Connecting Networks TogetherRouter Figure 5.9 is a functional diagram of a router. A database of routes is stored and maintained by all routers. Called a routing table, it contains information concerning routes between the node owning the table and the potential destination nodes. At a minimum it includes the destination ID, intermediate interface ID(s) and forwarding address...
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Nonbroadcast Multiple Access LinksRouting How frames are routed over a packet-switched network depends on the instructions given by the users. Three basic styles, similar to the routing techniques employed in router driven networks, can be distinguished: ã Distributed routing: On the basis of information about traffic conditions and equipment status (network map, port status), each...
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Internet ModelCombines user’s data with generic function software to create a user’s data block identified as information retrieval, file transfer, and mail. ã Encapsulates the user’s data block with a header (application header, AH) and identifies the source port from which it is sent, and to which any reply must be addressed. ã Passes the application protocol ...
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Sử dụng InventorMục lục Lời nói đầu Ch-ơng 1: Tổng quan về thiết kế tham số và h-ớng đối t-ợng 1.1. Khái niệm về thiết kế tham số và h-ớng đối t-ợng 1.2. Môi tr-ờng thiết kế của Mechanical Desktop 1.3. Môi tr-ờng thiết kế của Autodesk Inventer 1.4. Định h-ớng ng-ời dùng Mechanical Desktop và Autodesk Inventer Ch-ơng 2: Những khái niệm ban đầu 2.1. ...
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Clear Channel AssessmentThe OFDM PHY specification leaves implementers a great deal of latitude in selecting techniques for noting a busy channel. Received signal strength thresholds determine whether the channel is in use, but the main guideline for 802.11a equipment is that it must meet certain performance standards. Implementations are free to use the Packet Length fie...
43 trang | Chia sẻ: tlsuongmuoi | Ngày: 15/01/2013 | Lượt xem: 2145 | Lượt tải: 0- ISM emission rules and maximum throughput
Spectrum allocation policies are the limiting factor of frequency-hopping 802.11 systems. As an example, consider the three major rules imposed by the FCC in the U.S.:[2] [2] These rules are in rule 247 of part 15 of the FCC rules (47 CFR 15.247). 1. There must be at least 75 hopping channels in the band, which is 83.5-MHz wide. 2. Hopping channels...
43 trang | Chia sẻ: tlsuongmuoi | Ngày: 15/01/2013 | Lượt xem: 2082 | Lượt tải: 0 - Preauthentication
Stations must authenticate with an access point before associating with it, but nothing in 802.11 requires that authentication take place immediately before association. Stations can authenticate with several access points during the scanning process so that when association is required, the station is already authenticated. This is called preauthe...
43 trang | Chia sẻ: tlsuongmuoi | Ngày: 15/01/2013 | Lượt xem: 2076 | Lượt tải: 0 - Traffic Indication Map
Four fields make up the body of the TIM information element: DTIM Count This one-byte field is the number of Beacons that will be transmitted before the next DTIM frame. DTIM frames indicate that buffered broadcast and multicast frames will be delivered shortly. Not all Beacon frames are DTIM frames. DTIM Period This one-byte field indicates the nu...
43 trang | Chia sẻ: tlsuongmuoi | Ngày: 15/01/2013 | Lượt xem: 2078 | Lượt tải: 0 - Wireless Networks: The Definitive Guide tập 2
After frame transmission has completed and the DIFS has elapsed, stations may attempt to transmit congestion-based data. A period called the contention window or backoff window follows the DIFS. This window is divided into slots. Slot length is mediumdependent; higher-speed physical layers use shorter slot times. Stations pick a random slot and wai...
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Copyright Preface Prometheus Untethered: The Possibilities of Wireless LANs Audience Overture for Book in Black and White, Opus 2 Conventions Used in This Book How to Contact Us Acknowledgments Chapter 1. Introduction to Wireless Networks Section 1.1. Why Wireless? Section 1.2. A Network by Any Other Name . Chapter 2. Overview of 802.11 Networks Se...
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