Question: In the context of 3GPP security architecture, what is the primary scenario where encryption/integrity algorithm change is required?
Option 1: At "UE not involved" SRNC relocation for both DCH and FACH cases.
Option 2: At inter-network handover with SRNC relocation.
Option 3: At intra-network handover without SRNC relocation.
Option 4: During normal operation without any handover or relocation.
Explanation: According to the security architecture, algorithm change is only required at inter-network handover. This is because operators are expected to upgrade all their RNCs with backup algorithms UEA2 and UIA2 before they need to be enabled, making intra-network handovers less likely to require algorithm changes.