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
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Malkin & Harkin Standards Track [Page 5]
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