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Network Working Group                                         P. HoffmanRequest for Comments: 4248                                VPN ConsortiumObsoletes:1738                                             October 2005Category: Standards TrackThe telnet URI SchemeStatus 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 inRFC 1738.  The purpose of   this document is to allowRFC 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>/Hoffman                     Standards Track                     [Page 1]

RFC 4248                 The telnet URI Scheme              October 2005   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.Hoffman                     Standards Track                     [Page 2]

RFC 4248                 The telnet URI Scheme              October 20054.  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: paul.hoffman@vpnc.orgHoffman                     Standards Track                     [Page 3]

RFC 4248                 The telnet URI Scheme              October 2005Full Copyright Statement   Copyright (C) The Internet Society (2005).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   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   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at ietf-   ipr@ietf.org.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Hoffman                     Standards Track                     [Page 4]