Overview: Real Time Protocols for Brower-based Applications
draft-ietf-rtcweb-overview-04
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 8825.
|
|
|---|---|---|---|
| Author | Harald T. Alvestrand | ||
| Last updated | 2012-06-20 | ||
| Replaces | draft-alvestrand-rtcweb-overview | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
| Document shepherd | (None) | ||
| IESG | IESG state | Became RFC 8825 (Proposed Standard) | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-ietf-rtcweb-overview-04
Network Working Group H. Alvestrand
Internet-Draft Google
Intended status: Standards Track June 20, 2012
Expires: December 22, 2012
Overview: Real Time Protocols for Brower-based Applications
draft-ietf-rtcweb-overview-04
Abstract
This document gives an overview and context of a protocol suite
intended for use with real-time applications that can be deployed in
browsers - "real time communication on the Web".
It intends to serve as a starting and coordination point to make sure
all the parts that are needed to achieve this goal are findable, and
that the parts that belong in the Internet protocol suite are fully
specified and on the right publication track.
This document is a work item of the RTCWEB working group.
Requirements Language
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].
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 December 22, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
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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 . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Principles and Terminology . . . . . . . . . . . . . . . . . . 5
2.1. Goals of this document . . . . . . . . . . . . . . . . . . 5
2.2. Relationship between API and protocol . . . . . . . . . . 5
2.3. On interoperability and innovation . . . . . . . . . . . . 6
2.4. Terminology . . . . . . . . . . . . . . . . . . . . . . . 7
3. Architecture and Functionality groups . . . . . . . . . . . . 8
4. Data transport . . . . . . . . . . . . . . . . . . . . . . . . 12
5. Data framing and securing . . . . . . . . . . . . . . . . . . 13
6. Data formats . . . . . . . . . . . . . . . . . . . . . . . . . 13
7. Connection management . . . . . . . . . . . . . . . . . . . . 13
8. Presentation and control . . . . . . . . . . . . . . . . . . . 14
9. Local system support functions . . . . . . . . . . . . . . . . 14
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
11. Security Considerations . . . . . . . . . . . . . . . . . . . 15
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
13.1. Normative References . . . . . . . . . . . . . . . . . . . 16
13.2. Informative References . . . . . . . . . . . . . . . . . . 18
Appendix A. Transport and Middlebox specification . . . . . . . . 19
A.1. System-provided interfaces . . . . . . . . . . . . . . . . 19
A.2. Middle box related functions . . . . . . . . . . . . . . . 19
A.3. Transport protocols implemented . . . . . . . . . . . . . 20
Appendix B. Change log . . . . . . . . . . . . . . . . . . . . . 20
B.1. Changes from
draft-alvestrand-dispatch-rtcweb-datagram-00 to -01 . . . 20
B.2. Changes from draft-alvestrand-dispatch-01 to
draft-alvestrand-rtcweb-overview-00 . . . . . . . . . . . 20
B.3. Changes from draft-alvestrand-rtcweb-00 to -01 . . . . . . 20
B.4. Changes from draft-alvestrand-rtcweb-overview-01 to
draft-ietf-rtcweb-overview-00 . . . . . . . . . . . . . . 21
B.5. Changes from -00 to -01 of draft-ietf-rtcweb-overview . . 21
B.6. Changes from -01 to -02 of draft-ietf-rtcweb-overview . . 21
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B.7. Changes from -02 to -03 of draft-ietf-rtcweb-overview . . 21
B.8. Changes from -03 to -04 of draft-ietf-rtcweb-overview . . 22
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 22
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1. Introduction
The Internet was, from very early in its lifetime, considered a
possible vehicle for the deployment of real-time, interactive
applications - with the most easily imaginable being audio
conversations (aka "Internet telephony") and videoconferencing.
The first attempts to build this were dependent on special networks,
special hardware and custom-built software, often at very high prices
or at low quality, placing great demands on the infrastructure.
As the available bandwidth has increased, and as processors and other
hardware has become ever faster, the barriers to participation have
decreased, and it has become possible to deliver a satisfactory
experience on commonly available computing hardware.
Still, there are a number of barriers to the ability to communicate
universally - one of these is that there is, as of yet, no single set
of communication protocols that all agree should be made available
for communication; another is the sheer lack of universal
identification systems (such as is served by telephone numbers or
email addresses in other communications systems).
