Subject: [MMUSIC] 3PCC mute of call leg

From: Steven Egan <[email-masked]>
Date: Wed, 16 Feb 2005 14:48:59 +0000

Hi,
I am looking to implement the following:

1. Application initiates 2 party call (3PCC)
2. Both UA1 and UA2 are in a voice call
3. Application mutes UA2 (so it cannot send or receive media)
4. Application allows UA2 back into the call

Everything for step 1 and 2 works fine.  With step 3, I am sending a 
re-invite to UA2 containing an SDP of the format:

v=0
o=UserAgent 2462 2442 IN IP4 192.168.25.13
s=SIP Call
c=IN IP4 192.168.25.13
t=0 0
m=audio 18302 RTP/AVP 0 19
c=IN IP4 0.0.0.0
a=rtpmap:0 PCMU/8000
a=rtpmap:19 CN/8000
a=ptime:20

When I send this to a Cisco 7960 SIP phone, it puts the UA on hold (so 
it neither receives or sends media), which is what I am looking for. 
However, when I use the same method to mute a user agent using the Cisco 
AS5350, the UA cannot transmit but can receive media.
What is the standard method of muting a UA in 3PCC, so that the UA 
cannot send or receive media.
Cheers,
Steven

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From: Paul Kyzivat <[email-masked]>
Date: Wed, 16 Feb 2005 11:26:39 -0500

> AS5350, the UA cannot transmit but can receive media.

The offer and the answer each specify one direction. Your offer prevents 
media from flowing in one direction - in this case from the AS5350. It 
does not prevent it from flowing toward the AS5350, nor does it say what 
that device should do with any media it might receive.

If you want to prevent a flow in the other direction, you will need to 
send a reinvite to the other endpoint, blocking the flow from it.

> cannot send or receive media.

The use of "c=IN IP4 0.0.0.0" is no longer preferred for hold. The 
preferred for one-way hold is to a=sendonly to one side and a=recvonly 
to the other side. For a two-way hold, a=inactive to both sides would be 
preferred. You *might* get away with sending a=inactive to one side, but 
I wouldn't count on it.

That of course depends on whether the devices you are using support 
that. I don't know if these particular devices do.

	Paul