Question: In IMS (IP Multimedia Subsystem), for registration-independent load balancing of Transit Functions, which of the following can be utilized to distribute received service requests among available Transit Functions?
Option 1: Only IBCF (Interconnection Border Control Function) entities, due to their inherent routing capabilities.
Option 2: Solely through external mechanisms like DNS (Domain Name System), without involving IMS functional entities.
Option 3: Exclusively by I-CSCF (Interrogating-Call Session Control Function) entities, as they are the primary entry points for service requests.
Option 4: Either an IMS functional entity (e.g., IBCF or I-CSCF) with load balancing functionality or external mechanisms like DNS.
Explanation: The correct answer is Option 4 because, according to the principles of load balancing in IMS for Transit Functions, the distribution of service requests can indeed be managed by an IMS entity that is directly interacting with the Transit Function (such as an IBCF or an I-CSCF) utilizing its internal load balancing capabilities. Alternatively, this can also be achieved through external mechanisms not inherent to IMS entities, like the Domain Name System (DNS), which can apply load balancing algorithms based on collected load information of Transit Functions.