ccna 200 301 book pdf download

ccna 200 301 book pdf download.12.2 Basic content 320Because DSL uses both analog (voice) and digital (data) signals on the telephone line, the telephone company must, to some extent, separate these signals on the telephone company side of that connection. To do this, the local loopback must be connected to a DSL access multiplexer (DSLAM) at the nearby telephone company's central office (CO, center office) ±o The DSLAM separates the digital data to the router on the lower right side for Internet connectivity. DSLAM also separates the analog voice signal to the voice converter at the top right.DSL offers many advantages, especially over analog and ISDN dial-up options. For example, many subscriber DSLs are based on asymmetric DSL (ADSL), whereas ADSL supports speeds in the range of about 5 Mbit/s and up to 24 Mbit/s under ideal conditions0 In addition, ADSL supports asymmetric speeds, which better match most subscriber traffic models. Asymmetric speeds refer to the fact that the transmission speed to the home (downstream) is much faster than the transmission speed to the ISP (upstream). Asymmetric speeds are useful for Internet access for home users because clicking on a Web page will only send a few hundred bytes upstream to the Internet, but may trigger up to millions of bytes of data to be sent from upstream to the home.Of course, there is a downside to each option, including DSL. DSL can have a higher overhead than dial-up-it may cost more money for most people-but it does have a higher overhead in general. As a technology, DSL also has limitations. DSL only works within a certain distance from the phone company to the residence, and the speed decreases as the distance of the working cable increases. Therefore, the quality of service or the availability of service may be affected by the distance between the residence and the company.Wired InternetAnalog modems, ISDN and DSL all use the local link (phone line) from the local phone company. In contrast, the following option uses cable from what has become a major competitor of the telephone company in most markets: the cable company.Wired Internet creates an Internet access service that, in general, has many similarities to DSL if you don't pay attention to the details. Like DSL, Wired Internet makes full use of existing cables, i.e., it uses cable television cable (CATV) cables to manipulate data. Like DSL, wired Internet uses asymmetric speeds and sends data downstream faster than upstream, making wired Internet very suitable for most user locations. As with DSL, Wired Internet still allows Internet access services to be run along with the normal services (cable TV) on the cable.Wired Internet also uses the same basic concept as DSL home cable, except that it uses CATV cable instead of telephone lines. The left side of Figure 15-10 shows a TV connected to a CATV cable when normally connected. at another cable outlet, the cable modem is connected to the same cable. The Internet service operates using one frequency, just like another TV channel, except that it is reserved for Internet service.320 Chapter 15 Identifying Other WAN TypesFigure 15-10 Home Cable Internet Link Wiring and Equipment Similar to DSL. on the CATV company side of the connection (on the right side of the figure). the CATV company must separate the data and video traffic. The data traffic goes to the lower right and reaches the Internet through the router. video comes from the video receiving antenna dish and is then distributed to the TV in the home.