The 'tn3270' URI Scheme
A web-style address for opening a Telnet 3270 mainframe terminal session.
Yevstifeyev, M., "The 'tn3270' URI Scheme", RFC 6270, DOI 10.17487/RFC6270, June 2011, <https://www.rfc-editor.org/info/rfc6270>.
@misc{rfc6270,
series = {Request for Comments},
number = 6270,
howpublished = {RFC 6270},
publisher = {RFC Editor},
doi = {10.17487/RFC6270},
url = {https://www.rfc-editor.org/info/rfc6270},
author = {M. Yevstifeyev},
title = {{The 'tn3270' URI Scheme}},
pagetotal = 6,
year = 2011,
month = jun,
} RFC text
Contents
Internet Engineering Task Force (IETF) M. Yevstifeyev
Request for Comments: 6270 June 2011
Updates: 1041, 1738, 2355
Category: Standards Track
ISSN: 2070-1721
The 'tn3270' URI Scheme
Abstract
This document is the specification of the 'tn3270' Uniform Resource
Identifier (URI) scheme, which is used to designate the access to the
resources available via Telnet 3270 mode (TN3270) and Telnet 3270
Enhanced mode (TN3270E). It updates RFC 1041 and RFC 2355, which
specify these protocols, and RFC 1738, which firstly mentioned this
URI scheme without defining its syntax and semantics.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6270.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................2
1.1. Terminology ................................................3
2. URI Scheme Definition ...........................................3
2.1. URI Scheme Syntax ..........................................3
2.2. URI Scheme Semantics .......................................3
3. Security Considerations .........................................3
4. IANA Considerations .............................................4
5. References ......................................................4
5.1. Normative References .......................................4
5.2. Informative References .....................................5
Appendix A. Acknowledgments ........................................6
1. Introduction
This document specifies the 'tn3270' Uniform Resource Identifier
(URI) scheme, which is used to designate the access to the resources
available via Telnet 3270 mode (TN3270) and Telnet 3270 Enhanced mode
(TN3270E).
Telnet 3270 mode (TN3270) is a name used to denote the special mode
of Telnet session [RFC0854]. If it is used, the 3270 data stream
[GA23-0059] is used when transmitting data during the Telnet session,
whereas the Telnet 3270 Regime option [RFC1041] is used to enable and
negotiate its use. (See [RFC1576] for some other background
information on TN3270.) Telnet 3270 Enhanced mode (TN3270E) has a
similar principle; see RFC 2355 [RFC2355] for its specification.
The 'tn3270' URI scheme was firstly mentioned in RFC 1738 [RFC1738]
as used in URIs that designate the access to "Interactive 3270
emulation sessions". Following the creation of the URI schemes
registry per RFC 4395 [RFC4395], this scheme was added to the
"Provisional URI Schemes" sub-registry in the "Uniform Resource
Identifier (URI) Schemes" IANA registry [URIREG]. However, RFC 1738
[RFC1738] does not give any definition of syntax or semantics of the
'tn3270' URIs and does not have any guidelines for registration of
this scheme.
Since there is no acceptable specification of the 'tn3270' URI, there
is a risk that somebody might try to implement it with some new,
possibly undocumented, syntax, just by looking at the IANA registry.
In order to minimize such risk, this document gives a precise
definition of syntax, semantics, use of this URI, and it registers
the corresponding scheme. It also updates RFC 2355 [RFC2355], RFC
1738 [RFC1738], and RFC 1041 [RFC1041].
The generic syntax of URIs is described in RFC 3986 [RFC3986].
Registration procedures for new URI schemes are defined in RFC 4395
[RFC4395].
1.1. Terminology
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 [RFC2119].
2. URI Scheme Definition
2.1. URI Scheme Syntax
The 'tn3270' URI takes the following form (the syntax below is non-
normative):
tn3270://<userinfo>@<host>:<port>/
where the <userinfo> part with the "@" (at) sign character, as well
as the <port> part with the preceding ":" (colon) character, is
OPTIONAL.
