Internet DRAFT - draft-cbran-rtcweb-nat
draft-cbran-rtcweb-nat
Network Working Group C. Bran
Internet-Draft Plantrontics
Intended status: Standards Track M. Kaufman
Expires: May 1, 2012 Skype
C. Jennings
Cisco
J. Rosenberg
Skype
October 29, 2011
WebRTC Network Address Translation
draft-cbran-rtcweb-nat-02
Abstract
This document outlines the network address translation (NAT)
traversal requirements and for WebRTC client applications.
Status of this Memo
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This Internet-Draft will expire on May 1, 2012.
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to this document. Code Components extracted from this document must
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Connection Management Requirements . . . . . . . . . . . . . . 3
3.1. NAT Traversal Requirements . . . . . . . . . . . . . . . . 3
3.2. Data Transmission Requirements . . . . . . . . . . . . . . 3
3.3. IPv4 to IPv6 Transition Requirements . . . . . . . . . . . 4
3.4. Legacy Phone System Interoperability Requirements . . . . . 4
4. Connection Management Mechanism . . . . . . . . . . . . . . . . 4
4.1. ICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1.1. ICE as a Consent Mechanism . . . . . . . . . . . . . . 4
4.2. Web Browsers and ICE . . . . . . . . . . . . . . . . . . . 5
4.2.1. Native ICE Support . . . . . . . . . . . . . . . . . . 5
4.2.2. STUN Configuration . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
8. Normative References . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
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1. Introduction
An integral part of the of the Web Real Time Communications (WebRTC)
will be the ability for client application implementations to have
native, secure Network Address Translation (NAT) [RFC1631] traversal
capabilities. This document provides requirements and implementation
specifications WebRTC client NAT traversal.
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. Connection Management Requirements
This section identifies the requirements for RTC-Web client
applications to connection requirements.
3.1. NAT Traversal Requirements
A majority of WebRTC clients will be web browsers and used behind a
NAT and or firewall. WebRTC clients will use a UDP-based data
transmission scheme for multimedia sessions [Open Issue: what draft
should be cited for this requirement?]. UDP has well know NAT
traversal problems and without native capabilities to traverse a NAT,
WebRTC clients will be extremely limited in their functionality.
Fortunately NAT traversal for UDP is a solved problem, but solutions
require that clients transmitting media between each other need to
use the same NAT traversal algorithms. Without a consistent, well
specified NAT traversal mechanism WebRTC client implementations would
likely be inoperable with each other. To address the identified
problems WebRTC clients are REQUIRED to implement the NAT traversal
mechanism as defined in Section 4.
3.2. Data Transmission Requirements
Whenever a calling WebRTC client attempts to establish a connection,
the receiving WebRTC client MUST provide consent before the calling
client can transmit data to the receiver. Providing consent on the
receiving end before data transmission commence is needed to help to
prevent malicious attacks by the calling client. All WebRTC clients
are REQUIRED to implement connection management that provides a
consent mechanism for media transmission. Furthermore it is REQUIRED
that consent be given by the recipient before an WebRTC client can
transmit media.
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As a note providing consent to open a media connection does not
involve user-level consent, rather it is the responsibility of the
WebRTC client application (e.g. web browser) to enforce this
requirement.
3.3. IPv4 to IPv6 Transition Requirements
RTC-Web clients MUST support IPv4 to IPv6 transition.
3.4. Legacy Phone System Interoperability Requirements
There is no way to meet all the connection management requirements
and maintain compatibility with all legacy phone systems. It is
highly desirable that the WebRTC connection management mechanism be
interoperable with legacy phone systems such as a VOIP endpoints,
PSTN gateways and SIP trunks.
4. Connection Management Mechanism
This section specifies the connection management system that will
address the identified requirements.
4.1. ICE
To address the NAT traversal, data transmission, and interoperability
requirements all WebRTC client applications are REQUIRED to implement
ICE [RFC5245]. Implicit to ICE, and listed here for clarity, WebRTC
client implementations will are also REQUIRED to implement STUN
[RFC3489] and TURN [RFC5766].
