Question: What protocol is used for IP header compression in control plane CIoT 5GS optimization?
Option 1: Ethernet Header Compression (EHC) protocol
Option 2: Packet Data Convergence Protocol (PDCP)
Option 3: Robust Header Compression (ROHC) protocol specified in IETF RFC 5795
Option 4: Internet Protocol version 6 (IPv6) header compression
Explanation: ROHC protocol is used for IP header compression in control plane CIoT 5GS optimization, as specified in the text. This protocol is designed to compress IP headers efficiently and is widely used in various networks.