routers? In case R3 is the router, why and how does redirection happens


Posted by Céline Di Venuto at 11:56
Comments (2)
two more office-hours sessions
in BC 229, on March 7th and 9th, from 16:00 to 17:00.

(the exam is on March 11th)

teaching assistants
Posted by Slavisa Sarafijanovic at 16:47
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