Protocol Field TCP, ICMP, UDP, IGMP

CISSPGOAL

Hi,

How do i verify the protocol field is correct to help me understand further

If the protocol field has a value of 6 then it would indicate it was TCP.
ICMP protocol would be 1.
UDP protocol would be 17.
IGMP protocol would be 2.

JDMurray

The IPv4 Protocol field contains s value to indicate the OSI Layer 3 Protocol Data Unit contained within the IP packet. Compare this value with the list of protocol numbers to determine which PDU is in the IP packet. The most common values on most IP networks are 1 (ICMP), 6 (TCP), and 17 (UDP).

To verify that the value in the Protocol field is correct, you would need to parse the information in the PDU to check if its data format matches the protocol indicated by the Protocol value. For example, if the PDU contains an ICMP message, but the Protocol value int the IPv4 header is 6, you have a mismatch and the Protocol number is assumed to be incorrect.

Are you studying for the GIAC GCIA exam?