The ISA module provides security utilities for IPsec-related service entities that are assigned to interfaces and SAPs. These entities (such as card, MS-ISA2 module, and IES or VPRN services) must be enabled in order for the security services to process. The module only listens to requests for security services from configured remote endpoints. In the case of a VPN concentrator application, these remote endpoints could come from anywhere on the Internet. In the cases where a point-to-point tunnel is configured, the module listens only to messages from that endpoint.