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rfc:rfc3351

Network Working Group N. Charlton Request for Comments: 3351 Millpark Category: Informational M. Gasson

                                                        Koru Solutions
                                                             G. Gybels
                                                            M. Spanner
                                                                  RNID
                                                           A. van Wijk
                                                              Ericsson
                                                           August 2002
    User Requirements for the Session Initiation Protocol (SIP)
                in Support of Deaf, Hard of Hearing
                  and Speech-impaired Individuals

Status of this Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

 This document presents a set of Session Initiation Protocol
 (SIP) user requirements that support communications for deaf, hard of
 hearing and speech-impaired individuals.  These user requirements
 address the current difficulties of deaf, hard of hearing and
 speech-impaired individuals in using communications facilities, while
 acknowledging the multi-functional potential of SIP-based
 communications.
 A number of issues related to these user requirements are further
 raised in this document.
 Also included are some real world scenarios and some technical
 requirements to show the robustness of these requirements on a
 concept-level.

Charlton, et al. Informational [Page 1] RFC 3351 SIP for Deaf, Hard of Hearing and Speech Impaired August 2002

Table of Contents

 1. Terminology and Conventions Used in this Document................2
 2. Introduction.....................................................3
 3. Purpose and Scope................................................4
 4. Background.......................................................4
 5. Deaf, Hard of Hearing and Speech-impaired Requirements for SIP...5
    5.1 Connection without Difficulty................................5
    5.2 User Profile.................................................6
    5.3 Intelligent Gateways.........................................6
    5.4 Inclusive Design.............................................7
    5.5 Resource Management..........................................7
    5.6 Confidentiality and Security.................................7
 6. Some Real World Scenarios........................................8
    6.1 Transcoding Service..........................................8
    6.2 Media Service Provider.......................................9
    6.3 Sign Language Interface......................................9
    6.4 Synthetic Lip-reading Support for Voice Calls...............10
    6.5 Voice-Activated Menu Systems................................10
    6.6 Conference Call.............................................11
 7. Some Suggestions for Service Providers and User Agent
    Manufacturers...................................................13
 8. Acknowledgements................................................14
    Security Considerations.........................................14
    Normative References............................................15
    Informational References........................................15
    Author's Addresses..............................................15
    Full Copyright Statement........................................17

1. Terminology and Conventions Used in this Document

 In this document, the key words "MUST", "MUST NOT","REQUIRED",
 "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
 and "OPTIONAL" are to be interpreted as described in BCP 14,
 RFC2119[1] and indicate requirement levels for compliant SIP
 implementations.
 For the purposes of this document, the following terms are considered
 to have these meanings:
 Abilities:  A person's capacity for communicating which could include
 a hearing or speech impairment or not.  The terms Abilities and
 Preferences apply to both caller and call-recipient.
 Preferences:  A person's choice of communication mode.  This could
 include any combination of media streams, e.g., text, audio, video.

Charlton, et al. Informational [Page 2] RFC 3351 SIP for Deaf, Hard of Hearing and Speech Impaired August 2002

 The terms Abilities and Preferences apply to both caller and
 call-recipient.
 Relay Service:  A third-party or intermediary that enables
 communications between deaf, hard of hearing and speech-impaired
 people, and people without hearing or speech-impairment.  Relay
 Services form a subset of the activities of Transcoding Services (see
 definition).
 Transcoding Services:  A human or automated third party acting as an
 intermediary in any session between two other User Agents (being a
 User Agent itself), and transcoding one stream into another (e.g.,
 voice to text or vice versa).
 Textphone:  Sometimes called a TTY (teletypewriter), TDD
 (telecommunications device for the deaf) or a minicom, a textphone
 enables a deaf, hard of hearing or speech-impaired person to place a
 call to a telephone or another textphone.  Some textphones use the
 V.18[3] protocol as a standard for communication with other textphone
 communication protocols world-wide.
 User:  A deaf, hard of hearing or speech-impaired individual.  A user
 is otherwise referred to as a person or individual, and users are
 referred to as people.
 Note:  For the purposes of this document, a deaf, hard of hearing, or
 speech-impaired person is an individual who chooses to use SIP
 because it can minimize or eliminate constraints in using common
 communication devices.  As SIP promises a total communication
 solution for any kind of person, regardless of ability and
 preference, there is no attempt to specifically define deaf, hard of
 hearing or speech-impaired in this document.

