ECN question + TCP Cubic multiplicative decrease+ Old quizzes not yet available

ECN question + TCP Cubic multiplicative decrease+ Old quizzes not yet available

by Christoph Andreas Ungricht -
Number of replies: 1

Hi guys

I have three questions:

Is it possible to get the old tests for quiz 6?

When both TCP congestion control and ECN are used, does TCP still go into fast recovery when a loss is detected by fast retransmit or it only goes into fast recovery when the ECE flag is received?

Is the multiplicative decrease in TCP Cubic 0.7 in both fast recovery and slow start?

Thanks in advanced!

Best,

Chris

In reply to Christoph Andreas Ungricht

Re: ECN question + TCP Cubic multiplicative decrease+ Old quizzes not yet available

by Ludovic Thomas -

Hi, 

"When both TCP congestion control and ECN are used, does TCP still go into fast recovery when a loss is detected by fast retransmit or it only goes into fast recovery when the ECE flag is received?"

Yes, fast recovery will be triggered either after fast re-transmit (triple dupack) or after ECN detection. Both mechanisms will be active.

"Is the multiplicative decrease in TCP Cubic 0.7 in both fast recovery and slow start?"

Fast recovery: new congestion window gets 0.7*old congestion window

After timeout: new slow start threshold gets 0.7*old congestion window but you go back to slow start (so the new congestion window goes back to the slow start inital value).

Ludovic