The normative syntax of the 'tn3270' URI is defined in <tn3270-uri>
ABNF [RFC5234] rule:
tn3270-uri = "tn3270:" "//" authority ["/"]
where the <authority> rule is specified in RFC 3986 [RFC3986].
The semantics of each part of the 'tn3270' URI are defined below, in
Section 2.2.
2.2. URI Scheme Semantics
The <host> part of the 'tn3270' URI, which is REQUIRED, denotes the
host to which the TN3270 or TN3270E connection is to be established.
The <userinfo> part is considered to define the information for use
in the Telnet Authentication option [RFC2941], which might be used
during the TN3270 or TN3270E session. The <port> part, if present,
denotes the port on which the TCP connection to the <host> is to be
established. If it is absent, the default port SHALL be 23, as
registered in [PORTREG].
3. Security Considerations
Generic security considerations for the usage of URIs are discussed
in Section 7 of [RFC3986].
Since 'tn3270' URIs provide access to services that are available via
TN3270 and TN3270E, which do not add any new security issues to the
Telnet session, as they are a modified form of it, there are no other
security considerations for 'tn3270' URIs that are not discussed in
RFC 4248 [RFC4248], the 'telnet' URI scheme specification.
The Telnet protocol, as well as TN3270 and TN3270E, is inherently
insecure. Those needing remote login access and related services are
encouraged to use a more secure technology, such as Secure Shell
[RFC4251].
4. IANA Considerations
IANA updated the registration of the 'tn3270' URI scheme using the
following registration template (see [RFC4395]):
URI scheme name: tn3270
Status: Permanent
URI scheme syntax: see Section 2.1 of RFC 6270
URI scheme semantics: see Section 2.2 of RFC 6270
URI scheme encoding considerations: there are no other encoding
considerations for 'tn3270' URIs that are not described in RFC
3986 [RFC3986]
Protocols that use the scheme: Telnet 3270 mode (TN3270) [RFC1041]
and Telnet 3270 Enhanced Mode (TN3270E) [RFC2355]
Security considerations: see Section 3 of RFC 6270
Contact: IESG <iesg@ietf.org>
Author/Change controller: IETF <ietf@ietf.org>
References: see Section 5 of RFC 6270
5. References
5.1. Normative References
[RFC1041] Rekhter, Y., "Telnet 3270 regime option", RFC 1041,
January 1988.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2355] Kelly, B., "TN3270 Enhancements", RFC 2355, June 1998.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, RFC
3986, January 2005.
[RFC4248] Hoffman, P., "The telnet URI Scheme", RFC 4248, October
2005.
[RFC5234] Crocker, D., Ed., and P. Overell, "Augmented BNF for
Syntax Specifications: ABNF", STD 68, RFC 5234, January
2008.
5.2. Informative References
[GA23-0059] IBM Corporation, "IBM 3270 Information Display System.
Data Stream Programmer's Reference", IBM Publication
GA23-0059, July 1992.
[PORTREG] Internet Assigned Numbers Authority (IANA) Registry,
"Port Numbers", <http://www.iana.org>.
[RFC0854] Postel, J. and J. Reynolds, "Telnet Protocol
Specification", STD 8, RFC 854, May 1983.
[RFC1576] Penner, J., "TN3270 Current Practices", RFC 1576, January
1994.
[RFC1738] Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform
Resource Locators (URL)", RFC 1738, December 1994.
[RFC2941] Ts'o, T., Ed., and J. Altman, "Telnet Authentication
Option", RFC 2941, September 2000.
[RFC4251] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
Protocol Architecture", RFC 4251, January 2006.
[RFC4395] Hansen, T., Hardie, T., and L. Masinter, "Guidelines and
Registration Procedures for New URI Schemes", BCP 35, RFC
4395, February 2006.
[URIREG] Internet Assigned Numbers Authority (IANA) Registry,
"Uniform Resource Identifier (URI) Schemes",
<http://www.iana.org>.
