The metric assigned to each network depends on the type of protocol. Some simple protocol, like RIP, treats each network as equals. The （71） of passing through each network is the same; it is one （72） 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 （73） through a network can have different costs (metrics). For example, if maximum （74） is the desired type of service, a satellite link has a lower metric than a fiber-optic line. On the other hand, if minimum （75） 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.
73（）
A．flow
B．window
C．route
D．cost
