The Criticality Diagnostics IE is sent by the eNB or the MME when parts of a received message have not been comprehended or were missing, or if the message contained logical errors. When applicable, it contains information about which IEs were not comprehended or were missing.
For more detail refer to 3GPP 36.413 (http://www.etsi.org/deliver/etsi_ts/136400_136499/136413/08.07.00_60/ts_136413v080700p.pdf)
I found two MME UE S1-AP IDs i.e. MME UE S1AP ID (Mandatory) and MME UE S1AP ID 2 (optional).
I got why mandatory one is present but what's use of optional one.
Can someone please explain it ?
What is the Significance of Repetition Period and Number of Broadcasts Requested IE's in WRITE-REPLACE WARNING REQUEST?