ds typically being slower than download speeds. Business customers also usually select a different form of e-mail addressing. Although consumers generally opt for the lower-cost dynamic IP addressing, business customers most often choose static IP addressing. IP addresses use a numerical format such as 123.555.46.329 that is translated into words such as ABCcompany.com. With static IP, customers select their own unique fixed-IP address using their domain name (such as ABCcompany) for their e-mail address. Customers with dynamic IP service use their carrier's domain name; for example, Mary@providername.net. Using Digital Subscriber Line for Internet Access The use of dynamic IP addresses enables carriers to assign IP addresses on-the-fly from a pool of addresses as each e-mail message is transmitted. In this way, they don't use up as many scarce IP addresses. DSL as the Predominant Worldwide Wired Internet Access Technology In June 2010, Point Topic CEO Oliver Johnson said the following in an e-mail message: DSL is still the lowest subscription cost (and lowest deployment cost) wireline access technology and is very popular in many markets with relatively low per capita income. Very few of these deployments are under .5Mbps. In most of the world, carriers are slow to invest in fiber-optic cabling all the way to homes. This is not solely due to the high costs for the fiber itself. Rather, the expenses for digging trenches are prohibitive. Moreover, the investment for existing copper cabling has usually long since been recuperated; it is a sunk cost that still generates steady cash flows from monthly customer fees for non-Voice over Internet Protocol (VoIP), analog telephone service. (Sunk costs are those that are fully depreciated and thus don't impact profits.) Asynchronous Digital Subscriber Line (ADSL) is the prevalent type of DSL ser- vice. (See Table 5-3 in the "Appendix" at the end of this chapter for information on the types of DSL.) ADSL2, the second generation of ADSL, supports 40Mbps on short loop lengths