TCP IP Illustrated

The client sends 1 byte at a time to the server and

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Unformatted text preview: sword, what we type is sent to the server as cleartext. Each character of the password that we type is sent as is. Anyone who can read the raw network packets can read the characters of our password. Newer implementations of the Rlogin client, such as 4.4BSD, first try to use Kerberos, which avoids sending cleartext passwords across the network. This requires a compatible server that also supports Kerberos. ([Curry 1992] describes Kerberos in more detail.) 4. The server normally sends a request to the client asking for the terminal's window size (described later). The client sends 1 byte at a time to the server and all echoing is done by the server. We saw this in Section 19.2. Also, the Nagle algorithm is normally enabled (Section 19.4), causing multiple input bytes to be sent as a single TCP segment across slower networks. The operation is simple: everything typed by the user is sent to the server, and everything sent by the server to the client is displayed on the terminal. Additional commands exist that can be sent from the client to the server and from the server to the client. Let's first describe the scenarios that require these commands. Flow Control By default, flow control is done by the Rlogin client. The client recognizes the ASCII STOP and START characters (Control-S and Control-Q) typed by the user, and stops or starts the terminal output. If this isn't done, each time we type Control-S to stop the terminal output, the Control-S character is sent across the network to the server, and the server stops writing to the network-but up to a window's worth of output may have been already written by the server and will be displayed before the output is stopped. Hundreds or thousands of bytes of data will scroll down the screen before the output stops. Figure 26.3 shows this scenario. Figure 26.3 Rlogin connection if server performs STOP/START processing. To an interactive user this delayed response to the Control-S character is bad. file:///D|/Documents%20and%20Sett...
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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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