局域网中使用的传输介质有双绞线、同轴电缆和光纤等。10BASE-T采用3类UTP，规定从收发端到有源集线器的距离不超过(41)m。100BASE-TX把数据传输速率提高了 10倍，同时网络的覆盖范围(42)。假设tPHY表示工作站的物理层时延，C表示光速，S表示网段长度，tR表示中继器的时延，在10BASE-5最大配置的情况下，冲突时槽约等于(43)。光纤分为单模光纤和多模光纤，与多模光纤相比，单模光纤的主要特点是(44)，为了充分利用其容量，可使用(45)技术同时传输多路信号。

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In low-speed network, it is usually adequate to wait for congestion to occur and then react to it by telling the source of packets to slow down. In high-speed networks, this approach often works poorly, because in the(71)between sending the notification and notification arriving at the source, thousands of additional(72)may arrive. In ATM network, a major tool for preventing(73)is(74)control. When a host wants a new virtual(75),it must describe the traffic to be offered and the service expected.

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To a router, a flow is a(66)of packets that share the same Characterstics, such as traveling the same(67),using the same(68),having the same kind of security, and so on. A router that supports the handling of flow labels has a(69)table. The table has an entry for each active flow label; each entry defines the(70)required by the corresponding flow label.

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