Query on preferring the Offer / Answer model of placing a user on hold.
The method for placing a user on hold with the media address of 0.0.0.0 is deprecated in favour of the method described in RFC3264 with a=sendonly.
Take two scenarios:
Scenario 1. UA X is being placed on hold by UA Y, knowing that all UA's are to support the older method Y could just use 0.0.0.0 - this would work but this assumption means that rather than be deprecated this method is actually preferred !. This seems to be common at the moment.
Scenario 2. UA X is being placed on hold by UA Y, Y takes a guess and uses a=sendonly to place X on hold - this is hit and miss, if X does not support this it will return a 606 Not Acceptable (SDP mismatch) or similar and then I need to rely on logic in Y to formulate a new Re-Invite with the 0.0.0.0 method.
Can this be a candidate for the Supported header field ?, if a option tag could be defined for the 3264 method of hold then UA's can indicate their support for it, taking the guess work out it. I am unsure if this is the right candidate for the supported header and am wary of causing a trend to advertise suport for large amount of SIP extensions.
Example with a UA advertising it's support for the Offer / Answer model method of placing a call on hold, proposed option tag of "3264Hold" <-- feel free to call it something else !.
*************************************************************************************************************************
INVITE sip:[EMAIL PROTECTED]:5060;user=phone SIP/2.0
Via: SIP/2.0/UDP 137.147.132.249:5060
From: <sip:[EMAIL PROTECTED]>;tag=1F7823B4-871
To: <sip:[EMAIL PROTECTED]>
Date: Thu, 12 Feb 2004 07:16:00 GMT
Call-ID: [EMAIL PROTECTED]
Supported: timer,100rel, 3264Hold
Min-SE: 1800
Cisco-Guid: 621192735-1549930968-2254358604-370246430
User-Agent: Cisco-SIPGateway/IOS-12.x
Allow: INVITE, OPTIONS, BYE, CANCEL, ACK, PRACK, COMET, REFER, SUBSCRIBE, NOTIFY, INFO
CSeq: 102 INVITE
Max-Forwards: 6
Remote-Party-ID: <sip:[EMAIL PROTECTED]>;party=calling;screen=yes;privacy=off
Timestamp: 1076570160
Contact: <sip:[EMAIL PROTECTED]:5060>
Expires: 180
Allow-Events: telephone-event
Content-Type: application/sdp
Content-Length: 279
*******************************************************************************************************************************
Thanks and regards,
Wayne Davies
email: [EMAIL PROTECTED]
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