The metric assigned to each network depends on the type of protocol.Some simple protocol, like RIP, treats each network as equals. The（1） of passing through each network is the same; it is one（2）count. So if a packet passes through 10 network to reach the destination, the total cost is 10 hop counts. Other protocols, such as OSPF, allow the administrator to assign a cost for passing through a network based on the type of service required. A （3） through a network can have different costs (metrics). For example, if maximum（4） is the desired type of service, a satellite link has a lower metric than a fiber-optic line. On the other hand, if minimum（5）is the desired type of service, a fiber-optic line has a lower metric than a satellite line. OSPF allow each router to have several routing table based on the required type of Service.
（4）是（）
A.packet
B.throughput
C.error
D.number