●Most IP layer-based proxy mechanisms, such as network address translation (NAT), only support uni-directional proxy, from the internal network to external network (the Internet). The proxy establishes the communication channel by __(66)__ IP addresses. The IP addresses must be __(67)__. These proxy mechanisms prevent applications that must establish return data channels from establishing their data channels, such as, multimedia applications. IP layer-based proxy mechanisms need additional software __(68)__ for each application that uses __(69)__ channels. SOCKS identifies communication targets through domain names, overcoming the restriction of using private IP addresses. SOCKS can use domain names to establish communication between separate LANs, with __(70)__ IP addresses.

试卷相关题目

• 1●设有程序段i=1;while (i<=n)i=i*2;上面程序段的时间复杂度为__(65)__。

  A.O(n)

  B.O(log n)

  C.O( nlog n)

  D.O(n2)

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• 2●设二维随机变量（X，Y）服从N（0，0，1，1，0）正态分布，Φ(x)为标准正态分布函数，下列说法不正确的是__(64)__。

  A.随机变量 X 和 Y 均服从 N(0，1) 分布

  B.随机变量 X 和 Y 相互独立

  C.X 和 Y 的联合分布函数为Φ(x)与Φ(y)的乘积

  D.Cov（X，Y）=1

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• 3●若对所有 f>j，aij=O(i=1，2，…，n；j=1，2，…，n)，则称矩阵 A=(ay)n×n 为上三角矩阵。设 Mn(R) 表示实数集R上全体 n×n 阶上三角矩阵的集合，“*”表示矩阵乘法，则 <Mn(R)，*> 为__(62)__。

  A.可交换独异点

  B.非可交换的独异点

  C.非可交换的群

  D.阿贝尔群

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• 4●设有一台计算机，它有一条加法指令，每次可计算三个数的和。如果要计算 79 个数的和，至少要执行的加法指令次数为__(61)__。

  A.37

  B.38

  C.39

  D.40

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• 5●设 Rl 和 R2 为非空集 A 上的任意二元关系，“¤”表示关系的复合运算，如下断言中正确的是__(60)__。

  A.Rl¤R2 = R2¤R1

  B.若 Rl 和 R2 均为对称的，则 Rl 和 R2 也为对称的

  C.若 Rl 和 R2 均为传递的，则 Rl 和 R2 也为传递的

  D.对自然数集 N 上的二元关系 R{|x∈N∧y∈N∧(x≠y)}，R 的传 递闭包 t(R)=N×N

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• 6●The approach we propose is a system-oriented methodology for knowledge acquisition This orientation emphasizes ongoing documentation throughout each cycle and technique applied. Program-wide documentation is suggested, both for the purpose of internal __(71)__ and for later verification and __(72)__ efforts. The documentation system we propose includes a central "knowledge acquisition __(73)__ " which is __(74)__ to reflect knowledge acquisition plans, session nodes, and domain expert participation. Specifically, __(75)__ within the database system include knowledge acquisition forms, which document plans for, and notes from,knowledge acquisition session, domain expert file, and rule content forms.

  A.interchange

  B.interface

  C.communication

  D.message

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