RFC1784

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.

  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.

  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.

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]