Network Working Group                                         P. Hoffman
Request for Comments: 4248                                VPN Consortium
Obsoletes: 1738                                             October 2005
Category: Standards Track


                        The telnet URI Scheme

Status of this Memo

  This document specifies an Internet standards track protocol for the
  Internet community, and requests discussion and suggestions for
  improvements.  Please refer to the current edition of the "Internet
  Official Protocol Standards" (STD 1) for the standardization state
  and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

  Copyright (C) The Internet Society (2005).

Abstract

  This document specifies the telnet Uniform Resource Identifier (URI)
  scheme that was originally specified in RFC 1738.  The purpose of
  this document is to allow RFC 1738 to be made obsolete while keeping
  the information about the scheme on standards track.

1.  Introduction

  URIs were previously defined in [RFC2396], which was updated by
  [RFC3986].  Those documents also specify how to define schemes for
  URIs.

  The first definition for many URI schemes appeared in [RFC1738].
  Because that document has been made obsolete, this document copies
  the telnet URI scheme from it to allow that material to remain on
  standards track.

2.  Scheme Definition

  The Telnet URL scheme is used to designate interactive services that
  may be accessed by the Telnet protocol [STD8].

  A telnet URL takes the form:

  telnet://<user>:<password>@<host>:<port>/





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  The final "/" character may be omitted.  If :<port> is omitted, the
  port defaults to 23.  The :<password> can be omitted, as well as the
  whole <user>:<password> part.  Few implementations handle the user
  name and password very well, if at all.

  This URL does not designate a data object, but rather an interactive
  service.  Remote interactive services vary widely in the means by
  which they allow remote logins; in practice, the <user> and
  <password> supplied are advisory only: clients accessing a telnet URL
  merely advise the user of the suggested username and password.

  Many RFCs have added various services to the Telnet protocol for
  better authentication, encryption of traffic, or both.  Those RFCs
  have not specified new URI schemes for Telnet to invoke those
  services (along the lines of "https" being a different URI scheme
  from "http").  Some modern telnet clients attempt to invoke those
  more-secure versions of Telnet when resolving a "telnet" URL.

3.  Security Considerations

  There are many security considerations for URI schemes discussed in
  [RFC3986].

  The Telnet protocol normally uses passwords in the clear for
  authentication, and normally offers no privacy.  In normal telnet,
  both the user's identity and their password are exposed without any
  protection; after that, the contents of the entire Telnet session is
  exposed without any protection.

  Many extensions have been made to Telnet to make it more secure in
  different ways.  In particular, [RFC2941] gives a framework based on
  a telnet option that many other security extensions have leveraged
  off of.  These extensions are certainly worthwhile methods for
  reducing the obvious problems with exposing the user's name,
  password, and plaintext of the session in the clear.

  Although some modern telnet clients attempt to invoke those more-
  secure versions of Telnet when resolving a "telnet" URL, other telnet
  clients do not, so a user cannot rely on this type of security unless
  it is explicitly enabled and the results of the security negotiation
  are checked.










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4.  Normative References

  [STD8]     Postel, J. and J. Reynolds, "Telnet Protocol
             Specification", STD 8, RFC 854, May 1983.

5.  Informative References

  [RFC1738]  Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform
             Resource Locators (URL)", RFC 1738, December 1994.

  [RFC2396]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
             Resource Identifiers (URI): Generic Syntax", RFC 2396,
             August 1998.

  [RFC2941]  Ts'o, T. and J. Altman, "Telnet Authentication Option",
             RFC 2941, September 2000.

  [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
             Resource Identifier (URI): Generic Syntax", STD 66,
             RFC 3986, January 2005.

Author's Address

  Paul Hoffman
  VPN Consortium
  127 Segre Place
  Santa Cruz, CA  95060
  US

  EMail: [email protected]





















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Full Copyright Statement

  Copyright (C) The Internet Society (2005).

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Acknowledgement

  Funding for the RFC Editor function is currently provided by the
  Internet Society.







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