CLUE WG A. Romanow Internet-Draft Cisco Systems Intended status: Informational S. Botzko Expires: June 15, 2014 M. Barnes Polycom December 12, 2013 Requirements for Telepresence Multi-Streams draft-ietf-clue-telepresence-requirements-07.txt Abstract This memo discusses the requirements for specifications, that enable telepresence interoperability by describing behaviors and protocols for Controlling Multiple Streams for Telepresence (CLUE). In addition, the problem statement and related definitions are also covered herein. 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 June 15, 2014. 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 Romanow, et al. Expires June 15, 2014 [Page 1] Internet-Draft CLUE Telepresence Requirements December 2013 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 5 5. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 7 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 8. Security Considerations . . . . . . . . . . . . . . . . . . . 11 9. Informative References . . . . . . . . . . . . . . . . . . . . 11 Appendix A. Changes From Earlier Versions . . . . . . . . . . . . 12 A.1. Changes from draft -06 . . . . . . . . . . . . . . . . . . 12 A.2. Changes from draft -05 . . . . . . . . . . . . . . . . . . 12 A.3. Changes from draft -04 . . . . . . . . . . . . . . . . . . 13 A.4. Changes from draft -03 . . . . . . . . . . . . . . . . . . 13 A.5. Changes from draft -02 . . . . . . . . . . . . . . . . . . 13 A.6. Changes from draft -01 . . . . . . . . . . . . . . . . . . 13 A.7. Changes From Draft -00 . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 Romanow, et al. Expires June 15, 2014 [Page 2] Internet-Draft CLUE Telepresence Requirements December 2013 1. Introduction Telepresence systems greatly improve collaboration. In a telepresence conference (as used herein), the goal is to create an environment that gives the users a feeling of (co-located) presence - the feeling that a local user is in the same room with other local users and the remote parties. Currently, systems from different vendors often do not interoperate because they do the same tasks differently, as discussed in the Problem Statement section below. The approach taken in this memo is to set requirements for a future specification(s) that, when fulfilled by an implementation of the specification(s), provide for interoperability between IETF protocol based telepresence systems. It is anticipated that a solution for the requirements set out in this memo likely involves the exchange of adequate information about participating sites; information that is currently not standardized by the IETF. The purpose of this document is to describe the requirements for a specification that enables interworking between different SIP-based [RFC3261] telepresence systems, by exchanging and negotiating appropriate information. In the context of the requirements in this document and related solution documents, this includes both point to point SIP sessions as well as SIP based conferences as described in the SIP conferencing framework [RFC4353] and the SIP based conference control [RFC4579] specifications. Non IETF protocol based systems, such as those based on ITU-T Rec. H.323, are out of scope. These requirements are for the specification, they are not requirements on the telepresence systems implementing the solution/protocol that will be specified. Telepresence systems of different vendors, today, can follow radically different architectural approaches while offering a similar user experience. CLUE will not dictate telepresence architectural and implementation choices; however it will describe a protocol architecture for CLUE and how it relates to other protocols. CLUE enables interoperability between telepresence systems by exchanging information about the systems' characteristics. Systems can use this information to control their behavior to allow for interoperability between those systems. A telepresence session requires at least one sending and one receiving endpoint. Multiparty telepresence sessions include more than two endpoints, and centralized infrastructure such as Multipoint Control Units (MCUs) or equivalent. CLUE specifies the syntax, semantics, and control flow of information to enable the best possible user experience at those endpoints. Romanow, et al. Expires June 15, 2014 [Page 3] Internet-Draft CLUE Telepresence Requirements December 2013 Sending endpoints, or MCUs, are not mandated to use any of the CLUE specifications that describe their capabilities, attributes, or behavior. Similarly, it is not envisioned that endpoints or MCUs must ever take into account information received. However, by making available as much information as possible, and by taking into account as much information as has been received or exchanged, MCUs and endpoints are expected to select operation modes that enable the best possible user experience under their constraints. The document structure is as follows: Definitions are set out, followed by a description of the problem of telepresence interoperability that led to this work. Then the requirements to a specification addressing the current shortcomings are enumerated and discussed. 