TCP in depth: windows and congestion
The receiver's window and the sliding window, the congestion window and its threshold, slow start, congestion avoidance and the reaction to the two kinds of loss (Tahoe, Reno).
- 28 cards
- 6 topics
- Free
The outline, topic by topic
Each topic is weighted the way the exam weighs it.
- Concepts
- Questions
- Sort and link
- The numbers
- The curves
- Scenarios
A few cards from the deck
Flow control: what is it?
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The mechanism by which the receiver announces, in every segment, the space it has left in memory so that the sender does not overwhelm it.
It protects the machine at the other end, not the network. The Window field in the header carries this advertised window; at 0, the sender stops and probes now and then.
Congestion window of 1 at round 0, threshold of 16, no loss. What is the window at round 5?
- 17
- 32
- 20
- 16
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17
Slow start: 1, 2, 4, 8, 16 at rounds 0 to 4, the threshold is reached. Then congestion avoidance: +1 per round, so 17 at round 5. 32 would forget that growth becomes linear.
The sender never has more unacknowledged bytes than the … of the congestion window and the window … by the receiver.
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The sender never has more unacknowledged bytes than the minimum of the congestion window and the window advertised by the receiver.
Two independent brakes: the receiver (flow control) and the network (congestion control). The tighter of the two rules.