Knowledge sharing about the computer network one ~

Computer network These basic knowledge, previously learned, but it is love play never learn, so basically no impression, now normal re-fill.

The so-called network is a series of devices that can be used to communicate with each other. In this definition, a device can be a host (or another salutation, end system), such as a mainframe computer, a desktop, a laptop, a workstation, a mobile phone, or a security system. In this definition, the device can also be a connecting device, such as a router to connect a network to another network, a switch that connects different devices, or a modem that changes the form of data, and so on.

LAN (lan,local area Network) and WAN (wan,wide area Network), the difference is in the scope, the local area network is usually limited in size, across an office, a building or a campus, and the wide area network has a greater geographical span, can span a town, A state, a country, even across the world. The local area network interconnects the host, and the WAN interconnects connected devices such as switches, routers, or modems.

When two networks connect to each other, they form an internetwork, or Internet, which is a internetwork.

The internet can be layered as a backbone network, a supplier network, and a customer network. At the top level, the backbone is owned by communications companies, which are interconnected through a number of complex switching systems. We refer to these switching systems as network peering junctions (peering point). On the second floor, there are smaller networks, called vendor networks, that pay for the use of some of the backbone's services. These vendor networks are connected to the backbone and sometimes to other vendor networks. On the edge of the Internet, there are networks that really use Internet-based services, which are customer networks that pay for services from vendor networks.

Backbone and supplier networks are also known as Internet Service Providers (ISPs), which are often referred to as international Internet service providers, and the supplier network is known as a domestic or regional Internet service provider.

The internet connects large and small networks with each other by connecting devices to form the basic structure. Then, if you just connect the parts together, it's obvious that nothing will happen. In order to generate communication, both hardware and software equipment are required. It's like when you're doing a complex calculation, we need both computers and programs. The combination of these hardware and software is coordinated through protocol layering.

The protocol defines the rules that transmitters, receivers, and all intermediate devices must adhere to to ensure effective communication. Simple communication may require only a simple protocol, and when communication becomes complex, it may be necessary to assign the task to a different protocol layer, in which case we need a protocol, or protocol layering, for each protocol layer.

Protocol layering allows us to simplify large tasks into smaller, simpler tasks. This is a modularity, where modularity refers to a separate protocol layer. A protocol layer (module) can be defined as a black box with input and output without considering how the input will be output.

Another advantage of protocol layering is the ability to separate services from their implementations. Each tier uses a lower level of service and provides services to a higher tier, and we don't have to consider how that layer is implemented.

Another advantage of protocol layering is that because communication systems often have not only two-end systems, but also intermediate systems that require only a few protocol tiers rather than all protocol tiers, the entire system becomes more complex if we do not use protocol layering, because then we have to make every system as complex as the end system.

Protocol layering needs to follow the principle: 1, each protocol layer can be opposite and the opposite direction of work; 2, in a protocol hierarchy, two objects in each layer must be identical.

This article mainly introduces the introduction of protocol layering, what is the network, why the protocol layered in the network to pass information.

Knowledge sharing about the computer network one ~