BEHAVEInternet Engineering Task Force (IETF) M. Petit-HugueninInternet-DraftRequest for Comments: 7065 Impedance MismatchIntended status:Category: Standards Track S. NandakumarExpires: March 31, 2014ISSN: 2070-1721 G. Salgueiro P. Jones Cisco SystemsSeptember 27,November 2013 Traversal Using Relays around NAT (TURN) Uniform Resource Identifiersdraft-petithuguenin-behave-turn-uris-08Abstract This document specifies the syntax of Uniform Resource Identifier (URI) schemes for the Traversal Using Relays around NAT (TURN) protocol. It defines two URI schemes to provision the TURN Resolution Mechanism[RFC5928].(RFC 5928). Status of This Memo ThisInternet-Draftissubmitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documentsan Internet Standards Track document. This document is a product of the Internet Engineering Task Force (IETF).Note that other groups may also distribute working documents as Internet-Drafts. The listIt represents the consensus ofcurrent Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents validthe IETF community. It has received public review and has been approved fora maximumpublication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 ofsix monthsRFC 5741. Information about the current status of this document, any errata, and how to provide feedback on it may beupdated, replaced, or obsoleted by other documentsobtained atany 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 31, 2014.http://www.rfc-editor.org/info/rfc7065. Copyright Notice Copyright (c) 2013 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 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Definitions of theTURN"turn" andTURNS"turns" URI . . . . . . . . . .. .3 3.1. URI Scheme Syntax . . . . . . . . . . . . . . . . . . . . 3 3.2. URI Scheme Semantics . . . . . . . . . . . . . . . . . . 4 4.Implementation Status . . . . . . . . . . . . . . . . . . . . 4 4.1. turnuri . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.2. libjingle . . . . . . . . . . . . . . . . . . . . . . . . 5 4.3. Firefox . . . . . . . . . . . . . . . . . . . . . . . . . 5 5.Security Considerations . . . . . . . . . . . . . . . . . . .6 6.4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . .6 6.1. TURN4 5.1. "turn" URI Registration . . . . . . . . . . . . . . . . .. 6 6.2. TURNS5 5.2. "turns" URI Registration . . . . . . . . . . . . . . . .. 7 7.5 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . .8 8.6 7. References . . . . . . . . . . . . . . . . . . . . . . . . .8 8.1.6 7.1. Normative References . . . . . . . . . . . . . . . . . .8 8.2.6 7.2. Informative References . . . . . . . . . . . . . . . . .97 Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . .97 Appendix B. Design Notes . . . . . . . . . . . . . . . . . . . .9 Appendix C. Release notes . . . . . . . . . . . . . . . . . . . 10 C.1. Modifications between petithuguenin-behave-turn-uris-08 and petithuguenin-behave-turn-uris-07 . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 107 1. Introduction This document specifies the syntax and semantics of the Uniform Resource Identifier (URI) scheme for the Traversal Using Relays around NAT (TURN) protocol. The TURN protocol is a specification allowing hosts behind NAT to control the operation of a relay server. The relay server allows hosts to exchange packets with its peers. The peers themselves may also be behind NATs. RFC 5766 [RFC5766] defines the specifics of the TURN protocol. The "turn" and "turns" URI schemes are used to designate a TURN server (also known as a relay) on Internet hosts accessible using the TURN protocol. 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 TURN server to carry out the TURN protocol. This also implies those endpoints and/or applications to be provisioned with appropriate configuration required to identify the TURN 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"turn/turns""turn" and "turns" URIscheme helpsschemes help alleviate most of these issues by providing a consistent way to describe,configureconfigure, and exchange the information identifying a TURN server. This would also prevent the shortcomings inherent with encoding similar information in non-uniform syntaxes such as the ones proposed in [WEBRTC], for example. [RFC5928] defines a resolution mechanism to convert a secure flag, a host name or IP address, a potentially empty port, and a potentially empty transport to a list of IP address, port, and TURN transport tuples. To simplify the provisioning of TURN clients, this document definesa TURNthe "turn" anda TURNS"turns" URIschemeschemes that can carry the four components needed for the resolution mechanism. 