nches and adding new conduit if existing conduit or trenches are already at capacity. Mitigating Interference to Achieve Higher Capacity An important innovation in the Ethernet over Copper standard is its ability to mitigate interference caused by noise from transmissions on other cables within the same bun- dle. In a similar fashion to the noise cancellation techniques described earlier, in the section, "Advances in DSL Technology," Ethernet decreases the impact of interference by continually monitoring the circuit and eliminating noise caused by other cables in the bundle. Ethernet over Copper provides more bandwidth and costs less than multiple T1 circuits. Thus, it is marketed to small and midsize customers that now use multiple T1 circuits, and customers wanting the greater flexibility that Ethernet provides. If a cus- tomer initially uses a 2Mbps Ethernet service, it can later increase it to 5 or 25Mbps by requesting an upgrade from its provider. Upgrades do not require hardware changes at the customer's site; thus, they can be implemented faster than new T1 circuits. However, attainable speeds do depend on factors that include the distance from the telephone company's central office and the condition of the cabling. Customers need to be within 20,000 feet (3.72 miles) from the central office. Increasing the number of pairs of cabling bonded together overcomes some of these distance limitations and Broadband and Wide Area Network Services impairments. (See the section "DSL as the Predominant Worldwide Wired Internet Access Technology," earlier in this chapter, for a description of impairments.) Providers That Offer Ethernet over Copper in the First Mile Incumbent telephone companies, those that own last-mile cabling, and competitive carriers offer Ethernet over Copper. Incumbent telephone companies include AT&T, Verizon, Telefónica in Spain, and Telstra in Australia. Ethernet is less complex, can be implemented faster, and has more flexible capacities than traditional T1 circuits. Ethernet gear is also less