Network Working Group                                          G. Malkin
Request for Comments: 1785                                Xylogics, Inc.
Updates: 1350                                                  A. Harkin
Category: Informational                              Hewlett Packard Co.
                                                             March 1995


                   TFTP Option Negotiation Analysis

Status of this Memo

  This memo provides information for the Internet community.  This memo
  does not specify an Internet standard of any kind.  Distribution of
  this memo is unlimited.

Abstract

  The TFTP option negotiation mechanism, proposed in [1], is a
  backward-compatible extension to the TFTP protocol, defined in [2].
  It allows file transfer options to be negotiated prior to the
  transfer using a mechanism which is consistent with TFTP's Request
  Packet format.  The mechanism is kept simple by enforcing a request-
  respond-acknowledge sequence, similar to the lock-step approach taken
  by TFTP itself.

  This document was written to allay concerns that the presence of
  options in a TFTP Request packet might cause pathological behavior on
  servers which do not support TFTP option negotiation.

Test Results

  A TFTP client, modified to send TFTP options, was tested against five
  unmodified servers:

     DEC   DEC 3000/400 alpha   OSF1 V3.0
     SGI   IP17 mips            IRIX 5.2
     SUN   sun4c sparc          SunOS 5.1
     IBM   RS/6000 Model 320    AIX 3.4
     SUN   sun4m                SunOS 4.1.3

  In each case, the servers ignored the option information in the
  Request packet and the transfer proceeded as though no option
  negotiation had been attempted.  In addition, the standard BSD4.3
  source for TFTPD, the starting point for many implementations, was
  examined.  The code clearly ignores any extraneous information in
  Request packets.

  From these results and examinations, it is clear that the TFTP option



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RFC 1785            TFTP Option Negotiation Analysis          March 1995


  negotiation mechanism is fully backward-compatible with unmodified
  TFTP servers.

Security Considerations

  Security issues are not discussed in this memo.

References

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

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

Related Documents

  Malkin, G., and A. Harkin, "TFTP Blocksize Option", RFC 1783,
      Xylogics, Inc., Hewlett Packard Co., March 1995.

  Malkin, G., and A. Harkin, "TFTP Timeout Interval and Transfer Size
      Options", RFC 1784, 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]








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