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Network Working Group                                          G. MalkinRequest for Comments: 1785                                Xylogics, Inc.Updates:1350                                                  A. HarkinCategory: Informational                              Hewlett Packard Co.                                                              March 1995TFTP Option Negotiation AnalysisStatus 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 optionMalkin & 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.comMalkin & Harkin                                                 [Page 2]