CertiGuide to Security+  9  Chapter 3:  Infrastructure Security (Domain 3.0; 20%)       9  3.1  Devices

3.1.6  RAS (Remote Access Server) 1 2 3.1.8 VPN (Virtual Private Network)

Your organization’s telecommunications facilities are also part of its IT infrastructure. The PBX, or Private Branch Exchange, is the controller of the telephone network within an organization²⁷⁹. It coordinates access to a limited number of “outside” telephone lines, each of which has its own telephone number, by a greater number of “inside” lines within the company. PBX’s are often used by medium and large-sized companies because it’s less expensive than connecting an outside line directly to each internal line. For example, a site might have 400 internal lines, or extensions, and 80 external lines. Another benefit of PBX’s is that users within the organization can reach other users connected to the PBX by dialing their short (3 or 4 digit) “extension” rather than a full telephone number. Many PBX’s contain what is known as a remote maintenance, or remote diagnostic, port that is used by the PBX vendor to reconfigure the phone system, upload and install software updates, download logs and perform other privileged operations. As you can see, a PBX is “phone system server” of sorts.

3.1.6  RAS (Remote Access Server) 1 2 3.1.8 VPN (Virtual Private Network)