Đang chuẩn bị liên kết để tải về tài liệu:
CompTIA Network+ Certification Study Guide part 5

Không đóng trình duyệt đến khi xuất hiện nút TẢI XUỐNG Tải xuống

CompTIA’s Network+ certification Study Guide part 5 is a globally-recognized, vendor neutral exam that has helped over 235,000 IT professionals reach further and higher in their careers. The 2009 Network+ exam (N10-004) is a major update with more focus on security and wireless aspects of networking. Our new study guide has been updated accordingly with focus on network, systems, and WAN security and complete coverage of today’s wireless networking standards. | 26 CHAPTER 1 Network Fundamentals on a bus network it only listens or sends data. It doesn t take data and then resend or regenerate it so each computer isn t essential to the network as a whole. If one computer fails it doesn t crash the entire network. Another benefit of this topology is that it is inexpensive as less cable is used than other topologies we ll discuss. As we ll see later some topologies have redundant connections or require a significant amount of cable. In a bus topology every computer is connected to a single cable. Having a single cable however does cause other problems. If the cable breaks then each segment has an end that isn t terminated and the entire network goes down. If the trunk is long enough this can make it difficult to isolate where the break is. Another disadvantage of this topology is that it isn t very scalable. The number of computers is limited to the length of the cable and as your company grows it can be difficult changing the size and layout of the network. Also if changes or repairs are made to the cable the network is down because there is no redundancy and termination of the cable is required. STAR Hierarchical In a star topology computers aren t connected to one another but are all connected to a central hub or switch. When a computer sends data to other computers on the network it is sent along the cable to a central hub or switch which can then pass the packets to the other computers or devices that are connected to it. As seen in Figure 1.4 when the computers are cabled to the hub each point in the network can appear similar to points in a star hence the name of this topology . Although this is an older topology that comes from the time when terminals were connected to mainframes as a centralized point it is still a FIGURE 1.4 A Star Topology. popular topology. Because cables run to a central point if one cable breaks or fails in some way only the computer that is connected to that cable is unable to use the network.