RTCWEB S. Nandakumar Internet-Draft G. Salgueiro Intended status: Standards Track P. Jones Expires: March 17, 2013 Cisco Systems M. Petit-Huguenin Impedance Mismatch May 7, 2013 URI Scheme for Session Traversal Utilities for NAT (STUN) Protocol draft-nandakumar-rtcweb-stun-uri-04 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 provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on March 17, 2013. Copyright Notice Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved. Nandakumar, et al. Expires March 17, 2013 [Page 1] Internet-Draft STUN URI September 2012 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. This document may not be modified, and derivative works of it may not be created, except to format it for publication as an RFC or to translate it into languages other than English. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Definition of the STUN or STUNS URI . . . . . . . . . . . . . 3 3.1. URI Scheme Syntax . . . . . . . . . . . . . . . . . . . . 3 3.2. URI Scheme Semantics . . . . . . . . . . . . . . . . . . 4 4. Implementation Status . . . . . . . . . . . . . . . . . . . . 4 4.1. libjingle . . . . . . . . . . . . . . . . . . . . . . . . 5 4.2. Firefox . . . . . . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6.1. STUN URI Registration . . . . . . . . . . . . . . . . . . 6 6.2. STUNS URI Registration . . . . . . . . . . . . . . . . . 6 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 8.1. Normative References . . . . . . . . . . . . . . . . . . 7 8.2. Informative References . . . . . . . . . . . . . . . . . 8 Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 8 Appendix B. Design Notes . . . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 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. Nandakumar, et al. Expires March 17, 2013 [Page 2] Internet-Draft STUN URI September 2012 The "stun" and "stuns" URI schemes are 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. 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 3. Definition of the STUN or STUNS URI 3.1. URI Scheme Syntax The "stun" URI takes the following form (the example below is non- normative): stun:: stuns:: Note that the part and the preceding ":" (colon) character, is OPTIONAL. A STUN/STUNS URI has the following formal ABNF syntax [RFC5234]: stunURI = scheme ":" stun-host [ ":" stun-port ] scheme = "stun" / "stuns" stun-host = IP-literal / IPv4address / reg-name stun-port = *DIGIT IP-literal = "[" ( IPv6address / IPvFuture ) "]" IPvFuture = "v" 1*HEXDIG "." 1*( unreserved / sub-delims / ":" ) IPv6address = 6( h16 ":" ) ls32 / "::" 5( h16 ":" ) ls32 / [ h16 ] "::" 4( h16 ":" ) ls32 Nandakumar, et al. Expires March 17, 2013 [Page 3] Internet-Draft STUN URI September 2012 / [ *1( h16 ":" ) h16 ] "::" 3( h16 ":" ) ls32 / [ *2( h16 ":" ) h16 ] "::" 2( h16 ":" ) ls32 / [ *3( h16 ":" ) h16 ] "::" h16 ":" ls32 / [ *4( h16 ":" ) h16 ] "::" ls32 / [ *5( h16 ":" ) h16 ] "::" h16 / [ *6( h16 ":" ) h16 ] "::" h16 = 1*4HEXDIG ls32 = ( h16 ":" h16 ) / IPv4address IPv4address = dec-octet "." dec-octet "." dec-octet "." dec-octet dec-octet = DIGIT ; 0-9 / %x31-39 DIGIT ; 10-99 / "1" 2DIGIT ; 100-199 / "2" %x30-34 DIGIT ; 200-249 / "25" %x30-35 ; 250-255 reg-name = *( unreserved / pct-encoded / sub-delims ) , , and are specified in [RFC3986]. The core rules and 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 MUST be used when STUN is run over TLS-over-TCP (or in the future DTLS-over-UDP) and the "stun" scheme MUST be used otherwise. The required part of the "stun" URI denotes the STUN server host. For the optional DNS Discovery procedure mentioned in the Section 9 of RFC5389, "stun" URI scheme implies UDP as the transport protocol for SRV lookup and "stuns" URI scheme indicates TCP as the transport protocol. The part, if present, denotes the port on which the STUN server is awaiting connection requests. If it is absent, the default port is 3478 for both UDP and TCP. The default port for STUN over TLS is 5349 as per Section 9 of RFC 5389 [RFC5389]. 4. Implementation Status Note to RFC Editor: Please remove this section before publication. This section records the status of known implementations of the protocol defined by this specification at the time of posting of this Internet-Draft, and is based on a proposal described in Nandakumar, et al. Expires March 17, 2013 [Page 4] Internet-Draft STUN URI September 2012 [RUNNING-CODE]. According to [RUNNING-CODE], "this will allow reviewers and working groups to assign due consideration to documents that have the benefit of running code, by considering the running code as evidence of valuable experimentation and feedback that has made the implemented protocols more mature. It is up to the individual working groups to use this information as they see fit". 