In some IMS call flow, I saw SUBSCRIBE message from UE to IMS server. I want to know in what cases/scenarios, UE sends SUBSCRIBE message to server and server sends NOTIFY message to UE ?
Redirection (3xx), Client failure (4xx), Server failure (5xx) and Global failure (6xx) in which scenarios these codes are used ?
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 ?
