What does the 'IP protocol field' (or IPv6 'Next Header' field) contain, and give three example values?

• A.The IPv4 Protocol field (8 bits) identifies the Layer 4 (or encapsulated) protocol in the payload; it allows the receiving IP stack to demultiplex the payload to the correct handler. Values: 1 = ICMP; 6 = TCP; 17 = UDP; 47 = GRE (Generic Routing Encapsulation); 50 = ESP (IPsec Encapsulating Security Payload); 51 = AH (IPsec Authentication Header); 89 = OSPF; 132 = SCTP
• B.The protocol field contains the IP version number (4 or 6) for dual-stack routing, so a router automatically reads it first and hands the datagram to the matching parser before any address is examined which is how a single interface can carry both families without a second header to check on the way through the forwarding path of the box which first received that frame
• C.The protocol field contains the TCP or UDP port number of the encapsulated segment; IP packets contain a source port field used by routers for load sharing. A segment carries exactly one application message; larger messages require multiple sessions. Flow control at Layer 4 is implemented with CSMA/CD backoff timers. The presentation layer is where routers make forwarding decisions between subnets