tailieunhanh - CCNA Self-Study CCNA INTRO Exam Certification Guide phần 9

ừ cáp thả và chuyển nó ra cả các dòng khác. Lưu ý rằng các kết nối, kết nối tròn phổ biến trên hầu hết các hệ thống cáp . Khi sử dụng một modem cáp, các công ty truyền hình cáp trở thành ISP của bạn. Tất cả mọi thứ giữa ngôi nhà của bạn và các bộ định tuyến ở cuối đầu là một liên kết vật lý đơn lẻ và dữ liệu. | 462 Chapter 15 Remote Access Technologies from the drop cable and passes it out both of the other lines. Note that the connector the round connector common on most CATV cabling is called an f-connector. When using a cable modem the CATV company becomes your ISP. Everything between your house and the router at the head end is a single physical and data link. The PC in your home uses a router owned by the cable company housed at the head-end site as its default gateway. In fact the PC typically uses DHCP to discover its IP address and the IP address of its default gateway the DHCP server would be inside the cable company s IP network typically at the head-end site. Conceptually what happens between the home and the cable head end is similar to a single LAN segment. The details of course are different but the cable installation provides a combination of Layer 1 and Layer 2 protocols to let a PC deliver IP packets to a router inside the cable network. So as you read about the details of what happens between the home and the router at the head end keep in mind that the goal is simply to deliver IP packets between the home and the head-end router and vice versa. Layer 1 and Layer 2 between the Home and the Head End Cable TV systems originally were built to send TV video and audio signals to lots of places with no need to receive a signal back. In other words the idea of having someone s TV send some information back to the cable company was not even under consideration. Because the original CATV architecture allowed for sending signals from the head end outward and the capability for two-way communication was added later data over cable standards treats data going toward the home differently than data coming from the home. In fact CATV terminology refers to the data going toward the home as downstream data and data from the home as upstream data. Downstream data uses standards that are consistent with some of the standards for sending digital video over cable. In fact .