The statement that both VXLAN and TRILL are host-centric overlay solutions is false. VXLAN is a host-centric overlay technology where the encapsulation and decapsulation (by a VTEP) typically occur at the edge of the network, often within the hypervisor on the host itself. In contrast, TRILL (Transparent Interconnection of Lots of Links) is a network-centric protocol. It is implemented on network switches (called RBridges) to provide optimal Layer 2 multipathing, effectively replacing the Spanning Tree Protocol (STP). End hosts are completely unaware of the TRILL protocol operating within the network fabric.

A. This is the correct and standard definition of an overlay network, which logically separates the virtual network from the underlying physical infrastructure.

C. Nuage Networks VNS (Virtualized Network Services), which is part of the Nokia Virtualized Services Platform (VSP), uses VXLAN as a primary data plane encapsulation method to create overlay tunnels.

D. A core principle of overlay networking is the decoupling of the virtual and physical networks. The underlay forwards encapsulated packets based on their outer headers, remaining unaware of the inner packet's contents or the overlay topology.

1. For VXLAN (Host-Centric):

IETF RFC 7348, "Virtual eXtensible Local Area Network (VXLAN): A Framework for Overlaying Virtualized Layer 2 Networks over Layer 3 Networks", Section 1, Page 3. "VXLAN is a Layer 2 overlay scheme over a Layer 3 network. It uses MAC Address-in-User Datagram Protocol (MAC-in-UDP) encapsulation to provide a means to extend Layer 2 segments across a Layer 3 network... The VXLAN Tunnel Endpoint (VTEP) is the entity that originates and/or terminates VXLAN tunnels." (VTEPs are commonly implemented in hypervisors).

2. For TRILL (Network-Centric):

IETF RFC 6325, "Routing Bridges (RBridges): Base Protocol Specification", Section 1.1, Page 6. "TRILL is transparent to end stations. An end station cannot tell whether it is attached to a single bridge, a set of bridges running TRILL, or a set of bridges running Spanning Tree."

3. For Nuage Networks VNS using VXLAN:

Nokia, "Virtualized Services Platform Fundamentals Guide, Release 21.10.R1", Document ID: 3HE 17379 AAAD TQZZA, Section: VSP architecture overview. The documentation states, "The VSP uses VXLAN or GRE tunnels in the data plane to provide Layer 2 or Layer 3 overlay services between endpoints."

4. For Overlay Definition and Transparency:

Nokia, "SR OS R21.10.R1 Services Architecture Guide", Document ID: 3HE 17193 AAAD TQZZA, Section: EVPN for VXLAN Tunnels. "VXLAN is a technology that allows network operators to create virtual Layer 2 networks that are decoupled from the physical network." This decoupling ensures the underlay is transparent to the overlay's operations.