[AVTCORE] Re: Missing Flash from RFC4733

[Dan Mongrain <[e-mail]>]

Interface with a gateway connected to a legacy analog telephone line, you
need to signal a hookflash in order to get a secondary dial tone to request
network features. Widely used in Public Safety when connected to analog
9-1-1 trunks, hookflash is necessary to conference another PSAP on the call
when transferring the call.

Dan


*Dan Mongrain, eng.*Principal Engineer,
VESTA Solutions
www.VESTAPublicSafety.com

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On Tue, Nov 5, 2024 at 10:40 AM Bernard Aboba <[e-mail]>
wrote:

> It appears that code 16 was never implemented in WebRTC DTMF (1+ Billion
> endpoints).
>
> What is the scenario for use of hookflash?
>
> On Thu, Oct 24, 2024 at 2:15 PM Roman Shpount <[e-mail]> wrote:
>
>> Bernard,
>>
>> There were implementations of code 16 before the publication of RFC 4733.
>> These implementations continue to exist.
>> _____________
>> Roman Shpount
>>
>>
>> On Thu, Oct 24, 2024 at 4:43 PM Bernard Aboba <[e-mail]>
>> wrote:
>>
>>> Has there been any implementation of code 16 since publication of RFC
>>> 4733?
>>>
>>> On Oct 24, 2024, at 13:28, Gunnar Hellström <gunnar.hellstrom=
>>> [e-mail]> wrote:
>>>
>>> 
>>>
>>> Brian,
>>>
>>> You seem to be right that code 16 can be assigned to Flash now.
>>>
>>>
>>>
>>> RFC 4733 has an Appendix A about differences from RFC 2733.
>>>
>>>
>>>
>>> It has a paragraph starting:
>>> “Finally, this document establishes an IANA registry for event codes
>>>
>>>    and establishes criteria for their documentation.  This document
>>>
>>>    provides an initial population for the new registry, consisting
>>>
>>>    solely of the sixteen DTMF events.”
>>>
>>>
>>>
>>> And continuing saying:
>>>
>>> “The remaining events defined in RFC 2833
>>> <https://urldefense.proofpoint.com/v2/url?u=https-3A__www.rfc-2Deditor.org_rfc_rfc2833&d=DwMFaQ&c=q3cDpHe1hF8lXU5EFjNM_C93KOmcBXCBnhee2v6PYlc&r=n9aaU9xSQM4-mK_yF4tJzi7SeOWS3tTUWut1BhcRBI5vMR5LUWrTKzC_1DF8wC_4&m=zEQknjtSEBwPYxn86rXo1ta7f6QXNAEsj8p-ZO2VcezUNBGMCTvID3FYxJdlJA75&s=atXQQOyEeHvGKWt9sxD-8mFPoKlHULjVc53KUuG2X6w&e=>
>>>
>>>    are deprecated because they do not appear to have been implemented,
>>>
>>>    but their codes have been conditionally reserved in case any of them
>>>
>>>    is needed in the future. “
>>>
>>>
>>>
>>> And then a table indicating the differences from RFC 2733, where one row
>>> says:
>>>
>>> Event Codes | RFC 2833
>>> <https://urldefense.proofpoint.com/v2/url?u=https-3A__www.rfc-2Deditor.org_rfc_rfc2833&d=DwMFaQ&c=q3cDpHe1hF8lXU5EFjNM_C93KOmcBXCBnhee2v6PYlc&r=n9aaU9xSQM4-mK_yF4tJzi7SeOWS3tTUWut1BhcRBI5vMR5LUWrTKzC_1DF8wC_4&m=zEQknjtSEBwPYxn86rXo1ta7f6QXNAEsj8p-ZO2VcezUNBGMCTvID3FYxJdlJA75&s=atXQQOyEeHvGKWt9sxD-8mFPoKlHULjVc53KUuG2X6w&e=>
>>> Description                  | Disposition |
>>>
>>> 16                       | Line flash (deprecated)               |
>>> Reserved
>>>
>>>
>>>
>>> So 16 for Flash is reserved and free to allocate if needed.
>>>
>>>
>>>
>>> It seems that it would be sufficient with a small document motivating
>>> the addition in the IANA registry of these event codes.
>>> (audio-telephone-event-registry)
>>>
>>>
>>>
>>> /Gunnar
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> ------------------------------------------------------------
>>>
>>> Gunnar Hellström
>>>
>>> GHAccess
>>>
>>> [e-mail]
>>>
>>> Tel: [phone]
>>>
>>>
>>>
>>> *From:* Brian Rosen <br=[e-mail]>
>>> *Sent:* den 24 oktober 2024 20:23
>>> *To:* [e-mail]
>>> *Subject:* [AVTCORE] Missing Flash from RFC4733
>>>
>>>
>>>
>>> RFC 2833 defined the use of code 16 for flash. RFC 4733 obsoleted RFC
>>> 2833 but did not define a code for flash, although it did reserve code 16.
>>> Flash is still in use, and the lack of an explicit code is a problem.  It’s
>>> still used in some emergency calling systems for example. Would there be
>>> any objection to fixing this one way or another (update 4733 to define code
>>> 16 as Flash)?
>>>
>>>
>>>
>>> Brian
>>> _______________________________________________
>>> Audio/Video Transport Core Maintenance
>>> To unsubscribe send an email to [e-mail]
>>>
>>> _______________________________________________
>>> Audio/Video Transport Core Maintenance
>>> To unsubscribe send an email to [e-mail]
>>>
>> _______________________________________________
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