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（5）处应选择（） A.address。 identifier。 interface。 element。
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（4）处应选择（） A.connections。 resources.。 bridges。 routers。
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。
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（） A.routers。 stations。 servers。 switches。
论IRF技术在网络规划与设计中的应用 IRF的含义就是智能弹性架构（IntelligentResilientFramework），支持IRF的多台设备可互相连接起来形成一个"联合设备"，这台"联合设备"称为一个Fabric，而将组成Fabric的每个设备称为一个Unit。多个Unit组成Fabric后，无论在管理上还是在使用上，就成为了一个整体。它既可以随时通过增加Unit来扩展设备的端口数量和交换能力，从而大大提高了设备的可扩展性；同时也可以通过多台Unit之间的互相备份来增强设备的可靠性；并且整个Fabric作为一台设备进行管理，用户管理起来也非常方便。 请围绕"IRF技术在网络规划与设计中的应用"论题，依次对以下三个方面进行论述。 （1）简述你参与规划与设计过的计算机网络的概要和你所担任的工作。 （2）简述IRF技术的主要特点和优势。详细论述你是如何使用IRF技术进行网络规划与设计的，以及在你的方案中，如何体现出IRF技术的优点。 （3）根据系统应用情况，简要评述你所规划与设计的计算机网络存在的问题，以及如何改进。
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（）
