[asterisk-users] Asterisk doesn't relay remote MOH during hold

[Richard Brady]

Hi Tony

I can see where you guys are coming from on this and have already
enumerated your argument in my own email.

But there are very real reasons for a PBX to signal the hold even when
it wants to send its own MOH:

1. Bandwidth: under your scheme the PBX would continue to receive
bandwidth-consuming media without using it.
2. Privacy: the far-end has an expectation of privacy while on hold
and should have the option to mute automatically when held.
3. Feature richness: signalling the hold enables such innovative
features such as reverse hold.
4. ISDN interworking: ISDN supports this and SIP should be compatible
with that (as per standard ITU-T Q.1912.5)

Also, can you explain why the PBX would use a=sendonly but not
dispatch media. Why not a=inactive for that case?

> IMHO, PBX-A would be broken if it passed this along the Hold message to downstream and then started servicing the MOH itself

Remember it is not a hold message, it is a media attribute and we are
discussing how that should be interpreted within the context of the
hold feature in traditional telephony.

I would also like to point out in my defence that there are several
telephone systems in the field which behave as I described (Nortel
BCM50, Aastra Intelligate, Mitel 3300 to name a few).

Regards,
Richard


> I have to agree with Kevin on this one.
>
> I fail to understand how you have a PBX-A talking to Asterisk talking to PBX-B and the PBX-A placing the call on hold.  Typically you should have a Client/Phone to PBX-A to Asterisk to PBX-B to Client/Phone/VoiceMail.
>
> If the Client signals Hold, the PBX should NOT be passing that Hold status on but transition audio stream from Client to MOH (assuming MOH is handled).  Asterisk shouldn't notice a thing except more RTP packets (or less if it is my teenage daughter on the phone as the case may be).
>
> IMHO, PBX-A would be broken if it passed this along the Hold message to downstream and then started servicing the MOH itself on the RTP stream.  That just doesn't make sense.
>
> Now if PBX-A were not a PBX and were a SIP Router, and the SIP Router was attempting this, I can see how it would Re-Invite, but it shouldn't pass the hold status onto Asterisk.
>
> Need some clarity here.
>
> Tony Plack