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Updates:
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Keywords: TFTP-Opt, trivial file transfer protocol, booting, client, server, extension
Network Working Group G. Malkin
Request for Commments: 2349 Bay Networks
Updates: 1350 A. Harkin
Obsoletes: 1784 Hewlett Packard Co.
Category: Standards Track May 1998
TFTP Timeout Interval and Transfer Size Options
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (1998). All Rights Reserved.
Abstract
The Trivial File Transfer Protocol [1] is a simple, lock-step, file
transfer protocol which allows a client to get or put a file onto a
remote host.
This document describes two TFTP options. The first allows the client
and server to negotiate the Timeout Interval. The second allows the
side receiving the file to determine the ultimate size of the
transfer before it begins. The TFTP Option Extension mechanism is
described in [2].
Timeout Interval Option Specification
The TFTP Read Request or Write Request packet is modified to include
the timeout option as follows:
+-------+---~~---+---+---~~---+---+---~~---+---+---~~---+---+
| opc |filename| 0 | mode | 0 | timeout| 0 | #secs | 0 |
+-------+---~~---+---+---~~---+---+---~~---+---+---~~---+---+
opc
The opcode field contains either a 1, for Read Requests, or 2,
for Write Requests, as defined in [1].
Malkin & Harkin Standards Track [Page 1]
RFC 2349 TFTP Timeout Interval and Transfer Size Options May 1998
filename
The name of the file to be read or written, as defined in [1].
This is a NULL-terminated field.
mode
The mode of the file transfer: "netascii", "octet", or "mail",
as defined in [1]. This is a NULL-terminated field.
timeout
The Timeout Interval option, "timeout" (case in-sensitive).
This is a NULL-terminated field.
#secs
The number of seconds to wait before retransmitting, specified
in ASCII. Valid values range between "1" and "255" seconds,
inclusive. This is a NULL-terminated field.
For example:
+-------+--------+---+--------+---+--------+---+-------+---+
| 1 | foobar | 0 | octet | 0 | timeout| 0 | 1 | 0 |
+-------+--------+---+--------+---+--------+---+-------+---+
is a Read Request, for the file named "foobar", in octet (binary)
transfer mode, with a timeout interval of 1 second.
If the server is willing to accept the timeout option, it sends an
Option Acknowledgment (OACK) to the client. The specified timeout
value must match the value specified by the client.
Transfer Size Option Specification
The TFTP Read Request or Write Request packet is modified to include
the tsize option as follows:
+-------+---~~---+---+---~~---+---+---~~---+---+---~~---+---+
| opc |filename| 0 | mode | 0 | tsize | 0 | size | 0 |
+-------+---~~---+---+---~~---+---+---~~---+---+---~~---+---+
opc
The opcode field contains either a 1, for Read Requests, or 2,
for Write Requests, as defined in [1].
filename
The name of the file to be read or written, as defined in [1].
This is a NULL-terminated field.
Malkin & Harkin Standards Track [Page 2]
RFC 2349 TFTP Timeout Interval and Transfer Size Options May 1998
mode
The mode of the file transfer: "netascii", "octet", or "mail",
as defined in [1]. This is a NULL-terminated field.
tsize
The Transfer Size option, "tsize" (case in-sensitive). This is
a NULL-terminated field.
size
The size of the file to be transfered. This is a NULL-
terminated field.
For example:
+-------+--------+---+--------+---+--------+---+--------+---+
| 2 | foobar | 0 | octet | 0 | tsize | 0 | 673312 | 0 |
+-------+--------+---+--------+---+--------+---+--------+---+
is a Write Request, with the 673312-octet file named "foobar", in
octet (binary) transfer mode.
In Read Request packets, a size of "0" is specified in the request
and the size of the file, in octets, is returned in the OACK. If the
file is too large for the client to handle, it may abort the transfer
with an Error packet (error code 3). In Write Request packets, the
size of the file, in octets, is specified in the request and echoed
back in the OACK. If the file is too large for the server to handle,
it may abort the transfer with an Error packet (error code 3).
Security Considerations
The basic TFTP protocol has no security mechanism. This is why it
has no rename, delete, or file overwrite capabilities. This document
does not add any security to TFTP; however, the specified extensions
do not add any additional security risks.
References
[1] Sollins, K., "The TFTP Protocol (Revision 2)", STD 33, RFC 1350,
October 92.
[2] Malkin, G., and A. Harkin, "TFTP Option Extension", RFC 2347,
May 1998.
Malkin & Harkin Standards Track [Page 3]
RFC 2349 TFTP Timeout Interval and Transfer Size Options May 1998
Authors' Addresses
Gary Scott Malkin
Bay Networks
8 Federal Street
Billerica, MA 01821
Phone: (978) 916-4237
EMail: gmalkin@baynetworks.com
Art Harkin
Internet Services Project
Information Networks Division
19420 Homestead Road MS 43LN
Cupertino, CA 95014
Phone: (408) 447-3755
EMail: ash@cup.hp.com
Malkin & Harkin Standards Track [Page 4]
RFC 2349 TFTP Timeout Interval and Transfer Size Options May 1998
Full Copyright Statement
Copyright (C) The Internet Society (1998). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Malkin & Harkin Standards Track [Page 5]