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Versions: 00 01 02 03 04 05 06 07 08 RFC 7064
RTCWEB S. Nandakumar
Internet-Draft G. Salgueiro
Intended status: Standards Track P. Jones
Expires: April 27, 2012 Cisco Systems
October 25, 2011
URI Scheme for Session Traversal Utilities for NAT (STUN) Protocol
draft-nandakumar-rtcweb-stun-uri-00
Abstract
This document is the specification of the syntax and semantics of the
Uniform Resource Identifier (URI) scheme for the Session Traversal
Utilities for NAT (STUN) protocol.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
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This Internet-Draft will expire on April 27, 2012.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. URI Scheme Definition . . . . . . . . . . . . . . . . . . . . . 3
3.1. URI Scheme Syntax . . . . . . . . . . . . . . . . . . . . . 3
3.2. URI Scheme Semantics . . . . . . . . . . . . . . . . . . . 4
4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
5.1. The 'stun' URI Scheme Registration . . . . . . . . . . . . 5
5.2. The 'stuns' URI Scheme Registration . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
This document specifies the syntax and semantics of the Uniform
Resource Identifier (URI) scheme for the Session Traversal Utilities
for NAT (STUN) protocol.
STUN is a protocol that serves as a tool for other protocols in
dealing with Network Address Translator (NAT) traversal. It can be
used by an endpoint to determine the IP address and port allocated to
it by a NAT, to perform connectivity checks between two endpoints,
and used as a keepalive protocol to maintain NAT bindings. RFC 5389
[RFC5389] defines the specifics of the STUN protocol.
The 'stun/stuns' URI scheme is used to designate a standalone STUN
server or any Internet host performing the operations of a STUN
server in the context of STUN usages (Section 14 RFC 5389 [RFC5389]).
With the advent of standards such as WEBRTC [WEBRTC], we anticipate a
plethora of endpoints and web applications to be able to identify and
communicate with such a STUN server to carry out the STUN protocol.
This also implies those endpoints and/or applications to be
provisioned with appropriate configuration required to identify the
STUN server. Having an inconsistent syntax has its drawbacks and can
result in non-interoperable solutions. It can result in solutions
that are ambiguous and have implementation limitations on the
different aspects of the syntax and alike. The 'stun/stuns' URI
scheme helps alleviate most of these issues by providing a consistent
way to describe, configure and exchange the information identifying a
STUN server. This would also prevent the shortcomings inherent with
encoding similar information in non-uniform syntaxes such as the ones
proposed in the WEBRTC Standards [WEBRTC], for example.
The 'stun/stuns' URI scheme adheres to the generic syntax defined in
RFC 3986 [RFC3986].
2. 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].
3. URI Scheme Definition
3.1. URI Scheme Syntax
The 'stun/stuns' URI takes the following form (the syntax below is
non-normative):
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stun:<userinfo>@<host>:<port>
stuns:<userinfo>@<host>:<port>
Where <userinfo> with the "@" (at) sign character, as well as the
<port> part and the preceding ":" (colon) character, is OPTIONAL.
The normative syntax of the 'stun' URI is defined as shown in the
following Augmented Backus-Naur Form (ABNF) [RFC5234]. rule:
stun-uri = stun-scheme ":" [ userinfo "@" ] host [ ":" port ]
stun-scheme = "stun"/"stuns"
userinfo = user
user = 1*(%x21-24 / %x26-39 / %x3B-3F / %x41-7F
/ escaped)
; The symbols "%", ":", "@", and symbols
; with a character value below 0x21 may
; be represented as escaped sequences.
host = hostname / IPv4address / IPv6reference
hostname = *( domainlabel "." ) toplabel [ "." ]
domainlabel = alphanum / alphanum *( alphanum / "-" ) alphanum
toplabel = ALPHA / ALPHA *( alphanum / "-" ) alphanum
IPv4address = 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT
IPv6reference = "[" IPv6address "]"
IPv6address = hexpart [ ":" IPv4address ]
hexpart = hexseq / hexseq "::" [ hexseq ] / "::" [ hexseq ]
hexseq = hex4 *( ":" hex4 )
hex4 = 1*4HEXDIG
port = 1*DIGIT
alphanum = ALPHA / DIGIT
escaped = "%" HEXDIG HEXDIG
The current ABNF proposal doesn't specify a mechanism for handling
different transports. We have identified a possible solution and
will be included in the future version of the draft.
The <host>, <port> and <userinfo> rules are described in Appendix A
of RFC 3986 [RFC3986]. The core rules <ALPHA>, <DIGIT> and
<HEXDIGIT> are used as described in Appendix B of RFC 5234 [RFC5234].
3.2. URI Scheme Semantics
The STUN protocol supports sending messages over UDP, TCP or TLS-
over-TCP. The 'stuns' URI scheme SHALL be used when STUN is run over
TLS-over-TCP (or DTLS-over-UDP in the future) and the 'stun' scheme
SHALL be used otherwise. The <host> part of the 'stun' URI, which is
REQUIRED, denotes the STUN server host. The <userinfo> part is
OPTIONAL and MAY NOT be utilized within the 'stun/stuns' URI scheme.
