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Một khi bạn đã thành lập chương trình liên mạng của bạn, bạn phải thiết kế một cách để xử lý các mối liên kết giữa các trang web trong cùng một vùng hoặc khu vực kiểm soát hành chính. Trong thiết kế mạng WAN khu vực, cho dù bạn đang sử dụng dịch vụ packetswitching hoặc điểm-điểm mối liên kết, | 428 Chapter 8 Designing the Infrastructure such as variable length subnet mask VLSM classless inter-domain routing CIDR and a routing protocol that can support these methods. Possible Types of Topology Design Once you have established your internetwork scheme you must design a way for handling interconnections among sites within the same region or area of administrative control. In designing regional WANs whether you are using packetswitching services or point-to-point interconnections three basic design approaches are common throughout the industry Star topologies Fully meshed topologies Partially meshed topologies In the following pages I will try to help you understand these topologies and how you can use them to your advantage. Remember though that the discussions presented in this chapter address the application of these topologies specifically to packet-switching services. Note__ Illustrations in this chapter use lines to show the connection of specific routers on the PSDN network. These connections are considered virtual connections as the circuits are mapped within the routers themselves. Normally all physical connections are generally made to switches within the PSDN. Unless otherwise specified the connecting lines represent virtual connections within the PSDN. Star Topologies The star topology also known as a hub and spoke is a grouping of network devices that has a single internetworking hub and provides connections for the external cloud networks to the backbone and access to each other although only through the core router. Figure 8.3 illustrates a packet-switched star topology for a regional internetwork. One of the main advantages of a star topology is that there is simplified management and minimized tariff costs or tolls.Whereas tolls aren t much of a factor www.syngress.com Designing the Infrastructure Chapter 8 429 Figure 8.3 Star Topologies for a Regional Internetwork these .
