IPv4 - The Standard Internet Protocol
- Autoconfiguration  Automatic configuration of networking stack
- QoS  Network Quality of Service Algorithms
- TCP  TCP extensions
Q: Why can I ping an IP address when the interface is down?
A: Linux uses a "host based" addressing model, IP addresses are owned by
the host, not individual interfaces. So as long as the IP address is
configured to some interface, we will accept packets destined to
that IP address as ours.