中英文资料
网。
4.4.2互联网
互联网是一个全球性的联结政府、学术、公司、公共领域和私人计算机系统的网络。它基于互联网的网络技术协议组件。这继承了由美国国防部开发研制的高等研究计划署网络(阿帕网)。互联网也是万维网(WWW)的通信主干。
4.4.3内部网和外部网
内部网和外部网是一个计算机网络的延伸部分，它通常是一个局域网。 内部网是一系列网络的集合，它使用网际协议和基于网际协议的工具，如浏览器和文件传输应用程序，他们由单一管理实体进行管理。管理实体只对授权的用户开放内联网。通常内部网是一个机构的内部网络。一个大的内联网一般会有至少一个网络服务器，为用户提供组织过的信息。
外部网被限制在单一的组织或实体的范围内，通常它也会被限制连接到一个或多个组织或实体。但不一定是受信任的组织或实体，例如公司的客户可能获得企业内部网的访问权限，同时从安全的观点来讲客户可能不会被认为是可信赖的。从技术上讲，外部网也被分类为CAN、MAN、WAN或者其他类型的网络。尽管外联网不能只包括单一的一个局域网，它必须拥有至少一个与外部网络的连接。
4.4.4覆盖网络
覆盖网络是一个建立在另一个计算机上面网络上面的虚拟网络。覆盖网络中的每个节点通过虚拟的或者逻辑上的链接相连，每个节点都对应一条路径，或者在底层网络通过许多物理链接来连接网络。
中英文资料
覆盖网络的样本: 在SONET光纤上的IP
中英文资料
Computer network
From Wikipedia, the free encyclopedia
\networks\redirects here. For the periodical, see Computer Networks (journal).
A computer network, often simply referred to as a network, is a collection of computers and devices interconnected by communications channels that facilitate communications among users and allows users to share resources. Networks may be classified according to a wide variety of characteristics. A computer network allows sharing of resources and information among interconnected devices. History
Early networks of communicating computers included the military radar system Semi-Automatic Ground Environment (SAGE) and its relative the commercial airline reservation system Semi-Automatic Business Research Environment (SABRE), started in the late 1950s.[1][2]
When Russia launched His SPUTNIK Satellite in Space In 1957.The American Started Agency Names ADVANCE RESEARCH PROJECT AGENCY (ARPA) & launched His 1st Satellite Within 18 Month After Establishment.Then Sharing Of The Information In Another Computer They Use ARPANET.And This All Responsibility On America's Dr.LIED LIEDER.Then in 1969,ARPANET Comes in INDIA And INDIAN Switched This Name To NETWORK. In the 1960s, the Advanced Research Projects Agency (ARPA) started funding the design of the Advanced Research Projects Agency Network (ARPANET) for the United States Department of Defense. Development of the network began in 1969, based on designs developed during the 1960s.[3] The ARPANET evolved into the modern Internet. Purpose
Computer networks can be used for a variety of purposes:
Facilitating communications. Using a network, people can communicate efficiently and easily via email, instant messaging, chat rooms, telephone, video telephone calls, and video conferencing.
中英文资料
Sharing hardware. In a networked environment, each computer on a network may access and use hardware resources on the network, such as printing a document on a shared network printer.
Sharing files, data, and information. In a network environment, authorized user may access data and information stored on other computers on the network. The capability of providing access to data and information on shared storage devices is an important feature of many networks.
Sharing software. Users connected to a network may run application programs on remote computers. Information preservation. Security.
Network classification
The following list presents categories used for classifying networks. Connection method
Computer networks can be classified according to the hardware and software technology that is used to interconnect the individual devices in the network, such as optical fiber, Ethernet, wireless LAN, HomePNA, power line communication or G.hn. Ethernet as it is defined by IEEE 802 utilizes various standards and mediums that enable communication between devices. Frequently deployed devices include hubs, switches, bridges, or routers. Wireless LAN technology is designed to connect devices without wiring. These devices use radio waves or infrared signals as a transmission medium. ITU-T G.hn technology uses existing home wiring (coaxial cable, phone lines and power lines) to create a high-speed (up to 1 Gigabit/s) local area network. Wired technologies
Twisted pair wire is the most widely used medium for telecommunication. Twisted-pair cabling consist of copper wires that are twisted into pairs. Ordinary telephone wires consist of two insulated copper wires twisted into pairs. Computer networking cabling consist of 4 pairs of copper cabling that can be utilized for both voice and data transmission. The use of two wires twisted together helps to reduce crosstalk and electromagnetic induction. The transmission speed ranges from 2