2. Introduction

 The background for this document is the recent development of SIP[2]
 and SIP-based communications, and a growing awareness of deaf, hard
 of hearing and speech-impaired issues in the technical community.
 The SIP capacity to simplify setting up, managing and tearing down
 communication sessions between all kinds of User Agents has specific
 implications for deaf, hard of hearing and speech-impaired
 individuals.

Charlton, et al. Informational [Page 3] RFC 3351 SIP for Deaf, Hard of Hearing and Speech Impaired August 2002

 As SIP enables multiple sessions with translation between multiple
 types of media, these requirements aim to provide the standard for
 recognizing and enabling these interactions, and for a communications
 model that includes any and all types of SIP-networking abilities and
 preferences.

3. Purpose and Scope

 The scope of this document is firstly to present a current set of
 user requirements for deaf, hard of hearing and speech-impaired
 individuals through SIP-enabled communications.  These are then
 followed by some real world scenarios in SIP-communications that
 could be used in a test environment, and some concepts of how these
 requirements can be developed by service providers and User Agent
 manufacturers.
 These recommendations make explicit the needs of a currently often
 disadvantaged user-group and attempt to match them with the capacity
 of SIP.  It is not the intention here to prioritize the needs of
 deaf, hard of hearing and speech-impaired people in a way that would
 penalize other individuals.
 These requirements aim to encourage developers and manufacturers
 world-wide to consider the specific needs of deaf, hard of hearing
 and speech-impaired individuals.  This document presents a
 world-vision where deafness, hard of hearing or speech impairment are
 no longer a barrier to communication.

4. Background

 Deaf, hard of hearing and speech-impaired people are currently
 often unable to use commonly available communication devices.
 Although this is documented[4], this does not mean that developers or
 manufacturers are always aware of this.  Communication devices for
 deaf, hard of hearing and speech-impaired people are
 currently often primitive in design, expensive, and non-compatible
 with progressively designed, cheaper and more adaptable communication
 devices for other individuals.  For example, many models of textphone
 are unable to communicate with other models.
 Additionally, non-technical human communications, for example sign
 languages or lip-reading, are non-standard around the world.

Charlton, et al. Informational [Page 4] RFC 3351 SIP for Deaf, Hard of Hearing and Speech Impaired August 2002

 There are intermediary or third-party relay services (e.g.
 transcoding services) that facilitate communications, uni- or bi-
 directional, for deaf, hard of hearing and speech-impaired people.
 Currently relay services are mostly operator-assisted (manual),
 although methods of partial automation are being implemented in some
 areas.  These services enable full access to modern facilities and
 conveniences for deaf, hard of hearing and speech-impaired people.
 Although these services are somewhat limited, their value is
 undeniable as compared to their previous complete unavailability.
 Yet communication methods in recent decades have proliferated:
 email, mobile phones, video streaming, etc.  These methods are an
 advance in the development of data transfer technologies between
 devices.
 Developers and advocates of SIP agree that it is a protocol that not
 only anticipates the growth in real-time communications between
 convergent networks, but also fulfills the potential of the Internet
 as a communications and information forum.  Further, they agree that
 these developments allow a standard of communication that can be
 applied throughout all networking communities, regardless of
 abilities and preferences.

5. Deaf, Hard of Hearing and Speech-impaired Requirements for SIP

 Introduction
 The user requirements in this section are provided for the benefit of
 service providers, User Agent manufacturers and any other interested
 parties in the development of products and services for deaf, hard of
 hearing and speech-impaired people.
 The user requirements are as follows:

5.1 Connection without Difficulty

 This requirement states:
 Whatever the preferences and abilities of the user and User Agent,
 there SHOULD be no difficulty in setting up SIP sessions.  These
 sessions could include multiple proxies, call routing decisions,
 transcoding services, e.g., the relay service Typetalk[5] or other
 media processing, and could include multiple simultaneous or
 alternative media streams.

Charlton, et al. Informational [Page 5] RFC 3351 SIP for Deaf, Hard of Hearing and Speech Impaired August 2002

 This means that any User Agent in the conversation (including
 transcoding services) MUST be able to add or remove a media stream
 from the call without having to tear it down and re-establish it.

