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TCP/IP Tutorial and Technical Overview - IBM Redbooks

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Figure 14-6 shows an example of a common security negotiation using these<br />

comm<strong>and</strong>s.<br />

FTP client<br />

<br />

AUTH TLS<br />

234 Security environment established<br />

- ready for negotiations<br />

<br />

PBSZ 0<br />

200 PBSZ=0 is the protection buffer size<br />

PROT P<br />

200 Data connection set to private<br />

USER userid<br />

331 Send password please<br />

PASS password<br />

230 userid is logged on. Working directory<br />

is /tmp<br />

Figure 14-6 An example of FTP TLS processing<br />

Most FTP client <strong>and</strong> server implementations provide configuration options to<br />

automate the security negotiation using the previous comm<strong>and</strong>s. This makes the<br />

implementation of secure FTP easier for the user because users do not need to<br />

underst<strong>and</strong> or implement the details of the security during the FTP session itself,<br />

<strong>and</strong> only are prompted for a user ID <strong>and</strong> possibly a password.<br />

14.2 Trivial File Transfer Protocol (TFTP)<br />

FTP server<br />

The Trivial File Transfer Protocol (TFTP) is a st<strong>and</strong>ard protocol with STD number<br />

33. Its status is elective <strong>and</strong> it is described in RFC 1350 – The TFTP Protocol<br />

(Revision 2). Updates to TFTP are in the RFCs: 1785, 2347, 2348, <strong>and</strong> 2349.<br />

Chapter 14. File-related protocols 529

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