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

 

 

Call Transfer:

In our DEXXX phones the following option is available:

 

Unattended call transfer:

Possible options: Early attended OR Semi-attended

 

In our DECT systems (N510 IP PRO and N720 IP PRO) and the DEXXX phones the following options are available:

Hold on transfer target:

Possible options: for attended transfer AND/OR for unattended transfer

 

Screenshots of the WebGui.

N510 IP PRO                                                                                   N720 IP PRO                                                      DEXXX IP PRO

 

Explanation of used method.

Implemented 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 is aligned with Gigaset product behavior.


Acceptance criteria/ definition:

 
1. DExx devices have implemented the "semi-attended" call transfer method as defined in RFC5589. This method does not replace already existing "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 provisioning - (new parameter is introduced) 
3. Default method set is "Early attended call transfer" 
4. In addition to unattended call method selection, the user can select whether transfer target is put on hold. For that reason WEB-GUI provides a switch "Hold on transfer target" to enable/disable this functionality 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 functionality is not available (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 (now Unify) or others. It extends above methods by putting/removing the SIP INVITE before the SIP REFER. It can be done by placing or not the check-mark near the feature ‘Hold on transfer target’: 

The options are: 
- Attended Transfer Call: 
o Hold on transfer target: YES (check-mark checked) 
o Hold on transfer target: NO (check-mark unchecked) 
- Semi-Attended Transfer 
o Hold on transfer target: YES (check-mark checked) 
o Hold on transfer target: NO (check-mark unchecked)