TCP IP Illustrated

A longer transfer was run taking about 15 minutes and

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Unformatted text preview: ong with the first segment of data in Exercise 18.9.) This generates the ICMP error in line 4 and we see that the router bsdi generates the newer ICMP error containing the MTU of the outgoing interface. It appears that before this error makes it back to solaris, the FIN is sent (line 5). Since slip never received the 512 bytes of data discarded by the router bsdi, it is not expecting this sequence number (513), so it responds in line 6 with the expected sequence number (1). At this time the ICMP error has made it back to solaris and it retransmits the 512 bytes of data in two 256-byte segments (lines 7 and 9). Both are sent with the DF bit set, file:///D|/Documents%20and%20Settings/bigini/Docum...i/homenet2run/tcpip/tcp-ip-illustrated/tcp_fut.htm (4 of 20) [12/09/2001 14.47.33] Chapter 24. TCP Futures and Performance since there could be another router beyond bsdi with a smaller MTU. A longer transfer was run (taking about 15 minutes) and after moving from the 512-byte initial segment to 256-byte segments, solaris never tried the higher segment size again. Big Packets or Small Packets? Conventional wisdom says that bigger packets are better [Mogul 1993, Sec. 15.2.8] because sending fewer big packets "costs less" than sending more smaller packets. (This assumes the packets are not large enough to cause fragmentation, since that introduces another set of problems.) The reduced cost is that associated with the network (packet header overhead), routers (routing decisions), and hosts (protocol processing and device interrupts). Not everyone agrees with this [Bellovin 1993]. Consider the following example. We send 8192 bytes through four routers, each connected with a Tl telephone line (1,544,000 bits/sec). First we use two 4096-byte packets, as shown in Figure 24.3. Figure 24.3 Sending two 4096-byte packets through four routers. The basic problem is that routers are store-and-forward devices. They normally receive the entire input packet, validate the IP header including the IP checksum,...
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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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