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It is provided so as to be compatible with certain non-standard
standalone STUN server implementations that enforce clients to
authenticate. The <port> part, if present,denotes the port on which
the STUN server is awaiting connection requests. For a standalone
STUN server the port SHALL default to 3478 for both UDP and TCP. The
default port for TLS SHALL be 5349.
4. Examples
URI identifying a STUN Server at example.com listening on port 1234:
stun:example.com:1234
A URI to identify a STUN server at example.com listening on the
default TLS port 5349:
stuns:example.com
URI to identify a short-term or a long-term credential for the
connection to STUN server, example.com, on port 1234:
stun:username:password@example.com:1234
5. IANA Considerations
This document instructs IANA to register the 'stun' and 'stuns' URI
schemes in the "Permanent URI Schemes" sub-registry in the "Uniform
Resource Identifier (URI) Schemes" IANA registry [URIREG]. These
registrations follows the URI Scheme Registration Template detailed
in Section 5.4 of RFC 4395 [RFC4395].
5.1. The 'stun' URI Scheme Registration
IANA registration of the the 'stun' URI scheme:
URI scheme name: stun
Status: Permanent
URI scheme syntax: see Section 3.1 of RFC XXXX [This document]
URI scheme semantics: see Section 3.2 of RFC XXXX [This document]
URI scheme encoding considerations: there are no other encoding
considerations for 'stun' URIs that are not described in RFC 5389
[RFC5389].
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Protocols that use the scheme: Session Traversal Utilities for NAT
(STUN)
Security Considerations: see Section 6 of RFC XXXX [This document]
Contact: IESG <iesg@ietf.org>
Author/Change controller: IETF <ietf@ietf.org>
References: See Section 8 of RFC XXXX [This document]
5.2. The 'stuns' URI Scheme Registration
IANA registration of the the 'stuns' URI scheme:
URI scheme name: stuns
Status: Permanent
URI scheme syntax: see Section 3.1 of RFC XXXX [This document]
URI scheme semantics: see Section 3.2 of RFC XXXX [This document]
URI scheme encoding considerations: there are no other encoding
considerations for 'stuns' URIs that are not described in RFC 5389
[RFC5389].
Protocols that use the scheme: Session Traversal Utilities for NAT
(STUN) when run over TLS-over-TCP.
Security Considerations: see Section 6 of RFC XXXX [This document]
Contact: IESG <iesg@ietf.org>
Author/Change controller: IETF <ietf@ietf.org>
References: See Section 8 of RFC XXXX [This document]
6. Security Considerations
Generic security considerations for the usage of URIs are discussed
in Section 7 of RFC 3986 [RFC3986]
The URI Scheme defined by this document for the Session Traversal
Utilities for NAT (STUN) protocol does not introduce any security
considerations beyond those detailed in Section 16 of RFC 5389
[RFC5389].
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The STUN protocol supports two opional credential mechanisms as
described in the Section 10 of RFC 5389 [RFC5389]. For the short-
term credential mechanism (Section 10.1 of RFC 5389 [RFC5389]), the
security of such a credential SHALL be the responsibility of the STUN
usage mechanism, say ICE (RFC 5245 [RFC5245]). For the long-term
credential mechanism (Section 10.2 of RFC 5389 [RFC5389]), such a
credential MUST be passed over a secure transport such as HTTPS (RFC
2818 [RFC2818]).
7. Acknowledgements
Many thanks to Cullen Jennings for his detailed review and thoughtful
comments on this document.
We acknowledge the existence of
draft-petithuguenin-behave-turn-uri-bis-04 document as a parallel
effort in defining the URI scheme for TURN. Awareness of this draft
came late in the process and we have not had to time to reach out to
the author of that memo and discuss opportunities to collaborate on a
single document. It is our intentions to do so.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
"Session Traversal Utilities for NAT (STUN)", RFC 5389,
October 2008.
8.2. Informative References
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC4395] Hansen, T., Hardie, T., and L. Masinter, "Guidelines and
Registration Procedures for New URI Schemes", BCP 35,
RFC 4395, February 2006.
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[RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
(ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols", RFC 5245,
April 2010.
[URIREG] Internet Assigned Numbers Authority (IANA) Registry,
"Uniform Resource Identifier (URI) Schemes",
<http://www.iana.org/assignments/uri-schemes.html> .
[WEBRTC] W3C, "WebRTC 1.0: Real-time Communication Between
Browsers",
<http://dev.w3.org/2011/webrtc/editor/webrtc.html> .
Authors' Addresses
Suhas Nandakumar
Cisco Systems
170 West Tasman Drive
San Jose, CA 95134
US
Email: snandaku@cisco.com
Gonzalo Salgueiro
Cisco Systems
7200-12 Kit Creek Road
Research Triangle Park, NC 27709
US
Email: gsalguei@cisco.com
Paul E. Jones
Cisco Systems
7025 Kit Creek Road
Research Triangle Park, NC 27709
US
Email: paulej@packetizer.com
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