[asterisk-users] Asterisk as UAC: How to put call OnHold

[Johannes Zweng]

Hi!

Maybe I am missing something or am a little blind at the moment, but I
didn't find out how asterisk can place a call on hold when acting as user
agent client to another SIP server.

Scenario:
----------
Asterisk registers to another SIP server (provider) as user agent.
An inbound call from this other SIP server comes in and arrives at asterisk.
Asterisk performs some actions in the dialplan and should place the call on
hold after some time, so that the caller only hears the on hold music from
my provider (not streamed by my Asterisk).

Technically speaking I want asterisk to send a re-INVITE message containing
an updated SDP body with the attribute "a=sendonly" or "a=inactive" added
so that the SIP server of my provider (where Asterisk is registered to as
user) will recognize that the call should be placed on hold.


A good example of what I want to achieve is presented in Section 2.1 of RFC
5359 (Session Initiation Protocol Service Examples) (
http://tools.ietf.org/html/rfc5359#section-2.1) where "Bob" would be my
Asterisk (as UAC), "Alice" is the external caller and "Proxy" is the
provider's SIP server.


Question:
----------
Is there any way to perform this from the dialplan or by means of the
manager API? Is there an application like "Hold"?


Kind regards and greetings from Austria,
John :-)
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