tailieunhanh - the best damn cisco internetworking book period phần 3

một sự giàu có của lợi ích. Toàn bộ tòa nhà và cơ sở có thể thiết lập một sự hiện diện mạng lưới với tối thiểu của dây. Không còn là cần thiết để cài đặt một giọt mạng có dây trong mỗi vị trí, đó có thể là một tốn kém và mất thời gian cam kết. Mạng không dây cho phép người dùng điện thoại di động, | 190 Chapter 3 Wireless Networking Introduction Wireless networks have become integral to many organizations over the past few years and no ability to remain connected and mobile without wires provides a wealth of benefits. Entire buildings and campuses can establish a network presence with a minimum of wires. No longer is it necessary to install a wired network drop in every location which can be an expensive and time consuming undertaking. Wireless networking allows users to be mobile yet still be able perform tasks such as checking their e-mails accessing servers and use the resources of the Internet. Integrating both wired network and wireless LAN WLAN technologies into a single device allows the administrator to have the best of both worlds. In addition to the radio technologies that enable WLANs other technologies are employed to provide security efficiency and stability to the wireless local area network. Because WLAN radio devices use various aspects of radio technology this chapter first reviews radio frequency RF fundamentals such as the practical information necessary to understand the functionality of any WLAN radio device including Cisco Aironet products. Because this subject matter represents such a broad range of topics and technologies discussing them all in one chapter is difficult at best. Instead this chapter focuses on the fundamentals and standards as they directly relate to WLANs. It discusses current wireless technologies and the advantages and disadvantages of various wireless technology implementations with greater attention given to the technology used by Cisco Aironet devices. Understanding the Fundamentals of Radio Frequencies RF in wireless communications describes devices or equipment that use radio waves to transmit images and sounds from one transmission point to one or more reception points. In networking RF is used to describe network devices access points APs bridges and so on that use radio waves to transmit or receive