Question: In a Lawful Interception (LI) architecture, which reference point is specifically used for carrying user plane information from the Serving Gateway (S-GW)/Broadband-Broadcast Integrated Fixed Network Function (BBIFF) to the Lawful Interception Management System Function (LMISF)?
Option 1: Xib - For control plane information exchange between LMISF and S-GW/BBIFF
Option 2: Xia - For user plane information from S-GW/BBIFF to external networks
Option 3: Xia - For carrying user plane information from the S-GW/BBIFF to the LMISF
Option 4: None of the above, as both Xia and Xib are for control plane signaling
Explanation: In Lawful Interception architecture, Xia is designated for transmitting user plane information, crucial for intercepting actual communication content (e.g., voice, data), as opposed to control signals. Thus, Xia carries user plane information from S-GW/BBIFF to LMISF, facilitating lawful interception.