tailieunhanh - CCNA 1 and 2 Companion Guide, Revised (Cisco Networking Academy Program) part 10

Cisco Networking Academy Program CCNA 1 and 2 Companion Guide, Revised part 10 is the Cisco approved textbook to use alongside version of the Cisco Networking Academy Program CCNA 1 and CCNA 2 web-based courses. The topics covered provide you with the necessary knowledge to begin your preparation for the CCNA certification exam (640-801, or 640-821 and 640-811) and to enter the field of network administration. | B Page 59 Tuesday May 20 2003 2 53 PM Analogies That Describe Digital Bandwidth 59 representing massive amounts of information flowing back and forth across the globe in seconds or less. In a sense it might be appropriate to say that the Internet is bandwidth. The demand for bandwidth is ever-increasing As soon as new network technologies and infrastructures are built to provide greater bandwidth new applications are created to take advantage of the greater capacity. The delivery over the network of rich media content including streaming video and audio requires tremendous amounts of bandwidth. IP telephony systems are now commonly installed in place of traditional voice systems adding further to the need for bandwidth. The successful networking professional must anticipate the need for increased bandwidth and plan accordingly. Analogies That Describe Digital Bandwidth The idea that information flows suggests two analogies that might make it easier to visualize bandwidth in a network. Because both water and traffic are said to flow consider the following Bandwidth is like the width of a pipe as shown in Figure 2-13 A network of pipes brings fresh water to homes and businesses and carries wastewater away. This water network is made up of pipes with different diameters. A city s main water pipe might be 2 meters in diameter whereas a kitchen faucet might have a diameter of only 2 centimeters. The width of the pipe determines the pipe s water-carrying capacity. Thus the water is analogous to data and pipe width is analogous to bandwidth. Many networking experts say they need to put in bigger pipes when they want to add more information-carrying capacity. Bandwidth is like the number of lanes on a highway as shown in Figure 2-14 A network of roads serves every city or town. Large highways with many traffic lanes are joined by smaller roads with fewer traffic lanes. These roads lead to even smaller narrower roads and eventually to the driveways of homes and .