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+Network Working Group                                        F. da Cruz
+Request for Comments: 2839                                    J. Altman
+Category: Informational                             Columbia University
+                                                               May 2000
+
+                        Internet Kermit Service
+
+Status of this Memo
+
+   This memo provides information for the Internet community.  It does
+   not specify an Internet standard of any kind.  Distribution of this
+   memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2000).  All Rights Reserved.
+
+ABSTRACT
+
+   This document describes a new file transfer service for the Internet
+   based on Telnet Protocol for option negotiation and Kermit Protocol
+   for file transfer and management.  The Internet Kermit Service
+   provides access to both authenticated and anonymous users.  The use
+   of Kermit protocol over a Telnet connection provides several
+   advantages over FTP, including easy traversal of firewalls, transfers
+   over multiple transports, and security via a combination of supported
+   Telnet authentication and encryption option negotiations, plus
+   significant functional benefits.  While this document describes a new
+   service for the Internet, the clients for this service already exist
+   on most platforms in the form of Telnet clients that support the
+   Kermit file transfer protocol.  These clients are available not only
+   from Columbia University's Kermit Project but also numerous third
+   parties.
+
+TABLE OF CONTENTS
+
+   1. INTRODUCTION ................................................ 2
+   2. BACKGROUND .................................................. 3
+   2.1. History ................................................... 3
+   2.2. Motivation ................................................ 4
+   3. THE INTERNET KERMIT SERVICE MODEL ........................... 7
+   3.1. Server-Side Kermit Server ................................. 7
+   3.2. Client-Side Kermit Server ................................. 8
+   3.3. Loosely Coupled Operation ................................. 9
+   4. SECURITY CONSIDERATIONS .....................................10
+   4.1. AUTHENTICATION ............................................10
+   4.1.1. Telnet Authentication ...................................10
+   4.1.2. Telnet over TLS option ..................................11
+
+
+
+da Cruz & Altman             Informational                      [Page 1]
+
+RFC 2839                Internet Kermit Service                 May 2000
+
+
+   4.1.3. Plaintext Authentication via Kermit REMOTE LOGIN ........11
+   4.1.4. Plaintext Authentication via Command Prompt .............11
+   4.1.5. Anonymous Login .........................................12
+   4.2. ENCRYPTION (PRIVACY) ......................................12
+   4.2.1  Telnet Encryption .......................................12
+   4.2.2  Telnet Start_TLS ........................................12
+   5. SERVICES ....................................................13
+   5.1. Features for System Administrators ........................13
+   5.2. Features for Users ........................................14
+   5.3. User Interface ............................................16
+   6. REFERENCES ..................................................18
+   7. AUTHORS' ADDRESSES ..........................................19
+   8. Full Copyright Statement ....................................20
+
+PREFACE
+
+   This document describes an Internet Kermit Service (IKS) which
+   provides an alternative to FTP for the transfer of files.  This
+   service is based upon both the TELNET protocol and the Kermit file
+   transfer protocol.
+
+1. INTRODUCTION
+
+   The Internet Kermit Service:
+
+   1. Provides direct access to Kermit file transfer and management
+      services without requiring the user to first login to a shell
+      account;
+
+   2. Provides Kermit file transfer and management services to anonymous
+      users;
+
+   3. Provides services to all Telnet clients that support Kermit file
+      transfer protocol via a simple, predictable, scriptable, and
+      well-documented textual interface;
+
+   4. Provides direct and tightly-coupled access to a Kermit server when
+      requested via the Telnet Kermit Option [TKO].
+
+   This memo assumes knowledge of Transmission Control Protocol, the
+   Telnet Protocol [TEL], the Kermit File Transfer Protocol [KER,PRF],
+   Telnet Kermit Option [TKO], and the commands and features of Kermit
+   software [CKB,CMG,K95].
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+   document are to be interpreted as described in RFC 2119 [BCP].
+
+
+
+
+da Cruz & Altman             Informational                      [Page 2]
+
+RFC 2839                Internet Kermit Service                 May 2000
+
+
+   Definitions:
+
+   Kermit server
+      A software program that is ready to accept and act upon commands
+      in the form of well-defined Kermit packets [KER].
+
+   Kermit client
+      A software program that receives requests through its user
+      interface from a human user (or a script or other source) and
+      translates them to command packets, which it sends to a Kermit
+      server, thus initiating a Kermit protocol transaction such as the
+      transfer of one or more files.
+
+2. BACKGROUND
+
+2.1. History
+
+   "Kermit" is the name of an extensible platform- and medium-
+   independent file transfer and management protocol [KER,PRF] and of a
+   suite of communications software programs that implement it and
+   integrate it with other communications functions [CMG,CKB,K95].
