l developments). In addition, they are the basis for wireline infrastructure in developing countries. This is the result of decreas- ing fiber costs and increasing copper costs, which makes the cost of new fiber and copper about the same. Using PONs for Remote Administration and Bandwidth Allocation PONs enable up to 32 locations to share the bandwidth on a pair of fibers. An advantage of PONs is that changes to the allocation of capacity among the 32 premises can be carried out remotely by computer commands rather than by dispatching a technician. Carrier Networks Thus, the programmability of PON devices enables carriers to manage complex net- works more efficiently. Gigabit Ethernet Passive Optical Network Gigabit Ethernet Passive Optical Network (GPON) is more flexible, and faster than the three earlier PON standards. Most new PON installations are based on GPON. How- ever, a new, faster standard, 10Gbps Ethernet Passive Optical Network (10G-EPON), has been ratified. It supports 10Gbps speeds to customers. 10G-EPON equipment has started to be introduced. For more information about the PON standards, see Table 4-2 in the "Appendix" section, at the end of this chapter. Gigabit Ethernet is suited for both circuit-switched traffic such as T1 as well as IP voice and data. An important advantage of GPONs and 10G-EPONs is that they can be configured in redundant rings. If one ring fails, traffic is rerouted onto a backup ring (protect ring) and backup PON equipment. Because of their high speed, flexibility, and redundancy, GPONs and 10G-EPONs are well suited for high-definition digital tele- vision and for transporting corporate data to storage networks in metropolitan areas. Verizon uses GPONs for its FIOS fiber-optic service to home installations. This service supports speeds of 15Mbps to 50Mbps downstream from Verizon to the cus- tomer, and 5Mbps to 35Mbps upstream from the subscriber to Verizon. For an addi- tional fee, Verizon offers symmetrical service by which upstream and downstream channel speeds are the sam