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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:  gmalkin@xylogics.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 [Page 4]