设某单位路由器建立了以下的路由表，若收到分组的目的IP地址为128.96.37.151，则转发的端口是(63)，若收到分组的目的IP是128.96.35.151，则转发的端口是(64)，若该路由器是该单位与Internet连接的路由器，则该单位分得的IP地址是(65)。在一个网络中子网数目划分增多时，可供分配给主机的正常IP地址总数会(66)。在将主机地址设置为192.168.1.2时，则主机访问Internet时(67)。

目的IP          子网掩码      转发端口

 128.96.36.0      255.255.255.128    E1

 128.96.36.128     255.255.255.128    E2

 128.96.37.0      255.255.255.128    R2

 128.96.37.128     255.255.255.128    R3

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While the Internet is inherently insecure, businesses still need to preserve the privacy of data as it travels over the network. To help do that, the Internet Engineering Task Force an international group of network designers, operators, vendors, and researchers concerned with the evolution of(71)has developed a suite of(72)called Internet Protocol Security(IPSec).

 IPSec creates a standard platform. to develop secure networks and electronic(73)between two machines. Secure tunneling via IPSec creates(74)connections in a network through which data packets can move. It creates these tunnels between remote users and within a local network. It also(75)each data packet in a new packet that contains the information neccessary to set up, maintain and tear down the tunnel when it's no longer needed.

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One of the difficulties in building an SQL-like query lange for the Web is the absence of a database schema for this huge, heterogeneous repository of information. However, if we are interested in HTML documents only, we can construct a virtual(66)from the implicit structure of these files. Thus, at the highest level of(67), every such document is identified by its Uniform. Resource Locator(URL), has a title and a text Also, Web servers provide some additional information such as the type, length, and the last modification date of a document. So, for data mining purposes, we can consider the site of all HTML documents as arelation:

 Document(url,(68), text, type, length, modify)

 Where all the(69)are character strings. In this framework, anindividual document is identified with a(70)in this relation. Of course, if some optional information is missing from the HTML document, the associate fields will de left blank, but this is not uncommon in any database.

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