Border Gateway Protocol（BGP) is inter－autonomous system （71) protocol. BGP is based on a
Border Gateway Protocol(BGP) is inter-autonomous system (71) protocol. BGP is based on a routing method called path vector routing. Distance vector routing is not a good candidate for inter-autonomous system routing because there are occasions on which the route with the smallest (72) count is not the preferred route. For example, we may not want a packet through an not secure even though it is the shortest route. Also, distance vector routing is unstable due to the fact that the routers announce only the number of hop counts to the destination without actually defining the path that leads to that (73) ．A router that recevives a distance vector advertisement packet may be fooled if the shortest path is actually calculated through the receiving router itself. Link (74) routing is also not a good candidate for inter-autonomous system routing because an Internet is usually too big for this routing method. To use link state routing for the whole internet would require each routex to have a huge link state database. It would also take a long time for each router to calculate its rousting (75) using the Dijkstra algorism.
（71）
A. routing
B. switching
C. transmitting
D. receiving
(72)
A. path
B. hop `
C. route
D. packet
(73）
A. connection
B. window
C. source
D. destination
(74)
A. status
B. search
C. state
D. research
(75）
A. table
B. state
C. metric
D. cost
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参考答案：A,B,D,C,A参考译文边界网关协议(BGP)是自治系统之间的路由协议。BGP基于一种叫做通路矢量路由的路由算法。距离矢量路由算法对于自治系统之间的路由选择不是一种好方法，因为会出现一种情况，最小跳步数路由并不是所期望的路由。例如，我们不希望分组通过一个不安全的自治系统，虽然它是最短路由。同时，距离矢量路由不合适还由于下面的事实，路由器只宣布到达目标的跳步数，而没有实际定义到达那个目标的通路。如果要计算的最短通路实际上通过接收路由器本身，则接收到距离矢量公告分组的路由器就被欺骗了。对于自治系统间的路由，链路状态算法也不是好的选项，因为互联网对于这种路由方法是太大了。把链路状态算法用于整个互联网，则要求每一个路由器维护一个巨大的链路状态数据库。这就要求每一个路由器花费很长时间根据Dijkstra算法计算它的路由表。参考答案(71)A(72)B(73)D(74)C(75)A