Type of Diagram: What is the purpose of the UDM entity in the diagram? 
  
  Is the SMF entity responsible for registering the UE with the network?
  
  What is the format of the PUT request sent by the UDM entity to the SMF entity?
  
  Which entity initiates the registration process, and what is the response from the other entity?
  
  What is the significance of the "403 Forbidden" status code in the diagram?