Section: 6.2.16 Handling of header compression for control plane CIoT optimizations
Content: The UE and the SMF may use: - IP header compression for PDU sessions of "IPv4", "IPv6" or "IPv4v6" PDU session type; and - Ethernet header compression for PDU sessions of "Ethernet" PDU session type. Both the UE and the AMF indicate whether header compression for control plane CIoT 5GS optimization is supported during registration procedures (see subclause 5.5.1). If both the UE and the network support header compression, the header compression configuration for each PDU session is negotiated during the PDU session establishment procedure and PDU session modification procedure as specified in subclauses 6.3.2, 6.4.1 and 6.4.2. For IP header compression, ROHC protocol specified in IETF RFC 5795 [39B] is used. The IP header compression configuration used for IP header compression is (re-)negotiated between the UE and the SMF using the IP header compression configuration IE as specified in subclauses 6.3.2.2, 6.4.1.2, 6.4.1.3 and 6.4.2.2, respectively. For Ethernet header compression, Ethernet Header Compression (EHC) protocol specified in 3GPP TS 38.323[ NR; Packet Data Convergence Protocol (PDCP) specification ]  [29] is used. The Ethernet header compression configuration used for Ethernet header compression is (re-)negotiated between the UE and the SMF using the Ethernet header compression configuration IE as specified in subclauses 6.3.2.2, 6.4.1.2, 6.4.1.3 and 6.4.2.2, respectively.