很多不同的厂家生产各种型号的计算机，它们运行完全不同的操作系统，但 T C P / I P协议 族允许它们互相进行通信。这一点很让人感到吃惊，因为它的作用已远远超出了起初的设想。 T C P / I P起源于 6 0年代末美国政府资助的一个分组交换网络研究项目，到 9 0年代已发展成为计 算机之间最常应用的组网形式。它是一个真正的开放系统，因为协议族的定义及其多种实现 可以不用花钱或花很少的钱就可以公开地得到。它成为被称作“全球互联网”或“因特网 (Internet)”的基础，该广域网（ WAN）已包含超过100万台遍布世界各地的计算机。 本章主要对 T C P / I P协议族进行概述，其目的是为本书其余章节提供充分的背景知识。如 果读者要从历史的角度了解有关 TCP/IP的早期发展情况，请参考文献 [Lynch 1993]。

Use of this specification is your acknowledgement that you agree to and will comply with the following notices and disclaimers. You are advised to seek appropriate legal, engineering, and other professional advice regarding the use, interpretation, and effect of this specification. Use of Bluetooth specifications by members of Bluetooth SIG is governed by the membership and other related agreements between Bluetooth SIG and its members, including those agreements posted on Bluetooth SIG’s website located at www.bluetooth.com. Any use of this specification by a member that is not in compliance with the applicable membership and other related agreements is prohibited and, among other things, may result in (i) termination of the applicable agreements and (ii) liability for infringement of the intellectual property rights of Bluetooth SIG and its members. Use of this specification by anyone who is not a member of Bluetooth SIG is prohibited and is an infringement of the intellectual property rights of Bluetooth SIG and its members. The furnishing of this specification does not grant any license to any intellectual property of Bluetooth SIG or its members. THIS SPECIFICATION IS PROVIDED “AS IS” AND BLUETOOTH SIG, ITS MEMBERS AND THEIR AFFILIATES MAKE NO REPRESENTATIONS OR WARRANTIES AND DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING ANY WARRANTIES OF MERCHANTABILITY, TITLE, NON-INFRINGEMENT, FITNESS FOR ANY PARTICULAR PURPOSE, OR THAT THE CONTENT OF THIS SPECIFICATION IS FREE OF ERRORS. For the avoidance of doubt, Bluetooth SIG has not made any search or investigation as to third parties that may claim rights in or to any specifications or any intellectual property that may be required to implement any specifications and it disclaims any obligation or duty to do so. TO THE MAXIMUM EXTENT PERMITTED BY APPLICABLE LAW, BLUETOOTH SIG, ITS MEMBERS AND THEIR AFFILIATES DISCLAIM ALL LIABILITY ARISING OUT OF OR RELATING TO USE OF THIS SPECIFICATION AND ANY INFORMATION CONTAINED IN THIS SPECIFICATION, INCLUDING LOST REVENUE, PROFITS, DATA OR PROGRAMS, OR BUSINESS INTERRUPTION, OR FOR SPECIAL, INDIRECT, CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY, AND EVEN IF BLUETOOTH SIG, ITS MEMBERS OR THEIR AFFILIATES HAVE BEEN ADVISED OF THE POSSIBILITY OF THE DAMAGES.

使用无线网络是一种获得解放的、自由的经历。但是在这种经历的背后存在着一个复杂的协议；并且当数据不只限于在物理线路上传输时甚至会产生一些更为复杂的问题。怎样构造网络才能让移动用户话动自如？怎样扩展无线网络才能让它在任何需要的地方都可用？ 无线网络会产生哪些安全问题？怎样把无线网络调整到最佳性能？怎样提供足够的容量来支持最初预期的用户？怎样处理因更多的用户接人网络所带来的各种问题？ 《802.11无线网络权威指南》第二版讨论了上述所有问题及其他相关问题。本书主要是为部署或维护无线网络的严谨的系统管理员或网络管理员编写的。书中广泛讨论了无线网络的安全问题，包插使用WEP标准的安全问题，并讨论了动态WEP和802.1X.802.1li安 全标准。由于对于任何严谨的网络管理员来说网络监控都是一项必需的 工作，因此本书有专门的章节阐述如何使用Ethereal及其他工具进行网络分析和故障排除。 （<802.11无线网络权威指南》同时还介绍了无线网络的最新发展。除了802.11b和1la标准之外，本书同时涵盖802.11g，并前瞻了正在成为标准的802.1ln协议。这个新的版本扩展了网络规划及架构的讨论，并特别关注了访问点之间的移动性、频谱管理和功率控制。本书是目前唯一的讲述了如何衡量无线网络性能及如何调整网络到最佳性能的工具书。 最后，《802.11无线网络权威指南》展示了怎样配置无线网卡和Linux. Windows与MAC OS X系统，以及怎样处理访问点。很少有一本书能够把你需要掌握的理论和完成工作所需要的实际经验与建议有机地结合在一起。《802.11 无线网络权威指南》就是这样的一本好 书。如果你负责管理无线网络，你就需要这本书。