Border Gateway Protocol(BGP) is inter－autonomous system (71) protocol. BGP is based on a

Question

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 receives 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 router 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

Answer 1

正确答案：A,B,D,C,A
边界网关协议(BGP)是自治系统间的路由协议。BGP是基于路径选择的向量路由方法。距离向量路由作为自治系统间的路由不是一个好的选择,因为具有最小跳数的路由并不一定是最合适的路由。例如，我们不想一个数据包通过即使路径最短但不安全的路线，距离向量路由具有不确定性,因为它只告知了到达目的地路径的跳数，而没有真正定义具体的路径。如果接收路由器接收到了一个通过它本身来计算得到的距离向量广播包，那么显然它是被愚弄的。链路状态路由作为自治系统间的路由也不是一个好的选择，因为在使用链路状态路由时，整个互联网将要求每个路由器有一个庞大的链路状态资料库，这就需要花费大量的时间去为路由器计算其路由表。