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. Definitions The following terms are used throughout this document and serve as reference for other documents. Audio Mixing: refers to the accumulation of scaled audio signals to produce a single audio stream. See RTP Topologies, [RFC5117]. Conference: used as defined in [RFC4353], A Framework for Conferencing within the Session Initiation Protocol (SIP). Endpoint: The logical point of final termination through receiving, decoding and rendering, and/or initiation through capturing, encoding, and sending of media streams. An endpoint consists of one or more physical devices which source and sink media streams, and exactly one [RFC4353] Participant (which, in turn, includes exactly one SIP User Agent). In contrast to an endpoint, an MCU may also send and receive media streams, but it is not the initiator nor the final terminator in the sense that Media is Captured or Rendered. Endpoints can be anything from multiscreen/multicamera rooms to handheld devices. Romanow, et al. Expires June 15, 2014 [Page 4] Internet-Draft CLUE Telepresence Requirements December 2013 Endpoint Characteristics: include placement of Capture and Rendering Devices, capture/render angle, resolution of cameras and screens, spatial location and mixing parameters of microphones. Endpoint characteristics are not specific to individual media streams sent by the endpoint. Layout: How rendered media streams are spatially arranged with respect to each other on a single screen/mono audio telepresence endpoint, and how rendered media streams are arranged with respect to each other on a multiple screen/speaker telepresence endpoint. Note that audio as well as video is encompassed by the term layout--in other words, included is the placement of audio streams on speakers as well as video streams on video screens. Local: Sender and/or receiver physically co-located ("local") in the context of the discussion. MCU: Multipoint Control Unit (MCU) - a device that connects two or more endpoints together into one single multimedia conference [RFC5117]. An MCU may include a Mixer [RFC4353]. Media: Any data that, after suitable encoding, can be conveyed over RTP, including audio, video or timed text. Model: a set of assumptions a telepresence system of a given vendor adheres to and expects the remote telepresence system(s) also to adhere to. Remote: Sender and/or receiver on the other side of the communication channel (depending on context); not Local. A remote can be an Endpoint or an MCU. Render: the process of generating a representation from a media, such as displayed motion video or sound emitted from loudspeakers. Telepresence: an environment that gives non co-located users or user groups a feeling of (co-located) presence - the feeling that a Local user is in the same room with other Local users and the Remote parties. The inclusion of Remote parties is achieved through multimedia communication including at least audio and video signals of high fidelity. 4. Problem Statement In order to create a "being there" experience characteristic of telepresence, media inputs need to be transported, received, and coordinated between participating systems. Different telepresence Romanow, et al. Expires June 15, 2014 [Page 5] Internet-Draft CLUE Telepresence Requirements December 2013 systems take diverse approaches in crafting a solution, or, they implement similar solutions quite differently. They use disparate techniques, and they describe, control and negotiate media in dissimilar fashions. Such diversity creates an interoperability problem. The same issues are solved in different ways by different systems, so that they are not directly interoperable. This makes interworking difficult at best and sometimes impossible. Worse, many telepresence systems use proprietary protocol extensions to solve telepresence-related problems, even if those extensions are based on common standards such as SIP. Some degree of interworking between systems from different vendors is possible through transcoding and translation. This requires additional devices, which are expensive, often not entirely automatic, and they sometimes introduce unwelcome side effects, such as additional delay or degraded performance. Specialized knowledge is currently required to operate a telepresence conference with endpoints from different