[cisco-voip] CUCM SIP Early Attended Transfers

[Anthony Holloway]

All,

Does anyone have any experience with CUCM, SIP Phones, SIP Trunks, and
early attended transfers (AKA hitting the transfer button a second time
quickly)?  I'm not hearing ringback on the transferee phone.

Components in play:

CUCM 10.5(2)
CUBE 15.4 (SIP-SIP)

Scenario:

   1. PSTN Phone A calls into enterprise
   2. IP Phone B answers
   3. IP Phone B Presses Transfer Key
   4. PSTN Phone A hears MOH
   5. IP Phone B Dials Transfer Target and hears ringback
   6. IP Phone B Presses Transfer Key Again
   7. PSTN Phone A hears silence until call connects then two way audio

I found this reference in the CUCM System Guide on SIP:

http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/sip_msg/line_std/11_0_1/CUCM_BK_SB03D18E_00_sip-line-messaging-standard-1101/CUCM_BK_SB03D18E_00_sip-line-messaging-standard-1101_chapter_00.html#CUCM_CN_E798E831_00

Specifically these two seemingly contradictory sentences:

"The transferee receives a ringback while the target phone is alerting."

"The transferee will not receive a ringback although the target is
alerting."

Seems like it's just not going to work.  What do you think?
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