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119] when they appear in ALL CAPS. When these words are not in ALL CAPS (such as "should" or "Should"), they have their usual English meanings, and are not to be interpreted as RFC 2119 key words. 3. Definitions of theTURN"turn" andTURNS"turns" URI 3.1. URI Scheme SyntaxA TURN/TURNS URI hasThe "turn" and "turns" URIs have the following formal ABNF syntax [RFC5234]: turnURI = scheme ":" host [ ":" port ] [ "?transport=" transport ] scheme = "turn" / "turns" transport = "udp" / "tcp" / transport-ext transport-ext = 1*unreserved<host>,<host> and <port> are specified in [RFC3986]. While these two ABNF productions are defined in [RFC3986] as components of the generic hierarchical URI, this does not imply thatthattheturn"turn" andturns"turns" schemes are hierarchical URIs. Developers MUST NOT use a generic hierarchical URI parser to parse aturn"turn" orturns"turns" URI. The <host>,<port><port>, and <transport> components are passed without modification to the [RFC5928] algorithm. <secure> is set to false if <scheme> is equal to"turn""turn", and set to true if <scheme> is equal to "turns" and passed to the [RFC5928] algorithm with the other components. 3.2. URI Scheme Semantics The "turn" and "turns" URI schemes are used to designate a TURN server (also known as a relay) on Internet hosts accessible using the TURN protocol. The TURN protocol supports sending messages over UDP,TCPTCP, or TLS-over-TCP. The "turns" URI scheme MUST be used when TURN is run over TLS-over-TCP(or(or, in thefuture DTLS-over-UDP)future, DTLS-over-UDP), and the "turn" scheme MUST be used otherwise. The required <host> part of the "turn" URI denotes the TURN server host. As specified in [RFC5766] and [RFC5928], the <port> part, if present, denotes the port on which the TURN server is awaiting connection requests. If it is absent, the default port is 3478 for both UDP and TCP. The default port for TURN over TLS is 5349.[4. Implementation Considerations] 5.4. Security Considerations Security considerations for the resolution mechanism are discussed in Section 5 of [RFC5928]. Note that this section contains normative text defining authentication procedures to be followed by turn clients when TLS is used. The "turn" and "turns" URI schemes do not introduce any specific security issues beyond the security considerations discussed in [RFC3986].While the turn and turns URIs doAlthough a "turn" or "turns" URI does notthemselvesitself include the username or password that will be used to authenticate the TURN client, in certain environments, such as WebRTC, the username and password will almost certainly be provisioned remotely by an external agent at the same time as aturns"turns" URI is sent to that client. Thus, in such situations, if the username and password were received inclearthe clear, there would be little or no benefit to using aturns"turns" URI. For thisreasonreason, a TURN client MUST ensure that the username, password,and turns URI"turns" URI, and any other security-relevant parameters are received with equivalent security before using theturns"turns" URI. Receiving those parameters over another TLS session can provide the appropriate level of security, if both TLS sessions are similarly parameterised,e.g.e.g., with commensurate strength ciphersuites.6.5. IANA Considerations This section contains the registration information for the "turn" and "turns" URI Schemes (in accordance with [RFC4395]).6.1. TURN5.1. "turn" URI Registration URI scheme name: turn 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 "turn" URI scheme is intended to be used by applications with a need to identify a TURN server to be used for NAT traversal. Interoperability considerations: N/A Security considerations: See Section5.4. Contact: Marc Petit-Huguenin <petithug@acm.org> Author/Change controller: The IESG References:RFCXXXX [[NOTE TORFCEDITOR: Please change XXXX to the number assigned to this specification, and remove this paragraph on publication.]] 6.2. TURNS7065 5.2. "turns" URI Registration URI scheme name: turns 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 "turns" URI scheme is intended to be used by applications with a need to identify a TURN server to be used for NAT traversal over a secure connection. Interoperability considerations: N/A Security considerations: See Section5.4. Contact: Marc Petit-Huguenin <petithug@acm.org> Author/Change controller: The IESG References:RFCXXXX [[NOTE TORFCEDITOR: Please change XXXX to the number assigned to this specification, and remove this paragraph on publication.]] 