Refer to the exhibit. You are asked to implement a network design that consists of two sites, the main office and one branch office connected via the Internet. Communications between these sites must be secure. The main office site also supports 30 local users and 15 remote mobile workers. Before gaining access to the internal network, both the local users and the mobile workers should be authenticated using a scalable solution. Before you begin the implementation, you need to identify which security component is missing in the design.