[Virtualization] Linux based techniques? IP communication?

1.
I am aware of the following mechanisms for the SUN/Solaris based
servers:
- Domains (HW level)
- Logical domains(Using Hypervisor)
- Container/zones

What are the similar mechanisms available for the Linux servers? What
are the very commonly/widely used among them?


2.
Does the IP communication between the multiple logical servers that are
located on the same physical server happen as usual, or will it be like
a simple inter-process-communication on the same server(optimized)?