RFC 2389 (rfc2389) - Page 2 of 9

Feature negotiation mechanism for the File Transfer Protocol

RFC 2389             Feature negotiation mechanism           August 1998




Table of Contents

          Abstract  ................................................   1
    1     Introduction  ............................................   2
    2     Document Conventions  ....................................   2
    2.1   Basic Tokens  ............................................   3
    2.2   Server Replies  ..........................................   3
    3     Knowledge of Extra Capabilities - the FEAT Command  ......   3
    3.1   Feature (FEAT) Command Syntax  ...........................   4
    3.2   FEAT Command Responses  ..................................   4
    3.3   Rationale for FEAT  ......................................   6
    4     The OPTS Command  ........................................   6
    5     Security Considerations  .................................   7
    6     References  ..............................................   8
          Acknowledgements  ........................................   8
          Editors' Addresses  ......................................   8
          Full Copyright Statement  ................................   9




1. Introduction

   This document amends the File Transfer Protocol (FTP) [1].  Two new
   commands are added: "FEAT" and "OPTS".

   These commands allow a client to discover which optional commands a
   server supports, and how they are supported, and to select among
   various options that any FTP command may support.

2. Document Conventions

   This document makes use of the document conventions defined in BCP14
   [2].  That provides the interpretation of some capitalized words like
   MUST, SHOULD, etc.

   Terms defined in [1] will be used here as defined there.  These
   include ASCII, reply, server-FTP process, user-FTP process, server-
   PI, user-PI, and user.

   Syntax required is defined using the Augmented BNF defined in [3].
   Some general ABNF definitions are required throughout the document,
   those will be defined here.  At first reading, it may be wise to
   simply recall that these definitions exist here, and skip to the next
   section.




Hethmon & Elz               Standards Track