RE: [Ecrit] ECRIT support for TTY/TDD calls

["Gunnar Hellstrom" <[e-mail]>]

Re: [Ecrit] ECRIT support for TTY/TDD callsWhat would sos.police.tty  do and
how would it be invoked?

If it could lead to a text capable IP terminal, it should be called
sos.police.real-time-text    or so.

If it helps to find a PSTN based PSAP with text capabilities, it could be
called sos.police.txp

tty is a US term.

Gunnar

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-
Gunnar Hellström, Omnitor
[e-mail]
Mob: [phone]
Phone: [phone]
www.omnitor.se
  -----Original Message-----
  From: Brian Rosen [mailto:[e-mail]]
  Sent: Thursday, February 16, 2006 12:17 AM
  To: 'Gunnar Hellstrom'; [e-mail]; 'Aquil, Kamran'; 'François D.
Ménard'
  Cc: 'Gregg Vanderheiden'
  Subject: RE: [Ecrit] ECRIT support for TTY/TDD calls


  All I get out of this for ecrit is that we need entries for sos.police.tty
in the service registry



  Brian




----------------------------------------------------------------------------
--

  From: Gunnar Hellstrom [mailto:[e-mail]]
  Sent: Wednesday, February 15, 2006 5:47 PM
  To: [e-mail]; 'Aquil, Kamran'; [e-mail]; François D. Ménard
  Cc: Gregg Vanderheiden
  Subject: RE: [Ecrit] ECRIT support for TTY/TDD calls



  It is quite widely accepted now that real-time text transmitted with its
own text coded RTP payload RFC 4103 is used to carry text that may be
gatewayed to/from TTY/TDD/textphones in PSTN.



  It is discussed in
http://www.ietf.org/internet-drafts/draft-ietf-sipping-toip-03.txt



  And it is documented in
http://www.ietf.org/internet-drafts/draft-sinnreich-sipdev-req-08.txt



  Also other standardisation bodies have picked up the real-time text
concept in IP networks, and pointed at RFC 4103 (or its compatible
predecessor RFC2793 ). E.g. 3GPP and ETSI.

  A couple of years ago we had an intensive discussion in the SIMPLE mail
list about the possibility to use MSRP to carry the real-time text medium,
but we concluded that it would cause too much overhead or too much delay for
the users, so that RTP was recommended instead. The most common use of MSRP
is to not transmit until end of sentence, while for real time text,
transmission is required with at most 500 ms interval as long as there is
anything to transmit in order to maintain the real-time feeling of being in
touch in a conversation through this medium.



  Quite commonly you will connect a text RTP stream and an audio RTP stream
and possibly a video RTP stream in the same call, so that you will get an
enhanced multimedia phone call with all supported media



  The ecrit requirements also mentions this correspondence

  in www.ietf.org/internet-drafts/draft-ietf-ecrit-requirements-03.txt


     Re4.  Multiple Modes: Multiple communication modes, such as audio,
        video and text messaging MUST be supported.

        Motivation: In PSTN, voice and text telephony (often called TTY or
        textphone in North America) are the only commonly supported media.
        Emergency calling must support a variety of media.  Such media
        should include voice, conversational text (RFC 4103 [9]), instant
        messaging and video.



  I am working in a European group where one of the goals is to agree on
handling text users'  requirements on emergency calling in IP networks. Of
course we want to agree on global solutions if possible.



  Address mapping is one important and tricky question for text users. It is
true that different countries have different approaches on emergency calling
with PSTN Text telephones (TTYs). Some have the same number as voice users,
while others have specific numbers. On the SIP side it would be good to have
the same URL and make any required routing based on declared media, mode and
language capabilities and preferences.



  Text capable gateways are not at all as common as VoIP gateways, so if the
PSAP is still in PSTN, there is a need to have a good mechanism for routing
emergency calls from SIP into PSTN through a text capable gateway. I cannot
say that the mechanisms for finding the right gateway and make the proper
address mapping to a PSTN number is solved yet for the text calls, and it
would be excellent if we could have that topic in mind in the discussions
and get proper methods documented.



  I have drafted, but not yet submitted a registration of a SIP URL and an
ENUM subservice for real-time text. It might be helpful for finding text
gateways and mapping addresses and (text) numbers, but I would like to see
some scenarios thoroughly discussed before adding SIP URL and another ENUM
subservice.



  Would there be any benefit of being allowed to enter TXP:112    or having
ENUM to find an appropriate address if I   call 112 from a SIP multimedia
phone declaring text capabilities with m=text in sdp?





  Gunnar

  --------------------------------------------------------------------------
---

  Gunnar Hellström, Omnitor

  [e-mail]

    -----Original Message-----
    From: [e-mail] [mailto:[e-mail]]On Behalf Of
François D. Ménard
    Sent: Wednesday, February 15, 2006 5:14 PM
    To: [e-mail]; 'Aquil, Kamran'; [e-mail]
    Subject: Re: [Ecrit] ECRIT support for TTY/TDD calls


    I made a contribution to CISC NTWG on use of SIP for transporting TDD
traffic:

    http://www.crtc.gc.ca/cisc/COMMITTE/N-docs/NTCO0338.doc

    I think it may be relevant to ECRIT.

    -=Francois=-


    On 2/15/06 10:51 AM, "Brian Rosen" <[e-mail]> wrote:

    Within the scope of our work, I don’t see how TDD services are impacted
until we get to the architecture effort, which probably has to have some
sections on that subject.
    With respect to the mapping protocol, I do not believe there is any
impact at all.
    With respect to the sos service urn, I do not believe there is any
impact at all

    Ecrit doesn’t have scope to talk about any kind of gateways or codec
support.

    Ah!  My BCP on phones and proxies may need some mention, although this
is the IETF, and I don’t think the ploy of forcing the entire PSTN to
support TDD just so 9-1-1 TDD will work.  That effort would have to be in
the general SIP arena.

    Brian



----------------------------------------------------------------------------

    From: [e-mail] [mailto:[e-mail]] On Behalf
Of Aquil, Kamran
    Sent: Wednesday, February 15, 2006 10:31 AM
    To: [e-mail]
    Subject: [Ecrit] ECRIT support for TTY/TDD calls


    Folks,



    Like to know if there are specific ECRIT requirements recognizing
support for Telecommunications Device for the Deaf (TDD) services for the
hearing impaired. If not is this left for VOIP/SIP gateways to perform this
requirement of translating the TDD calls to Text and Speech encoding. Wanted
to make sure how ECRIT meet requirement for TDD services.



    Regards,
    Kamran Aquil
    Intelligent Transportation Systems- Division
    Mitretek Systems.







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