RFC 7065
Traversal Using Relays around NAT (TURN) Uniform Resource Identifiers
RFC 7065 ✨ Traversal Using Relays around NAT (TURN) Uniform Resource Identifiers
Okay bestie, this is RFC 7065 🦋, all about TURN Uniform Resource Identifiers. It was written by M. Petit-Huguenin (Impedance Mismatch 💅), S. Nandakumar, G. Salgueiro, and P. Jones, all at Cisco Systems. It's a Standards Track doc, ISSN 2070-1721, dated November 2013 🌸. The header doesn't list anything it obsoletes or updates, so it's not replacing or patching any other RFC 🫶.
Abstract ✨
This doc spells out the syntax of the Uniform Resource Identifier (URI) schemes for the Traversal Using Relays around NAT (TURN) protocol. It defines two URI schemes, "turn" and "turns", to provision the TURN Resolution Mechanism (RFC 5928) 🎀.
Status of This Memo 📜
This is an Internet Standards Track document. 🌈
This doc 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). More info on Internet Standards is in Section 2 of RFC 5741 🧚.
Info about the current status of this document, any errata, and how to send feedback on it can be found at 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), as in effect on the date this document was published. Please read these carefully, because they spell out 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 they're provided without warranty as described in the Simplified BSD License 🍓.
Table of Contents 🗂️
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Definitions of the "turn" and "turns" URI . . . . . . . . . . 4
3.1. URI Scheme Syntax . . . . . . . . . . . . . . . . . . . . 4
3.2. URI Scheme Semantics . . . . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
5.1. "turn" URI Registration . . . . . . . . . . . . . . . . . 5
5.2. "turns" URI Registration . . . . . . . . . . . . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Normative References . . . . . . . . . . . . . . . . . . 7
7.2. Informative References . . . . . . . . . . . . . . . . . 7
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 8
Appendix B. Design Notes . . . . . . . . . . . . . . . . . . . . 81. Introduction 🌸
This doc spells out the syntax and semantics of the Uniform Resource Identifier (URI) scheme for the Traversal Using Relays around NAT (TURN) protocol. 💖
TURN lets hosts sitting behind NAT control the operation of a relay server. The relay server lets those hosts swap packets with its peers, and the peers themselves might be behind NATs too. RFC 5766 [RFC5766] is where the specifics of the TURN protocol live 🦋.
The "turn" and "turns" URI schemes are used to designate a TURN server (aka a relay) on Internet hosts you can reach using the TURN protocol. With standards like WebRTC [WEBRTC] around, we expect a plethora of endpoints and web apps to want to identify and talk to a TURN server. That means endpoints and/or apps need the right config to find it. An inconsistent syntax adds ambiguity, and it can lead to non-interoperable solutions and implementation limitations 🙈. The "turn" and "turns" schemes help fix most of that by giving one consistent way to describe, configure, and exchange the info that identifies a TURN server ✨.
[RFC5928] defines a resolution mechanism that turns a secure flag, a host name or IP address, a potentially empty port, and a potentially empty transport into a list of IP address, port, and TURN transport tuples 🧚.
To make provisioning TURN clients simpler, this doc defines the "turn" and "turns" URI schemes, which can carry the four components the resolution mechanism needs 👑.
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 aren't in ALL CAPS (like "should" or "Should"), they just have their usual English meanings, and they're not RFC 2119 key words 🤓.
3. Definitions of the "turn" and "turns" URI ✨
3.1. URI Scheme Syntax 🎀
The "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> and <port> are specified in [RFC3986]. Even though these two ABNF productions are defined in [RFC3986] as components of the generic hierarchical URI, that does NOT mean the "turn" and "turns" schemes are hierarchical URIs 🙅♀️. Developers MUST NOT use a generic hierarchical URI parser to parse a "turn" or "turns" URI. Don't do it, bestie 💀.
The <host>, <port>, and <transport> components are passed through without modification to the [RFC5928] algorithm. <secure> is set to false if <scheme> is equal to "turn", and set to true if <scheme> is equal to "turns", and then it gets passed to the [RFC5928] algorithm along with the other components 🦋.
3.2. URI Scheme Semantics 🌈
Same vibe as before: "turn" and "turns" designate a TURN server (aka a relay) on Internet hosts that are reachable using the TURN protocol. TURN supports sending messages over UDP, TCP, or TLS-over-TCP 💖. The "turns" URI scheme MUST be used when TURN is run over TLS-over-TCP (or, in the 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's absent, the default port is 3478 for both UDP and TCP. The default port for TURN over TLS is 5349 🌸.
4. Security Considerations 🔥
Security considerations for the resolution mechanism are discussed in Section 5 of [RFC5928]. Heads up: this section contains normative text that defines authentication procedures turn clients must follow when TLS is used 🔐.
The "turn" and "turns" URI schemes don't introduce any specific security issues beyond the security considerations discussed in [RFC3986] ✨.
Now the serious part, bestie. 🚨 A "turn" or "turns" URI doesn't itself include the username or password that will be used to authenticate the TURN client. But in certain environments, like WebRTC, the username and password will almost certainly be provisioned remotely by an external agent at the same time a "turns" URI is sent to that client 😭. So in those situations, if the username and password were received in the clear, there'd be little or no benefit to using a "turns" URI 💀. For this reason, a TURN client MUST ensure that the username, password, "turns" URI, and any other security-relevant parameters are received with equivalent security before it uses the "turns" URI 🛡️. Receiving those parameters over another TLS session can provide the appropriate level of security, as long as both TLS sessions are similarly parameterised, e.g., with commensurate strength ciphersuites 🫶.
💫 to be continued in part 2 💫
7.2. Informative References 📚
Okay bestie, these are the extra reads that help explain the spec, and they aren't strictly required to implement it 🤓
[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. 🌐
Appendix A. Examples ✨
Okay so Table 1 shows how the <secure>, <port>, and <transport> parts get filled in from different URIs. For all of these examples, the <host> part is "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 1Appendix B. Design Notes 🧚
Here's the tea on the decisions we made, bestie 🫶
- One thing people kept bringing up was dropping the
ssuffix from the scheme and putting the secure option into a parameter, like;proto=tls. We said no to that 🙅♀️ The STUN URI doesn't have a;proto=parameter, and we would've lost the matching vibe between the TURN and STUN URIs 💜 - Following the advice in Section 2.2 of RFC 4395, and since the TURN URI doesn't describe a hierarchy, TURN URIs are opaque URIs 🦋
<password>isn't in the URIs because it's deprecated [RFC3986] 😭 And<username>and<auth>aren't in there either, since they don't help with the resolution mechanism 🙈- As discussed at IETF 72 in Dublin, the URI doesn't have generic parameters, so we don't run into compatibility problems 🌈
Authors' Addresses 💌
The authors, the squad behind this one, are listed below 🫶
Marc Petit-Huguenin
Impedance Mismatch
EMail: petithug@acm.org
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📦 where this page comes from
- ietf: rfc7065 2013-11
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms