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Versions: 00 01 draft-ietf-rtcweb-use-cases-and-requirements

RTCWEB Working Group                                         C. Holmberg
Internet-Draft                                              S. Hakansson
Intended status: Standards Track                             G. Eriksson
Expires: September 15, 2011                                     Ericsson
                                                          March 14, 2011


         Web Real-Time Communication Use-cases and Requirements
                  draft-holmberg-rtcweb-ucreqs-01.txt

Abstract

   This document describes web based real-time communication use-cases.
   Based on the use-cases, the document also derives requirements
   related to the browser, and the API used by web applications to
   request and control media stream services provided by the browser.

Status of this Memo

   This Internet-Draft is submitted to IETF 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 September 15, 2011.

Copyright Notice

   Copyright (c) 2011 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
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   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.



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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Definitions  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   4.  Use-cases  . . . . . . . . . . . . . . . . . . . . . . . . . .  3
     4.1.  Introduction . . . . . . . . . . . . . . . . . . . . . . .  3
     4.2.  Use-case: Simple Video Communication Service . . . . . . .  3
       4.2.1.  Description  . . . . . . . . . . . . . . . . . . . . .  3
       4.2.2.  Derived Requirements . . . . . . . . . . . . . . . . .  4
     4.3.  Use-case: Multiparty video communication . . . . . . . . .  4
       4.3.1.  Description  . . . . . . . . . . . . . . . . . . . . .  4
       4.3.2.  Derived Requirements . . . . . . . . . . . . . . . . .  4
     4.4.  Use-case: Multiparty on-line game with voice
           communication  . . . . . . . . . . . . . . . . . . . . . .  4
       4.4.1.  Description  . . . . . . . . . . . . . . . . . . . . .  4
       4.4.2.  Derived Requirements . . . . . . . . . . . . . . . . .  5
     4.5.  Use-case: Video conferencing system with central server  .  5
       4.5.1.  Description  . . . . . . . . . . . . . . . . . . . . .  5
       4.5.2.  Derived Requirements . . . . . . . . . . . . . . . . .  5
     4.6.  Use-case: Hockey game viewer . . . . . . . . . . . . . . .  5
       4.6.1.  Description  . . . . . . . . . . . . . . . . . . . . .  5
       4.6.2.  Derived Requirements . . . . . . . . . . . . . . . . .  6
     4.7.  Use-case: Telephony terminal . . . . . . . . . . . . . . .  6
       4.7.1.  Description  . . . . . . . . . . . . . . . . . . . . .  6
       4.7.2.  Derived Requirements . . . . . . . . . . . . . . . . .  6
   5.  Requirements . . . . . . . . . . . . . . . . . . . . . . . . .  6
     5.1.  General  . . . . . . . . . . . . . . . . . . . . . . . . .  6
     5.2.  Browser requirements . . . . . . . . . . . . . . . . . . .  6
     5.3.  API requirements . . . . . . . . . . . . . . . . . . . . .  8
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
     7.1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . 10
     7.2.  Browser Considerations . . . . . . . . . . . . . . . . . . 10
     7.3.  Web Application Considerations . . . . . . . . . . . . . . 10
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
   9.  Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 11
     10.2. Informative References . . . . . . . . . . . . . . . . . . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11










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1.  Introduction

   This document presents a few use-case of web applications that are
   executed in a browser and use real-time communication capabilities.
   Based on the use-cases, the document derives requirements related to
   the browser and the API used by web applications in the browser.

   The document focuses on requirements related to real-time media
   streams.  Requirements related to privacy, signalling between the
   browser and web server etc are currently not considered.


2.  Conventions

   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 BCP 14, RFC 2119
   [RFC2119].


3.  Definitions

   TBD


4.  Use-cases

4.1.  Introduction

   This section describes web based real-time communication use-cases,
   from which requirements are later derived.