5.2 User Profile

 This requirement states:
 Deaf, hard of hearing and speech-impaired user abilities and
 preferences (i.e., user profile) MUST be communicable by SIP, and
 these abilities and preferences MUST determine the handling of the
 session.
 The User Profile for a deaf, hard of hearing or speech-impaired
 person might include details about:
  1. How media streams are received and transmitted (text, voice, video,

or any combination, uni- or bi-directional).

  1. Redirecting specific media streams through a transcoding service

(e.g., the relay service Typetalk)

  1. Roaming (e.g., a deaf person accessing their User Profile from a

web-interface at an Internet cafe)

  1. Anonymity: i.e., not revealing that a deaf person is calling, even

through a transcoding service (e.g., some relay services inform the

   call-recipient that there is an incoming text call without saying
   that a deaf person is calling).
   Part of this requirement is to ensure that deaf, hard of hearing
   and speech-impaired people can keep their preferences and abilities
   confidential from others, to avoid possible discrimination or
   prejudice, while still being able to establish a SIP session.

5.3 Intelligent Gateways

 This requirement states:
 SIP SHOULD support a class of User Agents to perform as gateways for
 legacy systems designed for deaf, hard of hearing and speech-impaired
 people.
 For example, an individual could have a SIP User Agent acting as a
 gateway to a PSTN legacy textphone.

Charlton, et al. Informational [Page 6] RFC 3351 SIP for Deaf, Hard of Hearing and Speech Impaired August 2002

5.4 Inclusive Design

 This requirement states:
 Where applicable, design concepts for communications (devices,
 applications, etc.) MUST include the abilities and preferences of
 deaf, hard of hearing and speech-impaired people.
 Transcoding services and User Agents MUST be able to connect with
 each other regardless of the provider or manufacturer.  This means
 that new User Agents MUST be able to support legacy protocols through
 appropriate gateways.

5.5 Resource Management

 This requirement states:
 User Agents SHOULD be able to identify the content of a media stream
 in order to obtain such information as the cost of the media stream,
 if a transcoding service can support it, etc.
 User Agents SHOULD be able to choose among transcoding services and
 similar services based on their capabilities (e.g., whether a
 transcoding service carries a particular media stream), and any
 policy constraints they impose (e.g., charging for use).  It SHOULD
 be possible for User Agents to discover the availability of
 alternative media streams and to choose from them.

5.6 Confidentiality and Security

 This requirement states:
 All third-party or intermediaries (transcoding services) employed in
 a session for deaf, hard of hearing and speech-impaired people MUST
 offer a confidentiality policy.  All information exchanged in this
 type of session SHOULD be secure, that is, erased before
 confidentiality is breached, unless otherwise required.
 This means that transcoding services (e.g., interpretation,
 translation) MUST publish their confidentiality and security
 policies.

Charlton, et al. Informational [Page 7] RFC 3351 SIP for Deaf, Hard of Hearing and Speech Impaired August 2002

6. Some Real World Scenarios

 These scenarios are intended to show some of the various types of
 media streams that would be initiated, managed, directed, and
 terminated in a SIP-enabled network, and shows how some resources
 might be managed between SIP-enabled networks, transcoding services
 and service providers.
 To illustrate the communications dynamic of these kinds of scenarios,
 each one specifically mentions the kind of media streams transmitted,
 and whether User Agents and Transcoding Services are involved.

6.1 Transcoding Service

 In this scenario, a hearing person calls the household of a deaf
 person and a hearing person.
 1. A voice conversation is initiated between the hearing
    participants:
    ( Person A) <-----Voice ---> ( Person B)
 2. During the conversation, the hearing person asks to talk with the
    deaf person, while keeping the voice connection open so that voice
    to voice communications can continue if required.
 3. A Relay Service is invited into the conversation.
 4. The Relay Service transcodes the hearing person's words into text.
 5. Text from the hearing person's voice appears on the display of the
    deaf person's User Agent.
 6. The deaf person types a response.
 7. The Relay Service receives the text and reads it to the hearing
    person:
    (         ) <------------------Voice----------------> (         )
    (Person A ) -----Voice---> ( Voice To Text  ) -Text-> (Person B )
    (         ) <----Voice---- (Service Provider) <-Text- (         )
 8. The hearing person asks to talk with the hearing person in the
    deaf person's household.
 9. The Relay Service withdraws from the call.

