Virtual private networks (VPNs) are used to provide administrative personnel with secure communication channels through security systems and into trust zones. They allow staff who perform system administration tasks to have access to ports and systems that are not allowed from the public Internet.
IPSec is an encryption protocol for point-to-point communications at the network level, and may be used within a trust zone but not to give access into a trust zone. TLS enables encryption of communications between systems and services and would likely be used to secure the VPN communications, but it does not represent the overall concept being asked for in the question.
SSH allows for secure shell access to systems, but not for general access into trust zones.

A Type 2 hypervisor differs from a Type 1 hypervisor in that it runs on top of another operating system rather than directly tied into the underlying hardware of the virtual host servers. With this type of implementation, additional security and architecture concerns come into play because the interaction between the operating system and the hypervisor becomes a critical link. The hypervisor no longer has direct interaction and control over the underlying hardware, which means that some performance will be lost due to the operating system in the middle needing its own resources, patching requirements, and operational oversight.

The recovery time objective (RTO) measures the amount of time necessary to recover operations to meet the BCDR plan. The recovery service level (RSL) measures the percentage of operations that would be recovered during a BCDR situation. The recovery point objective (RPO) sets and defines the amount of data an organization must have available or accessible to reach the predetermined level of operations necessary during a BCDR situation. SRE is provided as an erroneous response.