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Hi, Is there any agreed upon method for communicating a flash-hook signal
using SIP? Specifically, I am trying to figure out if there's a good way
to accomplish take-back-and-transfer using a SIP to PSTN media gateway. I have run up against this problem using two different commercial PSTN/VoIP media gateways: when sending a SIP REFER message to
perform a blind PSTN to PSTN call transfer, the gateway hairpins the call,
which consumes two voice channels on the gateway and, in our network, an
associated switch. I can understand why it is implemented this way, because
REFER allows for both attended and un-attended call transfer, and I don't
think the gateway has a way to distinguish between the two. So I'm trying
to figure out if anyone uses SIP to communicate a flash-hook signal to a
gateway that can be used to perform blind call transfer on a switch. Or, if
there's a better way to do this that I haven't seen documented in
any SIP related specification, please point me to it. Thanks in advance, Chris Kramp |
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