+
+   The Kermit protocol was first developed at Columbia University in New
+   York City in 1981 for transferring files without errors between
+   diverse types of computers over potentially hostile communication
+   links.  Since 1981, the Kermit Project at Columbia University has
+   expanded the protocol, developed communications software that
+   implements it upon key platforms, and worked with volunteer
+   programmers at other sites adapting Kermit protocol to other
+   platforms or communication methods.  The Kermit Project also serves
+   as the central point of Kermit software development, support,
+   information, and distribution throughout the world.
+
+   Kermit software is now available for nearly every computer and
+   operating system in existence.  The major features of the most
+   popular Kermit programs are:
+
+   -  Connection establishment and maintenance for a variety of
+      connection methods including direct serial, dialup, TCP/IP, X.25,
+      DECnet, and NETBIOS.
+
+   -  Terminal emulation.
+
+   -  Error-free transfer of both text and binary files, individually or
+      in groups.
+
+   -  Character-set translation during both terminal emulation and
+      text-mode file transfer -- a unique feature of Kermit software.
+
+
+
+da Cruz & Altman             Informational                      [Page 3]
+
+RFC 2839                Internet Kermit Service                 May 2000
+
+
+   -  Remote file management through the client/server protocol.
+
+   -  A powerful and portable scripting language allowing complete
+      automation of any task that can be performed manually.
+
+   Kermit's command and script language is consistent across all
+   platforms and communication methods, thus offering a unified method
+   for accomplishing a wide range of communication tasks manually or
+   under script control.
+
+   A single Kermit program combines the functions of many different
+   programs such as uucp, cu, tip, telnet, rlogin, ftp, iconv, and
+   expect:  it is a Telnet and Rlogin client that can also transfer
+   files; it is a file transfer program that can also convert character
+   sets; it is a dialout program that can use dialing directories and
+   understands country codes and area codes; it is fully scriptable; it
+   offers both client/server and interactive modes of operation.  In its
+   desktop versions (particularly for DOS, Windows, and OS/2) it offers
+   all the features of communications software that are usually lacking
+   from Internet client software (key mapping, colors, scrollback, mouse
+   functions, printer control, etc)
+
+   Kermit software is widely used throughout the academic, government,
+   and corporate spheres, both in the USA and internationally.
+
+   In addition to the Kermit software developed and/or distributed by
+   the Kermit Project at Columbia University, hundreds of other software
+   products -- commercial, shareware, and freeware -- also include some
+   level of support for the Kermit protocol.  Thus there are hundreds,
+   perhaps thousands, of independent and interoperable Kermit protocol
+   implementations based upon the open Kermit protocol specification
+   [KER].
+
+   The Internet has formed the primary mechanism by which users and
+   developers of Kermit software have collaborated to produce feature
+   and command sets that continually evolve to meet their needs as
+   technology changes.
+
+2.2. Motivation.
+
+   Kermit protocol and software makes connections from one computer to
+   another and transfers data between them.  Countless people "live" in
+   Kermit all day long; as a customizable Telnet or Rlogin (or serial
+   communication) client with a wide selection of terminal emulations
+   and convenience features, it is their window onto the Internet.
+
+
+
+
+
+
+da Cruz & Altman             Informational                      [Page 4]
+
+RFC 2839                Internet Kermit Service                 May 2000
+
+
+   Others use it in more creative ways, including some that involve key
+   parts of the Internet, e.g. in batch or cron jobs that update news or
+   Web servers or fetch email, or to monitor routers, terminal servers,
+   and hubs and dial pagers when faults are detected.  It is used by
+   vendors of telecommunications equipment for remote diagnosis,
+   patching, and updates.  Telecom managers often use Kermit scripts to
+   configure PBXs, muxes, routers, or terminal servers.  In the world of
+   commerce, Kermit is widely used for financial transactions, EDI,
+   medical claim submission, and so forth.  It is used with mobile
+   barcode readers in warehousing and inventory applications.  It is
+   found in US Postal Service sorting and scanning equipment.  It
+   connects many of the logistics and supply systems throughout the
+   military.  It is found in fast-food restaurant cash registers,
+   milling and die-cutting machines, textile looms and cutters, printing
+   presses, and medical diagnostic equipment.  It was the communications
+   backbone of the 1994 Brazilian national election -- the largest in
+   history.
+
+   And yet there has never been a strong, explicit connection of Kermit
+   with the Internet.  In the early years, Kermit acted as a kind of
+   do-it-yourself network, enabling ordinary users to make connections
+   that were not already there, and for some years was the predominant
+   method of connecting a personal computer to the ARPAnet (e.g. by
+   dialing a TAC).
+
+   Nowadays, however, with so many of the world's computers on the
+   Internet, the role of Kermit software and protocol is changing.
+   Kermit users on the network would like to have the features,
+   functions, and interface they are accustomed to -- especially the
+   automation features -- available for use in settings where presently
+   only tools like FTP are available -- and even more so in situations
+   where standard software like FTP can't be used.
