IP Field Size (bits) Class Version 4 Static-Known Header Length 4 Static-Known Type of Service 8 Changing Packet Length 16 Inferred Id 16 Changing Reserved Flag 1 Static-Known May Fragment Flag 1 Inferred Last Fragment Flag 1 Static-Known Fragment Offset 13 Static-Known Time To Live 8 Changing Protocol 8 Static-Known Header Checksum 16 Inferred Source Address 32 Static-Def Destination Address 32 Static-Def