● The TTL field was originally designed to hold a time stamp, which was decremented by each visited router. The datagram was (   ) when the value became zero. However, for this scheme, all the machines must have synchronized clocks and must know how long it takes for a datagram to go from one machine to another. Today, this field is used mostly to control the (   ) number of hops (routers) visited by the datagram. When a source host sends the datagram, it (   ) a number in this field. Each router that processes the datagram decrements this number by 1. If this value, after being decremented, is zero, the router discards the datagram.This field is needed because routing tables in the Internet can become corrupted.A datagram may travel between two or more routers for a long time without ever getting delivered to the (   ).This field limits the (   ) of a datagram.

（71）A．received

B.discarded

C.rejected

D.tansferred

（72）A．maximum

B.minimum

C.exact

D.certain

（73）A．controls

B.transmits

C.stores

D.receives

（74）A．switch

B.router

C.source host

D.destination host

（75）A．lifetime

B.moving time

C.receiving time

D.transmitting time

點擊注冊會員>>>即可獲取網絡工程師免費在線真題、觀看免費公開課！

真題自測：軟考各科目歷年真題及答案解析

更多資訊可關注希賽網軟考頻道，問題咨詢請撥打客服電話400-111-9811。