+
+   An Internet Kermit Service can fill this role, and augment the data
+   transfer power and flexibility of other Internet applications such as
+   Web browsers:
+
+   -  Like FTP, Kermit provides a service that can be accessed from many
+      different platforms with a consistent set of commands, but unlike
+      FTP, these commands include programming constructions such as
+      variables, arrays, looping and selection mechanisms, and local and
+      remote procedure calls.
+
+   -  Like FTP, Kermit provides both text- and binary-mode data
+      transfer, as well as file management capabilities.  But Kermit
+      also offers numerous features lacking from FTP, such as
+
+
+
+
+
+da Cruz & Altman             Informational                      [Page 5]
+
+RFC 2839                Internet Kermit Service                 May 2000
+
+
+      character-set translation, flexible file selection mechanisms,
+      attribute preservation, and so on (see Section 5.3 for a longer
+      list).
+
+   -  Unlike standard FTP, Kermit can transfer data through multiple
+      firewalls, proxies, and network address translators (NATs) on a
+      single port.
+
+   -  Unlike FTP, Kermit can transfer data across a combination of
+      transports (e.g. dial-up to a terminal server and thence to an
+      Internet host).
+
+   -  Authentication and data transfer can take place over secure
+      connections (mutually authenticated and encrypted) using
+      established Telnet authentication and encryption options.
+
+   -  Unlike traditional Kermit use over Telnet, anonymous access is
+      possible, and the considerable overhead of the intervening Telnet
+      server and pseudoterminal service is eliminated.
+
+   Until now the primary obstacles to an Internet Kermit Service have
+   been:
+
+   -  Issues of authentication, privacy, and anonymous access.  These
+      have been addressed in our implementation, as described Section 4
+      of this document.
+
+   -  Issues of coordination and control.  A Kermit software program can
+      be in any of several "modes": at its command prompt or menu,
+      awaiting commands from the user; in terminal mode, in which the
+      user's keystrokes are sent to the remote computer or service; or
+      in protocol mode, in which two Kermit programs communicate via
+      well-defined Kermit packets [KER].  Commands or operations valid
+      in one mode do not necessarily work in another.  Until now, it has
+      been the user's responsibility to switch modes at one or both ends
+      of the connection as needed.  A companion document [TKO] to this
+      one specifies a mechanism to closely couple the client and server
+      via Telnet protocol negotiations, allowing each to know the
+      other's state and to switch to the appropriate mode automatically
+      so a valid and useful relationship obtains at all times.
+
+   -  Lack of a standard TCP port.  The "registered" port 1649 was
+      assigned by IANA for this purpose (27 September 1995) and is named
+      "Kermit". (renamed from "Inspect".)
+
+
+
+
+
+
+
+da Cruz & Altman             Informational                      [Page 6]
+
+RFC 2839                Internet Kermit Service                 May 2000
+
+
+3. THE INTERNET KERMIT SERVICE MODEL
+
+   The Internet Kermit Service (IKS) uses a standard Telnet [TEL]
+   connection, in which all Telnet rules apply.  Unlike FTP, which
+   requires additional TCP connections, IKS uses a single channel for
+   both signaling and data transfer.  The connection is multiplexed via
+   (a) Telnet options, and (b) Kermit protocol messages.  This allows
+   existing Telnet clients that also support the Kermit protocol,
+   whether or not they support the Telnet Kermit Option [TKO], to use
+   the IKS and take advantage of all relevant Telnet options including
+   authentication and encryption.
+
+   The system Internet services daemon (e.g. inetd) waits for a
+   connection on the Kermit socket (1649) and then starts the IKS on the
+   new connection.  The IKS performs the familiar Telnet negotiations
+   including the Telnet Kermit option.  Unlike a standard Telnet server,
+   the IKS does not support the ability to present the user with an
+   interactive system shell.  The Kermit socket is used only for file
+   transfer and management functions provided by Kermit file transfer
+   protocol and the Kermit script language.
+
+   Once the connection is established, the Telnet Kermit Option is
+   negotiated in both directions.  The results determine which of the
+   following configurations is used by the Telnet client and Server:
+
+    . Server-side Kermit Server (SKS)
+    . Client-side Kermit Server (CKS)
+    . No Kermit Server (NKS)
+
+   Different procedures and functions apply to each configuration.  The
+   configuration may be changed at any time by Telnet Kermit Option
+   subnegotiations, which assure that the Telnet client and server are
+   always in compatible states.
+
+   The three configurations are described in the following sections.
+
+3.1. Server-Side Kermit Server
+
+   In the Server-Side Kermit Server (SKS) configuration, the Telnet
+   server is the Kermit server and the Telnet client is the Kermit
+   client.  This configuration is used when both Telnet client and IKS
+   support the Telnet Kermit Option and the IKS sends WILL KERMIT to the
+   Telnet client and receives DO KERMIT from the Telnet client [TKO].
