This is an extra brief scrape of a net communication layers – just to keep it around to look at. To understand the difference in Layer 4 / Layer 7 DDOS attacks.
7 – Application Layer. Constructing appropriate data that another application that supports same protocol would understand. Generally by using “Layer 7” term it’s common to combine layers 5-7.
6 – Presentation Layer. A bit less fuzzy – represents compression, encryption, encoding etc.
5 – Session Layer. Generally to establish a bond between sides for further communication. Quite fuzzy.
4 – Transport Layer. TCP, generally. Establishes and manages connection, controls flow, retransmissions. TCP connection: client sends SYN, server responds with that SYN and new ACK, client sends over that ACK and a new ACK.
3 – Network Layer. Logical addressing, routing. ICMP.
2 – Data Link Layer. Ethernex, WiFi (802.11), all that jazz. Responsible for Logical Link Control, data framing (putting into proper frames), addressing
1 – Physical Layer. Establishing hardware specification, encoding/decoding signals, transmitting signals. The only layer that actually transfers data.