动态主机配置协议DHCP是对BOOTP协议的扩充，DHCP与BOOTP的主要区别是 DHCP具有(26)机制。DHCP协议支持的中继代理(Relay Agent)是(27)，它可以在不同的网段之间传送报文。DHCP具有多种地址分配方案，对于移动终端(比如笔记本电脑)最适合的分配方案是(28)。使用Windows2000操作系统的DHCP客户机，如果启动时无法与DHCP服务器通信，它将(29)。因为DHCP报文是装入(30)数据单元中传送的，所以它是不安全的。

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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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