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<pre>Network Working Group P. Hoffman
Request for Comments: 4248 VPN Consortium
Obsoletes: <a href="./rfc1738">1738</a> October 2005
Category: Standards Track
<span class="h1">The telnet URI Scheme</span>
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 <a href="./rfc1738">RFC 1738</a>. The purpose of
this document is to allow <a href="./rfc1738">RFC 1738</a> to be made obsolete while keeping
the information about the scheme on standards track.
<span class="h2"><a class="selflink" id="section-1" href="#section-1">1</a>. Introduction</span>
URIs were previously defined in [<a href="./rfc2396" title=""Uniform Resource Identifiers (URI): Generic Syntax"">RFC2396</a>], which was updated by
[<a href="./rfc3986" title=""Uniform Resource Identifier (URI): Generic Syntax"">RFC3986</a>]. Those documents also specify how to define schemes for
URIs.
The first definition for many URI schemes appeared in [<a href="./rfc1738" title=""Uniform Resource Locators (URL)"">RFC1738</a>].
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.
<span class="h2"><a class="selflink" id="section-2" href="#section-2">2</a>. Scheme Definition</span>
The Telnet URL scheme is used to designate interactive services that
may be accessed by the Telnet protocol [<a href="#ref-STD8" title=""Telnet Protocol Specification"">STD8</a>].
A telnet URL takes the form:
telnet://<user>:<password>@<host>:<port>/
<span class="grey">Hoffman Standards Track [Page 1]</span></pre>
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<span class="grey"><a href="./rfc4248">RFC 4248</a> The telnet URI Scheme October 2005</span>
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.
<span class="h2"><a class="selflink" id="section-3" href="#section-3">3</a>. Security Considerations</span>
There are many security considerations for URI schemes discussed in
[<a href="./rfc3986" title=""Uniform Resource Identifier (URI): Generic Syntax"">RFC3986</a>].
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, [<a href="./rfc2941" title=""Telnet Authentication Option"">RFC2941</a>] 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.
<span class="grey">Hoffman Standards Track [Page 2]</span></pre>
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<span class="grey"><a href="./rfc4248">RFC 4248</a> The telnet URI Scheme October 2005</span>
<span class="h2"><a class="selflink" id="section-4" href="#section-4">4</a>. Normative References</span>
[<a id="ref-STD8">STD8</a>] Postel, J. and J. Reynolds, "Telnet Protocol
Specification", STD 8, <a href="./rfc854">RFC 854</a>, May 1983.
<span class="h2"><a class="selflink" id="section-5" href="#section-5">5</a>. Informative References</span>
[<a id="ref-RFC1738">RFC1738</a>] Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform
Resource Locators (URL)", <a href="./rfc1738">RFC 1738</a>, December 1994.
[<a id="ref-RFC2396">RFC2396</a>] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifiers (URI): Generic Syntax", <a href="./rfc2396">RFC 2396</a>,
August 1998.
[<a id="ref-RFC2941">RFC2941</a>] Ts'o, T. and J. Altman, "Telnet Authentication Option",
<a href="./rfc2941">RFC 2941</a>, September 2000.
[<a id="ref-RFC3986">RFC3986</a>] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
<a href="./rfc3986">RFC 3986</a>, January 2005.
Author's Address
Paul Hoffman
VPN Consortium
127 Segre Place
Santa Cruz, CA 95060
US
EMail: paul.hoffman@vpnc.org
<span class="grey">Hoffman Standards Track [Page 3]</span></pre>
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<span class="grey"><a href="./rfc4248">RFC 4248</a> The telnet URI Scheme October 2005</span>
Full Copyright Statement
Copyright (C) The Internet Society (2005).
This document is subject to the rights, licenses and restrictions
contained in <a href="https://www.rfc-editor.org/bcp/bcp78">BCP 78</a>, and except as set forth therein, the authors
retain all their rights.
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OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
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Acknowledgement
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Internet Society.
Hoffman Standards Track [Page 4]
</pre>
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