Grading scheme

Problem 2

Question 1

• 1/2 point per correct row (correct source, destination, and purpose)
• 1/4 point if the port numbers are wrong

Question 2(a)

• 1 point for DNS, connection setup, HTTP request, and HTTP response propagation delay
• 3 points for correct transmission delays (-1 if student computed transmission delay for DNS, connection setup, and/or HTTP request)

Question 2(b)

Question 3(b)

• 2 points for correctly computing how long it took the web server to send all the logo responses
• 5 points for correctly computing when the web server starts sending the logo responses

Problem 3

Question 1

• 1.5 point for SEQ and ACKs (-0.5 for wrong duplicate ACKs)
• 0.5 point for correctly increasing the congestion window (1, 1, 2, 4, 8)
• 1 point for correctly showing the timeout
• 1 point for setting congestion window to 1 and ssthreshold to 4 after the timeout
• 1 point for state of congestion control algorithm
• 0.5 for starting with slow start
• 0.5 for staying in slow start after receiving ACK 16

Notes 

• If a student set the timeout to SEQ 9 instead of SEQ 8, consider it correct as it has low impact on the continuation of diagram
• If a student increases the congestion window right after receiving the SYN ACK and not the ACK of first data segment, deduct 1 (0.5 for cwnd increase and 0.5 for SEQ&ACKS) and continue the rest normally.
• If a student increases the congestion window on a duplicate ACK deduct 1.5 (0.5 for cwnd increase and 1 for SEQ&ACKS) and continue the rest normally.

Question 2

• 2 points for computing time correctly (7.5 RTT)
  • Deduct 0.5 if the student computed 8RTT instead of 7.5RTT
• 1 point for saying 17bytes / 7.5RTT

Question 3