five years. What relevance do bandwidth and transfer rate have to you? Well, wider can be faster, which means shorter download times. Consider these examples: Download Time 768Kbps Type and Size of File 56Kbps (Narrowband) (Broadband [e.g., DSL]) Photo from ski trip (1MB) 4 minutes 25 seconds MP3 of favorite song (1.5MB) 6 minutes 40 seconds Gaming demo (2.5MB) 10 minutes 60 seconds PowerPoint presentation for 25 minutes 2 minutes sales meeting (6MB) xxxiv Introduction Table I.1 Common Bandwidth Units Prefix Meaning Transfer Rate Kilobits per second (Kbps) Kilo = 1 thousand 1,000bps Megabits per second (Mbps) Mega = 1 million 1,000,000bps Gigabits per second (Gbps) Giga = 1 billion 1,000,000,000bps Terabits per second (Tbps) Tera = 1 trillion 1,000,000,000,000bps Petabits per second (Pbps) Peta = 1,000 trillion 1,000,000,000,000,000bps Exabits per second (Ebps) Exa = 1 billion billion 1,000,000,000,000,000,000bps Shorter download times mean greater productivity. Much of the economic growth of the late 1990s has been attributed to productivity gains realized as a result of new communications and IT products: Workers with broadband are more productive than workers using dialup, and the greater the productivity of a coun- try, the stronger the economy. To get an idea of how bandwidth affects transfer time, think about download- ing the entire Library of Congress, which is often used as the yardstick for the mea- sure of all human knowledge. Table I.2 shows how long it would take to download the Library of Congress at various data rates. Table 1.2 Transfer Times for Downloading the Library of Congress Data Rate Transfer Time 2400bps 1,900.0 years 56Kbps 81.5 years 1.5Mbps 3.0 years 1.7Gbps 23.5 hours 10Gbps 2.35 hours 100Gbps 14.1 minutes 1Tbps 1.41 minutes 1Pbps 8.26 seconds 1Ebps 0.826 seconds Adapting to New Traffic Patterns Table 1.3 Backbone Bandwidth Requirements of Various Applications Application Backbone Bandwidth Required Online virtual reality 1,000Tbps to 10,000Tbps 3D holography 30,000Tbps to 70,000Tbps 