cilities: access, switching, and transmission. Access facilities are used to connect the customer to the carrier's network at one or more locations. Access facilities are also commonly called local loops. Because of the fact that these access facilities serve only a single customer, they are typically a dedicated private line between the customer and the nearest central office. Access facilities are usually provided by a local exchange carrier and almost always connect the customer to a long distance carrier, or IXC. Charges for access facilities are based on a single one-time installation charge and a fixed monthly charge. Switching facilities are made available by either local or long distance service providers from a set of switching systems shared among PRACTICAL IP AND TELECOM FOR BROADCAST ENGINEERING AND OPERATIONS many customers. Switch facilities can be programmed or configured to switch traffic within a private network connecting multiple sites of a single customer, and provide access to long distance service outside the network. Switching facilities typically include a port or connec- tion charge, plus a usage charge each time the user accesses the network and uses it for whatever service has been arranged for. Transmission facilities are the pipes used to connect switching facil- ities, classically referred to as trunks. You may hear the term access trunk, which refers to the customer side of a switch, or inter- machine trunk, which refers to a connection between two switching facilities. Charges for transmission facilities are similar to access facilities, a one time installation charge, followed by a fixed monthly charge based on bandwidth. NETWORK SERVICES Network services are established after equipment and facilities are installed and connected together. Network services require the equipment and facilities to be configured to meet specific service description parameters. One of the most critical tasks in designing and building networks is preparation of a service description for each service req