Network Working Group                                          G. Malkin
Request for Comments: 1784                                Xylogics, Inc.
Updates: 1350                                                  A. Harkin
Category: Standards Track                            Hewlett Packard Co.
                                                             March 1995


           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.

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].

  This document assumes that the reader is familiar with the
  terminology and notation of both [1] and [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].

     filename
        The name of the file to be read or written, as defined in [1].
        This is a NULL-terminated field.



Malkin & Harkin                                                 [Page 1]

RFC 1784                      TFTP Options                    March 1995


     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 insensitive).
        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" octets,
        inclusive.  This is a NULL-terminated field.

  For example:

     +-------+--------+---+--------+---+--------+---+--------+---+
     |   1   | foobar | 0 | binary | 0 | timeout| 0 |    1   | 0 |
     +-------+--------+---+--------+---+--------+---+--------+---+

  is a Read Request, for the file named "foobar", in 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.

     mode
        The mode of the file transfer: "netascii", "octet", or "mail",
        as defined in [1].  This is a NULL-terminated field.




Malkin & Harkin                                                 [Page 2]

RFC 1784                      TFTP Options                    March 1995


     tsize
        The Transfer Size option, "tsize" (case insensitive).  This is
        a NULL-terminated field.

     size
        The size of the file to be transfered, specified as a
        NULL-terminated ASCII string.

  For example:

     +-------+--------+---+--------+---+--------+---+--------+---+
     |   2   | foobar | 0 | binary | 0 | tsize  | 0 | 673312 | 0 |
     +-------+--------+---+--------+---+--------+---+--------+---+

  is a Write Request, with the 673312-octet file named "foobar", in
  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

  Security issues are not discussed in this memo.

References

  [1] Sollins, K., "The TFTP Protocol (Revision 2)", STD 33, RFC 1350,
      MIT, July 1992.

  [2] Malkin, G., and A. Harkin, "TFTP Option Extension", RFC 1782,
      Xylogics, Inc., Hewlett Packard Co., March 1995.















Malkin & Harkin                                                 [Page 3]

RFC 1784                      TFTP Options                    March 1995


Authors' Addresses

      Gary Scott Malkin
      Xylogics, Inc.
      53 Third Avenue
      Burlington, MA  01803

      Phone:  (617) 272-8140
      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]
































Malkin & Harkin                                                 [Page 4]