Question: What is a key limitation of GIBA (Generic Bootstrapping Architecture) in terms of access network independence compared to full IMS security?
Option 1: GIBA does not support multiple APNs for accessing IMS services within a single PLMN.
Option 2: GIBA relies on bearer-level security, creating a dependency between SIP and the PS bearer, limiting its use over non-3GPP access networks like WLAN.
Option 3: GIBA requires the UE to always use an IMPI derived from the IMSI for all REGISTER requests, reducing flexibility in identity management.
Option 4: GIBA mandates a one-to-one relationship between the IMSI and IMPI, restricting simultaneous registrations from different terminals.
Explanation: This is correct because GIBA's reliance on bearer-level security creates a dependency between SIP signaling and the underlying PS bearer. This dependency limits GIBA's ability to support access network independence, particularly for scenarios where IMS services are offered over non-3GPP access networks like WLAN, unlike the full IMS security solution which does not have this limitation.