TCP IP Illustrated

E same offsets and lengths assume that this time

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Unformatted text preview: gets fragmented into four pieces. Assume that fragments 1 and 2 make it to the destination, with fragments 3 and 4 being lost. The application then times out and retransmits the UDP datagram 10 seconds later and this datagram is fragmented identically to the first transmission (i.e., same offsets and lengths). Assume that this time fragments 1 and 2 are lost but fragments 3 and 4 make it to the destination. Also assume that the reassembly timer on the receiving host is 60 seconds, so when fragments 3 and 4 of the retransmission make it to the destination, fragments 1 and 2 from the first transmission have not been discarded. Can the receiver reassemble the IP datagram from the four fragments it now has? 11.6 How do you know that the fragments in Figure 11.15 really correspond to lines 5 and 6 in Figure 11.14? 11.7 After the host gemini had been up for 33 days, the netstat program showed that 129 IP datagrams out of 48 mi1110n had been dropped because of a bad header checksum, and 20 TCP segments out of 30 mi1110n had been dropped because of a bad TCP checksum. Not a single UDP datagram was dropped, however, because of a UDP checksum error, out of the approximately 18 mi1110n UDP datagrams. Give two reasons why. (Hint: See Figure 11.4.) 11.8 In our discussion of fragmentation we never said what happens to IP options in the IP header-are they copied as part of the IP header in each fragment, or left in the first fragment only? We've described the following IP options: record route (Section 7.3), time-stamp (Section 7.4), strict and loose source routing (Section 8.5). How would you expect fragmentation to handle these options? Check your answer with RFC 791. 11.9 In Figure 1.8 we said that incoming UDP datagrams are demultiplexed based on the destination UDP port number. Is that correct? file:///D|/Documents%20and%20Settings/bigini/Doc...omenet2run/tcpip/tcp-ip-illustrated/udp_user.htm (29 of 29) [12/09/2001 14.46.58] Chapter 12. Broadcasting and Multicasting Broadcasting and Multicasting 12.1 Introduction We mentioned in Chapter 1 that there...
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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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