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105 bytes received in 4.1 seconds (0.83 Kbytes/s)
sun % uncompress stevens.tcpipivl.errata.Z
sun % more stevens.tcpipivl.errata
The uncompress is because many files available for anonymous FTP are compressed file:///D|/Documents%20and%20Settings/bigini/Docum.../homenet2run/tcpip/tcp-ip-illustrated/ftp_file.htm (21 of 24) [12/09/2001 14.47.49] Chapter 27. FTP: File Transfer Protocol using the Unix compress(l) program, resulting in a file extension of .Z. These files
must be transferred using the binary file type, not the ASCII file type.
Anonymous FTP from an Unknown IP Address
We can tie together some features of routing and the Domain Name System using
anonymous FTP. In Section 14.5 we talked about pointer queries in the DNS - taking an
IP address and returning the hostname. Unfortunately not all system administrators set up
their name servers correctly with regard to pointer queries. They often add new hosts to
the file required for name-to-address mapping, but forget to add them to the file for
address-to-name mapping. We often see this with traceroute, when it prints an IP
address instead of a hostname.
Some anonymous FTP servers require that the client have a valid domain name. This
allows the server to log the domain name of the host that's doing the transfer. Since the
only client identification the server receives in the IP datagram from the client is the IP
address of the client, the server can call the DNS to do a pointer query, and obtain the
domain name of the client. If the name server responsible for the client host is not set up
correctly, this pointer query can fail. To see this error we'll do the following steps.
1. Change the IP address of our host slip (see the figure on the inside front cover)
to 188.8.131.52. This is a valid IP address for the author's subnet, but not entered
into the name server for the noao.edu domain.
2. Change the destination IP address of the SLIP link on bsdi to 184.108.40.206.
3. Add a ro...
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- Spring '12