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发布时间：2006-06-28 04:58     点击：

Standard Ethernet configuration efficiency is typically rated at 50-60 percent of the 10-Mbps bandwidth. Full-duplex Ethernet offers 100 percent efficiency in both directions. (10-Mbps transmit, and 10-Mbps receive.) This produces a theoretical 20-Mbps of throughput.

Full-duplex Ethernet circuitry permits simultaneous two-way traffic.

Full-duplex Requirements

In order to implement full-duplex Ethernet, you require the following:

Two full 10-Mbps or 100-Mps data paths.

Full-duplex Ethernet controllers or an Ethernet controller for each path.

Loopback and collision detection disabled.

Software drivers supporting two simultaneous data paths.

Adherence to Ethernet distance constraints:

10BaseT/100BaseTX (100 metres)

10BaseFL (2 kilometres)

100BaseFX (2 kilometres)

46) Identify reasons why the industry uses a layered model.

Most communications environments separate the communication functions and application processing. This separation of networking functions is called layering. For the OSI model, seven numbered layers indicate distinct functions. Within the Transmission Control Protocol/Internet Protocol (TCP/IP), for example, distinct functions fit into five named layers. Regardless of the number of layers, the reasons for this division of network functions include the following:

Divide the interrelated aspects of network operation into less complex elements.

Define standard interface for plug-and-play compatibility and multivendor integration.

Enable engineers to specialise to design and development efforts on modular functions.

Promote symmetry in the different internetwork modular functions so they interoperate

Prevent changes in one area from impacting other areas, so each area can evolve more quickly.

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