Development of The Universal Solution has proved hard, however, for
all the usual reasons.
The last few years have also seen a new platform rise for deployment
of services: The browser-embedded application, or "Web application".
It turns out that as long as the browser platform has the necessary
interfaces, it is possible to deliver almost any kind of service on
it.
Traditionally, these interfaces have been delivered by plugins, which
had to be downloaded and installed separately from the browser; in
the development of HTML5, application developers see much promise in
the possibility of making those interfaces available in a
standardized way within the browser.
This memo describes a set of building blocks that can be made
accessible and controllable through a Javascript API in a browser,
and which together form a sufficient set of functions to allow the
use of interactive audio and video in applications that communicate
directly between browsers across the Internet. The resulting
protocol suite is intended to enable all the applications that are
described as required scenarios in the RTCWEB use cases document
[I-D.ietf-rtcweb-use-cases-and-requirements].
Other efforts, for instance the W3C WebRTC, Web Applications and
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Device API working groups, focus on making standardized APIs and
interfaces available, within or alongside the HTML5 effort, for those
functions; this memo concentrates on specifying the protocols and
subprotocols that are needed to specify the interactions that happen
across the network.
2. Principles and Terminology
2.1. Goals of this document
The goal of the RTCWEB protocol specification is to specify a set of
protocols that, if all are implemented, will allow an implementation
to communicate with another implementation using audio, video and
data sent along the most direct possible path between the
participants.
This document is intended to serve as the roadmap to the RTCWEB
specifications. It defines terms used by other pieces of
specification, lists references to other specifications that don't
need further elaboration in the RTCWEB context, and gives pointers to
other documents that form part of the RTCWEB suite.
By reading this document and the documents it refers to, it should be
possible to have all information needed to implement an RTCWEB
compatible implementation.
2.2. Relationship between API and protocol
The total RTCWEB/WEBRTC effort consists of two pieces:
o A protocol specification, done in the IETF
o A Javascript API specification, done in the W3C
[W3C.WD-webrtc-20120209]
Together, these two specifications aim to provide an environment
where Javascript embedded in any page, viewed in any compatible
browser, when suitably authorized by its user, is able to set up
communication using audio, video and auxiliary data, where the
browser environment does not constrain the types of application in
which this functionality can be used.
The protocol specification does not assume that all implementations
implement this API; it is not intended to be necessary for
interoperation to know whether the entity one is communicating with
is a browser or another device implementing this specification.
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The goal of cooperation between the protocol specification and the
API specification is that for all options and features of the
protocol specification, it should be clear which API calls to make to
exercise that option or feature; similarly, for any sequence of API
calls, it should be clear which protocol options and features will be
invoked. Both subject to constraints of the implementation, of
course.
2.3. On interoperability and innovation
The "Mission statement of the IETF" [RFC3935] states that "The
benefit of a standard to the Internet is in interoperability - that
multiple products implementing a standard are able to work together
in order to deliver valuable functions to the Internet's users."
Communication on the Internet frequently occurs in two phases:
o Two parties communicate, through some mechanism, what
functionality they both are able to support
o They use that shared communicative functionality to communicate,
or, failing to find anything in common, give up on communication.
There are often many choices that can be made for communicative
functionality; the history of the Internet is rife with the proposal,
standardization, implementation, and success or failure of many types
of options, in all sorts of protocols.
The goal of having a mandatory to implement function set is to
prevent negotiation failure, not to preempt or prevent negotiation.
The presence of a mandatory to implement function set serves as a
strong changer of the marketplace of deployment - in that it gives a
guarantee that, as long as you conform to a specification, and the
other party is willing to accept communication at the base level of
that specification, you can communicate successfully.
The alternative - that of having no mandatory to implement - does not
mean that you cannot communicate, it merely means that in order to be
part of the communications partnership, you have to implement the
standard "and then some" - that "and then some" usually being called
a profile of some sort; in the version most antithetical to the
Internet ethos, that "and then some" consists of having to use a
specific vendor's product only.
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2.4. Terminology
The following terms are used in this document, and as far as possible
across the documents specifying the RTCWEB suite, in the specific
meanings given here. Not all terms are used in this document. Other
terms are used in their commonly used meaning.
The list is in alphabetical order.
Agent: Undefined term. See "SDP Agent" and "ICE Agent".
