Which of the following would enable an enterprise to provide its business partners access to its intranet (i.e., extranet) across the Internet?

A. Virtual private network

A virtual private network (VPN) allows external partners to securely participate in the extranet using public networks as a transport or shared private networks. Because of its low cost, using public networks (Internet) as a transport is the principal method. VPNs rely on tunneling/encapsulation techniques, which allow the Internet Protocol (IP) to carry a variety of different protocols (e.g., SNA, IPX, NETBEUI). A client-server (choice B) does not address extending the network to business partners (i.e., client-server refers to a group of computers within an organization connected by a communications network where the client is the requesting machine and the server is the supplying machine). Choice C refers to remote users accessing a secured environment. It is the means, not the method, of providing access to a network. A network service provider (choice D) may provide services to a shared private network by providing Internet services, but it does not extend to an organizations intranet.