OSI MODEL

TCP/IP Model

How protocol stacks communicate

The basic principle of stack-based communication is that: Data from one layer of the stack can only be understood by the corresponding layer from the remote computer

This layer independence does have security implications: for example, giving a wrong IP address for a specific DNS service, id IP and DNS layers work together they would probably notice the fake IP, but because they work independently from each other they will not notice that. You need security software to check all the layers and make sure the headers are showing the correct info.

How TCP packets are created

IP V4 header

IP V6 header

IP fragment attacks

• Tiny fragment attack
• Fragment overlap attack
• Sending thousands of initial fragments without sending the rest of the packets could cause IP stack to crash.