API: Application Programming Interface - a specification of a set of
calls and events, usually tied to a programming language or an
abstract formal specification such as WebIDL, with its defined
semantics.
Browser: Used synonymously with "Interactive User Agent" as defined
in the HTML specification [W3C.WD-html5-20110525].
ICE Agent: An implementation of the ICE [RFC5245] protocol. An ICE
Agent may also be an SDP Agent, but there exist ICE Agents that do
not use SDP (for instance those that use Jingle).
Interactive: Communication between multiple parties, where the
expectation is that an action from one party can cause a reaction
by another party, and the reaction can be observed by the first
party, with the total time required for the action/reaction/
observation is on the order of no more than hundreds of
milliseconds.
Media: Audio and video content. Not to be confused with
"transmission media" such as wires.
Media path: The path that media data follows from one browser to
another.
Protocol: A specification of a set of data units, their
representation, and rules for their transmission, with their
defined semantics. A protocol is usually thought of as going
between systems.
Real-time media: Media where generation of content and display of
content are intended to occur closely together in time (on the
order of no more than hundreds of milliseconds). Real-time media
can be used to support interactive communication.
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SDP Agent: The protocol implementation involved in the SDP offer/
answer exchange, as defined in [RFC3264] section 3.
Signaling: Communication that happens in order to establish, manage
and control media paths.
Signaling Path: The communication channels used between entities
participating in signalling to transfer signaling. There may be
more entities in the signaling path than in the media path.
NOTE: Where common definitions exist for these terms, those
definitions should be used to the greatest extent possible.
TODO: Extend this list with other terms that might prove slippery.
3. Architecture and Functionality groups
The model of real-time support for browser-based applications does
not envisage that the browser will contain all the functions that
need to be performed in order to have a function such as a telephone
or a videoconferencing unit; the vision is that the browser will have
the functions that are needed for a Web application, working in
conjunction with its backend servers, to implement these functions.
This means that two vital interfaces need specification: The
protocols that browsers talk to each other, without any intervening
servers, and the APIs that are offered for a Javascript application
to take advantage of the browser's functionality.
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+------------------------+ On-the-wire
| | Protocols
| Servers |--------->
| |
| |
+------------------------+
^
|
|
| HTTP/
| Websockets
|
|
+----------------------------+
| Javascript/HTML/CSS |
+----------------------------+
Other ^ ^RTC
APIs | |APIs
+---|-----------------|------+
| | | |
| +---------+|
| | Browser || On-the-wire
| Browser | RTC || Protocols
| | Function|----------->
| | ||
| | ||
| +---------+|
+---------------------|------+
|
V
Native OS Services
Figure 1: Browser Model
Note that HTTP and Websockets are also offered to the Javascript
application through browser APIs.
As for all protocol and API specifications, there is no restriction
that the protocols can only be used to talk to another browser; since
they are fully specified, any device that implements the protocols
faithfully should be able to interoperate with the application
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running in the browser.
A commonly imagined model of deployment is the one depicted below.
+-----------+ +-----------+
| Web | | Web |
| | Signalling | |
| |-------------| |
| Server | path | Server |
| | | |
+-----------+ +-----------+
/ \
/ \ Application-defined
/ \ over
/ \ HTTP/Websockets
/ Application-defined over \
/ HTTP/Websockets \
/ \
+-----------+ +-----------+
|JS/HTML/CSS| |JS/HTML/CSS|
+-----------+ +-----------+
+-----------+ +-----------+
| | | |
| | | |
| Browser | ------------------------- | Browser |
| | Media path | |
| | | |
+-----------+ +-----------+
Figure 2: Browser RTC Trapezoid
On this drawing, the critical part to note is that the media path
("low path") goes directly between the browsers, so it has to be
conformant to the specifications of the RTCWEB protocol suite; the
signalling path ("high path") goes via servers that can modify,
translate or massage the signals as needed.
If the two Web servers are operated by different entities, the inter-
server signalling mechanism needs to be agreed upon, either by
standardization or by other means of agreement. Existing protocols
(for example SIP or XMPP) could be used between servers, while either
a standards-based or proprietary protocol could be used between the
browser and the web server.
For example, if both operators' servers implement SIP, SIP could be
used for communication between servers, along with either a
standardized signaling mechanism (e.g. SIP over Websockets) or a
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proprietary signaling mechanism used between the application running
in the browser and the web server. Similarly, if both operators'
servers implement XMPP, XMPP couild be used for communication between
XMPP servers, with either a standardized signaling mechanism (e.g.
