@@ -485,6 +485,46 @@ Each security level will consist of the security requirements necessary to mitig
> - How its functions are configured?
> - How it keeps itself secure and functioning?
The purpose of a virtual private network is to create a restricted-use network without requiring separate physically restricted infrastructure. The VPN software controls which nodes can participate in the restricted-use network and which functions or data the node is able to use or access.
Depending on the use case, VPNs provide different functions. Potential functions include:
* Controlling which nodes join the restricted-use network
* Restricting access to the data sent on the restricted-use network
* Obscuring the source or target of data sent on the restricted-use network
* Obscuring the pattern of data sent on the restricted-use network
* Preventing a node from connecting directly to the public network
* Routing restricted-use network traffic in or out of specific nodes
* Routing public network traffic to nodes on the restricted-use network
* Examining or filtering network traffic on the restricted-use network
The VPN itself is a collection of software running on different nodes. Each software element may have a different set of functionality and may be more or less trusted than other elements. How the functionality and trust are distributed vary according to the architecture and use case of the VPN.
For example, a VPN intended to protect the user of an endpoint node from surveillance would prefer an architecture that did not trust any node not controlled by the end user. A VPN intended to protect a corporate private network would trust all the nodes in the private network that are administered by the corporation, but not the endpoint nodes that are administered by employees.
Functionalities of nodes in VPNs (a node can have some or all):
* Authorization - grant nodes access to the restricted use network
* Edge - uses a public network to communicate with the restricted use network
* Gateway - provides link between public network and restricted use network
* Router - forward traffic between nodes in the restricted use network
* Filter - select which traffic may transit this node in the restricted use network
* Relays - assist nodes in connecting to the restricted use network
During reasonably foreseeable use, nodes may:
* Authorize other nodes to use the restricted use network
* Request authorization to use the restricted network
* Serve configuration information
* Update their configuration information
* Assist nodes in connecting to the restricted use network
* Send traffic between nodes on the restricted use network
* Send traffic from the restricted use network to the public network
* Send traffic from the public network to the restricted use network
* Filter traffic transiting a node according to complex rules
* Leave the restricted network
* Revoke the access of a node to the restricted use network
## 4.8 Operational Environment
> Describe the expected operating environment given the exclusions in Section 4.2. This includes:
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The technical requirements of the present document apply under the environmental profile for operation of the equipment, which shall be in accordance with its intended use. The equipment shall comply with all the technical requirements of the present document at all times when operating within the boundary limits of the operational environmental profile defined by its intended use.
The physical hardware the VPN product is using may be:
* In a secure professionally managed environment
* In a private home
* In a public area
### 4.7.2 Digital environment
VPNs can be expected to operate in a network environment alongside other Important PwDEs such as Identity Access Management, Network Interfaces, Routers, and Firewalls. Manufacturers shall harden VPN attack surfaces against potential attack vectors from compromised PwDEs, but in particular those considered Important and Critical. See clause TK for further information about the relationship between VPNs and related software.
A VPN requires an existing physical or virtual network whose resources it can use. The underlying network must provide the functions necessary to connect to at least one node of the VPN.
Functions the underlying network must provide:
* Physical equipment capable of transmitting network traffic
* Routing/forwarding of network traffic
A VPN product runs on a node in the context of an operating system, as an application, a library, a service, a driver, a kernel service, or a combination thereof. The operating system may provide:
* Network stack
* Virtual or physical network interfaces
* Network configuration
* DNS and other network services
* Certificate authority services
* Encryption
* Application support
* Packet filtering
* Denial of service protection
* Software installation and update
VPN products often include or are use in concert with:
