astute service providers realize that the continued support of legacy X.25 and asynchronous network element using separate operations network is cost (141) . For example, the maintenance of multiple networks can require additional staff. Often, this staff must be trained on multiple vendor technologies, sometimes requiring parallel groups specializing in each (142) . Hence, additional maintenance procedures must be maintained and administrative records are (143) . The duplication of transport facilities to carry (144) network traffic is an inefficient use of resources. And not surprisingly, more technologies installed in a central office means the necessity for more physical space and an increase in power connections and power consumption, migration of these (145) network elements to IP-based DCns is alogical strategy.
A．traditional
B．dominancy
C．redundancy
D．legacy
参考答案：D
解析：
[分析]： 聪明的供应商认识到，昂贵的成本不允许他们继续使用分隔的业务网络支持老版本的X.25协议和异步网络元素。例如，维护多个网络需要更多的人员。通常情况下，这些人员必须接受多家提供商的培训，有时甚至需要在每个平台上安排多个并行的工作团队。因此，必须维持额外的维护过程，且复制多个管理记录。成倍的传输设备用在交叉的网络通信中，这是资源的无效使用。而且，毫不奇怪的是，更多的技术安装在一个中心办公室，这意味着需要更大的物理空间，增大的电力连接和消耗。因此，把这些老的网络设备移植到基于IP的数据通信网络中是不符合逻辑的策略。