XMPP over Websockets or BOSH) or a proprietary signaling mechanism
used between the application running in the browser and the web
server.
The choice of protocols, and definition of the translation between
them, is outside the scope of the RTCWEB standards suite described in
the document.
The functionality groups that are needed in the browser can be
specified, more or less from the bottom up, as:
o Data transport: TCP, UDP and the means to securely set up
connections between entities, as well as the functions for
deciding when to send data: Congestion management, bandwidth
estimation and so on.
o Data framing: RTP and other data formats that serve as containers,
and their functions for data confidentiality and integrity.
o Data formats: Codec specifications, format specifications and
functionality specifications for the data passed between systems.
Audio and video codecs, as well as formats for data and document
sharing, belong in this category. In order to make use of data
formats, a way to describe them, a session description, is needed.
o Connection management: Setting up connections, agreeing on data
formats, changing data formats during the duration of a call; SIP
and Jingle/XMPP belong in this category.
o Presentation and control: What needs to happen in order to ensure
that interactions behave in a non-surprising manner. This can
include floor control, screen layout, voice activated image
switching and other such functions - where part of the system
require the cooperation between parties. XCON and Cisco/
Tandberg's TIP were some attempts at specifying this kind of
functionality; many applications have been built without
standardized interfaces to these functions.
o Local system support functions: These are things that need not be
specified uniformly, because each participant may choose to do
these in a way of the participant's choosing, without affecting
the bits on the wire in a way that others have to be cognizant of.
Examples in this category include echo cancellation (some forms of
it), local authentication and authorization mechanisms, OS access
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control and the ability to do local recording of conversations.
Within each functionality group, it is important to preserve both
freedom to innovate and the ability for global communication.
Freedom to innovate is helped by doing the specification in terms of
interfaces, not implementation; any implementation able to
communicate according to the interfaces is a valid implementation.
Ability to communicate globally is helped both by having core
specifications be unencumbered by IPR issues and by having the
formats and protocols be fully enough specified to allow for
independent implementation.
One can think of the three first groups as forming a "media transport
infrastructure", and of the three last groups as forming a "media
service". In many contexts, it makes sense to use a common
specification for the media transport infrastructure, which can be
embedded in browsers and accessed using standard interfaces, and "let
a thousand flowers bloom" in the "media service" layer; to achieve
interoperable services, however, at least the first five of the six
groups need to be specified.
4. Data transport
Data transport refers to the sending and receiving of data over the
network interfaces, the choice of network-layer addresses at each end
of the communication, and the interaction with any intermediate
entities that handle the data, but do not modify it (such as TURN
relays).
It includes necessary functions for congestion control: When not to
send data.
T are described in <WORKING GROUP DRAFT "TRANSPORTS">.
ICE is required for all media paths that use UDP; in addition to the
ability to pass NAT boxes, ICE fulfils the need for guaranteeing that
the media path is going to an UDP port that is willing to receive the
data.
The data transport protocols used by RTCWEB, as well as the details
of interactions with intermediate boxes, such as firewalls, relays
and NAT boxes, are intended to be described in a separate document;
for now, notes are gathered in Appendix A.
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5. Data framing and securing
The format for media transport is RTP [RFC3550]. Implementation of
SRTP [RFC3711] is required for all implementations.
The detailed considerations for usage of functions from RTP and SRTP
are given in [I-D.ietf-rtcweb-rtp-usage]. The security
considerations for the RTCWEB use case are in
[I-D.ietf-rtcweb-security], and the resulting security functions are
described in [I-D.ietf-rtcweb-security-arch].
Considerations for the transfer of data that is not in RTP format is
described in [I-D.ietf-rtcweb-data-channel], and the resulting
protocol is described in [I-D.jesup-rtcweb-data-protocol] (not yet a
WG document)
6. Data formats
The intent of this specification is to allow each communications
event to use the data formats that are best suited for that
particular instance, where a format is supported by both sides of the
connection. However, a minimum standard is greatly helpful in order
to ensure that communication can be achieved. This document
specifies a minimum baseline that will be supported by all
implementations of this specification, and leaves further codecs to
be included at the will of the implementor.
The mandatory to implement codecs, as well as any profiling
requirements for both mandatory and optional codecs, is described in
<WORKING GROUP DRAFT "MEDIA PROCESSING"> (candidate draft:
[I-D.cbran-rtcweb-codec].