Charlton, et al. Informational [Page 8] RFC 3351 SIP for Deaf, Hard of Hearing and Speech Impaired August 2002

6.2 Media Service Provider

 In this scenario, a deaf person wishes to receive the content of a
 radio program through a text stream transcoded from the program's
 audio stream.
 1. The deaf person attempts to establish a connection to the radio
    broadcast, with User Agent preferences set to receiving audio
    stream as text.
 2. The User Agent of the deaf person queries the radio station User
    Agent on whether a text stream is available, other than the audio
    stream.
 3. However, the radio station has no text stream available for a deaf
    listener, and responds in the negative.
 4. As no text stream is available, the deaf person's User Agent
    requests a voice-to-text transcoding service (e.g., a real-time
    captioning service) to come into the conversation space.
 5. The transcoding service User Agent identifies the audio stream as
    a radio broadcast.  However, the policy of the transcoding service
    is that it does not accept radio broadcasts because it would
    overload their resources far too quickly.
 6. In this case, the connection fails.
 Alternatively, continuing from 2 above:
 3. The radio station does provide text with their audio streams.
 4. The deaf person receives a text stream of the radio program.
 Note:  To support deaf, hard of hearing and speech-impaired people,
 service providers are encouraged to provide text with audio streams.

6.3 Sign Language Interface

 In this scenario, a deaf person enables a signing avatar (e.g.,
 ViSiCAST[6]) by setting up a User Agent to receive audio streams as
 XML data that will operate an avatar for sign-language.  For outgoing
 communications, the deaf person types text that is transcoded into an
 audio stream for the other conversation participant.

Charlton, et al. Informational [Page 9] RFC 3351 SIP for Deaf, Hard of Hearing and Speech Impaired August 2002

For example:

( )-Voice→(Voice To Avatar Commands) —-XMLData–>( ) ( hearing ) (deaf ) ( Person A)←Voice-( Text To Voice ) ←——-Text——– (Person B) ( ) (Service Provider) ( )

6.4 Synthetic Lip-speaking Support for Voice Calls

 In order to receive voice calls, a hard of hearing person uses lip-
 speaking avatar software (e.g., Synface[7]) on a PC.  The lip-
 speaking software processes voice (audio) stream data and displays a
 synthetic animated face that a hard of hearing person may be able to
 lip-read.  During a conversation, the hard of hearing person uses the
 lip-speaking software as support for understanding the audio stream.
 For example:
    (         ) <------------------Voice-------------->(         )
    ( hearing )                    ( PC with     )     ( hard of )
    ( Person A) -------Voice-----> ( lip-speaking)---->( hearing )
    (         )                    ( software    )     ( Person B)

6.5 Voice Activated Menu Systems

 In this scenario, a deaf person wishing to book cinema tickets with a
 credit card, uses a textphone to place the call.  The cinema employs
 a voice-activated menu system for film titles and showing times.
 1. The deaf person places a call to the cinema with a textphone:
       (Textphone) <-----Text ---> (Voice-activated System)
 2. The cinema's voice-activated menu requests an auditory response to
    continue.
 3. A Relay Service is invited into the conversation.
 4. The Relay Service transcodes the prompts of the voice-activated
    menu into text.
 5. Text from the voice-activated menu appears on the display of the
    deaf person's textphone.
 6. The deaf person types a response.

Charlton, et al. Informational [Page 10] RFC 3351 SIP for Deaf, Hard of Hearing and Speech Impaired August 2002

 7. The Relay Service receives the text and reads it to the voice-
    activated system:
 (           )         (Relay Service   )          (               )
 ( deaf      ) -Text-> (Provider        ) -Voice-> (Voice-Activated)
 ( Person A  ) <-Text- (Text To Voice   ) <-Voice- (System         )
 8. The transaction is finalized with a confirmed booking time.
 9. The Relay Service withdraws from the call.

6.6 Conference Call

 A conference call is scheduled between five people:
  1. Person A listens and types text (hearing, no speech)
  2. Person B recognizes sign language and signs back (deaf, no speech)
  3. Person C reads text and speaks (deaf or hearing impaired)
  4. Person D listens and speaks
  5. Person E recognizes sign language and reads text and signs
 A conference call server calls the five people and based on their
 preferences sets up the different transcoding services required.
 Assuming English is the base language for the call, the following
 intermediate transcoding services are invoked:
  1. A transcoding service (English speech to English text)
  2. An English text to sign language service
  3. A sign language to English text service
  4. An English text to English speech service
 Note:  In order to translate from English speech to sign language, a
 chain of intermediate transcoding services was used (transcoding and
 English text to sign language) because there was no speech-to-sign
 language available for direct translation.  Accordingly, the same
 applied for the translation from sign language to English speech.

