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25 Cards in this Set
- Front
- Back
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How is CUBIC related to BIC-TCP? |
CUBIC replaces the concave and convex window growth portions with a cubic function. |
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What is CUBIC's Congestion Epoch? |
A congestion event where TCP undergoes fast recovery. Window growth becomes independent of RTT |
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How does CUBIC perform floating point calculations? |
It uses the Newton-Raphson method. (A mathematical method for approximating the roots of a function) |
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What is window clamping? |
Window increments can be "clamped" to a maximum rate. CUBIC drops this feature since it is stable enough not to force a maximum. |
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Why is Scalable TCP scalable? |
It was designed to make recovery time from loss events constant regardless of window size. |
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What is highspeed TCP? |
It is an adjustable AIMD algorithm where the increase and decrease factors are adjusted by a convex function. |
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What type of function is the window growth function of HTCP? |
It is a quadratic function of uppercase delta, which stands for elapsed time. |
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What makes HTCP unique? |
The decrease factor is adjusted to be proportional to queue size. |
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What is TCP-Vegas? |
It measures lowercase delta, the difference between expected throughput and actual throughput based on round trip delays. When delta is less than a low threshold alpha, it increases the sending rate. When delta is greater than a high threshold beta, it decreases sending rate. |
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How does FAST increase its sending rate? |
It estimates query delay of a path based on RTT. It aggressively decreases if it's way low below a set threshold, but slowly decreases if close to the threshold. |
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What are the advantages of TCP-Westwood? |
It estimates bandwidth and sets its slow start estimate to it. It is good over wireless networks with frequent channel loss so the congestion window isn't reduced unnecessarily. |
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How does TCP-Illinois adjust its AIMD factors? |
It uses queuing delay to determine them instantaneously. |
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How does TCP-Hybla ensure fairness among flows with different RTTs? |
It scales the window increment rule. |
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What does TCP-Veno do with packet loss? |
It reduces congestion window by 20% as opposed to 50% |
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How does BIC-TCP reduce window size? |
1. Reduce window size by factor, beta. 2. Set W_max to window size before reduction. 3. Set W_min to window size after reduction. 4. Perform binary search for window size network can currently handle. Increase maximum is s_max. Smallest allowed window size is s_min. |
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What is BIC-TCP max probing? |
If during binary search, window size is found to be larger than the max, probing occurs. It uses normal AIMD to find it. |
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What problems with BIC-TCP does CUBIC address? |
BIC-TCP's growth function can be too aggressive for TCP. The different phases (binary search, max probing, s_max, s_min) can be complex to implement and analyze. |
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What is CUBIC's window growth function? |
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If the current window size (cwnd) is less than the window size standard TCP would reach in time t, how does CUBIC respond? |
CUBIC would be in TCP mode. |
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If CUBIC is not in TCP mode and cwnd > W_max, what region is CUBIC in? |
The concave region |
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If CUBIC is not in TCP mode and cwnd < W_max, what region is CUBIC in? |
The convex region |
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What is the average window size of AIMD? |
alpha = additive increase rate beta = multiplicative decrease rate |
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What is CUBIC fast convergence? |
The previous W_max is recorded as W_last_max. If W_last_max > W_current_man, W_current_max is reduced further, allowing time for new flow to catch up with window size. |
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What is the average window size of CUBIC? |
alpha = additive increase rate beta = multiplicative decrease rate |
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What types of networks does standard TCP perform well in? |
1. Networks with small bandwidth-delay product (BDP) 2. Networks with short RTT, but not necessarily small BDP |
