专业技术初级资格网络管理员基础知识2009年下半年网络管理员上午试题

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• 51● For （71） 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 （72） for every packet sent.Instead, when a connection is established, a route from the （73） machine to the destination machine is chosen as part of the connection setup and stored in tables inside the（74） . That route is used for all traffic flowing over the connection, exactly the same waythat the telephone system works. When the connection is released, the virtual circuit is alsoterminated. With connection-oriented service, each packet carries an （75） telling whichvirtual circuit it belongs to.

  A.connectionless

  B.connection-oriented

  C.datagram

  D.telegram

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