Question: What triggers a SECURITY MODE REJECT message with cause 'Conflict with already existing Integrity protection and/or Ciphering information' when a signalling connection is established towards a second core network domain, where integrity has already been initiated by the first domain?
Option 1: Receipt of a SECURITY MODE COMMAND with an unsupported ciphering alternative but supported integrity protection.
Option 2: Establishment of a new signalling connection without prior integrity protection or ciphering.
Option 3: Change in the Key Status IE to 'New' during an existing signalling connection.
Option 4: SECURITY MODE COMMAND specifying integrity protection and/or ciphering information that doesn't match the currently used alternatives.
Explanation: This is because, under specified conditions for abnormal situations in RANAP signalling, if the SECURITY MODE COMMAND's integrity protection and/or ciphering information doesn't align with what is presently being used (initiated by another domain), a conflict arises, necessitating a SECURITY MODE REJECT message to ensure consistency and security across interconnected domains.