+
+   In this case, the IKS immediately starts a Kermit server and reports
+   this to the Telnet client with a Telnet KERMIT START-SERVER
+   subnegotiation.
+
+
+
+
+da Cruz & Altman             Informational                      [Page 7]
+
+RFC 2839                Internet Kermit Service                 May 2000
+
+
+   The SKS configuration is appropriate when the user wishes to interact
+   only with the Telnet client's commands or menus.
+
+   If authentication was not performed with one of the Telnet
+   Authentication Option protocols, the Kermit server rejects all Kermit
+   protocol operations (except REMOTE LOGIN, REMOTE HELP, REMOTE EXIT,
+   BYE, or FINISH -- that is, the ones that request help, that log in,
+   that close the connection, or that change the status of the
+   connection) until:
+
+   - A Kermit REMOTE LOGIN command successfully authenticates the user;
+
+   - The login retry limit is reached;
+
+   - A Kermit BYE or REMOTE EXIT command is received, which closes the
+      connection;
+
+   - A Kermit FINISH command or a Telnet KERMIT REQ-KERMIT-STOP
+      subnegotiation is received to request the IKS exit from Kermit
+      server mode.  At this point, the IKS can either exit and close the
+      connection or issue an interactive login prompt, depending on how
+      it was started or configured by the system administrator.
+
+   Once the user is authenticated:
+
+   - The Telnet client configures itself for Kermit client/server
+      operation, with itself as the Kermit client, communicating with
+      the server only by Kermit packets, and optionally adjusting its
+      menus or commands to eliminate functions (such as terminal
+      emulation) that make no sense in this context.
+
+   - The relationship persists until the Telnet client and IKS agree to
+      terminate the Kermit server via Kermit protocol commands (BYE,
+      FINISH, or REMOTE EXIT), or by Telnet Kermit Option
+      subnegotiation, or by closing the connection.
+
+3.2. Client-Side Kermit Server
+
+   In the Client-Side Kermit Server (CKS) configuration, the Telnet
+   server is the Kermit client, and the Telnet client is the Kermit
+   server.  This configuration is used when the IKS has sent WONT KERMIT
+   or SB KERMIT STOP-SERVER, and the Telnet Client has sent WILL KERMIT
+   and SB KERMIT START-SERVER, indicating that it is prepared to accept
+   and process Kermit protocol packets.
+
+   In the CKS configuration, the Telnet client assumes the role of
+   Kermit server by virtue of its ability to recognize and process
+   Kermit protocol packets in its terminal emulator.  Thus the Telnet
+
+
+
+da Cruz & Altman             Informational                      [Page 8]
+
+RFC 2839                Internet Kermit Service                 May 2000
+
+
+   client must not send WILL KERMIT or the KERMIT START-SERVER
+   subnegotiation unless its terminal emulator is capable of recognizing
+   Kermit packets.
+
+   If the IKS is at top command level (as opposed to executing a
+   script), or when it reaches top level after finishing a script, it
+   issues its interactive command prompt.
+
+   At this point, the user may type commands or send scripted commands
+   to the IKS command prompt.  When a data-transfer command (such as
+   SEND) is issued by the user at the IKS prompt, a Kermit packet is
+   transmitted and recognized by the Telnet client, causing it to
+   automatically perform the requested action (e.g. receive a file), and
+   then resume its previous mode (terminal emulation or script
+   execution) when the data transfer is complete.
+
+   Thus, in the CKS configuration, data transfers are initiated by the
+   IKS rather than by the Telnet client.  This configuration is useful
+   when the user prefers the command interface or repertoire of the
+   server to that of the client.
+
+   If the IKS sends a Telnet KERMIT START-SERVER subnegotiation, the
+   relationship switches automatically to Server-Side Kermit Server
+   (Section 3.1), in which the Telnet client is the Kermit client and
+   the Telnet server is the Kermit server.
+
+   If the Telnet client sends a KERMIT STOP-SERVER subnegotiation, the
+   connection switches to No Kermit Server (Section 3.3) and the IKS
+   issues its command prompt.  At this point, neither side is a Kermit
+   server, and both sides may optionally disable Kermit protocol
+   commands.  Subsequent user action can designate one side or the other
+   as the Kermit server, as desired.
+
+3.3. No Kermit Server
+
+   If both Telnet client and IKS send WONT KERMIT or SB KERMIT STOP-
+   SERVER, or if the Kermit client and server are connected across
+   multiple hosts or transports, thus precluding end-to-end Telnet
+   negotiation, a Kermit server is not known to be available.  In the
+   KERMIT STOP-SERVER case, the Kermit partners can later switch back to
+   SKS or CKS, but in the other two cases, there is no such signaling
+   and loose coupling characterizes the entire session.
+
+   In the No Kermit Server (NKS) configuration, the IKS presents a
+   command prompt to the Telnet client.  As in the Client-Side Kermit
+   Server configuration, plain-text commands are issued to the IKS.