4.1. libjingle Name: libjingle 0.7.1 Description: Libjingle is a set of components provided by Google to implement Jingle protocols XEP-166 (http://xmpp.org/extensions/ xep-0166.html) and XEP-167 (http://xmpp.org/extensions/ xep-0167.html). Level of maturity: Beta. Coverage: Implements draft-nandakumar-rtcweb-stun-uri-01 without IPv6. Licensing: BSD 3-clauses license. Contact: https://code.google.com/p/chromium/ URL: https://code.google.com/p/chromium/codesearch#chromium/src/ third_party/libjingle/source/talk/app/webrtc/peerconnection.cc 4.2. Firefox Name: Firefox Aurora 21 Description: Mozilla Firefox is a free and open source web browser. Level of maturity: Beta. Coverage: Implements draft-nandakumar-rtcweb-stun-uri-03. Licensing: Mozilla Public License, v. 2.0. Contact: http://www.mozilla.org/en-US/firefox/channel/ URL: http://hg.mozilla.org/mozilla-central/file/4ff1e574e509/media/ webrtc/signaling/src/peerconnection/PeerConnectionImpl.cpp 5. Security Considerations Nandakumar, et al. Expires March 17, 2013 [Page 5] Internet-Draft STUN URI September 2012 The "stun" and "stuns" URI schemes do not introduce any specific security issues beyond the security considerations discussed in [RFC3986]. 6. IANA Considerations This section contains the registration information for the "stun" and "stuns" URI Schemes (in accordance with [RFC4395]). 6.1. STUN URI Registration URI scheme name: stun Status: permanent URI scheme syntax: See Section 3.1. URI scheme semantics: See Section 3.2. Encoding considerations: There are no encoding considerations beyond those in [RFC3986]. Applications/protocols that use this URI scheme name: The "stun" URI scheme is intended to be used by applications that might need access to a STUN server. Interoperability considerations: N/A Security considerations: See Section 5. Contact: Suhas Nandakumar Author/Change controller: The IESG References: RFCXXXX [[NOTE TO RFC EDITOR: Please change XXXX to the number assigned to this specification, and remove this paragraph on publication.]] 6.2. STUNS URI Registration URI scheme name: stuns Status: permanent URI scheme syntax: See Section 3.1. Nandakumar, et al. Expires March 17, 2013 [Page 6] Internet-Draft STUN URI September 2012 URI scheme semantics: See Section 3.2. Encoding considerations: There are no encoding considerations beyond those in [RFC3986]. Applications/protocols that use this URI scheme name: The "stuns" URI scheme is intended to be used by applications that might need access to a STUN server over a secure connection. Interoperability considerations: N/A Security considerations: See Section 5. Contact: Suhas Nandakumar Author/Change controller: The IESG References: RFCXXXX; [[NOTE TO RFC EDITOR: Please change XXXX to the number assigned to this specification, and remove this paragraph on publication.]] 7. Acknowledgements Many thanks to Cullen Jennings for his detailed review and thoughtful comments on this document. Thanks to Ted Hardie, Bjoern Hoehrmann for their comments, suggestions and questions that helped to improve the this document. This document was written with the xml2rfc tool described in [RFC2629]. 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. [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005. [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. Nandakumar, et al. Expires March 17, 2013 [Page 7] Internet-Draft STUN URI September 2012 8.2. Informative References [RFC2629] Rose, M.T., "Writing I-Ds and RFCs using XML", RFC 2629, June 1999. [RFC4395] Hansen, T., Hardie, T., and L. Masinter, "Guidelines and Registration Procedures for New URI Schemes", BCP 35, RFC 4395, February 2006. [RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing, "Session Traversal Utilities for NAT (STUN)", RFC 5389, October 2008. [WEBRTC] Bergkvist, A., Burnett, D., Jennings, C., and A. Narayanan, "WebRTC 1.0: Real-time Communication Between Browsers", World Wide Web Consortium WD WD- webrtc-20120821, August 2012, . [RUNNING-CODE] Sheffer, Y. and A. Farrel, "Improving Awareness of Running Code: the Implementation Status Section", draft-sheffer- running-code-04 (work in progress), April 2013. Appendix A. Examples Table 1 shows examples for 'stun/stuns'uri scheme. For all these examples, the component is populated with "example.org". +-----------------------+ | URI | +-----------------------+ | stun:example.org | | stuns:example.org | | stun:example.org:8000 | +-----------------------+ Table 1 Appendix B. Design Notes o One recurring comment was to stop using the suffix "s" on URI scheme, and to move the secure option to a parameter (e.g. ";proto=tls"). We decided against this idea because the need of ";proto=" for the STUN URI cannot be sufficiently explained and supporting it would render into an incomplete specification. This would also result in loosing symmetry between the TURN and STUN URIs. A more detailed account of the reasoning behind this is Nandakumar, et al. Expires March 17, 2013 [Page 8] Internet-Draft STUN URI September 2012 available at 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 Marc Petit-Huguenin Impedance Mismatch Email: petithug@acm.org Nandakumar, et al. Expires March 17, 2013 [Page 9]