Second term

And we are back!

Next Friday is our first lecture and the required reading are sections 4.1 and 4.2.1 of Kurose's. See you there.

Please note that semester marks have been published now (green column).

Update: By popular request first second term lecture has been moved to Wednesday February 8th. It will be held in classroom 1G 1.6 from 16:00 to 18:00.

Exercise 6

Some of you shown some concern about exercise number six of the exam. As a result I have reviewed the marking and a few of you have got your mark risen a bit. The main problem is twofold: whether you increase the congestion window by two or one after each acknowledge during slow start and what is the policy during congestion avoidance.

You can have a look at the proposed solution trace. And the policies on each case are as follows:

• Threshold: Same value on both sides of 3 MSS during all the exercise.
• Slow Start: each ACK increases CongWin value by one MSS.
• Congestion Avoidance: If during one RTT CongWin bytes are ACKed then CongWin is increased by one MSS (CongWin remains unchanged otherwise). 

However, those that may have chosen to increase by two MSS per ACK (given the fact delayed acknowledgments are used) during slow start also scored ok. Those that used a fractional increase of CongWin during Congestion Avoidance (ie. to increase MSS/CongWin per ACK) can also have a correct answer.

Interesting Java book

My friend Oscar Belmonte who is a professor at Jaume I university has published this interesting Java book you can download for free.