Midterm Exam Clarifications


Question: I was wondering for question 3, it says Describe why slow start can have a negative effect on the performance of HTTP are we supposed to assume that this HTTP refers to nonpersistent HTTP without pipelining?
Answer: Yes, Describe why slow start can have a negative effect on the performance of non-persistent HTTP without pipelining and explain how persistent HTTP with pipelining diminishes the impact of slow start. (though -- hint -- the pipelining part is not as important as the persistent part).

All references to figures from the book apply to the second edition of the text. A copy of the second edition is on reserve in the library if you need it.

Question: In question 5, can B send a message to A without C "hearing"? Also, is it possible for A and B to send messages at the same time?
Answer: Because we have not yet discussed broadcast channels in any great detail, you can make whatever assumptions you would like. But, make sure to state your assumptions.

Question: In question 7, if I end up with a window size that is X and a half segments, can I round up or down?
Answer: Yes. However, state your assumptions (i.e., make it clear that you are rounding).

Question: This is with refence to Q6 in exam. Since we always start with packet number 0, so the last packet to be sent would be packet 5? When you mention packet 4, it is actually the fifth packet in the sequence, isn't it?
Answer: I would start with 1 and assume the sender has packets numbered [1, 2, 3, 4, 5, 6] to send. If you want to start with packet 0 (or have already done the question assuming the sequence starts with packet 0), that's okay. Just state your assumption.

Question 3 Hint: Think about how/why downloading one web page is different from downloading another web page.


Sami Rollins