TCP IP Illustrated

Ihomenet2runtcpiptcp ip illustratedtcpfuthtm 8 of 20

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Unformatted text preview: increases: a T3 telephone line (45 Mbits/sec) wraps in 12 minutes, FDDI (100 Mbits/sec) in 5 minutes, and a gigabit network (1000 Mbits/sec) in 34 seconds. The problem here is not the bandwidth-delay product, but the bandwidth itself. In Section 24.6 we describe a way to handle this: the PAWS algorithm (protection against wrapped sequence numbers), which uses the TCP timestamp option. 4.4BSD contains all the options and algorithms that we describe in the following sections: the window scale option, the timestamp option, and the protection against wrapped sequence numbers. Numerous vendors are also starting to support these options. Gigabit Networks When networks reach gigabit speeds, things change. [Partridge 1994] covers gigabit networks in detail. Here we'll look at the differences between latency and bandwidth [Kleinrock 1992]. file:///D|/Documents%20and%20Settings/bigini/Docum...i/homenet2run/tcpip/tcp-ip-illustrated/tcp_fut.htm (8 of 20) [12/09/2001 14.47.34] Chapter 24. TCP Futures and Performance Consider sending a one million byte file across the United States, assuming a 30-ms latency. Figure 24.6 shows two scenarios, the top illustration uses a Tl telephone line (1,544,000 bits/sec) and the bottom uses a 1 gigabit/sec network. Time is shown along the x-axis, with the sender on the left and the receiver on the right, and capacity on the yaxis. The shaded area in both pictures is the one million bytes to send. Figure 24.6 Sending a 1-Mbyte file across networks with a 30-ms latency. Figure 24.6 shows the status of both networks after 30 ms. With both networks the first bit of data reaches the other end after 30 ms (the latency), but with the T1 network the capacity of the pipe is only 5,790 bytes, so 994,210 bytes are still at the sender, waiting to be sent. The capacity of the gigabit network, however, is 3,750,000 bytes, so the entire file uses just over 25% of the pipe. The last bit of the file reaches the receiver 8 ms after the first bit. The total time to transfer the file across t...
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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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