TCP IP Illustrated

4729 chapter 22 tcp persist timer exercises 221 in

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Unformatted text preview: on of the connection. 22.4 Summary TCP's persist timer is set by one end of a connection when it has data to send, but has been stopped because the other end has advertised a zero-sized window. The sender keeps probing the closed window using a retransmission interval similar to what we saw in Chapter 21. This probing of the closed window continues indefinitely. When we ran an example to see the persist timer we also encountered TCP's avoidance of the silly window syndrome. This is to prevent TCP from advertising small windows or from sending small segments. In our example we saw avoidance of the silly window syndrome by both the sender and the receiver. file:///D|/Documents%20and%20Settings/bigini/Docu...homenet2run/tcpip/tcp-ip-illustrated/tcp_pers.htm (10 of 11) [12/09/2001 14.47.29] Chapter 22. TCP Persist Timer Exercises 22.1 In Figure 22.3 notice the times of all the acknowledgments (segments 5, 7, 9, 11, 13, 15, and 17): 0.170, 5.170, 10.170, 15.170, 15.370, 20.170, and 25.170. Also notice the time differences between receiving the data and sending the ACK: 164.5, 18.5, 18.7, 18.8, 198.3, 18.5, and 19.1 ms. Explain what's probably going on. 22.2 In Figure 22.3 at time 25.174 a window of 767 is advertised, but 768 bytes are available in the receive buffer. Why the difference of 1 byte? file:///D|/Documents%20and%20Settings/bigini/Docu...homenet2run/tcpip/tcp-ip-illustrated/tcp_pers.htm (11 of 11) [12/09/2001 14.47.29] Chapter 23. TCP Keepalive Timer TCP Keepalive Timer 23.1 Introduction Many newcomers to TCP/IP are surprised to learn that no data whatsoever flows across an idle TCP connection. That is, if neither process at the ends of a TCP connection is sending data to the other, nothing is exchanged between the two TCP modules. There is no polling, for example, as you might find with other networking protocols. This means we can start a client process that establishes a TCP connection with a server, and walk away for hours, days, weeks or months, and the connection remai...
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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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