TCP IP Illustrated

We can see this with the following experiment we

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Unformatted text preview: at about the same time from different clients are automatically queued by UDP. The received UDP datagrams are passed to the application (when it asks for the next one) in the order they were received. It is possible, however, for this queue to overflow, causing the kernel's UDP module to discard incoming datagrams. We can see this with the following experiment. We start our sock program on the host bsdi running as a UDP server: bsdi % sock -s -u -v -E -R256 -r256 -P30 6666 from 140.252.13.33, to 140.252.13.63: from sun to broad cast 1111111111 address from 140.252.13.34, to 140.252.13.35: from svr4, to unicast 4444444444444 address We specify the following flags: -s to run as a server, -u for UDP, -v to print the client's IP address, and -E to print the destination IP address (which is supported by this system). Additionally we set the UDP receive buffer for this port to 256 bytes (-R), along with the size of each application read (-r). The flag -P30 tells it to pause for 30 seconds after creating the UDP port, before reading the first datagram. This gives us time to start the clients on two other hosts, send some datagrams, and see how the receive queueing works. Once the server is started, and is in its 30-second pause, we start one client on the host sun and send three datagrams: sun % sock -u -v 140.252.13.63 6666 to Ethernet broadcast address connected on 140.252.13.33.1252 to 140.252.13.63.6666 1111111111 11 bytes of data (with newline) 222222222 10 bytes of data (with newline) 33333333333 12 bytes of data (with newline) The destination address is the broadcast address (140.252.13.63). We also start a second client on the host svr4 and send another three datagrams: svr4 % sock -u -v bsdi 6666 connected on 0.0.0.0.1042 to 140.252.13.35.6666 4444444444444 14 bytes of data (with newline) 555555555555555 16 bytes of data (with newline) 66666666 9 bytes of data (with newline) The first thing we notice in the interactive output shown earlier on bsdi is that only two datagram...
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This test prep was uploaded on 04/04/2014 for the course ECE EL5373 taught by Professor Guoyang during the Spring '12 term at NYU Poly.

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