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Table Of Contents  The TCP/IP Guide
 9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)
      9  TCP/IP Key Applications and Application Protocols
           9  TCP/IP File and Message Transfer Applications and Protocols (FTP, TFTP, Electronic Mail, USENET, HTTP/WWW, Gopher)
                9  TCP/IP General File Transfer Protocols (FTP and TFTP)
                     9  Trivial File Transfer Protocol (TFTP)

Previous Topic/Section
Trivial File Transfer Protocol (TFTP)
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Pages in Current Topic/Section
12
3
Next Page
TFTP General Operation, Connection Establishment and Client/Server Communication
Next Topic/Section

TFTP Overview, History and Standards
(Page 3 of 3)

Overview of TFTP Operation

Communication and messaging in TFTP is very different than it is in FTP because of the different transport layer protocols used by each. FTP makes use of TCP's rich functionality, including its stream data orientation, to allow it to send bytes of data directly over the FTP data connection. TCP also takes care of reliable delivery of data for FTP, ensuring files are received correctly. In contrast, since TFTP uses UDP, it must package data into individual messages for both protocol control and data communication. TFTP must also take care of timing transmissions to detect lost datagrams and then retransmitting as needed.

TFTP servers allow connections from TFTP clients to perform file send and receive operations. Many hosts that run FTP servers will also run a separate TFTP server module as well. TFTP users initiate connections by starting a TFTP client program, which generally uses a command-line interface similar to that of many FTP clients; the main difference is the much smaller number of commands in TFTP.

Key Concept: For situations where the full File Transfer Protocol (FTP) is either unnecessary or impractical, the simpler Trivial File Transfer Protocol (TFTP) was developed. TFTP is like FTP in that it is used for general file transfer between a client and server device, but it is stripped down in its capabilities. Rather than including a full command set and using TCP for communication like FTP, TFTP can only be used for reading or writing a single file, and uses the fast but unreliable UDP for transport. It is often preferred in situations where small files must be transferred quickly and simply, such as bootstrapping diskless workstations.


TFTP Option Extension and TFTP Options

The basic operation of TFTP has not changed since RFC 1350 was published, but a new feature was added to the protocol in 1995. RFC 1782, TFTP Option Extension, defines a mechanism by which a TFTP client and TFTP server can negotiate certain parameters that will control a file transfer prior to the transfer commencing. This allows more flexibility in how TFTP is used, adding a slight amount of complexity to TFTP, but not a great deal.

The option extension is backwards-compatible with regular TFTP, and is only used if both server and client support it. Two subsequent RFCs define the actual options that can be negotiated: RFC 1783, TFTP Blocksize Option and RFC 1784, TFTP Timeout Interval and Transfer Size Options. This set of three RFCs (1782, 1783 and 1784) was replaced in 1998 by updated versions in RFCs 2347, 2348 and 2349.


Previous Topic/Section
Trivial File Transfer Protocol (TFTP)
Previous Page
Pages in Current Topic/Section
12
3
Next Page
TFTP General Operation, Connection Establishment and Client/Server Communication
Next Topic/Section

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Version 3.0 - Version Date: September 20, 2005

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