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To access the contents, click the chapter and section titles.
Wireless Networking Handbook
A WAN consists of routers and links. As previously mentioned, routers receive a routable data packet, such as Internet Protocol (IP) or Internetwork Packet Exchange (IPX), review the destination address located in the packet header, and decide which direction to send the packet next in order to forward it closer to the final destination. The routers maintain routing tables that adapt, via a routing protocol, to changes in the network. Refer to a later section (Routing Protocols) for a description of common routing protocols. WANs fall into two main classes: private and public. Figure 8.10 illustrates these two approaches. Private Point-to-Point WANWith private WANs, the user organization or company owns and manages most of the network equipment, such as routers and communications circuits. Traditionally, organizations have implemented private point-to-point WANs to support communications between remote terminals and centralized mainframe-based applications. The following identifies the ramifications of using a private WAN:
A common link between sites of a private point-to-point LAN is T1. T1 Bell labs originally developed T1 to multiplex multiple phone calls into a composite signal, suitable for transmission through a digital communications circuit. A T1 signal consists of a serial transmission of T1 frames, as shown in figure 8.11. Each frame transports an 8-bit sample of 24 separate channels. You can lease from a telephone service carrier an entire T1 circuit (1.544 Mbps) or only single channels (64 Mbps each).
Public Packet Switching WANA public WAN is owned and operated entirely by a service provider. With the development of distributed client-server applications, most organizations now require technologies suitable for highly meshed topologies. In other words, there is a need to support communications among the remote sites, not just in a centralized data center. Thus, you should seriously consider leasing the use of a public packet switching WAN to support todays demand for distributed computing. The following identifies the implications of using a public WAN:
The following briefly describes each of the technologies that support public packet switching WANs. You can lease these as services from carriers such as AT&T and Sprint within most metropolitan areas.
Information SecurityAs explained in Chapter 1, Introduction to Wireless Networking, wireless networks are prone to breaches of information security. When sending data over a wireless network, leased lines, or a public data network, you run the risk of someone stealing the information. If you plan to send sensitive information over a WAN, consider the use of encryption and other mechanisms to counteract this problem. For example, you can use encryption devices on all links to scramble the data, making it meaningless. For connections to the Internet, place a firewall at the entry point to the Internet. A firewall filters out unauthorized access from others on the Internet to your companys resources. A typical firewall configuration blocks all incoming traffic, but enables users from within to access Internet services.
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