4.2.  Use-case: Simple Video Communication Service

4.2.1.  Description

   In the service the users have loaded, and logged into, a video
   communication web application into their browsers, provided by the
   same service provider.  The web service publishes information about
   user login status, by pushing updates to the web application in the
   browsers.  By selecting an online peer user, a 1-1 video
   communication session between the browsers of the peers is initiated.
   The invited user might accept or reject the session.

   When the session has been established, a self-view, as well as the
   video sent from the remote peer, are displayed.  The users can change
   the display sizes during the session.  The users can also pause
   sending of media (audio, video, or both), and mute incoming media.



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   Any session participant can end the session at any time.

   One participant has an unreliable internet connection.  It sometimes
   has packet losses, and is sometimes goes down completely.

   One participant is located behind a Network Address Translator (NAT).

4.2.2.  Derived Requirements

   F1, F2, F3, F4, F5, F6, F8, F9, F10

   A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13

4.3.  Use-case: Multiparty video communication

4.3.1.  Description

   In this use case the simple video communication service is extended
   by allowing multiparty sessions.  No central server is involved - the
   browser of each participant sends and receives streams to and from
   all other session participants.

   The audio sent by each participant is a mono stream.  However, in
   order to enhance intelligibility, the web application pans the audio
   from different participants differently when rendering the audio.
   This is done automatically, but users can change how the different
   participants are placed in the (virtual) room.

   Each video stream received is by default displayed in a thumbnail
   frame within the browser, but users can change the display size.

4.3.2.  Derived Requirements

   F1, F2, F3, F4, F5, F6, F8, F9, F10, F11, F12, F13, F14

   A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15

4.4.  Use-case: Multiparty on-line game with voice communication

4.4.1.  Description

   In this use-case, the voice part of the multiparty video
   communication application is used in the context of an on-line game.
   The received voice audio media is rendered together with game sound
   objects.  For example, the sound of a tank moving from left to right
   over the screen must be rendered and played to the user together with
   the voice media.




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4.4.2.  Derived Requirements

   F1, F2, F3, F4, F5, F6, F8, F9, F11, F12, F13, F15, F21

   A1, A2, A3, A4, A5, A7, A8, A9, A10, A11, A12, A13, A14, A15, A17

4.5.  Use-case: Video conferencing system with central server

4.5.1.  Description

   An organization uses a video communication system that supports the
   establishment of multiparty video sessions using a central conference
   server.

   The browsers of all participants send an audio stream (mono or stereo
   depending on the equipment of a participant) to the central server.
   The central server mixes the audio streams and sends towards the
   participants a mixed stereo stream.

   All participants send two video streams towards the server, one low
   resolution and one high resolution.  At each participant one high
   resolution video is displayed in a large window, while a number of
   low resolution videos are displayed in smaller windows.  The server
   selects what video streams to be forwarded as main- and thumbnail
   videos, based on speech activity.

   The organization has an internal network set up with an aggressive
   firewall handling access to the internet.  If users can not
   physically access the internal network, they can establish a Virtual
   Private Network (VPN).

   It is essential that the communication can not be eavesdropped.

4.5.2.  Derived Requirements

   F1, F2, F3, F4, F5, F6, F7, F8, F9, F10, F14, F16, F17

   A1, A2, A3, A4, A5, A7, A8, A9, A10, A11, A12, A13, A15

4.6.  Use-case: Hockey game viewer

4.6.1.  Description

   An ice-hockey club uses an application that enables talent scouts to,
   in real-time, show and discuss games and players with the club
   manager.  The talent scouts use a mobile phone with two cameras, one
   front-facing and one rear facing.




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   The club manager uses a desktop for viewing the game and discussing
   with the talent scout.  The video stream captured by the front facing
   camera (that is capturing the game) of the mobile phone is shown in a
   big window on the desktop screen, while a thumbnail of the rear
   facing camera is overlaid.

   Most of the mobile phone screen is covered by a self view of the
   front facing camera.  A thumbnail of the rear facing cameras view is
   overlaid.

