This technology logically groups networked computers by function or department and enhances security by segregating data traffic, for example, by separating VoIP traffic. What is this technology called?

Domain 4: Communication and Network Security Practice Questions
Questions from the following topics are included in this domain:   
Assess secure network design principles.   
Implement secure network design principles.  
Secure network components using network access control devices.   
Implement secure design communication channels.  
Understand data communications and virtualized networks.