1. Logistics:
   * Assignment: 31 out of 56 have started.
   * No class next Wed; instead, will record and post lecture.
   * About half of you have still not participated.
   * Assignment 2 will be out this week; it will be harder (3 weeks).

2. Why is finding the BDP hard?
   * Clarify RTT vs. RTT_{min}.
   * C varies (WiFi/cellular)
   * RTT varies (path changes)
   * Multiple flows.

3. What happens if you set W to the incorrect value?
   * Underutilization
   * Queueing delay
   * Retransmissions
   --> The last two are especially likely and quite problematic: congestion collapse

4. Congestion collapse
   * Load increases, but utility decreases
   * Similar to tragedy of commons, thrashing, people in a crowded room.
   * One example: infinite buffers, user utility=throughput/delay
   * Another example: retransmission-based congestion collapse
   * Historical notes