在网络系统设计时,不可能使所有设计目标都能达到最优,下列措施中较为合理的是( )。
A.尽量让最低建设成本目标达到最优
B.尽量让最短的故障时间目标达到最优
C.尽量让最大的安全性目标达到最优
D.尽量让优先级较高的目标达到最优
Network Addres Translation(NAT) is an Internet standard that enbles a local-area network to use one set of IP addresses for internet traffic and another set of ( ) IP addresses for external traffic. The main use of NAT is to limit the number of public IP addresses that an organization or company must use, for both economy and ( ) purposes. NAT remaps an IP address space into another by modifying network address information in the ( ) header of packets while they are in transit across a traffic routing device. It has become an essential tool in conserving global address space in the face of ( ) address exhaustion. When a packet traverses outside the local network, NAT converts the private IP address to a public IP address. If NAT runs out of public addresses,the packets will be dropped and ( )"host unreachable"packets will be sent.
(1) A. local
B. private
C. public
D. dynamic
(2) A. political
B. fairness
C. efficiency
D. security
(3) A.MAC
B. IP
C.TCP
D. UDP
(4) A. IPv4
B. IPv6
C. MAC
D. logical
(5) A. BGP
B. IGMP
C. ICMP
D. SNMP