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Unformatted text preview: en the client and server-a control connection that is left up for
the duration of the client-server session, and a data connection that is created and deleted
The connection management used by FTP for the data connection has let us examine in
more detail the connection management requirements of TCP. We saw the interaction of
TCP's 2MSL wait state on clients that don't issue PORT commands.
FTP uses NVT ASCII from Telnet for all commands and replies across the control
connection. The default data transfer mode is often NVT ASCII also. We saw that newer
Unix clients automatically send a command to see if the server is an 8-bit byte Unix host, file:///D|/Documents%20and%20Settings/bigini/Docum.../homenet2run/tcpip/tcp-ip-illustrated/ftp_file.htm (23 of 24) [12/09/2001 14.47.49] Chapter 27. FTP: File Transfer Protocol and if so, use binary mode for all file transfers, which is more efficient.
We also showed an example of anonymous FTP, a popular form of software distribution
on the Internet.
27.1 In Figure 27.8, what would change if the client did the active open of the second data
connection instead of the server?
27.2 In the FTP client examples in this chapter we added the notation to lines such as
local: hello.c remote: hello.c
42 bytes received in 0.0037 seconds (11 Kbytes/s)
that the lines were output by the client. Without looking at the source code, how are we
certain these are not from the server? file:///D|/Documents%20and%20Settings/bigini/Docum.../homenet2run/tcpip/tcp-ip-illustrated/ftp_file.htm (24 of 24) [12/09/2001 14.47.49] Chapter 28. SMTP: Simple Mail Transfer Protocol SMTP: Simple Mail Transfer
Electronic mail (e-mail) is undoubtedly one of the most popular applications. [Caceres et
al. 1991] shows that about one-half of all TCP connections are for the Simple Mail
Transfer Protocol, SMTP. (On a byte count basis, FTP connections carry more data.)
[Paxson 1993] found that the average mail message contains around 1500 bytes of data,
but some messages contain megabytes of data...
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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.
- Spring '12