Re: [Sip-implementors] How to differentiate Hold RTP and voice RTP

[Roman Shpount]

In practice, there is no "typical" way of putting a call on hold. The very
meaning of that action is highly dependent on what you are looking at. If
you are looking at signaling coming from an IP phone, you seldom get
a=sendonly when someone is placing a call on hold. You will only see that
when someone is playing music on hold, which is more common for a PBX or
CPaaS. IP Phones normally do not play music on hold so you will see an
a=inactive or c=IN IP4 0.0.0.0 IP address. With CPaaS or PBX to an IP
phone, you will see a=sendonly or a=inactive, depending on if the music on
hold is configured. When communicating with a VoIP service provider over s
SIP trunks with SBC, it is unlikely you will see any signaling, IP, or SSRC
changes when a call is placed on hold. If you are directly dealing with IMS
or RCS environments, you will be overwhelmed with wonder when trying to
decipher the reasoning behind each signaling scenario.

So, YMMV
_
Roman Shpount


On Mon, Oct 10, 2022 at 10:17 PM Dale R. Worley  wrote:

> Ranjit Avasarala  writes:
> > Another way to check is the SDP.  for hold music,  the media attribute
> will
> > be sendonly.  where as for regular voice traffic it will sendrecv
>
> Yes, the "typical" way to tell that the far end has put you on hold is
> that they will send you a=sendonly in the SDP.  Of course, that isn't
> guaranteed to be done, but at least it is what people expect and many
> systems conform to that.
>
> In regard to trying to determine on-hold status from the RTP, that is
> not reliable.  If you can detect that the far end is sending music, it
> has likely put you on-hold.  But somtimes there are voice announcements
> during on-hold.
>
> Dale
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Re: [Sip-implementors] How to differentiate Hold RTP and voice RTP

[Dale R. Worley]

Ranjit Avasarala  writes:
> Another way to check is the SDP.  for hold music,  the media attribute will
> be sendonly.  where as for regular voice traffic it will sendrecv

Yes, the "typical" way to tell that the far end has put you on hold is
that they will send you a=sendonly in the SDP.  Of course, that isn't
guaranteed to be done, but at least it is what people expect and many
systems conform to that.

In regard to trying to determine on-hold status from the RTP, that is
not reliable.  If you can detect that the far end is sending music, it
has likely put you on-hold.  But somtimes there are voice announcements
during on-hold.

Dale
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Re: [Sip-implementors] How to differentiate Hold RTP and voice RTP

[Paul Kyzivat]

Arun,

On 9/22/22 10:56 AM, Arun Tagare wrote:

Thanks Ranjit,

Yes for the signalling part i am aware, but as shared earlier how the RTP
from N/w and other UE in same session be differentiate?

So SSRC will be different right?


*Nothing* is certain here!

The SSRC may be different, but not necessarily.

The IP of the media stream may change, but not necessarily.

Signaling *may* change the direction to sendonly, but not necessarily.

There are no rules for any of this. Lots of different implementations 
are possible. The answers you get here are generally what people have 
observed in the environments they are exposed to. A lot of this will be 
based on some widely deployed implementations. Whether any of those, and 
if so which, might apply to your environment is hard to say.


If figuring this out is important to you, then you need to monitor the 
environment you operate within. See if most calls have a consistent 
pattern, or one of a few consistent patterns. Then build to deal with 
what you find. And be prepared for the cases that don't fit your 
expectations.


Good luck,
Paul


On Thu, 22 Sep 2022 at 8:05 PM, Ranjit Avasarala 
wrote:


Hi Arun

Both are technically voice packets and use RTP protocol.  So that way both
are similar.  Also the voice traffic is end to end whereas hold music is
from the server.  Like announcement - may be from Application Server.  So
looking at the SSRC or Source in RTP Packets, you should be able to say
which entity is sending those packets.

Another way to check is the SDP.  for hold music,  the media attribute
will be sendonly.  where as for regular voice traffic it will sendrecv

Regards
Ranjit

On Thu, Sep 22, 2022 at 4:19 AM Amanpreet Singh <
amanpreeet.si...@gmail.com> wrote:


Arun, for what purpose would you like to inspect and differentiate the
hold
and audio RTP packets?
and based on the signaling messages, can't that be achieved.

Thanks,
Amanpreet Singh.


On Thu, Sep 22, 2022 at 12:30 PM Arun Tagare 
wrote:


Thanks Ranjit & Amanpreet, for your response

But my question is

MT <= Call Established ===> MO
MT <===> Voice RTP Packets flow <=> MO
MT <==Hold ===> MO
MT < HOLD Tone RTP packets == NW

Both Voice RTP packets and Hold RTP packets come to the same port right

?

How to differentiate these RTP packets

On Thu, Sep 22, 2022 at 11:06 AM Amanpreet Singh <
amanpreeet.si...@gmail.com> wrote:


Probably you can think of looking into the signaling messages(SDP in

case

of SIP) to differentiate when the call is on hold and when not i.e.

normal

audio RTP.

BTW what is the use case to differentiate call hold vs audio RTP?


Regards,
Amanpreet Singh.


On Wed, Sep 21, 2022 at 9:51 PM Arun Tagare 
wrote:


Hi All,

I have a doubt on the Hold call tone or music on hold tone RTP v/s

actual

voice RTP before hold

Can these RTP packets be able to differentiate?
If yes how?
if not why?

Thanks a lot to everyone in advance

--

With Regards

Arun A. Tagare
+91 9449 029729
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--

With Regards

Arun A. Tagare
+91 9449 029729


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--


With Regards

Arun A. Tagare
+91 9449 029729
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