DSL customers shrank from the fourth quarter of 2008 to the fourth quarter of 2009. According to the Fiber to the Home Council, by year-end 2009, there were more than 50 million homes and buildings connected to fiber-optic cabling worldwide. In contrast, according to UK-based market research firm Point Topic, Ltd., by year-end 2009, there were 303 million DSL subscribers. This is more than those connected directly to fiber. Interestingly, the overall number of both fiber and DSL customers grew between 2008 and 2009. Currently, the number of DSL subscribers is shrinking in locations such as North America and Scandinavia. It is generally expected that in the future, either fiber or high-speed wireless services will replace additional DSL. DSL as a Backup Option for Business Customers Midsize and large commercial and business customers in most developed countries lease DSL services primarily as a low-cost backup service in the event that their pri- mary Internet access circuits fail. Many of these primary circuits are installed on fiber- optic cabling. The large volume of revenue generated by enterprise customers makes a carrier's investment in fiber-optic cabling for business customers viable. Fiber cabling supports higher speeds than the copper cabling used for DSL. It also requires less maintenance by providers than copper cabling. However, the lower cost of DSL makes it a more affordable backup option than, for example, redundant T1/E1 circuits or lay- ing extra fiber. IP Addressing and Symmetric Speeds for Business Customers Very small business customers-those with fewer than 25 employees-still use DSL as their primary link to the Internet if fiber or low-priced T1 is not available to them. Because of the more complex requirements, business customers often choose more expensive DSL options than consumers. These options include higher speeds and sym- metric transmission, which means that they can send data at the same rate as they receive it. By contrast, most consumer DSL service is asymmetric, with upload spee