OSPF and ICMP messages are directly encapsulated in an IP da

OSPF and ICMP messages are directly encapsulated in an IP datagram. If we intercept an IP datagram, how can we tell whether the payload belongs to OSPF or ICMP?

Solution

The type of payload can be determined from the value of the protocol field.

The protocol field value for ICMP is 01.

The protocol field value for OSPF is 89.