remises (FTTP) offer Digi- tal Subscriber Line (DSL) service over twisted-pair cabling for Internet access. (Cable TV providers use other technologies over the coaxial cabling portion of their hybrid fiber/coaxial cabling plant.) Former telephone companies deploy DSL Access Multi- plexers (DSLAMs) to aggregate traffic from multiple DSL modems in neighborhoods and combine it into higher speeds before sending it to the Internet or data networks over fiber-optic cabling. DSLAMs are located in a carrier's central offices or in remote terminals, which are cabinets placed between the central office and the subscriber. connection between the DSLAM and an ISP is a potential site for network congestion. If capacity is insufficient, a customer might experience delays. Using Small DSLAMs and Mini-RAMs for TV and Higher-Speed Internet Access When providers such as AT&T and CenturyLink move fiber closer to customers in neighborhoods, they often support fewer customers per fiber run and use mini Remote Access Multiplexers (mini-RAMs). Shorter copper lengths support the higher speeds required for TV, movies, and Internet access. They connect this copper cabling to lower-cost, smaller DSLAMs and mini-RAMs. Mini-RAMs are about the size of two pizza boxes, stacked one atop the other. They can be located on utility poles or in stand-alone boxes on the ground and serve 10 to 24 customers (see Figure 4-9). Local power is not required because it is fed to mini-RAMs through the copper telephone lines either on the pole or underground. Carrier Networks DSLAM Mini-RAM aggregation switch Copper-to-DSL modems in homes Headend Central office Mini-RAM Fiber Internet DSLAM = Digital Subscriber Line Access Multiplexer PSTN = Public Switched Telephone Network Figure 4-9 Mini Remote Access Multiplexers (mini-RAMs), located in neighbor- hoods, deliver cable TV and high speed Internet access. Because the fiber is closer to customers, these cable configurations avoid most of the impairments found on longer copper lines farther from central offices.