TFTP Option Extension
RFC 1782
Document | Type |
RFC - Proposed Standard
(March 1995; No errata)
Obsoleted by RFC 2347
Updates RFC 1350
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Last updated | 2012-02-26 | ||
Stream | IETF | ||
Formats | plain text pdf htmlized bibtex | ||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 1782 (Proposed Standard) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group G. Malkin Request for Comments: 1782 Xylogics, Inc. Updates: 1350 A. Harkin Category: Standards Track Hewlett Packard Co. March 1995 TFTP Option Extension 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. 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 a simple extension to TFTP to allow option negotiation prior to the file transfer. Introduction The option negotiation mechanism proposed in this document is a backward-compatible extension to the TFTP protocol. It allows file transfer options to be negotiated prior to the transfer using a mechanism which is consistent with TFTPs Request Packet format. The mechanism is kept simple by enforcing a request-respond-acknowledge sequence, similar to the lock-step approach taken by TFTP itself. While the option negotiation mechanism is general purpose, in that many types of options may be negotiated, it was created to support the Blocksize option defined in [2]. Additional options are defined in [3]. This document assumes reader familiarity with the TFTP specification [1] and its terminology. Packet Formats TFTP options are appended to the Read Request and Write Request packets. A new type of TFTP packet, the Option Acknowledgment (OACK), is used to acknowledge a client's option negotiation request. A new error code, 8, is hereby defined to indicate that a transfer should be terminated due to option negotiation. Malkin & Harkin [Page 1] RFC 1782 TFTP Option Extension March 1995 Options are appended to a TFTP Read Request or Write Request packet as follows: +-------+---~~---+---+---~~---+---+---~~---+---+---~~---+---+--> | opc |filename| 0 | mode | 0 | opt1 | 0 | value1 | 0 | < +-------+---~~---+---+---~~---+---+---~~---+---+---~~---+---+--> >-------+---+---~~---+---+ < optN | 0 | valueN | 0 | >-------+---+---~~---+---+ The "0"s shown in these illustrations and the ones below are all all zero octets, i.e., NULL terminators for the preceeding fields. 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. mode The mode of the file transfer: "netascii", "octet", or "mail", as defined in [1]. This is a NULL-terminated field. opt1 The first option, in case-insensitive ASCII (e.g., "blksize"). This is a NULL-terminated ASCII field. value1 The value associated with the first option, in case-insensitive ASCII. This is a NULL-terminated field. optN, valueN The final option/value pair. Each NULL-terminated field is specified in case-insensitive ASCII. The options and values are all NULL-terminated, in keeping with the original request format. If multiple options are to be negotiated, they are appended to each other. The order in which options are specified is not significant. The maximum size of a request packet is 512 octets. Malkin & Harkin [Page 2] RFC 1782 TFTP Option Extension March 1995 The OACK packet has the following format: +-------+---~~---+---+---~~---+---+---~~---+---+---~~---+---+ | opc | opt1 | 0 | value1 | 0 | optN | 0 | valueN | 0 | +-------+---~~---+---+---~~---+---+---~~---+---+---~~---+---+ opc The opcode field contains a 6, for Option Acknowledgment. opt1 The first option acknowledgment, copied from the original request. value1 The acknowledged value associated with the first option. If and how this value may differ from the original request is detailed in the specification for the option. optN, valueN The final option/value acknowledgment pair. Negotiation Protocol The client appends options at the end of the Read Request or Write request packet, as shown above. Any number of options may beShow full document text