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 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 （75） telling which

virtual circuit it belongs to.

（71）A. connectionless B. connection-oriented C. datagram D. telegram

（72）A. processor B. device C. route D. terminal

（73）A. source B. route C. destination D. host

（74）A. connections B. resources C. bridges D. routers

（75）A. address B. identifier C. interface D. element