+
+
+
+
+
+da Cruz & Altman             Informational                      [Page 9]
+
+RFC 2839                Internet Kermit Service                 May 2000
+
+
+   In the loosely coupled NKS configuration, the Telnet client does not
+   know the state of the Telnet server, and so can not automatically
+   adjust its commands and menus to present only valid choices, or
+   automatically change its state to complement the server's; it is the
+   user's responsibility to assure that the "mode" (command prompt,
+   terminal emulation, server command wait) of each Kermit partner is
+   appropriate for each action.  Thus an Internet Kermit Server appears
+   as an ordinary remote Kermit program to any Telnet client that does
+   not implement the Telnet Kermit Option, or in which this feature is
+   disabled or can not be used.
+
+   The NKS configuration allows successful manual operation of the IKS
+   through Telnet clients that do not support the Telnet Kermit Option.
+   The Telnet client might or might not support Kermit "autodownload"
+   and "autoupload"; if it does not, then the user is forced to manually
+   issue command on both sides of the connection in the traditional and
+   familiar manner [CKB,CMG,K95].
+
+4. SECURITY CONSIDERATIONS
+
+4.1. AUTHENTICATION
+
+   Authentication is provided via one or more of the following methods:
+
+    - The Telnet AUTHENTICATION option;
+
+    - The Telnet START_TLS option;
+
+    - Plaintext userid/password verification.
+
+4.1.1. Telnet Authentication option
+
+   The use of one of the many Telnet authentication option methods
+   removes the need to transmit passwords in plaintext across public
+   networks.  In addition, the exchange of user authentication
+   information often provides a shared secret that can be used with the
+   Telnet Encryption Option protocols to encrypt the connection in one
+   or both directions.
+
+   Telnet authentication may also be used in conjunction with the Telnet
+   START_TLS option to negotiate end user identity over the encrypted
+   and host authenticated TLS channel.
+
+   The IKS currently supports Kerberos 4, Kerberos 5, Secure Remote
+   Password and Microsoft NTLM authentication methods via the Telnet
+   AUTH option.
+
+
+
+
+
+da Cruz & Altman             Informational                     [Page 10]
+
+RFC 2839                Internet Kermit Service                 May 2000
+
+
+4.1.2. Telnet over TLS option
+
+   The Telnet START_TLS option provides for the negotiation and
+   establishment of a TLS version 1 session after the initial telnet
+   connection.  The TLS connection provides host to client
+   authentication via the use of X.509 certificate chains.  TLS also
+   supports optional client to host authentication using host verified
+   X.509 certificates which may be used to authenticate a userid
+   provided by the client or be mapped to a userid based upon properties
+   of the certificate.
+
+4.1.3. Plaintext Authentication via Kermit REMOTE LOGIN
+
+   In the Server-Side Kermit Server configuration, if the client is not
+   yet authenticated, the client must log in using a REMOTE LOGIN
+   command, in which a Kermit packet containing user ID and password in
+   clear text is sent from the Telnet client to the Telnet server, which
+   then calls upon local mechanisms to authenticate the user.  Any
+   packets other than login (or REMOTE HELP, REMOTE EXIT, FINISH, or
+   BYE) packets are rejected (returned with an error message) until the
+   user is authenticated.  If the number of unsuccessful login attempts
+   exceeds the limit, the connection is closed.  Many Kermit client
+   programs support this login method already.
+
+   This method should be avoided whenever possible.  If plaintext
+   passwords are used, they should only be sent after the Telnet START-
+   TLS option has been negotiated (see 4.2.2).  Otherwise, passwords are
+   open to packet sniffing.
+
+4.1.4. Plaintext Authentication via Command Prompt
+
+   In the Client-Side Kermit Server and No Kermit Server configurations,
+   the server presents the user with a plain-text interactive interface
+   that begins with the server issuing "Username:" and "Password:"
+   prompts, just as if the user were logging in to a multiuser
+   timesharing system such as VMS or UNIX.  When a password is not
+   required an empty response can be given.  Invalid username-password
+   combinations result in a new series of prompts up to the login retry
+   limit, and then disconnection.
+
+   This method should be avoided whenever possible.  If plaintext
+   passwords are used, they should only be sent after the Telnet START-
+   TLS option has been negotiated (see 4.2.2).  Otherwise, passwords are
+   open to packet sniffing.
+
+
+
+
+
+
+
+da Cruz & Altman             Informational                     [Page 11]
+
+RFC 2839                Internet Kermit Service                 May 2000
+
+
+4.1.5. Anonymous Login
+
+   When the username is "anonymous" or "ftp", the IKS behaves like an
+   anonymous ftp server, in a manner appropriate to the underlying
+   platform.  In UNIX, for example, access is restricted to a designated
+   area of the file system.  A password might or might not be required,
+   according to the preference of the site administrator.