7. Connection management
The methods, mechanisms and requirements for setting up, negotiating
and tearing down connections is a large subject, and one where it is
desirable to have both interoperability and freedom to innovate.
The following principles apply:
1. The RTCWEB media negotiations will be capable of representing the
same SDP offer/answer semantics that are used in SIP [RFC3264],
in such a way that it is possible to build a signalling gateway
between SIP and the RTCWEB media negotiation.
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2. It will be possible to gateway between legacy SIP devices that
support ICE and appropriate RTP / SDP mechanisms, codecs and
security mechanisms without using a media gateway. A signaling
gateway to convert between the signaling on the web side to the
SIP signaling may be needed.
3. When a new codec is specified, and the SDP for the new codec is
specified in the MMUSIC WG, no other standardization would should
be required for it to be possible to use that in the web
browsers. Adding new codecs which might have new SDP parameters
should not change the APIs between the browser and javascript
application. As soon as the browsers support the new codecs, old
applications written before the codecs were specified should
automatically be able to use the new codecs where appropriate
with no changes to the JS applications.
The particular choices made for RTCWEB, and their implications for
the API offered by a browser implementing RTCWEB, are described in
[I-D.ietf-rtcweb-jsep]
8. Presentation and control
The most important part of control is the user's control over the
browser's interaction with input/output devices and communications
channels. It is important that the user have some way of figuring
out where his audio, video or texting is being sent, for what
purported reason, and what guarantees are made by the parties that
form part of this control channel. This is largely a local function
between the browser, the underlying operating system and the user
interface; this is being worked on as part of the W3C API effort, and
will be part of the peer connection API [W3C.WD-webrtc-20120209], and
the device control API [getusermedia]. Considerations for the
implications of wanting to identify correspondents are described in
[I-D.rescorla-rtcweb-generic-idp] (not a WG item).
9. Local system support functions
These are characterized by the fact that the quality of these
functions strongly influences the user experience, but the exact
algorithm does not need coordination. In some cases (for instance
echo cancellation, as described below), the overall system definition
may need to specify that the overall system needs to have some
characteristics for which these facilities are useful, without
requiring them to be implemented a certain way.
Local functions include echo cancellation, volume control, camera
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management including focus, zoom, pan/tilt controls (if available),
and more.
Certain parts of the system SHOULD conform to certain properties, for
instance:
o Echo cancellation should be good enough to achieve the suppression
of acoustical feedback loops below a perceptually noticeable
level.
o Privacy concerns must be satisfied; for instance, if remote
control of camera is offered, the APIs should be available to let
the local participant to figure out who's controlling the camera,
and possibly decide to revoke the permission for camera usage.
o Automatic gain control, if present, should normalize a speaking
voice into <whatever dB metrics makes sense here - most important
that we have one only>
The requirements on RTCWEB systems in this category are found in
<WORKING GROUP DRAFT "MEDIA PROCESSING">; the proposed API for
control of local devices are found in [getusermedia].
10. IANA Considerations
This document makes no request of IANA.
Note to RFC Editor: this section may be removed on publication as an
RFC.
11. Security Considerations
Security of the web-enabled real time communications comes in several
pieces:
o Security of the components: The browsers, and other servers
involved. The most target-rich environment here is probably the
browser; the aim here should be that the introduction of these
components introduces no additional vulnerability.
o Security of the communication channels: It should be easy for a
participant to reassure himself of the security of his
communication - by verifying the crypto parameters of the links he
himself participates in, and to get reassurances from the other
parties to the communication that they promise that appropriate
measures are taken.
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o Security of the partners' identity: verifying that the
participants are who they say they are (when positive
identification is appropriate), or that their identity cannot be
uncovered (when anonymity is a goal of the application).
The security analysis, and the requirements derived from that
analysis, is contained in [I-D.ietf-rtcweb-security].
12. Acknowledgements
The number of people who have taken part in the discussions
surrounding this draft are too numerous to list, or even to identify.
The ones below have made special, identifiable contributions; this
does not mean that others' contributions are less important.
Thanks to Cary Bran, Cullen Jennings, Colin Perkins, Magnus
Westerlund and Joerg Ott, who offered technical contributions on
various versions of the draft.
