TCP/IP Stack
The TCP/IP stack defines layered packet processing from link to application. The kernel handles encapsulation, routing, and connection state.
Understanding the TCP/IP layers
Input:
ss -tuna
Output:
Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port
tcp LISTEN 0 128 0.0.0.0:22 0.0.0.0:*
Shows active TCP/UDP sockets with states and endpoints.
References: