I know the fact P-CSCF establishes an IP sec tunnel with the UE but exact at which point it does not sure.
I was going through IMS call flow and came to know that an IP sec tunnel is established between UE and P-CSCF . I could not find out reasoning behind it.
Is it mandatory to establish a separate default bearer to exchange IMS signaling messages between UE and IMS network nodes ? Can't internet default bearer be used for the same ?
Which of the network node initiates dedicated bearer creation for the VoLTE call ?