Question

Which of the following statements best describe why WRED is useful for networks where the majority of traffic uses TCP?

a) TCP packets that are not dropped must be retransmitted
b) TCP packets must have priority over UDP packets
c) TCP packets cannot arrive out of sequence
d) TCP sources reduce traffic flow when congestion occurs

Answer 1

WRED is useful in TCP-based networks because it encourages TCP flows to reduce their transmission rate in response to early packet drops, thus preventing sudden congestion and ensuring smoother traffic flow.

correct answer is: d) TCP sources reduce traffic flow when congestion occurs

Step-by-step explanation:

The question asks why Weighted Random Early Detection (WRED) is useful in networks predominately using TCP. The correct answer is:

d) TCP sources reduce traffic flow when congestion occurs

Because TCP has congestion control mechanisms, it reacts to packet loss by reducing its transmission rate. WRED takes advantage of this by randomly dropping packets before a queue becomes full, avoiding sudden congestion and global synchronization, which can occur when many TCP flows reduce their rates simultaneously. By dropping packets early and at different rates depending on queue occupancy, WRED can smooth overall traffic flow and maximize network throughput.

However, statement (a) is incorrect; dropped TCP packets have to be retransmitted, which could add to congestion, not improve it. Statement (b) refers to priority settings that are unrelated to WRED's functionality, and statement (c) is incorrect because TCP can rearrange out-of-order packets to preserve data sequence.