7.7065 6. Acknowledgements Thanks to Margaret Wasserman, Magnus Westerlund, Juergen Schoenwaelder, Sean Turner, Ted Hardie, Dave Thaler, Alfred E. Heggestad, Eilon Yardeni, Dan Wing, Alfred Hoenes, and Jim Kleck for the comments,suggestionssuggestions, and questions that helped improvethe draft-petithuguenin-behave-turn-uri-bis document."Traversal Using Relays around NAT (TURN) Uniform Resource Identifiers" by M. Petit-Huguenin (October 2011). Many thanks to Cullen Jennings for his detailed review and thoughtful comments onthe draft-nandakumar-rtcweb-turn-uri document."URI Scheme for Traversal Using Relays around NAT (TURN) Protocol" by S. Nandakumar, et al. (October 2011). Thanks to Bjoern Hoehrmann, Dan Wing, Russ Housley, S. Moonesamy, Graham Klyne, Harald Alvestrand, Hadriel Kaplan, Tina Tsou, Spencer Dawkins, Ted Lemon, Barry Leiba, Pete Resnick, and Stephen Farrell for the comments,suggestionssuggestions, and questions that helped improve this document. The authors would also like to express their gratitude to Dan Wing for his assistance in shepherding this document. We also want to thank Gonzalo Camarillo, the Real-time Applications and Infrastructure Area Director, for sponsoring this document as well as his careful reviews.8.7. References8.1.7.1. 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. [RFC5766] Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using Relays around NAT (TURN): Relay Extensions to Session Traversal Utilities for NAT (STUN)", RFC 5766, April 2010. [RFC5928] Petit-Huguenin, M., "Traversal Using Relays around NAT (TURN) Resolution Mechanism", RFC 5928, August 2010.8.2.7.2. Informative References [RFC4395] Hansen, T., Hardie, T., and L. Masinter, "Guidelines and Registration Procedures for New URI Schemes", BCP 35, RFC 4395, February 2006. [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, <http://www.w3.org/TR/2012/WD-webrtc-20120821>.[RFC6982] Sheffer, Y. and A. Farrel, "Improving Awareness of Running Code: The Implementation Status Section", RFC 6982, July 2013.Appendix A. Examples Table 1 shows how the <secure>,<port><port>, and <transport> components are populated from various URIs. For all these examples, the <host> component is populated with "example.org". +---------------------------------+----------+--------+-------------+ | URI | <secure> | <port> | <transport> | +---------------------------------+----------+--------+-------------+ | turn:example.org | false | | | | turns:example.org | true | | | | turn:example.org:8000 | false | 8000 | | | turn:example.org?transport=udp | false | | UDP | | turn:example.org?transport=tcp | false | | TCP | | turns:example.org?transport=tcp | true | | TLS | +---------------------------------+----------+--------+-------------+ Table 1 Appendix B. Design Notes o One recurring comment was to stop using the suffix "s" on the URI scheme, and to move the secure option to a parameter (e.g. ";proto=tls"). We decided against this idea because the STUN URI does not have a ";proto=" parameter and we would have lost the symmetry between the TURN and STUN URIs. A more detailed account of the reasoning behind this is available at <http://blog.marc .petit-huguenin.org/2012/09/on-design-of-stun-and-turn-uri-formats.html>formats.html>. o Following the advice of Section 2.2 of RFC4395 section 2.2.,4395, and because the TURN URI does not describe a hierarchical structure, the TURN URIs are opaque URIs. o <password> is not used in the URIs because it is deprecated [RFC3986]. <username> and <auth> are not used in the URIs because they do not guide the resolution mechanism. o As discussed at IETF 72 in Dublin, thereisare no generic parameters in the URI to prevent compatibility issues.Appendix C. Release notes This section must be removed before publication as an RFC. C.1. Modifications between petithuguenin-behave-turn-uris-08 and petithuguenin-behave-turn-uris-07 o s/eventually/potentially/ o Changed the ABNF to use references from RFC 3986 instead of copying them. o Converted the design note about hierarchical parsers into a MUST NOT statement. o Updated the RFC 6982 forms for Chrome and Firefox. o Added text in security section about verifying that username, password and uris are received over a secure connection.Authors' Addresses Marc Petit-Huguenin Impedance MismatchEmail:EMail: petithug@acm.org Suhas Nandakumar Cisco Systems 170 West Tasman Drive San Jose, CA 95134 USEmail:EMail: snandaku@cisco.com Gonzalo Salgueiro Cisco Systems 7200-12 Kit Creek Road Research Triangle Park, NC 27709 USEmail:EMail: gsalguei@cisco.com Paul E. Jones Cisco Systems 7025 Kit Creek Road Research Triangle Park, NC 27709 USEmail:EMail: paulej@packetizer.com