vendors, for example to configure transcoding and translating devices. Often such conferences do not start as planned, or are interrupted by difficulties that arise. The general problem that needs to be solved can be described as follows. Today, each endpoint sends audio and video captures based upon an implicitly assumed model for rendering a realistic depiction based on this information. If all endpoints are manufactured by the same vendor, they work with the same model and render the information according to the model implicitly assumed by the vendor. However, if the devices are from different vendors, the models they each use for rendering presence can and usually do differ. The result can be that the telepresence systems actually connect, but the user experience suffers, for example because one system assumes that the first video stream is captured from the right camera, whereas the other assumes the first video stream is captured from the left camera. If Alice and Bob are at different sites, Alice needs to tell Bob about the camera and sound equipment arrangement at her site so that Bob's receiver can create an accurate rendering of her site. Alice and Bob need to agree on what the salient characteristics are as well as how to represent and communicate them. Characteristics may include number, placement, capture/render angle, resolution of cameras and screens, spatial location and audio mixing parameters of microphones. The telepresence multi-stream work seeks to describe the sender situation in a way that allows the receiver to render it Romanow, et al. Expires June 15, 2014 [Page 6] Internet-Draft CLUE Telepresence Requirements December 2013 realistically even though it may have a different rendering model than the sender. 5. Requirements Although some aspects of these requirements can be met by existing technology, such as SDP, they are stated here to have a complete record of what the requirements for CLUE are, whether new work is needed or they can be met by existing technology. Figuring this out will be part of the solution development, rather than part of the requirements. Note, the term "solution" is used in these requirements to mean the protocol specifications, including extensions to existing protocols as well as any new protocols, developed to support the use cases. The solution can introduce additional functionality that isn't mapped directly to these requirements - e.g., the detailed information carried in the signaling protocol(s). In cases where the requirements are directly related to a specific use case, a reference to the use case is provided. REQMT-1: The solution MUST support a description of the spatial arrangement of source video images sent in video streams which enables a satisfactory reproduction at the receiver of the original scene. This applies to each site in a point to point or a multipoint meeting and refers to the spatial ordering within a site, not to the ordering of images between sites. Use case point to point symmetric, and all other use cases. REQMT-1a: The solution MUST support a means of allowing the preservation of the order of images in the captured scene. For example, if John is to Susan's right in the image capture, John is also to Susan's right in the rendered image. REQMT-1b: The solution MUST support a means of allowing the preservation of order of images in the scene in two dimensions - horizontal and vertical. REQMT-1c: The solution MUST support a means to identify the point of capture of individual video captures in three dimensions. Romanow, et al. Expires June 15, 2014 [Page 7] Internet-Draft CLUE Telepresence Requirements December 2013 REQMT-1d: The solution MUST support a means to identify the area of coverage of individual video captures in three dimensions. REQMT-2: The solution MUST support a description of the spatial arrangement of captured source audio sent in audio streams which enables a satisfactory reproduction at the receiver in a spatially correct manner. This applies to each site in a point to point or a multipoint meeting and refers to the spatial ordering within a site, not the ordering of channels between sites. Use case point to point symmetric, and all use cases, especially heterogeneous. REQMT-2a: The solution MUST support a means of preserving the spatial order of audio in the captured scene. For example, if John sounds as if he is at Susan's right in the captured audio, John voice is also placed at Susan's right in the rendered image. REQMT-2b: The solution MUST support a means to identify the number and spatial arrangement of audio channels including monaural, stereophonic (2.0), and 3.0 (left, center, right) audio channels. REQMT-2c: The solution MUST support a means to identify the point of capture of individual audio captures in three