Which technology is most associated with tunneling? Response:

IPSec is a suite of protocols used for secure IP communications and can provide tunneling capabilities (e.g., tunnel mode VPNs), but GRE is primarily and more broadly associated with the underlying concept and protocol of tunneling itself.

Generic Routing Encapsulation (GRE) is a fundamental tunneling protocol that encapsulates a wide variety of network layer protocols inside virtual point-to-point links over an IP internetwork, making it synonymous with network tunneling.

IaaS (Infrastructure as a Service) is a cloud computing service model and not a network tunneling technology.

XML (Extensible Markup Language) is a markup language for encoding documents and is unrelated to network tunneling.