计算机网络是一组互连的计算机，它们以无线方式(computers that are connected wirelessly )或通过电缆连接，以共享媒体或数据。网络上的计算机（也称为节点）可以共享资源，包括访问互联网(access to the internet)、打印机和文件服务器，或允许电子通信。
计算机网络由至少两台计算机组成，它们可以通过无线电波、电缆、卫星、电话线或红外光束连接起来。还有其他媒介或设备可以帮助不同的设备进行通信，例如交换机、路由器、网桥或集线器，它们被称为网络设备。
总之，这些硬件和软件相结合，使计算机联网成为可能，使得互连的设备可以共享信息(share information)、数据、资源和其他网络设备。
计算机网络的类型(Types of Computer Networks)
有两种主要类型的计算机网络：有线和无线。
有线(Wired)网络使用介质在计算机（节点）之间传输数据，而无线网络使用无线电波在空中传输数据和信息，以便设备无需电缆即可连接到网络。
有线网络提供更高的速度、安全性和可靠性，而无线网络提供更大的灵活性、可扩展性和移动性。
然而，网络也可以根据其拓扑、设计、构建、规模和环境进行分类。
计算机网络拓扑(Computer Network Topology)
拓扑只是连接设备的布局，更像是与您看到的物理布局不对应的网络结构或虚拟形状。
例如，家庭或办公室网络中的计算机可能排列成方形或圆形，但拓扑不一定相同。
计算机(Computer)网络拓扑分为五种基本类型：总线型、星型、环形、网状和树型，但也有混合构建将这些拓扑中的两个或多个组合在一起以形成更复杂的网络。
总线网络拓扑
这种类型的计算机网络共享一个主干——一根电缆——将所有网络设备连接在一起。电缆充当共享通信的媒介，设备通过接口连接器接入或连接该电缆。任何与同一网络上的其他设备通信的设备都会广播一条消息，其他设备会看到(other devices will see)该消息，但它只会被预期的接收者接受和处理。
这种类型最适合使用少量设备，因为当添加数十台计算机时，其性能会受到影响。另外，如果电缆出现故障，您将无法使用网络。
星型网络拓扑
此网络拓扑具有一个集线器节点，所有设备都连接到该节点。它可以是网络交换机、集线器或路由器，但需要更多电缆，这与总线拓扑不同。
但是，如果电缆发生故障，它不会影响整个局域网；它只是取消对其中一台连接计算机的访问权限。但是，如果集线器节点发生故障，则整个网络都会受到影响。
网状网络拓扑
此网络拓扑通过点对点连接将模式互连。数据(Data)通过路由传输，节点通过路由逻辑计算出数据包到达目的地的最短距离。
它还使用了泛洪方法，不需要任何路由逻辑，而是将数据发送到网络中的所有节点。
网状(Mesh)拓扑通常用于无线网络，与总线拓扑相比，一台计算机的故障不会导致数据传输或网络本身的中断。这种类型通常出现在办公室或学校校园中。
环网拓扑
在这种网络拓扑中，计算机以环形或圆形形式连接，每个设备都有两个邻居用于通信目的。连接第一个和最后一个节点以将环路链接在一起，以便所有消息在到达目的地的途中通过一个环以相同的方向传播。这种拓扑结构可以有效地维持大
树形网络拓扑
树形网络拓扑是一种混合了总线和星形拓扑的网络结构。它由连接到总线上的多个星形拓扑组成，形成具有许多分支的树状形状，通常用于广域网，以承受分散的设备和未来的网络扩展。
混合网络拓扑
这种计算机网络拓扑结构由两个或多个拓扑结构组成，通常用于部门之间具有不同网络拓扑结构的大型企业。当所有都连接在一起时，它被称为混合拓扑。它们的共同点是灵活性和可扩展性，使它们适用于更大的网络。
通过了解网络拓扑类型和集线器、路由和广播等网络概念，您可以更轻松地构建家庭或办公室计算机网络。
计算机网络如何工作(How a Computer Network Works)
计算机网络以两种基本形式设计：客户端-服务器和点对点。
客户端-服务器网络包括存储文件、网页、电子邮件和客户端设备访问的应用程序的集中式服务器计算机。这些在商业中很常见。
相反，在点对点网络设计中，所有设备都支持类似的功能，并且在家庭中普遍使用。
要使计算机网络正常工作，您需要物理基础设施，例如路由器、交换机和无线接入点、操作设备的固件以及管理、监控和保护设备的软件。
网络还依赖标准协议来传达不同的数据类型或统一执行离散功能，而与设备无关。常见的协议包括家庭网络(found in home networks)和互联网中的TCP/IP
但是，并非所有设备都可以加入网络，除了那些具有物理连接到其他设备的特殊通信硬件的设备，而其他设备则根本不支持网络。
设备通常作为客户端或服务器工作。例如，您的手机、平板电脑、PC 或网络打印机(network printer)可以用作网络客户端。
另一方面，服务器保存客户端通常请求和使用的数据。它可以是游戏服务器或网络服务器，通常由大型磁盘存储、大量内存和高性能处理器组成。
但是，要使网络正常运行，您将需要一个网络集线器，它使节点能够直接将数据发送到其他节点，网络交换机为连接的节点打开多条路径以相互通信。
您还需要一个网络路由器(network router)来扩展网络交换机功能、中继器来接收通过网络连接发送的信号并使其能够传播得更远，以及将不兼容的网络链路连接在一起的网桥。
加强数据共享(Enhance Data Sharing)
随着今天的计算机被应用于多个领域，互联网的使用正在零星地改善，所有阶层的人都可以从其中的有用信息中受益。
因此，需要网络间计算机，尤其是对于组织和企业，以进一步帮助数据检索和共享，以及有效地使用和管理计算资源。
HDG Explains: What Is a Computer Network?