dimensions. REQMT-2d: The solution MUST support a means to identify the area of coverage of individual audio captures in three dimensions. REQMT-3: The solution MUST enable individual audio streams to be associated with one or more video image captures, and individual video image captures to be associated with one or more audio captures, for the purpose of rendering proper position. Use case is point to point symmetric, and all use cases. REQMT-4: The solution MUST enable interoperability between endpoints that have a different number of similar devices. For example, one endpoint may have 1 screen, 1 speaker, 1 camera, 1 mic, and another endpoint may have 3 screens, 2 Romanow, et al. Expires June 15, 2014 [Page 8] Internet-Draft CLUE Telepresence Requirements December 2013 speakers, 3 cameras and 2 microphones. Or, in a multi- point conference, one endpoint may have one screen, another may have 2 screens and a third may have 3 screens. This includes endpoints where the number of devices of a given type is zero. Use case is asymmetric point to point and multipoint. REQMT-5: The solution MUST support means of enabling interoperability between telepresence endpoints where cameras are of different picture aspect ratios. REQMT-6: The solution MUST provide scaling information which enables rendering of a video image at the actual size of the captured scene. REQMT-7: The solution MUST support means of enabling interoperability between telepresence endpoints where displays are of different resolutions. REQMT-8: The solution MUST support methods for handling different bit rates in the same conference. REQMT-9: The solution MUST support means of enabling interoperability between endpoints that send and receive different numbers of media streams. Use case heterogeneous and multipoint. REQMT-10: The solution MUST ensure that endpoints that support telepresence extensions can establish a session with a SIP endpoint that does not support the telepresence extensions. For example, in the case of a SIP endpoint that supports a single audio and a single video stream, an endpoint that supports the telepresence extensions would setup a session with a single audio and single video stream using existing SIP and SDP mechanisms. REQMT-11: The solution MUST support a mechanism for determining whether or not an endpoint or MCU is capable of telepresence extensions. REQMT-12: The solution MUST support a means to enable more than two endpoints to participate in a teleconference. Use case multipoint. Romanow, et al. Expires June 15, 2014 [Page 9] Internet-Draft CLUE Telepresence Requirements December 2013 REQMT-13: The solution MUST support both transcoding and switching approaches to providing multipoint conferences. REQMT-14: The solution MUST support mechanisms to allow media from one source endpoint or/and multiple source endpoints to be sent to a remote endpoint at a particular point in time. Which media is sent at a point in time may be based on local policy. REQMT-15: The solution MUST provide mechanisms to support the following: * Presentations with different media sources * Presentations for which the media streams are visible to all endpoints * Multiple, simultaneous presentation media streams, including presentation media streams that are spatially related to each other. Use case is presentation. REQMT-16: The specification of any new protocols for the solution MUST provide extensibility mechanisms. REQMT-17: The solution MUST support a mechanism for allowing information about media captures to change during a conference. REQMT-18: The solution MUST provide a mechanism for the secure exchange of information about the media captures. 6. Acknowledgements This draft has benefitted from all the comments on the mailing list and a number of discussions. So many people contributed that it is not possible to list them all. However, the comments provided by Roberta Presta, Christian Groves and Paul Coverdale during WGLC were particularly helpful in completing the WG document. 7. IANA Considerations There are no IANA considerations associated with this specification. Romanow, et al. Expires June 15, 2014 [Page 10] Internet-Draft CLUE Telepresence Requirements December 2013 8. Security Considerations Requirement REQMT-18 identifies the need to securely transport the information about media captures. It is important to note that session setup for a telepresence session will use SIP for basic session setup and either SIP or CCMP for a multi-party telepresence session. Information carried in the SIP signaling can be secured by the SIP security mechanisms as defined in [RFC3261]. In the case of conference control using CCMP, the security model and mechanisms as defined in the XCON Framework [RFC5239] and CCMP [RFC6503] documents would meet the requirement. Any additional signaling mechanism used to transport the information about media captures would need to define the mechanisms by the which the information is secure. The details for the mechanisms needs to be defined and described in the CLUE framework document and related solution document(s). 