4.6.2.  Derived Requirements

   F1, F2, F3, F4, F5, F6, F8, F9, F10, F14

   A1, A2, A3, A4, A5, A7, A8, A9, A10, A11, A12, A13, A15

4.7.  Use-case: Telephony terminal

4.7.1.  Description

   A mobile telephony operator allows its customers to use a web browser
   to access their services.  After a simple log in the user can place
   and receive calls in the same way as when using a normal mobile
   phone.  When a call is received or placed, the identity will be shown
   in the same manner as when a mobile phone used.

4.7.2.  Derived Requirements

   F1, F2, F3, F4, F5, F6, F8, F9, F10, F18, F20

   A1, A2, A3, A4, A7, A8, A9, A10, A11, A12, A13, A16


5.  Requirements

5.1.  General

   This section contains requirements, derived from the use-cases in
   section 4.

   NOTE: It is assumed that the user applications are executed on a
   browser.  Whether the capabilities to implement specific browser
   requirements are implemented by the browser application, or are
   provided to the browser application by the underlying Operating
   System (OS), is outside the scope of this document.

5.2.  Browser requirements




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   REQ-ID          DESCRIPTION
   ---------------------------------------------------------------
   F1              The browser MUST be able to use microphones and
                   cameras as input devices to generate streams.
   ----------------------------------------------------------------
   F2              The browser MUST be able to send streams to a
                   peer in presence of NATs.
   ----------------------------------------------------------------
   F3              Transmitted streams MUST be rate controlled.
   ----------------------------------------------------------------
   F4              The browser MUST be able to receive, process and
                   render streams from peers.
   ----------------------------------------------------------------
   F5              The browser MUST be able to render good quality
                   audio and video even in presence of reasonable
                   levels of jitter and packet losses.

                   TBD: What is a reasonable level?
   ----------------------------------------------------------------
   F6              The browser MUST be able to handle high loss and
                   jitter levels in a graceful way.
   ----------------------------------------------------------------
   F7              The browser MUST support fast stream switches.
   ----------------------------------------------------------------
   F8              The browser MUST detect when a stream from a
                   peer is not received any more
   ----------------------------------------------------------------
   F9              When there are both incoming and outgoing audio
                   streams, echo cancellation MUST be made available to
                   avoid disturbing echo during conversation.

                   QUESTION: How much control should be left to the
                   web application?
   ----------------------------------------------------------------
   F10             The browser MUST support synchronization of
                   audio and video.


                   QUESTION: How much control should be left to the
                   web application?
   ----------------------------------------------------------------
   F11             The browser MUST be able to transmit streams to
                   several peers concurrently.
   ----------------------------------------------------------------
   F12             The browser MUST be able to receive streams from
                   multiple peers concurrently.
   ----------------------------------------------------------------
   F13             The browser MUST be able to pan, mix and render



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                   several concurrent audio streams.
   ----------------------------------------------------------------
   F14             The browser MUST be able to render several
                   concurrent video streams
   ----------------------------------------------------------------
   F15             The browser MUST be able to process and mix
                   sound objects (media that is retrieved from another
                   source than the established media stream(s) with the
                   peer(s) with audio streams).
   ----------------------------------------------------------------
   F16             Streams MUST be able to pass through restrictive
                   firewalls.
   ----------------------------------------------------------------
   F17             It MUST be possible to protect streams from
                   eavesdropping.
   ----------------------------------------------------------------
   F18             The browser MUST support an audio media format
                   (codec) that is commonly supported by existing
                   telephony services.