+
+   If privacy is desired the Telnet START-TLS option should be used (see
+   4.2.2).
+
+4.2.  ENCRYPTION (PRIVACY)
+
+   As the Internet becomes ever more public and susceptible to
+   eavesdropping, it becomes increasingly necessary to provide methods
+   for private access to services.  Telnet provides two such mechanisms:
+
+    . Telnet Encryption option
+    . Telnet START-TLS option
+
+4.2.1.  Telnet Encryption option
+
+   The Telnet Encryption option, although it has never achieved RFC
+   status, has been used for years in conjunction with the Telnet Auth
+   option in Telnet clients and servers that support Kerberos 4,
+   Kerberos 5, Secure Remote Password, and others.  The IKS currently
+   supports the following encryption methods under the Telnet Encryption
+   option:
+
+    .  cast128_ofb64
+    .  cast5_40_ofb64
+    .  des_ofb64
+    .  cast128_cfb64
+    .  cast5_40_cfb64
+    .  des_cfb64
+
+4.2.2. Telnet over TLS option
+
+   Transport Layer Security (TLS), the successor to Secure Sockets Layer
+   (SSL), provides methods to implement Server authentication, Client
+   authentication, and Transport Layer encryption.  Unlike Telnet
+   Encryption, Start-TLS does not require the use of Telnet
+   Authentication in order to provide a private channel.  This means
+   that it can be used in conjunction with plaintext passwords and
+   anonymous connections.
+
+
+
+
+
+
+da Cruz & Altman             Informational                     [Page 12]
+
+RFC 2839                Internet Kermit Service                 May 2000
+
+
+5. SERVICES
+
+   The Internet Kermit Service includes features for both users and
+   system administrators.  The IKS is incorporated into  the 7.0 release
+   of Columbia University's C-Kermit software, which is the "master"
+   Kermit software program in terms of features and command language.
+   An overview of C-Kermit can be found at:
+
+     http://www.columbia.edu/kermit/ckermit.html
+     http://www.kermit-project.org/ckermit.html
+
+   When C-Kermit is employed as an Internet Kermit Service, it may offer
+   all its functions to "real" users (those who are authenticated as
+   specific users), and a safe subset of its functions to anonymous
+   users.
+
+   The Internet Kermit Service resembles an FTP server in that it
+   performs its own authentication and uses a well-defined protocol to
+   communicate with its client, but differs from the FTP server by also
+   offering (at the system manager's discretion) an interactive user
+   interface to the Telnet client when it is in terminal mode.  It also
+   differs from FTP in restricting all protocol messages and data
+   transfer to a single socket connection.
+
+   An IKS has been deployed at Columbia University for worldwide public
+   access to the Kermit FTP site:
+
+     telnet://kermit.columbia.edu:1649/
+     telnet://ftp.kermit-project.org:1649/
+
+5.1. Features for System Administrators
+
+   The system administrator can supply IKS configuration parameters as
+   command-line options or in a configuration file, or both in
+   combination.  Such parameters include:
+
+    . Whether anonymous logins are allowed.
+
+    . The file system or root directory to which anonymous users are
+      restricted.
+
+    . Specification of permissions and other attributes to be assigned
+      to files uploaded by anonymous users.
+
+    . Whether to make session entries in system logs.
+
+
+
+
+
+
+da Cruz & Altman             Informational                     [Page 13]
+
+RFC 2839                Internet Kermit Service                 May 2000
+
+
+    . Specific services to disable: reception of files, sending of
+      files, sending of email, printing, changing of directories,
+      getting directory listings, deleting files, etc (see next
+      section).
+
+    . Whether access to the interactive command prompt is allowed.
+
+5.2. Features for Users
+
+   The IKS supports a wide range of services, including, but not limited
+   to, the following:
+
+    . Authentication as a real user or anonymously.
+
+    . Transmission of files to which read access is allowed.
+
+    . Reception of files into directories or devices to which write
+      access is allowed.
+
+    . The ability to display a file on the client's screen.
+
+    . Ability to list files.
+
+    . Ability to change its working (default) directory.
+
+    . Ability to delete files to which write or delete access is
+      allowed.
+
+    . Ability to rename and copy files
+
+    . Ability to create and remove directories.
+
+    . The ability to route received files to a specified printer, or to
+      send them as email to a specified address list.
+
+    . Client control of server parameter settings, within limits
+      established by the server system administrator.
+
+    . Transmission of variables from client to server or vice versa.
+
+    . Remote and local script execution.
+
+    . Remote and local procedure execution.
+
+
+
+
+
+
+
+
+da Cruz & Altman             Informational                     [Page 14]
+
+RFC 2839                Internet Kermit Service                 May 2000
+
+
+   File transfer features include:
+
+    . Kermit text-mode transfers incorporate not only record-format
+      conversion, but also character-set translation;
+
+    . Kermit can switch automatically between text and binary mode on a
+      per-file basis when sending groups of files.