Charlton, et al. Informational [Page 11] RFC 3351 SIP for Deaf, Hard of Hearing and Speech Impaired August 2002

(Person A) —– Text —→ ( Text-to-SL ) — Video —→ (Person B)

  1. ——————— Text ——————–> (Person C)
  2. —- Text —→ (Text-to-Speech) — Voice —→ (Person D)
  3. ——————— Text ——————–> (Person E)
  4. —- Text —→ ( Text-to-SL ) — Video —→ (Person E)

(Person B) -Video→ (SL-to-Text) -Text→ (Text-to-Speech) → (Person A)

  1. — Video —→ ( SL-to-Text ) —- Text —→ (Person C)
  2. Video→ (SL-to-Text) -Text→ (Text-to-Speech) → (Person D)
  3. ——————– Video ——————–> (Person E)
  4. — Video —→ ( SL-to-Text ) —- Text —→ (Person E)

(Person C) ——————— Voice ——————–> (Person A)

         Voice->(Speech-to-Text)-Text->(Text-to-SL)-Video->(Person B)
         --------------------- Voice --------------------> (Person D)
         ---- Voice ----> (Speech-to-Text) ---- Text ----> (Person E)
         Voice->(Speech-to-Text)-Text->(Text-to-SL)-Video->(Person E)

(Person D) ——————— Voice ——————–> (Person A)

         Voice->(Speech-to-Text)-Text->(Text-to-SL)-Video->(Person B)
         ---- Voice ----> (Speech-to-Text) ---- Text ----> (Person C)
         ---- Voice ----> (Speech-to-Text) ---- Text ----> (Person E)
         Voice->(Speech-to-Text)-Text->(Text-to-SL)-Video->(Person E)

(Person E) -Video→ (SL-to-Text) -Text→ (Text-to-Speech) → (Person A)

  1. ——————– Video ——————–> (person B)
  2. — Video —→ ( SL-to-Text ) —- Text —→ (Person C)
  3. Video→ (SL-to-Text) -Text→ (Text-to-Speech) → (Person D)
 Remarks: - Some services might be shared by users and/or other
            services.
  1. Person E uses two parallel streams (SL and English Text).

The User Agent might perform time synchronisation when

            displaying the streams.  However, this would require
            synchronisation information to be present on the streams.
  1. The session protocols might support optional buffering of

media streams, so that users and/or intermediate services

            could go back to previous content or to invoke a
            transcoding service for content they just missed.
  1. Hearing impaired users might still receive audio as well,

which they will use to drive some visual indicators so

            that they can better see where, for instance, the pauses
            are in the conversation.

Charlton, et al. Informational [Page 12] RFC 3351 SIP for Deaf, Hard of Hearing and Speech Impaired August 2002

7. Some Suggestions for Service Providers and User Agent Manufacturers

 This section is included to encourage service providers and user
 agent manufacturers in developing products and services that can be
 used by as wide a range of individuals as possible, including deaf,
 hard of hearing and speech-impaired people.
  1. Service providers and User Agent manufacturers can offer to a deaf,

hard of hearing and speech-impaired person the possibility of being

   able to prevent their specific abilities and preferences from being
   made public in any transaction.
  1. If a User Agent performs auditory signalling, for example a pager,

it could also provide another signalling method; visual (e.g., a

   flashing light) or tactile (e.g., vibration).
  1. Service providers who allow the user to store specific abilities

and preferences or settings (i.e., a user profile) might consider

   storing these settings in a central repository, accessible no
   matter what the location of the user and regardless of the User
   Agent used at that time or location.
  1. If there are several transcoding services available, the User Agent

can be set to select the most economical/highest quality service.

  1. The service provider can show the cost per minute and any minimum

charge of a transcoding service call before a session starts,

   allowing the user a choice of engaging in the service or not.
  1. Service providers are encouraged to offer an alternative stream to

an audio stream, for example, text or data streams that operate

   avatars, etc.
  1. Service providers are encouraged to provide a text alternative to

voice-activated menus, e.g., answering and voice mail systems.

  1. Manufacturers of voice-activated software are encouraged to provide

an alternative visual format for software prompts, menus, messages,

   and status information.
  1. Manufacturers of mobile phones are encouraged to design equipment

that avoids electro-magnetic interference with hearing aids.

