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rfc:rfc2349

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]

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