+
+    . A selection of file collision options, including "make backup copy
+      of existing file and accept incoming file", "reject incoming
+      file", "accept incoming file only if newer than existing file",
+      etc.
+
+    . Numerous methods for selecting the files to be transferred,
+      including pattern matching, lists of filenames (or patterns),
+      exception lists, date and/or size ranges, etc.
+
+    . Filename conversion and file renaming.
+
+    . Automatic directory creation if elected and enabled.
+
+    . Standard mechanisms for directory traversal, allowing transmission
+      of entire directory trees or other file hierarchies even between
+      unlike file systems such as VMS, UNIX, and Windows.
+
+    . Atomic file movement: optionally, the source file can be deleted
+      (or renamed, or moved) when and only when it has been transferred
+      successfully.
+
+    . Kermit can retain file attributes including time stamps and
+      permissions (at the user's or system administrator's discretion),
+      even between unlike platforms;
+
+    . Recovery of interrupted transfers from the point of failure.
+
+    . File-transfer pipes and filters.
+
+   Script programming features include:
+
+    . Macros with parameter substitution.
+
+    . Built-in and user-defined variables and arrays, with global or
+      local scope.
+
+
+
+
+
+
+
+
+da Cruz & Altman             Informational                     [Page 15]
+
+RFC 2839                Internet Kermit Service                 May 2000
+
+
+    . Built-in and user-defined functions.  Built-in functions include:
+
+          - String functions
+          - Arithmetic functions
+          - Date / time functions
+          - File functions
+
+    . Input search for multiple simultaneous targets.
+
+    . IF-ELSE, WHILE, FOR, SWITCH, GOTO, C-like block structure.
+
+    . Every command returns a completion status that may be tested and
+      used as a basis for subsequent actions.
+
+5.3. User Interface
+
+   The Internet Kermit Service uses the Kermit command and script
+   language, as implemented in Columbia University's C-Kermit
+   communication software [CKB].  This program and its command language
+   are portable to all known varieties of UNIX, as well as to Windows
+   95/98/NT, OS/2, Digital (Open)VMS, Stratus VOS, Data General AOS/VS,
+   Plan 9, OS-9, QNX, the Commodore Amiga, and other platforms.  The
+   C-Kermit command language is a superset of that of other Kermit
+   software programs including MS-DOS Kermit for DOS and Windows 3.x,
+   IBM Mainframe Kermit for VM/CMS, MVS/TSO, CICS, and MUSIC, PDP-11
+   Kermit for RT-11, RSTS/E, RSX-11, and IAS, and dozens of other Kermit
+   programs.
+
+   It is far beyond the scope of this document to enumerate, let alone
+   describe, the commands and services of C-Kermit; this is the subject
+   of a 600-page book [CKB], augmented by hundreds of pages of online
+   material.  A brief overview is included here.
+
+   Commands are based on English words.  There is no plan at present to
+   support other natural languages (Italian, Portuguese, Norwegian,
+   Russian, Hebrew, Japanese, Cherokee, etc) as alternative bases for
+   command words, since this would reduce the portability of scripts.
+   However, since the command language includes a macro capability,
+   macros may be defined to provide selected commands in different
+   languages if desired.
+
+   Certain commands can apply either locally or remotely, for example
+   "CD" (Change Directory).  The convention is to prefix the command
+   with the word REMOTE if it is to apply remotely.  Example: "cd foo"
+   changes to the "foo" directory on the computer where the command was
+   given; "remote cd foo" sends a Kermit packet to the Kermit server
+   requesting it to change its directory to "foo".  The commands in this
+   category include:
+
+
+
+da Cruz & Altman             Informational                     [Page 16]
+
+RFC 2839                Internet Kermit Service                 May 2000
+
+
+     ASSIGN <variable> <value>      Assign a value to a variable.
+     CD <directory>                 Change working directory.
+     COPY <files> <destination>     Copy file(s)
+     DELETE <files>                 Delete file(s)
+     DIRECTORY [ <pattern> ]        List file(s)
+     EXIT                           Exit
+     HELP [ <topic-or-command> ]    Display help text
+     MKDIR <directory>              Create a directory
+     PRINT <files>                  Print file(s)
+     PWD                            Print working directory
+     RENAME <old> <new>             Rename file(s)
+     RMDIR <directory>              Remove a directory
+     SET <parameter> <value>        Change a parameter's value
+     TYPE <file>                    Display the contents of a file
+
+   As a convenience, REMOTE commands also have short synonyms: RASSIGN,
+   RCD, RCOPY, RDELETE, and so forth.
+
+   The basic file transfer commands are:
+
+     SEND [ modifiers ] <files>    Send file(s) (to server)
+     GET [ modifiers ] <files>     Get file(s) (from server)
+
+   These commands take a file name, pattern, or list, plus various
+   optional modifiers, including transfer mode specifiers (text,
+   binary), file selectors (date, size, exception list), aliasing, name
+   and path options, disposition specifiers, and so on.
