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].






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     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.





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     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.








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Authors' Addresses

  Gary Scott Malkin
  Bay Networks
  8 Federal Street
  Billerica, MA  01821

  Phone:  (978) 916-4237
  EMail:  [email protected]


  Art Harkin
  Internet Services Project
  Information Networks Division
  19420 Homestead Road MS 43LN
  Cupertino, CA  95014

  Phone: (408) 447-3755
  EMail: [email protected]
































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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.
























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