9. Informative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, June 2002. [RFC4353] Rosenberg, J., "A Framework for Conferencing with the Session Initiation Protocol (SIP)", RFC 4353, February 2006. [RFC4579] Johnston, A. and O. Levin, "Session Initiation Protocol (SIP) Call Control - Conferencing for User Agents", BCP 119, RFC 4579, August 2006. [RFC5117] Westerlund, M. and S. Wenger, "RTP Topologies", RFC 5117, January 2008. [RFC5239] Barnes, M., Boulton, C., and O. Levin, "A Framework for Centralized Conferencing", RFC 5239, June 2008. [RFC6503] Barnes, M., Boulton, C., Romano, S., and H. Schulzrinne, "Centralized Conferencing Manipulation Protocol", RFC 6503, March 2012. Romanow, et al. Expires June 15, 2014 [Page 11] Internet-Draft CLUE Telepresence Requirements December 2013 Appendix A. Changes From Earlier Versions Note to the RFC-Editor: please remove this section prior to publication as an RFC. A.1. Changes from draft -06 Addressing IETF LC comments/editorial nits resulting in the following changes: o Included expansion of CLUE in the abstract. o Deleted definitions for "Left" and "Right". o Section 5 - clarified that solution = protocol specifications to support requirements. o REQMT-1d, REQMT-2d: Changed term "extent" to "area of coverage" o REQMT-10 - clarified requirement with regards to interworking with non-CLUE endpoints o REQMT-15 - reworded to be more specific and normative o REQMT-16 - expanded on what is meant by "extensibility" A.2. Changes from draft -05 Addressing WGLC comments resulting in the following changes: o REQMT-12: Changed term "site" to "endpoint" o Intro: clarified that SIP based conferencing also is relevant to CLUE. o Intro: clarified that while CLUE doesn't dictate implementation choices, it does describe a framework for the protocol solution. o Clarified that mapping to use cases isn't comprehensive (i.e., only done when there is a direct correlation). o Added text that the requirements do not reflect all those required for the solution - i.e., the solution can provide more functionality as needed. o Editorial nits and clarifications - changed lc "must" to UC (REQMT-17). Romanow, et al. Expires June 15, 2014 [Page 12] Internet-Draft CLUE Telepresence Requirements December 2013 A.3. Changes from draft -04 o Removed REQMT-2c, related to issue #37 in the tracker. o Deleted REQMT-3b. Condensed REQMT-3 to subsume REQMT-3a. This is related to Issue #38 in the tracker. o Updated REQMT-14 based on (mailing list) resolution of Issue #39. o Deleted OPEN issue section as those were transferred to the ID tracker and have been resolved either by changes to this document or to earlier versions of the document A.4. Changes from draft -03 o Added a tad more text to the security section Paragraph 18. A.5. Changes from draft -02 o Updated IANA section - i.e., no IANA registrations required. o Added security requirement Paragraph 18. o Added some initial text to the security section. A.6. Changes from draft -01 o Cleaned up the Problem Statement section, re-worded. o Added Requirement Paragraph 17 in response to WG Issue #4 to make a requirement for dynamically changing information. Approved by WG o Added requirements #1.c and #1.d. Approved by WG o Added requirements #2.d and #2.e. Approved by WG A.7. Changes From Draft -00 o Requirement #2, The solution MUST support a means to identify monaural, stereophonic (2.0), and 3.0 (left, center, right) audio channels. changed to The solution MUST support a means to identify the number and spatial arrangement of audio channels including monaural, Romanow, et al. Expires June 15, 2014 [Page 13] Internet-Draft CLUE Telepresence Requirements December 2013 stereophonic (2.0), and 3.0 (left, center, right) audio channels. o Added back references to the Use case document. * Requirement #1 Use case point to point symmetric, and all other use cases. * Requirement #2 Use case point to point symmetric, and all use cases, especially heterogeneous. * Requirement #3 Use case point to point symmetric, and all use cases. * Requirement #4 Use case is asymmetric point to point, and multipoint. * Requirement #9 Use case heterogeneous and multipoint. * Requirement #12 Use case multipoint. Authors' Addresses Allyn Romanow Cisco Systems San Jose, CA 95134 USA Email: allyn@cisco.com Stephen Botzko Polycom Andover, MA 01810 US Email: stephen.botzko@polycom.com Mary Barnes Polycom Email: mary.ietf.barnes@gmail.com Romanow, et al. Expires June 15, 2014 [Page 14]