Unformatted text preview: to Selected Exercises the Ethernet (normally 5-10 ms), plus the routing time on sun and bsdi. So yes, the
observed times do appear correct.
19.3 In Figure 19.6 the time difference between segments 6 and 9 is 533 ms. In Figure
19.8 the time difference between segments 8 and 12 is 272 ms. (We measured the time
for the F2 key, not the Fl key, since the first echo of the Fl key was lost in the second
figure.) Chapter 20
20.1 Byte number 0 is the SYN and byte number 8193 is the FIN. The SYN and FIN each
occupy 1 byte in the sequence number space.
20.2 The first application write causes the first segment to be sent with the PUSH flag.
Since BSD/386 always uses slow start, it waits for the first ACK before sending any more
data. During this time the next three application writes occur, and the sending TCP
buffers the data to send. The next three segments do not contain the PUSH flag since
there is more data in the buffer to send. Eventually slow start catches up with the
application writes and every application write causes a segment to be sent, and since that
segment is the last one in the buffer, the PUSH flag is set.
20.3 Solving the bandwidth-delay equation for the capacity, it is 1,920 bytes for the first
case, and 2,062 for the satellite case. It appears that the receiving TCP is only advertising
a window of 2,048 bytes.
A window greater than 16,000 bytes should be able to saturate the satellite link.
20.4 No, because TCP can repacketize data after a timeout, as we'll see in Section 21.11.
20.5 Segment 15 is a window update sent automatically by the TCP module as a result of
the application reading data, which causes the window to open. This is similar to segment
9 in that figure. Segment 16, however, is a result of the application closing its end of the
20.6 This can cause the sender to inject packets into the network at a rate faster than the
network can really handle. This is called ACK compression or ACK smashing [Mogul
1993, Sec. 15.8.13]. This reference indicates that ACK compress...
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- Spring '12