                   QUESTION: G.711?
   ----------------------------------------------------------------



5.3.  API requirements


   REQ-ID          DESCRIPTION
   ----------------------------------------------------------------
   A1              The web application MUST be able to query the
                   user about the usage of cameras and microphones
                   as input devices.
   ----------------------------------------------------------------
   A2              The web application MUST be able to control how
                   streams generated by input devices are used.
   ----------------------------------------------------------------
   A3              The web application MUST be able to control the
                   local layout streams (locally generated streams
                   and streams received from a peer).
   ----------------------------------------------------------------
   A4              The web application MUST be able to initiate
                   sending of stream/stream components to a peer.
   ----------------------------------------------------------------
   A5              The web application MUST be able to control the
                   media format (codec) to be used for the streams
                   sent to a peer.




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                   NOTE: The level of control depends on whether
                   the codec negotiation is handled by the browser
                   or the web application.
   ----------------------------------------------------------------
   A6              After a media stream has been established, the
                   web application MUST be able to modify the media
                   format for streams sent to a peer.
   ----------------------------------------------------------------
   A7              The web application MUST be made aware of
                   whether the establishment of a stream with a
                   peer was successful or not.
   ----------------------------------------------------------------
   A8              The web application MUST be able to
                   pause/unpause the sending of a stream to a peer.
   ----------------------------------------------------------------
   A9              The web application MUST be able to mute/unmute
                   a stream received from a peer.
   ----------------------------------------------------------------
   A10             The web application MUST be able to cease the
                   sending of a stream to a peer.
   ----------------------------------------------------------------
   A11             The web application MUST be able to cease
                   processing and rendering of a stream received
                   from a peer.
   ----------------------------------------------------------------
   A12             The web application MUST be informed when a
                   stream from a peer is no longer received.
   ----------------------------------------------------------------
   A13             The web application MUST be informed when high
                   loss rates occur.
   ----------------------------------------------------------------
   A14             It MUST be possible for the web application to
                   control panning, mixing and other processing for
                   individual streams.
   ----------------------------------------------------------------
   A15             The web application MUST be able to identity the
                   context of a stream.
   ----------------------------------------------------------------





6.  IANA Considerations

   TBD





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7.  Security Considerations

7.1.  Introduction

   A malicious web application might use the browser to perform Denial
   Of Service (DOS) attacks on NAT infrastructure, or on peer devices.
   Also, a malicious web application might silently establish outgoing,
   and accept incoming, streams on an already established connection.

   Based on the identified security risks, this section will describe
   security considerations for the browser and web application.

7.2.  Browser Considerations

   The browser is expected to provide mechanisms for getting user
   consent to use device resources such as camera and microphone.

   The browser is expected to provide mechanisms in order to assure that
   streams are the ones the recipient intended to receive.

   The browser is needs to ensure that media is not sent, and that
   received media is not rendered, until the associated stream
   establishment and handshake procedures with the remote peer have been
   successfully finished.

   The browser needs to ensure that the stream negotiation procedures
   are not seen as Denial Of Service (DOS) by other entities.

7.3.  Web Application Considerations

   The web application is expected to ensure user consent in sending and
   receiving media streams.


8.  Acknowledgements

   Harald Alvestrand and Ted Hardie have provided comments and feedback
   on the draft.


9.  Change Log

   [RFC EDITOR NOTE: Please remove this section when publishing]

   Changes from draft-holmberg-rtcweb-ucreqs-00
   o  - Mapping between use-cases and requirements added (Harald
      Alvestrand, 090311)




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   o  - Additional security considerations text (Harald Alvestrand,
      090311)
   o  - Clarification that user applications are assumed to be executed
      by a browser (Ted Hardie, 080311)
   o  - Editorial corrections and clarifications


10.  References

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

10.2.  Informative References


Authors' Addresses

   Christer Holmberg
   Ericsson
   Hirsalantie 11
   Jorvas  02420
   Finland

   Email: christer.holmberg@ericsson.com


   Stefan Hakansson
   Ericsson
   Laboratoriegrand 11
   Lulea  97128
   Sweden

   Email: stefan.lk.hakansson@ericsson.com


   Goran AP Eriksson
   Ericsson
   Farogatan 6
   Stockholm  16480
   Sweden

   Email: goran.ap.eriksson@ericsson.com







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