Appendix A. Acknowledgments
Many thanks to Alfred Hoenes, Graham Klyne, Alexey Melnikov, Julian
Reschke, and Peter Saint-Andre for their input to this document.
Author's Addresses
Mykyta Yevstifeyev
8 Kuzovkov St., flat 25,
Kotovsk
Ukraine
EMail: evnikita2@gmail.com
AI ELI5
On this page
§1Why the Scheme Needed a Definition
RFC 6270 specifies the tn3270 URI scheme, used to designate access to resources available through Telnet 3270 mode (TN3270) and Telnet 3270 Enhanced mode (TN3270E).
The scheme was first mentioned in RFC 1738 for URIs that designate "Interactive 3270 emulation sessions". After the URI schemes registry was created under RFC 4395, it was added to the Provisional URI Schemes sub-registry. However, RFC 1738 gave no syntax, no semantics and no registration guidelines for it.
The RFC states the risk plainly: someone might implement the scheme with new, possibly undocumented, syntax just by looking at the IANA registry. This document removes that risk with a precise definition and a registration.
The name for this kind of address was already on a list, but nobody had said how to write one. So people could have made up their own rules. This document writes down the one true rule.
§1.1TN3270 and TN3270E
TN3270 is the name for a special mode of a Telnet session (RFC 854). In this mode the IBM 3270 data stream is used to carry data during the session, and the Telnet 3270 Regime option (RFC 1041) enables and negotiates its use.
TN3270E works on a similar principle and is specified in RFC 2355. For background on current practice, the RFC points to RFC 1576. The URI scheme is simply a way to point at a service that speaks either of these.
Big old IBM computers talk to screens in their own special way. TN3270 is a way to do that talking over a Telnet connection, and TN3270E is a newer take on the same idea.
§2.1URI Scheme Syntax
The informal (non-normative) form is tn3270://<userinfo>@<host>:<port>/. The userinfo part with its @, and the port part with its :, are OPTIONAL.
The normative rule is written in ABNF (RFC 5234) as tn3270-uri = "tn3270:" "//" authority ["/"]. The authority rule comes from RFC 3986, so the trailing slash is optional too.
An address starts with the word tn3270, then the name of the computer. You can add a user name in front and a door number after, but you do not have to.
tn3270://<userinfo>@<host>:<port>/
tn3270-uri = "tn3270:" "//" authority ["/"]§2.2URI Scheme Semantics
The host part is REQUIRED and names the host to which the TN3270 or TN3270E connection is to be made. If a port is present, it is the port for the TCP connection to the host. If it is absent, the default port SHALL be 23, as registered in the IANA port registry.
The userinfo part is considered to define information for the Telnet Authentication option (RFC 2941), which might be used during the session.
The computer name says where to call. If you give no door number, the call goes to door 23. A user name, if you give one, may be used to prove who you are.
§3Security Considerations
Generic URI security issues are covered in Section 7 of RFC 3986. TN3270 and TN3270E are modified forms of Telnet and add no new security issues to a Telnet session, so the only further considerations are those in RFC 4248, the specification of the telnet URI scheme.
The RFC adds that Telnet, TN3270 and TN3270E are inherently insecure. Anyone needing remote login access and related services is encouraged to use a more secure technology, such as Secure Shell (RFC 4251).
Talking over Telnet is like shouting across a room, since anyone can listen in. The advice is to use a safer method such as Secure Shell when it matters.
§4IANA Registration
IANA updated the registration of the scheme using the template from RFC 4395. The scheme name is tn3270 and its status is Permanent, rather than the earlier provisional listing.
The protocols that use it are Telnet 3270 mode (RFC 1041) and TN3270E (RFC 2355). The contact is the IESG, and the change controller is the IETF. Syntax and semantics point back to Sections 2.1 and 2.2 of this RFC.
The scheme name moved from a try-out list to the official list, with this document as its instruction sheet.