Thanks to Jonathan Rosenberg, Matthew Kaufman and others at Skype for
the ASCII drawings in section 1.
Thanks to Eric Rescorla, Justin Uberti, Henry Sinnreich, Colin
Perkins and Simon Leinen for document review.
13. References
13.1. Normative References
[I-D.ietf-mmusic-sctp-sdp]
Loreto, S. and G. Camarillo, "Stream Control Transmission
Protocol (SCTP)-Based Media Transport in the Session
Description Protocol (SDP)", draft-ietf-mmusic-sctp-sdp-00
(work in progress), July 2011.
[I-D.ietf-rtcweb-data-channel]
Jesup, R., Loreto, S., and M. Tuexen, "RTCWeb Datagram
Connection", draft-ietf-rtcweb-data-channel-00 (work in
progress), March 2012.
[I-D.ietf-rtcweb-jsep]
Uberti, J. and C. Jennings, "Javascript Session
Establishment Protocol", draft-ietf-rtcweb-jsep-00 (work
in progress), March 2012.
[I-D.ietf-rtcweb-rtp-usage]
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Perkins, C., Westerlund, M., and J. Ott, "Web Real-Time
Communication (WebRTC): Media Transport and Use of RTP",
draft-ietf-rtcweb-rtp-usage-01 (work in progress),
October 2011.
[I-D.ietf-rtcweb-security]
Rescorla, E., "Security Considerations for RTC-Web",
draft-ietf-rtcweb-security-01 (work in progress),
October 2011.
[I-D.ietf-rtcweb-security-arch]
Rescorla, E., "RTCWEB Security Architecture",
draft-ietf-rtcweb-security-arch-00 (work in progress),
January 2012.
[I-D.nandakumar-rtcweb-stun-uri]
Nandakumar, S., Salgueiro, G., and P. Jones, "URI Scheme
for Session Traversal Utilities for NAT (STUN) Protocol",
draft-nandakumar-rtcweb-stun-uri-00 (work in progress),
October 2011.
[I-D.tuexen-tsvwg-sctp-dtls-encaps]
Jesup, R., Loreto, S., Stewart, R., and M. Tuexen, "DTLS
Encapsulation of SCTP Packets for RTCWEB",
draft-tuexen-tsvwg-sctp-dtls-encaps-00 (work in progress),
March 2012.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264,
June 2002.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003.
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, March 2004.
[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
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Relays around NAT (TURN): Relay Extensions to Session
Traversal Utilities for NAT (STUN)", RFC 5766, April 2010.
13.2. Informative References
[I-D.cbran-rtcweb-codec]
Bran, C. and C. Jennings, "WebRTC Codec and Media
Processing Requirements", draft-cbran-rtcweb-codec-01
(work in progress), October 2011.
[I-D.ietf-rtcweb-use-cases-and-requirements]
Holmberg, C., Hakansson, S., and G. Eriksson, "Web Real-
Time Communication Use-cases and Requirements",
draft-ietf-rtcweb-use-cases-and-requirements-06 (work in
progress), October 2011.
[I-D.jesup-rtcweb-data-protocol]
Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data Channel
Protocol", draft-jesup-rtcweb-data-protocol-00 (work in
progress), March 2012.
[I-D.rescorla-rtcweb-generic-idp]
Rescorla, E., "RTCWEB Generic Identity Provider
Interface", draft-rescorla-rtcweb-generic-idp-00 (work in
progress), January 2012.
[RFC3935] Alvestrand, H., "A Mission Statement for the IETF",
BCP 95, RFC 3935, October 2004.
[W3C.WD-html5-20110525]
Hickson, I., "HTML5", World Wide Web Consortium
LastCall WD-html5-20110525, May 2011,
<http://www.w3.org/TR/2011/WD-html5-20110525>.
[W3C.WD-webrtc-20120209]
Bergkvist, A., Burnett, D., Narayanan, A., and C.
Jennings, "WebRTC 1.0: Real-time Communication Between
Browsers", World Wide Web Consortium WD WD-webrtc-
20120209, February 2012,
<http://www.w3.org/TR/2012/WD-webrtc-20120209>.
[getusermedia]
Burnett, D. and A. Narayanan, "getusermedia: Getting
access to local devices that can generate multimedia
streams", December 2011,
<http://dev.w3.org/2011/webrtc/editor/getusermedia.html>.
