【名词&注释】
数据传输、高频开关电源(high frequency switching power supply)、端口号(port number)、ATM交换机(atm switch)、长途电话(toll telephone)、主机名(name of controlling computer)、通信局(communication bureau)、开关电源系统
[单选题]ATM交换机按功能和用途可分为接入交换机和（）。
A. 专用交换机
B. 汇接交换机
C. 骨干交换机
D. 节点交换机
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举一反三：
[多选题]通信局(communication bureau)（站）所用高频开关电源系统均分负荷的方法有（ ）。
A. 限流并联
B. 限流串联
C. 主从均流
D. 自动平均均流
[单选题]下列关于TCP协议的描述中，错误的是（ ）。
A. T
B. CP是无连接的传输层协议
C. 使用校验和来检测传输差错
D. 提供可靠的数据传输服务
E. 具有流量控制和拥塞控制等功能
[单选题]我国用户进行国际长途电话直拨时，国际字冠是（67） 。
A. 00
B. 99
C. 100
D. 108
[单选题]为识别某计算机上的特定应用或服务，可使用（）。
A. 域名
B. 主机名(name of controlling computer)
C. IP地址和端口号
D. MA
E. C地址
[多选题]GPS 系统可以由（）组成。
A. GPS 卫星系统
B. 地球站
C. 地面控制系统
D. 用户设备
[单选题]ATM采用信元承载数据，在ATM中，信元的长度固定为53Byte，其中净荷是（）Byte。
A. 48
B. 40
C. 13
D. 5
[多选题]4G is one of those terms that keep coming back through marketing brochures for what the latest technologies happen to be in the cellphone market. Every carrier claims to have true 4G, and has been claiming that for years, regardless of what they actually use. The reason was simple because the real 4G specification, expected to be drafted by the International Telecommunication Union, was no where to be found. In fact, the ITU took way longer than being expected to come up with a decision, likely because of massive lobbying campaigns. After all, which company wants to have to redesign its entire network just to be able to keep saying they are 4G? Now however, they ITU has decided itself.What does this mean for carriers and users? First，let’s see what 4G really is. As expected, LTE is central to the ITU strategy,but more precisely,the organization went with LTE-Advanced,which is a stricter version of traditional LTE. To qualify as 4G，a network has to provide 100Mbps connections over wireless,and 1 Gbps over wired. The whole network has to be fully IPv6 compliant. Frequencies have to be variable over 40MHz to avoid interference. Finally, global roaming has to be seamless, along with transitions between wirless and wired connections. This is a real step forward, and a good decision, which ensures that real 4G services will meet a good level of services. Technically, LTE-Advanced is just one of two new standard that are now under the umbrella called IMT-Advanced. The other one is WiMAX 2 which is a further refinement of the WimMAX protocol. Based on the paragraph above，to qualify as 4G, a network has to satisfy （） criteria. The transitions between wireless and wired connections have to be （）. LTE-Advanced is a standard belonging to （）.
A. two
B. three
C. four
D. five A．limited
E. possible
F. seamless
G. deployed A．WiMAX
H. WiMAX 2
I. IPv6
J. IMT-Advanced
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