Question: In an S1 Application Protocol (S1AP) scenario, if an eNB receives a DOWNLINK S1 CDMA2000 TUNNELLING message with at least one E-RAB ID lacking associated DL GTP-TEID and DL Transport Layer Address, how should the eNB proceed with the included UL GTP-TEID IE and/or UL Transport Layer Address IE?
Option 1: Process them normally as part of the forwarding setup.
Option 2: Use default values for the missing DL parameters to process the UL IEs.
Option 3: Ignore the UL GTP-TEID IE and/or UL Transport Layer Address IE in this specific message.
Option 4: Send a failure notification to the MME and terminate the procedure.
Explanation: According to S1AP protocol rules for handling abnormal conditions, when an eNB encounters a logical error such as missing DL GTP-TEID and DL Transport Layer Address for at least one E-RAB ID in a DOWNLINK S1 CDMA2000 TUNNELLING message, it is specified that the eNB shall ignore the UL GTP-TEID IE and/or UL Transport Layer Address IE included in the same message. This ensures consistency in handling incomplete setup information to prevent potential protocol mismatches or errors in the E-UTRAN.