ing source. The Drive for Higher-Capacity Carrier Gigabit Ethernet Large providers such as CenturyLink, Telstra (in Australia), and Verizon are building 100Gbps backbone routes in their networks. The impetus behind 100Gbps Ethernet is the increasing amount of high-definition TV, Video-on-Demand (VOD), network-based storage, and mobile broadband traf- fic. Gigabit Ethernet is more flexible than SONET and more suited for data. It was expressly developed for IP traffic. In addition, Gigabit Ethernet is less costly to pur- chase, maintain, and install than SONET, and traffic from multiple sources can be eas- ily added and dropped off from switches. The wide availability of Gigabit Ethernet switches from many manufacturers has caused Ethernet switch prices to drop. Moreover, because of its standardization by the Technologies Used in Carrier Networks Institute of Electrical and Electronics Engineers (IEEE), vendors produce compatible Ethernet gear SO that providers are not locked into a single vendor's equipment. Carriers deploy Multi-Protocol Label Switching (MPLS) in conjunction with Carrier Gigabit Ethernet in their core networks. MPLS is a Layer 3 proto- col that switches traffic between IP addresses rather than Media Access Control (MAC) addresses. MAC addresses are assigned to individual computers. By contrast, IP addresses are assigned to the network or to the Virtual LAN (VLAN). Managing fewer addresses makes routing by using MPLS with its IP addressing less complex to manage. It also enables networks to scale to larger sizes. MPLS is an optional feature in routers. More information on MPLS can be found in Chapter 5. Carrier Ethernet can operate over copper and wireless media but only for shorter distances. Ethernet over copper is now offered by competitive carriers and some incumbent carriers as a way to provide higher, flexible speeds without the need to dig trenches for new fiber cabling. It operates at speeds ranging from 5Mbps to 100Mbps. Gigabit Ethernet and Ethernet are often used in conjunction with Pas