Calculations regarding slow-start strategy (TCP congestion control)

In summary, the conversation discussed the slow-start strategy in TCP congestion control and how it was taught in a high level without going into parameters and calculations. The speaker mentioned receiving a bonus on a test due to the unfairness of the material, but still had concerns about being asked about similar concepts in the final test. They also mentioned being familiar with terms such as MSS, RTT, and parameters, but not knowing how to use them or how the initial size of the threshold affects them. The speaker expressed confusion and lack of knowledge in approaching this type of problem.
  • #1
imso3k
1
0
Homework Statement
So I have this lecturer in Computer Networking who teaches material in a way higher level than the questions she gives us, we had this questions in a mini-test she did and I really don't know how to calculate & get the results she gave to those questions.

1.
A server sends an infinite size file to the client
Given that a slow-start-threshold is equal to infinity
In addition, given that the RTT is equal to 5.25 * (the delivery time of one packet)
How many times the server is canceled (ie starting from sending the first packet How many times the server waits and sends nothing) due to the slow-start phase

Answer : 3.

2.
A client requests a file from the server. The following data is given:
16000B file (we will neglect the header extension)
MSS = 1000B
Bandwidth = 8 Kbps
RTT = 1sec
Assuming that the initial size of the slow-start-threshold is infinite, how long (in units of sec) from the start of communication will the file reach its destination?

Answer : 19

3.
A client requests a file from the server. The following data is given:
18000B file (we will neglect the header extension)
MSS = 1000B
Bandwidth = 8 Kbps
RTT = 1sec
Assuming that the initial size of the slow-start-threshold is 1000B, how long (in units of sec) from the start of communication will the file connection reach its destination?
Answer : 21

And the last one :
The following values are known
RTT = 600sec
Bandwidth = 1 Mbps
MSS = 2000bit
How many packets can be sent in a row until we get the first ACK message?

Answer : 300k
Relevant Equations
If I had them, I wouldn't be asking for help.
Like I said, I was taught during the TCP congestion control lecture what is the slow-start strategy, how it works & looks in a very high level, we never saw anything related to parameters and calculations, and after the test she gave the entire class a bonus of 35 points because she knew it wasn't fair, but still I know we will be asked during our final test something similar, and yes I know what MSS, RTT and the parameters stand for, but what to do with them or how the initial size of the threshold affects them? I really don't.
So I literally have no clue since I was asked to do something I wasn't taught how to (not even an example, nothing).
 
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  • #2
imso3k said:
Relevant Equations:: If I had them, I wouldn't be asking for help.
There aren't any equations that will give you the answer, the way to answer this sort of question (and the way to tackle most problems in IT) is simply to write down what happens.

For instance with problem 2: what happens in the first 2 seconds?
 
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Likes berkeman

1. What is the slow-start strategy in TCP congestion control?

The slow-start strategy is a mechanism used in TCP (Transmission Control Protocol) to manage congestion on a network. It is designed to gradually increase the amount of data sent by a sender and monitor the network for any signs of congestion.

2. How does the slow-start strategy work?

The slow-start strategy works by initially sending a small number of packets and then doubling the number of packets sent after each successful transmission. This allows the sender to gradually increase the amount of data sent and monitor the network for congestion. If congestion is detected, the sender will reduce the amount of data sent to prevent further congestion.

3. What is the purpose of the slow-start threshold in TCP congestion control?

The slow-start threshold is a value that determines when the slow-start strategy should switch to the congestion avoidance phase. It is set to a specific value by the sender and is used to prevent the network from becoming congested by limiting the amount of data sent during the slow-start phase.

4. How does the slow-start threshold affect the performance of TCP congestion control?

The slow-start threshold can affect the performance of TCP congestion control by limiting the amount of data sent during the slow-start phase. If the threshold is set too low, it may take longer for the sender to reach the optimal transmission rate, resulting in slower data transfer. If the threshold is set too high, it may lead to congestion on the network.

5. Are there any drawbacks to using the slow-start strategy in TCP congestion control?

One potential drawback of the slow-start strategy is that it may take longer for the sender to reach the optimal transmission rate, resulting in slower data transfer. Additionally, if the network experiences sudden bursts of traffic, the slow-start strategy may not be able to effectively manage the congestion, leading to packet loss and decreased performance.

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