TCP IP Illustrated

172 why do all the internet protocols that weve

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Unformatted text preview: tes and verifies a mandatory end-to-end checksum. TCP is used by many of the popular applications, such as Telnet, Rlogin, FTP, and electronic mail (SMTP). Exercises 17.1 We've covered the following packet formats, each of which has a checksum in its corresponding header: IP, ICMP, IGMP, UDP, and TCP. For each one, describe what portion of an IP datagram the checksum covers and whether the checksum is mandatory or optional. 17.2 Why do all the Internet protocols that we've discussed (IP, ICMP, IGMP, UDP, TCP) quietly discard a packet that arrives with a checksum error? 17.3 TCP provides a byte-stream service where record boundaries are not maintained between the sender and receiver. How can applications provide their own record markers? 17.4 Why are the source and destination port numbers at the beginning of the TCP header? 17.5 Why does the TCP header have a header length field while the UDP header (Figure 11.2) does not? file:///D|/Documents%20and%20Settings/bigini/Docum.../homenet2run/tcpip/tcp-ip-illustrated/tcp_tran.htm (6 of 6) [12/09/2001 14.47.10] Chapter 18. TCP Connection Establishment and Termination TCP Connection Establishment and Termination 18.1 Introduction TCP is a connection-oriented protocol. Before either end can send data to the other, a connection must be established between them. In this chapter we take a detailed look at how a TCP connection is established and later terminated. This establishment of a connection between the two ends differs from a connectionless protocol such as UDP. We saw in Chapter 11 that with UDP one end just sends a datagram to the other end, without any preliminary handshaking. 18.2 Connection Establishment and Termination To see what happens when a TCP connection is established and then terminated, we type the following command on the system svr4: svr4 % telnet bsdi discard Trying ... Connected to bsdi. Escape character is '^]'. type Control, right bracket to talk to the Telnet client ^] terminate the connection tel...
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