Uniform Resource Identifier (URI) Scheme and Applicability Statement for the Trivial File Transfer Protocol (TFTP)
RFC - Informational
(October 2003; No errata)
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RFC 3617 (Informational)
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Network Working Group E. Lear
Request for Comments: 3617 Cisco Systems
Category: Informational October 2003
Uniform Resource Identifier (URI) Scheme and
Applicability Statement for the
Trivial File Transfer Protocol (TFTP)
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright (C) The Internet Society (2003). All Rights Reserved.
The Trivial File Transfer Protocol (TFTP) is a very simple TRIVIAL
protocol that has been in use on the Internet for quite a long time.
While this document discourages its continued use, largely due to
security concerns, we do define a Uniform Resource Identifier (URI)
scheme, as well as discuss the protocol's applicability.
The Trivial File Transfer Protocol (TFTP) has been around for quite
some time. Its common uses are to initially configure devices or to
load new versions of operating system code . As devices begin to
adopt use of Uniform Resource Identifiers (URIs) and Uniform Resource
Locators (URLs), for completeness we specify a way to reference files
that is still quite common. Use of a URI is a convenient way to
indicate underlying mechanism, server name or address, and file name.
WHILE WE DEFINE THE TFTP URI TYPE, WE STRONGLY RECOMMEND AGAINST THE
CONTINUED USE OF TFTP, FOR REASONS LISTED IN SECTION 5 (amongst
others). The definition of a URI merely allows tools that currently
use protocols such as TFTP to have a standard name space and
structure where one can understand the process used to resolve that
name. Indeed it is hoped that the definition of this URI will ease
transition to modern file transfer mechanisms.
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RFC 3617 URI Scheme for TFTP October 2003
2. Syntax of a TFTP URI
A TFTP URI has the following ABNF syntax :
tftpURI = "tftp://" host "/" file [ mode ]
mode = ";" "mode=" ( "netascii" / "octet" )
file = *( unreserved / escaped )
host = <as specified by RFC 2732 >
unreserved = <as specified in RFC 2396 >
escaped = <as specified in RFC 2396>
A TFTP URI specifies a file that is to be found or placed on a TFTP
server. The "mode" option is an option indicating how the file is to
be transferred. If left unspecified, the mode is assumed to be
"octet". A third "mail" mode was deprecated at the time RFC 1350 was
adopted, and is not specified.
2.1. Encoding Rules
Aside from syntax as described above, the TFTP protocol does not
specify length limits to either file names or file sizes. In the
case of file names, they may contain any character so long as those
characters are properly escaped as described above.
3. Semantics and Operations
As previously stated the TFTP URI is a reference to a file. The
allowed operations on a TFTP URI are read and write. When a TFTP URI
is read the underlying mechanisms retrieve the named file via the
TFTP protocol from the specified host with the optionally specified
mode. When a TFTP URI is written the underlying mechanisms transmit
a file via TFTP to a specified server to either the specified file
using the optionally specified mode. No other operations are
Note that it is not possible to retrieve file size information prior
to retrieval, nor is it possible to determine file existence or
permissions prior to transfer. Files transferred may or may not
arrive intact, as there is no guarantee of reliability or even
completeness. See the TFTP standard for more details. For more
robust file transfer, consider using either FTP or HTTP [5, 6].
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RFC 3617 URI Scheme for TFTP October 2003
This example references file "myconfigurationfile" on server
"example.com" and requests that the transfer occur in netascii mode.
This file references file "mystartupfile" on server "example.com".
The transfer should occur in octet mode, since no other mode was
5. Security Considerations and Concerns about TFTP's use
Use of TFTP has been historically limited to those devices where a
more full protocol stack is impractical due to either memory or CPU
constraints. While this still may be the case with a toaster, it is
unlikely to be the case for even the simplest piece of network
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