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Lectures notes for 2010 - KTH

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No error control<br />

Since UDP has no error control, the sender has to take responsibility <strong>for</strong> sending<br />

the datagram again if this datagram must be delivered.<br />

But how does the send know if a datagram was successfully delivered?<br />

• Unless the receiver sends a reply (or does some action due to<br />

receiving a given datagram) the sender will not know! [loss]<br />

• Note that without some additional mechanism - the sender doesn’t<br />

know if the datagram was delivered multiple times! [duplicates]<br />

If you want reliability you have to build your own protocol on top of UDP to<br />

achieve it. This includes deciding on your own retransmission scheme, timeouts,<br />

etc.<br />

Maguire No error control 4: 29 of 74<br />

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

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