Packet filter is a standard router equipped with some extra functionality. The extra functionality allows every incoming or outgoing packet to be inspected. Packets meeting some criterion are forwarded normally. Those that fail the test are dropped
Blue Zone is the hottest part of the flame that is where the flame has the most Oxygen and you are getting complete combustion. It is about 1400 degrees Centigrades. The Reddish part (Non - Luminous Zone) is the coolest part, about 800 deg C.