  1. All services for interpreting, transliterating, or facilitating

communications for deaf, hard of hearing and speech-impaired people

   are required to:

Charlton, et al. Informational [Page 13] RFC 3351 SIP for Deaf, Hard of Hearing and Speech Impaired August 2002

  1. Keep information exchanged during the transaction strictly

confidential

  1. Enable information exchange literally and simply, without

deviating and compromising the content

  1. Facilitate communication without bias, prejudice or opinion
  1. Match skill-sets to the requirements of the users of the service
  1. Behave in a professional and appropriate manner
  1. Be fair in pricing of services
  1. Strive to improve the skill-sets used for their services.
  1. Conference call services might consider ways to allow users who

employ transcoding services (which usually introduce a delay) to

   have real-time information sufficient to be able to identify gaps
   in the conversation so they could inject comments, as well as ways
   to raise their hand, vote and carry out other activities where
   timing of their response relative to the real-time conversation is
   important.

8. Acknowledgements

 The authors would like to thank the following individuals for their
 contributions to this document:
 David R. Oran, Cisco
 Mark Watson, Nortel Networks
 Brian Grover, RNID
 Anthony Rabin, RNID
 Michael Hammer, Cisco
 Henry Sinnreich, Worldcom
 Rohan Mahy, Cisco
 Julian Branston, Cedalion Hosting Services
 Judy Harkins, Gallaudet University, Washington, D.C.
 Cary Barbin, Gallaudet University, Washington, D.C.
 Gregg Vanderheiden, Trace R&D Center University of Wisconsin-Madison
 Gottfried Zimmerman, Trace R&D Center University of Wisconsin-Madison

Security Considerations

 This document presents some privacy and security considerations.
 They are treated in Section 5.6 Confidentiality and Security.

Charlton, et al. Informational [Page 14] RFC 3351 SIP for Deaf, Hard of Hearing and Speech Impaired August 2002

Normative References

 [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
     Levels", BCP 14, RFC 2119, March 1997.
 [2] 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.

Informational References

 [3] International Telecommunication Union (ITU), "Operational and
     interworking requirements for DCEs operating in the text
     telephone mode". ITU-T Recommendation V.18, November 2000.
 [4] Moore, Matthew, et al. "For Hearing People Only: Answers to Some
     of the Most Commonly Asked Questions About the Deaf Community,
     Its Culture, and the Deaf Reality". MSM Productions Ltd., 2nd
     Edition, September 1993.
 [5] http://www.typetalk.org.
 [6] http://www.visicast.co.uk.
 [7] http://www.speech.kth.se/teleface.

Authors' Addresses

 Nathan Charlton
 Millpark Limited
 52 Coborn Road
 London E3 2DG
 Tel: +44-7050 803628
 Fax: +44-7050 803628
 EMail: nathan@millpark.com
 Mick Gasson
 Koru Solutions
 30 Howland Way
 London SE16 6HN
 Tel: +44-20 7237 3488
 Fax: +44-20 7237 3488
 EMail: michael.gasson@korusolutions.com

Charlton, et al. Informational [Page 15] RFC 3351 SIP for Deaf, Hard of Hearing and Speech Impaired August 2002

 Guido Gybels
 RNID
 19-23 Featherstone Street
 London EC1Y 8SL
 Tel: +44-20 7296 8000
 Textphone: +44-20 7296 8001
 Fax: +44-20 7296 8199
 EMail: Guido.Gybels@rnid.org.uk
 Mike Spanner
 RNID
 19-23 Featherstone Street
 London EC1Y 8SL
 Tel: +44-20 7296 8000
 Textphone: +44-20 7296 8001
 Fax: +44-20 7296 8199
 EMail: mike.spanner@rnid.org.uk
 Arnoud van Wijk
 Ericsson EuroLab Netherlands BV
 P.O. Box 8
 5120 AA Rijen
 The Netherlands
 Fax: +31-161-247569
 EMail: Arnoud.van.Wijk@eln.ericsson.se
 Comments can be sent to the SIPPING mailing list.

Charlton, et al. Informational [Page 16] RFC 3351 SIP for Deaf, Hard of Hearing and Speech Impaired August 2002

Full Copyright Statement

 Copyright (C) The Internet Society (2002).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
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 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Charlton, et al. Informational [Page 17]

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