IMS Registration Sequence Diagram

This flow models two-pass IMS registration — an unauthenticated REGISTER followed by an authenticated one. To trace the same exchange in a real capture, VisualEther turns a Wireshark SIP PCAP into a sequence diagram and lets Claude Code explain why a registration was challenged or rejected.

This sequence diagram details the message interactions involved in IMS registration. IMS registration from a visited IMS network is covered. The interactions covered are:

1. Terminal attaching to the GPRS Network.
2. Terminal activates a PDP context.
3. An unauthenticated IMS registration is attempted.
4. IPSec security association is established between the User terminal and the P-CSCF.
5. Finally the terminal performs an IPSec protected registration that completes the authentication of the network and the terminal.

We look at the registration via multiple views into the registration interactions:

• IMS Registration
• IMS Registration Poster (11x17)
• IMS Registration Overview
• Registration Interactions between Visited and Home IMS Networks
• Registration Interactions between User Equipment, the Visited Network and the Home IMS Network
• UE Role Sequence Diagram
• UE Role Collaboration Diagram
• P-CSCF Role Sequence Diagram
• P-CSCF Role Collaboration Diagram
• I-CSCF Role Sequence Diagram
• I-CSCF Role Collaboration Diagram
• S-CSCF Role Sequence Diagram
• S-CSCF Role Collaboration Diagram