Additional ICE requirements:
o Support of ICE's Aggressive Nomination is REQUIRED
o Support of ICE's Regular Nomination is OPTIONAL
o WebRTC media gateways MAY implement ICE-Lite instead of full ICE
4.1.1. ICE as a Consent Mechanism
Of the connection management requirements listed above, the least
obvious is how ICE will satisfy being a consent mechanism for data
transmission Section 3.2. The reason ICE can satisfy this
requirement is due to its reliance on STUN transactions to succeed in
order to establish a connection. The success of a STUN transaction
can be viewed as semantically the same thing as a recipient providing
consent to transmit data. Conversely the failure of the STUN
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transaction would semantically map to the recipient rejecting the
request to transmit data.
4.2. Web Browsers and ICE
This section specifies the web browser implementation requirements
for WebRTC client connection management.
4.2.1. Native ICE Support
To meet the WebRTC connectivity requirements, web browser vendors
MUST natively support ICE [RFC5245]. Access to the web browser's ICE
implementation will be defined in the W3C WebRTC-API
specification[I.D.w3c-webrtc].
Alternate proposals have been made that advocate for natively
exposing STUN[RFC3489] APIs in the web browser. The ICE
implementation would be realized via a JavaScript library that uses
the browser's native STUN API. After reviewing the alternate
proposals the solution several issues were identified.
1. JavaScript running within "real world" web applications cannot
reliably handle the ICE timing and pacing requirements. An
example of this is long running JavaScript code from embedded
advertisers. A big JavaScript file can take a significant amount
of time to execute and can prevent web application timers from
firing in correctly. Given the pacing requirements for ICE are
in the 20ms range, it is highly likely that ICE will break if it
is implemented in a JavaScript library.
2. Multiple implementations of a JavaScript ICE library is a
logistical nightmare. Coordinating updates, bug fixes,
enhancements and a testing matrix for interoperability at
Internet scale will simply be impossible.
4.2.2. STUN Configuration
Web browsers MUST provide a mechanism to configure access to a STUN
server.
Below are some proposed mechanisms by which the STUN server could be
configured:
o A preference page, similar to the what web browser's use for
configuring web proxy settings
o Exposed as a JavaScript API and added to the W3C WebRTC-API
specification
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Regardless of the mechanism adopted by the web browser vendor, the
following configuration data is REQUIRED to be exposed and settable
through the web browsers configuration mechanism:
o STUN Server Address - the IPv4 or IPv6 address of the STUN server
o STUN Server Port
o Credentials to access the STUN server (these are not STUN
generated credentials)
5. IANA Considerations
This document makes no request of IANA.
Note to RFC Editor: this section may be removed on publication as an
RFC.
6. Security Considerations
To guard against spoofing RTC-Web client applications are REQUIRED
to:
o Internally encapsulate the generation of STUN transaction IDs
o Block read/write access to the generated STUN transaction IDs
7. Acknowledgements
This draft incorporates ideas and text from the IETF mailing list.
In particularly we would like to acknowledge, and say thanks for,
work we incorporated from Timothy Terriberry and Christopher
Blizzard.
8. Normative References
[I.D.w3c-webrtc]
Bergkvist, A., Burnett, D., Jennings, C., and A.
Narayanan, "WebRTC 1.0: Real-time Communication Between
Browsers", October 2011.
[RFC1631] Egevang, K. and P. Francis, "The IP Network Address
Translator (NAT)", RFC 1631, May 1994.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3489] Rosenberg, J., Weinberger, J., Huitema, C., and R. Mahy,
"STUN - Simple Traversal of User Datagram Protocol (UDP)
Through Network Address Translators (NATs)", RFC 3489,
March 2003.
[RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
(ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols", RFC 5245,
April 2010.
[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.
Authors' Addresses
Cary Bran
Plantrontics
345 Encinal Street
Santa Cruz, CA 95060
USA
Phone: +1 206 661-2398
Email: cary.bran@plantronics.com
Matthew Kaufman
Skype
3210 Porter Drive
Palo Alto, California 94304
US
Phone: +1 831 440 8771
Email: matthew.kaufman@skype.net
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Cullen Jennings
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Phone: +1 408 421-9990
Email: fluffy@cisco.com
Jonathan Rosenberg
Skype
3210 Porter Drive
Palo Alto, California 94304
US
Email: jdrosen@skype.net
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