FAQ Call transfer - Hold on transfer target

In all Gigaset IP PRO extensions there are extra options for the following function available via the WebGui: Call Transfer

Call Transfer:

Implement according to Unattended Call Transfer - Semi-Attended Transfer Call Flow which is explained in the RFC5589 

RFC 5589 SIP CC Transfer June 2009 

Transferor Transferee Transfer 
|                 |                 Target 
|                 |                  | 
dialog1      | INVITE/200 OK/ACK F1 F2 | 
|<-------------------| | 
dialog1 | INVITE (hold)/200 OK/ACK | 
|------------------->| | 
dialog2 | INVITE | | 
|---------------------------------------->| 
dialog2 | | 180 Ringing | 
|<----------------------------------------| 
Transferor hangs up but wants transfer to continue 
| | | 
| User Agent continues transfer operation | 
| | | 
dialog2 | | 200 OK | 
|<----------------------------------------| 
dialog2 | ACK | | 
|---------------------------------------->| 
dialog2 | Media Played to keep Target from hanging up 
|========================================>| 
dialog3 | REFER (Target-Dialog:1, | 
| Refer-To:sips:TransferTarget?Replaces=2) 
|------------------->| | 
dialog3 | 202 Accepted | | 
|<-------------------| | 
dialog3 | NOTIFY (100 Trying)| | 
|<-------------------| | 
dialog3 | 200 OK | | 
|------------------->| | 
dialog4 | INVITE (Replaces:dialog2)/200 OK/ACK 
| |------------------->| 
dialog2 | BYE/200 OK | | 
|<----------------------------------------| 
dialog3 | NOTIFY (200 OK) | | 
|<-------------------| | 
dialog3 | 200 OK | | 
|------------------->| | 
dialog1 | BYE/200 OK | | 
|------------------->| | 
dialog4 | | BYE/200 OK | 
| |<-------------------| 
Figure 11: Recommended Semi-Attended Transfer Call Flow 

Call transfer SIP refer mechanism should be aligned to Gigaset product behavior.

Acceptance criteria/ defintion of done: 
1. DExx devices implements "semi-attended" call transfer method as defined in RFC5589. This method does not replace already exisiting "Early attended call transfer" User can select which method of unattended call transfer want to use ("semi attended" or "early-attended". This can be done via WEB-GUI. Settings are global (affect all voip accounts) 
2. Unattended call transfer method can be also changed via provisionning - (new parameter to be intorduced) 
3. Default method set is "Early attended call transfer" 
4. In addition to unattended call method selection user can select whether transfer target is put on hold. For that reason WEB-GUI provides a switch "Hold on transfer target" to enable/disbale this funcionality for both attended and unattended call transfer. 
• "Hold on transfer target" can be enabled for Attended Call transfer or "Semi-Attended Call transfer" method (from Unattended Call Transfer), when "Early Attended Call transfer" is selected funcionality is not avaialble (grayed out) 
• "Hold on transfer target" setting is global - valid for all voip accounts 
• "Hold on transfer target" default settings are: For attended transfer -YES, For unattended transfer -NO 
• "Hold on transfer target" setting can be also provisioned 
- Attended Transfer (RFC5589 chapter 7.3) 
- Semi-Attended Transfer also known as “unattended transfer” (RFC5589 chapter 7.6) 
http://tools.ietf.org/html/rfc5589 
Also to be complementary with some PBXs on the market like HiPath or other it extends above methods by putting/removing the SIP INVITE before the SIP REFER. It can be done by placing or not the checkmark near the feature ‘Hold on transfer target’: 

So we have: 
- Attended Transfer Call: 
o Hold on transfer target: YES (checkmark checked) 
o Hold on transfer target: NO (checkmark unchecked) 
- Semi-Attended Transfer 
o Hold on transfer target: YES (checkmark checked) 
o Hold on transfer target: NO (checkmark unchecked)