(第3空)routing in circuit-switching networks has traditionally involved a static routing strategy with the use of( )paths to respond to increased load . modern routing strategies provide more adaptive and flexible approaches . the routing function of a packet-switching network attempts to find the least-cost route through the network , with cost based on the number of ( ),expected delay , or other metrics in virtually all packet-switching networks , some sort of adaptive routing technique is used . adaptive routing algorithms typically rely on the( )of information about traffic conditions among nodes . in most cases , adaptive strategies depend on status information that is( )at one place but used at another . there is a tradeoff here between the quality of the information and the amount of( ). the exchanged information is itself a load on the constituent networks, causing a performance degradation.