• Optical Fibers in the Local LoopOptical Fibers in the Local Loop

    In the local loop, carriers have installed fiber to carry multiplexed signal streams close to their destination. They terminate in optical network interfaces (ONIs) where twisted pairs are used to complete the connection to residences or small businesses. Several acronyms are used to identify such installations: ã FITL: fiber in the loop; ã FTTC: f...

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  • Transmission FacilitiesTransmission Facilities

    Electric currents, electromagnetic waves, and optical energy carry messages on transmission facilities. The availability of ubiquitous transport is a prerequisite for the operation of the networks described in earlier chapters. It is tempting for managers to fantasize about owning all the communication facilities needed to support an enterprise. Ho...

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  • Connecting Networks TogetherConnecting Networks Together

    Router 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 LinksNonbroadcast Multiple Access Links

    Routing 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 ModelInternet Model

    Combines 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 InventorSử dụng Inventor

    Mục 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 AssessmentClear Channel Assessment

    The 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...

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  • ISM emission rules and maximum throughputISM 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...

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  • PreauthenticationPreauthentication

    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...

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  • Traffic Indication MapTraffic 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...

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