Unformatted text preview: uting table entry on sun that directs datagrams for 18.104.22.168 to the
router bsdi. (Recall our discussion of this routing table in Section 9.2.)
Our host slip is still reachable across the Internet, because we saw in Section 10.4 that
the routers gateway and netb just sent any datagram destined for the subnet 140.252.13
to the router sun. Our router sun knows what to do with these datagrams from the
routing table entry we made in step 3 above. What we have created is a host with complete
Internet connectivity, but without a valid domain name. That is, a pointer query for the IP
address 22.214.171.124 will fail.
We now use anonymous FTP to a server that we know requires a valid domain name:
slip % ftp ftp.uu.net
Connected to ftp.uu.net.
220 ftp.UU.NET FTP server (Version 2.0WU(13) Fri Apr 9
20:44:32 EDT 1993) ready.
Name (ftp.uu.net:rstevens): anonymous file:///D|/Documents%20and%20Settings/bigini/Docum.../homenet2run/tcpip/tcp-ip-illustrated/ftp_file.htm (22 of 24) [12/09/2001 14.47.49] Chapter 27. FTP: File Transfer Protocol 530- Sorry, we're unable to map your IP address
126.96.36.199 to a hostname
530- in the DNS. This is probably because your nameserver
does not have a
530- PTR record for your address in its tables, or because
530- nameservers are not registered. We refuse service to
530- names we cannot resolve. If this is simply because
your nameserver is
530- hard to reach or slow to respond then try again in a
minute or so, and
530- perhaps our nameserver will have your hostname in its
cache by then.
530- If not, try reaching us from a host that is in the DNS
or have your
530- system administrator fix your servers.
530 User anonymous access denied..
Remote system type is UNIX.
Using binary mode to transfer files.
The error reply from the server is self-explanatory. 27.4 Summary
FTP is the Internet standard for file transfer. Unlike most other TCP applications, it uses
two TCP connections betwe...
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- Spring '12
- Encapsulation, Transmission Control Protocol, Internet Protocol Suite, User Datagram Protocol, TCP/IP protocol suite