+
+   In addition to the commands listed above, the following commands are
+   sent by the client to the server:
+
+     REMOTE QUERY                   Get value of variable or procedure
+     BYE                            Log out and close the connection
+     FINISH                         Request the server leave server mode
+
+   Like all Kermit client/server commands, these can be disabled if
+   desired.
+
+   Of course there are numerous other commands with purely local effect,
+   such as the many scripting commands.  These, plus all the commands
+   above, are fully documented in [CKB].  The repertoire grows over
+   time, but never in a way that invalidates existing scripts.
+
+   The system administrator can allow or forbid access to any of these
+   features, and to the command language as a whole.  In the latter
+   case, the IKS may be accessed only as a Kermit server, by giving
+   commands to the client.
+
+
+
+
+da Cruz & Altman             Informational                     [Page 17]
+
+RFC 2839                Internet Kermit Service                 May 2000
+
+
+6. REFERENCES
+
+   [TKO] Altman, J. and F. da Cruz, "Telnet Kermit Option", RFC 2840,
+         May 2000.
+
+   [BCP] Bradner, S., "Key words for use in RFCs to Indicate Requirement
+         Levels", BCP 14, RFC 2119, March 1997.
+
+   [KER] da Cruz, Frank, "Kermit, A File Transfer Protocol", Digital
+         Press/ Butterworth Heinemann, Newton, MA (1987).  379 pages,
+         ISBN 0-932376-88-6.
+
+   [CKB] da Cruz, Frank, and Christine M. Gianone, "Using C-Kermit",
+         Second Edition, Digital Press / Butterworth-Heinemann, Woburn,
+         MA (1997).  622 pages, ISBN 1-55558-164-1.
+
+   [CMG] Gianone, Christine M., "Using MS-DOS Kermit", Second Edition,
+         Digital Press / Butterworth-Heinemann, Woburn, MA (1992). 345
+         pages, ISBN 1-55558-082-3.
+
+   [K95] Gianone, Christine M., and Frank da Cruz, "Kermit 95", Manning
+         Publications, Greenwich CT, (1996). 88 pages, ISBN 1-884777-
+         14-7.
+
+   [PRF] Huggins, James K., "Kermit Protocol - Formal Specification and
+         Verification", in Boerger, E., "Specification and Validation
+         Methods", Oxford University Press (1995).  ISBN 0-19-853854-5.
+
+   [FTP] Postel, J. and J. Reynolds, "File Transfer Protocol (FTP)", STD
+         9, RFC 959, October 1985.
+
+   [TEL] Postel, J. and J. Reynolds, "Telnet Protocol Specification",
+         STD 8, RFC854, May 1983, et seq.; "Telnet Option
+         Specification", STD 8, RFC855, May 1983, et seq.
+
+   [IAN] Internet Assigned Numbers Authority:
+         http://www.iana.org/numbers.html
+         http://www.iana.org/assignment/port-numbers
+
+
+
+
+
+
+
+
+
+
+
+
+
+da Cruz & Altman             Informational                     [Page 18]
+
+RFC 2839                Internet Kermit Service                 May 2000
+
+
+7. AUTHORS' ADDRESSES
+
+   Frank da Cruz
+
+   EMail: fdc@columbia.edu
+
+
+   Jeffrey E. Altman
+
+   EMail:jaltman@columbia.edu
+
+
+   The Kermit Project
+   Columbia University
+   612 West 115th Street
+   New York NY 10025-7799
+   USA
+   http://www.columbia.edu/kermit/
+   http://www.kermit-project.org/
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+da Cruz & Altman             Informational                     [Page 19]
+
+RFC 2839                Internet Kermit Service                 May 2000
+
+
+8.  Full Copyright Statement
+
+   Copyright (C) The Internet Society (2000).  All Rights Reserved.
+
+   This document and translations of it may be copied and furnished to
+   others, and derivative works that comment on or otherwise explain it
+   or assist in its implementation may be prepared, copied, published
+   and distributed, in whole or in part, without restriction of any
+   kind, provided that the above copyright notice and this paragraph are
+   included on all such copies and derivative works.  However, this
+   document itself may not be modified in any way, such as by removing
+   the copyright notice or references to the Internet Society or other
+   Internet organizations, except as needed for the purpose of
+   developing Internet standards in which case the procedures for
+   copyrights defined in the Internet Standards process must be
+   followed, or as required to translate it into languages other than
+   English.
+
+   The limited permissions granted above are perpetual and will not be
+   revoked by the Internet Society or its successors or assigns.
+
+   This document and the information contained herein is provided on an
+   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is currently provided by the
+   Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+da Cruz & Altman             Informational                     [Page 20]
+