AudioCodes MediaPack MP-40 series, User Manual

Page: 169 / 180

User's Manual A. MediaPack Applications
Version 2.2 169 July 2007
A.4.1.2 Call Hold from the SIP Side
Call hold from the SIP side is similar to call hold on the ISDN side. The SIP user can use a
SIP RE-INVITE to put the call on hold. The following SDP attributes indicate a hold:
a=sendonly, a=inactive or IP = 0.0.0.0, or any combination of these parameters.
If the SIP peer puts a call on hold, the data-path is disabled. No signaling action occurs
towards the ISDN phone and no tone is beingplayed.
A.4.2 Call Transfer
The MediaPack supports call transfer using the SIP REFER mechanism. A user which has
two calls (one on hold and one active), can initiate a transfer to connect the two remote
parties.
A.4.2.1 Call Transfer Initiated by the SIP Peer
There are two types of call transfers:
„
Consultation Transfer (Refer and Replaces):
The common way to perform a consultation transfer is as follows:
In the transfer scenario there are three parties: Party A (transferring), Party B
(transferred), and Party C (transferred to).
a. A Calls B.
b. B answers.
c. A holds the call, and then dials a call to C.
d. A connects B to C, and then A disconnects.
e. After the transfer is complete, the B and C parties engage in a call.
„
Blind Transfer (Refer):
Blind transfer is performed after a call is established between A and B, and then party
A decides to immediately transfer the call to C, without speaking with C. Party A can
perform this by sending a REFER message.
The result of the transfer is a call between B and C (similar to consultation transfer,
but skipping the consultation stage).
Call Transfer requires no configuration.