A computer network is a set of interconnected computers that are connected wirelessly or via cabling for the purpose of sharing media or data. The computers on a network, also known as nodes, can share resources including access to the internet, printers, and file servers, or allow electronic communications.
A computer network consists of at least two computers that may be linked via radio waves, cables, satellites, telephone lines, or infrared light beams. There are other mediums or devices that help the different devices communicate such as a switch, router, bridge or hub, which are known as network devices.
Altogether, these hardware and software combine to make computer networking possible such that the interconnected devices can share information, data, resources, and other network devices.
Types of Computer Networks
There are two main types of computer networks: wired and wireless.
Wired networks use a medium to transport data between the computers (nodes), while wireless networks use radio waves to transport data and information over the air so that devices can connect to the network without cables.
While wired networking offers greater speed, security and reliability, wireless networks offers more flexibility, scalability and mobility.
However, networks can also be classified based on their topology, design, build, scale and environment.
Computer Network Topology
The topology is simply the layout of the connected devices, more like a structure or virtual shape of the network that doesn’t correspond to the physical layout you see.
For instance, the computers in a home or office network may be arranged in a square or circular style, but the topology isn’t necessarily the same.
Computer network topologies are classified into five basic types: bus, star, ring, mesh and tree, but there are hybrid builds that combine two or more of these topologies to form a more complex network.
Bus Network Topology
This type of computer network shares a backbone – a single cable – that connects all the network devices together. The cable acts as a medium for shared communication that the devices tap into or attach to with an interface connector. Any device that communicates with another on the same network broadcasts a message, which other devices will see, but it’ll only be accepted and processed by the intended recipient.
This type is best with few devices, as its performance is affected when more than a few dozen computers are added to it. Plus, if the cable fails, you can’t use the network.
Star Network Topology
This network topology features a hub node to which all devices connect. It can be either a network switch, hub or router, but requires more cable, unlike the bus topology.
In case of a cable failure though, it doesn’t affect the entire local area network; it just takes down access for one of the connected computers. However, if the hub node fails, then the whole network gets affected.
Mesh Network Topology
This network topology interconnects the modes through a point-to-point connection. Data is transmitted via routes, where the nodes work out the shortest distance the packets can use to get to their destination, by using routing logic.
It also uses the flooding method, which doesn’t need any routing logic but sends data to all the nodes in the network.
Mesh topology is commonly used for wireless networks and compared to the bus topology, failure of one computer doesn’t cause a break in data transmission or in the network itself. This type is usually found in offices or school campuses.
Ring Network Topology
In this network topology, computers are connected in a ring or circular format, with each device having two neighbors for communication purposes. The first and last nodes are connected to link the loop together such that all messages travel in the same direction through a ring on the way to their destination. This topology can effectively sustain large
Tree Network Topology
The tree network topology is a network structure that’s a hybrid of the bus and star topologies. It consists of multiple star topologies joined onto a bus to form a tree-like shape with its many branches, and is commonly used with wide area networks to withstand spread-out devices and future network expansion.
Hybrid Network Topology
This computer network topology comprises of two or more topologies, and is commonly used in larger enterprises whose departments have different network topologies from one another. When all are connected together, it is referred to as a hybrid topology. The common thing they have is flexibility, and scalability that makes them suitable for larger networks.
By understanding the type of network topologies and networking concepts like hubs, routes, and broadcasts, it’ll be easier for you to build a home or office computer network.
How a Computer Network Works
A computer network is designed in two basic forms: client-server and peer-to-peer.
The client-server network comprises centralized server computers that store files, web pages, email, and applications that client devices access. These are commonly used in business.
Conversely, in a peer-to-peer network design, all the devices support similar functions, and are commonly used in homes.
For a computer network to work properly, you’ll need physical infrastructure such as routers, switches, and wireless access points, the firmware to operate the equipment, and the software to manage, monitor and secure it.
Networks also rely on standard protocols to communicate different data types or perform discrete functions uniformly, regardless of the equipment. The common protocols include TCP/IP that’s found in home networks and on the internet.
Not all devices can join a network though, except those with special communications hardware that physically connect to other devices, while others don’t support networking at all.
Devices generally work as either a client or a server. For example, your phone, tablet, PC or network printer can function as a network client.
A server, on the other hand, holds the data that the client generally makes requests for and consumes. It can be a game server or web server, and usually consists of large disk storage, lots of memory and high performance processors.
For the network to run properly though, you’re going to need a network hub, which enables nodes to send data directly to other nodes, network switch to open up multiple paths for connected nodes to communicate with each other.
You’ll also need a network router to expand the network switch capabilities, repeater to receive signals sent across the network connection and enable them to travel further, and network bridge that connects incompatible network links together.
Enhance Data Sharing
With computers today being applied to multiple fields, and internet usage is sporadically improving such that all classes of people benefit from the useful information therein.
There’s therefore a need to inter-network computers, especially for organizations and enterprises, to further help in data retrieval and sharing, plus efficiently using and managing computing resources.
