t uses the IP and provides VPN functionality. VPNs have the features and functionality of private networks. However, unlike private lines, which are not shared and are for the exclusive use of a single orga- nization, MPLS operates on network links shared by other customers. The links are virtually private, and they still offer many of the features found on private lines such as user control and privacy. In addition, they are less costly than private lines to lease and operate. Broadband and Wide Area Network Services Prior to the advent of MPLS, older VPNs offered by carriers were slower and more cumbersome to implement and to add or delete locations. The most commonly used older VPN was frame relay. (See the section "Private Lines, Network Topology, and Frame Relay," later in this chapter, for an explanation of frame relay.) In addition to higher speeds and less-cumbersome implementations, MPLS has the capability to classify traffic SO that voice and video have higher priorities than services such as file transfer and e-mail, which are less sensitive to delay. Because of these and other capabilities managed by providers, MPLS is also referred to as a man- aged network service. MPLS is inherently more secure than the Internet because it is transmitted over a carrier's private data network. For added protection from hackers, customers often use separate circuits to access MPLS service and the Internet. This is more costly than combining both services on the same line, but it isolates MPLS transmissions even fur- ther from viruses and attacks sent over the Internet. Figure 5-2 illustrates an example of segregated circuits for Internet access and MPLS service. MPLS network Internet Access lines Customer premises Router LAN switch @@@@@@@@ VolP phone LAN = Local Area Network VolP = Voice over Internet Protocol Figure 5-2 Implementing separate access to the Internet and a Multi-Protocol Label Switching (MPLS) network. Multi-Protocol Label Switching for Interoffice Connections MPLS Implementation When customers sign u