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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

Malkin & Harkin [Page 1]  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:  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 2]