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Lectures notes for 2010 - KTH

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ICMP Source Quench Error<br />

Since UDP has no flow control, a node could receive datagrams faster than it can<br />

process them. In this situation the host may send an ICMP source quench.<br />

Note: “may be generated” - it is not required to generate this error<br />

Stevens (Vol. 1, pp. 160-161) gives the example of sending 100 1024-byte<br />

datagrams from a machine on an ethernet via a router and SLIP line to another<br />

machine:<br />

destination<br />

source<br />

SLIP<br />

link<br />

Figure 1: simplified from Stevens, Vol. 1, inside cover<br />

• SLIP link is ~1000 times slower than the ethernet<br />

• 26 datagrams are transmitted, then a source quench is sent <strong>for</strong> each<br />

successive datagram<br />

Maguire Building a UDP packet from scratch 4: 27 of 74<br />

maguire@kth.se <strong>2010</strong>.03.21 Internetworking/Internetteknik

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