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Versions: 00 RFC 2349

draft-malkin-tftpexts-options-00.txt            G. Malkin / Bay Networks
TFTP Blocksize Option                    A. Harkin / Hewlett Packard Co.
                                                            January 1998


            TFTP Timeout Interval and Transfer Size Options


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].


Status of this Memo

   This document is an Internet-Draft.  Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
   and its working groups.  Note that other groups may also distribute
   working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   To learn the current status of any Internet-Draft, please check the
   "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow
   Directories on ds.internic.net (US East Coast), nic.nordu.net
   (Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific
   Rim).


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 |
      +-------+---~~---+---+---~~---+---+---~~---+---+---~~---+---+



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      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 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" 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].




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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.

      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 | 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

   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)", Request for
        Comments 1350 (STD 33), October 1992.

   [2]  Malkin, G., Harkin, A., "TFTP Option Extension", Internet Draft,



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        draft-ietf-tftpexts-options-02.txt, December 1994.


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





























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