For (1) service, we need a virtual-circuit subnet. Let us see how that works. The idea behind virtual circuits is to avoid having to choose a new (2) for every packet sent. Instead,when a connection is established, a route from the(3) machine to the destination machine is chosen as part of the connection setup and stored in tables inside the (4) . That route is used for all traffic flowing over the connection, exactly the same way that the telephone system works.When the connection is released, the virtual circuit is also terminated. With connection-oriented service, each packet carries an (5) telling which virtual circuit it belongs to.空白（3）处应选择（） A.source。 route。 destination。 host。
For (1) service, we need a virtual-circuit subnet. Let us see how that works. The idea behind virtual circuits is to avoid having to choose a new (2) for every packet sent. Instead,when a connection is established, a route from the(3) machine to the destination machine is chosen as part of the connection setup and stored in tables inside the (4) . That route is used for all traffic flowing over the connection, exactly the same way that the telephone system works.When the connection is released, the virtual circuit is also terminated. With connection-oriented service, each packet carries an (5) telling which virtual circuit it belongs to.空白（2）处应选择（） A.processor。 device。 route。 terminal。
For (1) service, we need a virtual-circuit subnet. Let us see how that works. The idea behind virtual circuits is to avoid having to choose a new (2) for every packet sent. Instead,when a connection is established, a route from the(3) machine to the destination machine is chosen as part of the connection setup and stored in tables inside the (4) . That route is used for all traffic flowing over the connection, exactly the same way that the telephone system works.When the connection is released, the virtual circuit is also terminated. With connection-oriented service, each packet carries an (5) telling which virtual circuit it belongs to.空白（1）处应选择（） A.connectionless。 connection-oriented。 datagram。 telegram。
Both bus and tree topologies are characterized by the use of multipoint (1).For the bus, all stations attach, through appropriate hardware (2) known as a tap, directly to a linear transmission medium, or bus. Full-duplex operation between the station and the tap allows data to be transmitted onto the bus and received from the(3). A transmission from any station propagates the length of the medium in both directions and can be received by all other (4). At each end of the bus is a (5) , which absorbs any signal, removing it from the bus.空白（3）处应选择（） A.tree。 bus。 star。 ring。
论校园网／企业网的网络规划与设计 校园网（或企业网）是计算机网络的一大分支，有着非常广泛的应用及代表性。对于校园网／企业网，完备的应用是关键，而稳定可靠的网络是基础，完善的安全和管理手段是保障。由于学校／企业的类型和规模的不同，校园网／企业网的规划设计有着多种解决方案。校园网的规划、设计、硬件建设、软件建设以及网络的使用、扩充等都要从全局、长远的角度出发，充分考虑网络的安全性、易用性、可靠性和经济性等。 请围绕"论校园网／企业网的网络规划与设计"论题，依次对以下三个方面进行论述。 （1）概要叙述你参与设计实施的网络项目以及你所担任的主要工作。 （2）具体讨论在校园网／企业网网络规划与设计中的主要工作内容和你所采用的原则、方法和策略，以及遇到的问题和解决措施。 （3）分析你所规划和设计的校园网／企业网网络的实际运行效果。你现在认为应该做哪些方面的改进以及如何加以改进。
Both bus and tree topologies are characterized by the use of multipoint (1).For the bus, all stations attach, through appropriate hardware (2) known as a tap, directly to a linear transmission medium, or bus. Full-duplex operation between the station and the tap allows data to be transmitted onto the bus and received from the(3). A transmission from any station propagates the length of the medium in both directions and can be received by all other (4). At each end of the bus is a (5) , which absorbs any signal, removing it from the bus.
空白（4）处应选择（）