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Appendix A. Transport and Middlebox specification
The draft referred to as "transport and middle boxes" in Section 4
has not been written yet. This appendix contains some keywords to
what it should say; this also serves the purpose of linking to the
drafts-in-progress that are relevant to this specification.
A.1. System-provided interfaces
The protocol specifications used here assume that the following
protocols are available as system-level interfaces:
o UDP. This is the protocol assumed by most protocol elements
described.
o TCP. This is used for HTTP/WebSockets, as well as for TURN/SSL
and ICE-TCP.
For both protocols, we assume the ability to set the DSCP code point
of the sockets opened. We do not assume that the DSCP codepoints
will be honored, and we do assume that they may be zeroed or changed,
since this is a local configuration issue.
We do not assume that the implementation will have access to ICMP or
raw IP.
A.2. Middle box related functions
The primary mechanism to deal with middle boxes is ICE, which is an
appropriate way to deal with NAT boxes and firewalls that accept
traffic from the inside, but only from the outside if it's in
response to inside traffic (simple stateful firewalls).
In order to deal with symmetric NATs, TURN MUST be supported.
In order to deal with firewalls that block all UDP traffic, TURN over
TCP MUST be supported. (QUESTION: What about ICE-TCP?)
The following specifications MUST be supported:
o ICE [RFC5245]
o TURN, including TURN over TCP [[QUESTION: and TURN over TLS]],
[RFC5766].
For referring to ICE servers, we use the STUN URI,
[I-D.nandakumar-rtcweb-stun-uri].
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A.3. Transport protocols implemented
For data transport, we implement SCTP over DTLS over ICE. This is
specified in [I-D.tuexen-tsvwg-sctp-dtls-encaps]. Negotiation of
this transport in SCTP is defined in [I-D.ietf-mmusic-sctp-sdp].
Appendix B. Change log
This section may be deleted by the RFC Editor when preparing for
publication.
B.1. Changes from draft-alvestrand-dispatch-rtcweb-datagram-00 to -01
Added section "On interoperability and innovation"
Added data confidentiality and integrity to the "data framing" layer
Added congestion management requirements in the "data transport"
layer section
Changed need for non-media data from "question: do we need this?" to
"Open issue: How do we do this?"
Strengthened disclaimer that listed codecs are placeholders, not
decisions.
More details on why the "local system support functions" section is
there.
B.2. Changes from draft-alvestrand-dispatch-01 to
draft-alvestrand-rtcweb-overview-00
Added section on "Relationship between API and protocol"
Added terminology section
Mentioned congestion management as part of the "data transport" layer
in the layer list
B.3. Changes from draft-alvestrand-rtcweb-00 to -01
Removed most technical content, and replaced with pointers to drafts
as requested and identified by the RTCWEB WG chairs.
Added content to acknowledgements section.
Added change log.
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Spell-checked document.
B.4. Changes from draft-alvestrand-rtcweb-overview-01 to
draft-ietf-rtcweb-overview-00
Changed draft name and document date.
Removed unused references
B.5. Changes from -00 to -01 of draft-ietf-rtcweb-overview
Added architecture figures to section 2.
Changed the description of "echo cancellation" under "local system
support functions".
Added a few more definitions.
B.6. Changes from -01 to -02 of draft-ietf-rtcweb-overview
Added pointers to use cases, security and rtp-usage drafts (now WG
drafts).
Changed description of SRTP from mandatory-to-use to mandatory-to-
implement.
Added the "3 principles of negotiation" to the connection management
section.
Added an explicit statement that ICE is required for both NAT and
consent-to-receive.
B.7. Changes from -02 to -03 of draft-ietf-rtcweb-overview
Added references to a number of new drafts.
Expanded the description text under the "trapezoid" drawing with some
more text discussed on the list.
Changed the "Connection management" sentence from "will be done using
SDP offer/answer" to "will be capable of representing SDP offer/
answer" - this seems more consistent with JSEP.
Added "security mechanisms" to the things a non-gatewayed SIP devices
must support in order to not need a media gateway.
Added a definition for "browser".
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B.8. Changes from -03 to -04 of draft-ietf-rtcweb-overview
Made introduction more normative.
Several wording changes in response to review comments from EKR
Added Appendix A to hold references and notes that are not yet in a
separate document.
Author's Address
Harald T. Alvestrand
Google
Kungsbron 2
Stockholm, 11122
Sweden
Email: harald@alvestrand.no
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