Transport Layer - Freie Universität Berlin
Transport Layer - Freie Universität Berlin
Transport Layer - Freie Universität Berlin
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Timer Management with TCP<br />
● TCP uses several timers<br />
● Retransmission timer (for repeating a transmission)<br />
● But: how to select the timer value?<br />
● Probability density of the time till an acknowledgement arrives:<br />
Probability<br />
Wahrscheinlichkeit<br />
0.3<br />
0.2<br />
0.1<br />
0<br />
10 20 30 40 50<br />
Round Roundtrip-Time Trip Time [ms]<br />
Data Link <strong>Layer</strong><br />
T<br />
Probability<br />
Wahrscheinlichkeit<br />
0.3<br />
0.2<br />
0.1<br />
0<br />
10 20 30 40 50<br />
Round<br />
Roundtrip-Time<br />
Trip Time<br />
[ms]<br />
[ms]<br />
<strong>Transport</strong> <strong>Layer</strong><br />
T1 T2 Problem on the<br />
transport layer:<br />
Univ.-Prof. Dr.-Ing. Jochen H. Schiller ▪ cst.mi.fu-berlin.de ▪ Telematics ▪ Chapter 8: <strong>Transport</strong> <strong>Layer</strong><br />
● T 1 is too small:<br />
too many<br />
retransmissions<br />
● T 2 is too large:<br />
inefficient for<br />
actual packet loss<br />
8.61
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