# Stanford course

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If a voice call has missing data it makes it hard to understand the speaker. Therefore, we commonly allow time for a limited number of retransmissions before playing the sound to the listener. If the network path (in each direction) has total packetization delay of 15ms, total propagation delay of 25ms, and queuing delay varying between 0ms and 10ms, how large (in milliseconds) does the playback buffer need to be if we want to allow for one retransmission?
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75 ??
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nopes ............ what approach you used ?
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The minimum e2e delay is 40ms. The maximum time for data to show up and be played back is 50ms (1st time, but missing) + 50ms (for the sender to find out) + 50ms (for the 2nd try to reach the receiver) = 150ms. Therefore, the playback buffer needs to hold at least 150ms - 40ms = 110ms of data.

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