What network topology is generally used in WAN?—Vecloud

The topological structure of a computer network refers to the physical connection of network devices. The topological structure of the network mainly has three structures: bus network, ring network and star network, as well as other topological structures, such as: hybrid topology, distributed structure (mesh topology), tree structure, and honeycomb topology. .
1. Bus structure The
bus structure is a way to connect all end users using the same medium or cable, that is, the physical media connecting end users is shared by all devices.
In a point-to-point link configuration, half-duplex operation only needs to use a simple mechanism to ensure that two end users work in turn. In the point-to-multipoint mode, the access to the line is determined by the inquiry of the control end. But in the lan environment, all data stations are equal. One point to many points cannot be adopted. Instead, carrier sense multiple access with collision detection is used (it is a media access method used in a bus-sharing network). , Abbreviated as csma/cd).
This structure has the advantages of low cost, flexible network access for data end users, and the failure of a site or one end user does not affect the communication of other sites or end users.
The disadvantage is that only one end user can send data at a time, and the other end users must wait until they get the right to send. The media access acquisition mechanism is more complicated. However, due to the simple wiring requirements, easy expansion, end-user failure, additions and deletions do not affect the work of the entire network, it is the simplest one to use in the lan technology.
2. Star
structure The star structure is convenient for centralized control, because the communication between end users must pass through the central station. Because of this feature, it also brings advantages such as easy maintenance and safety, and the communication between other end users will not be affected when the end user equipment shuts down due to a failure. But the central system must have extremely high reliability, because once it is damaged, the entire system tends to be paralyzed.
3. Ring structure
Ring structure is used more in lan. The transmission medium in this structure goes from one end user to another end user until all end users are connected into a ring. This structure eliminates the dependence of end users on the central system during communication.
The characteristic of the ring structure is that each end user is connected to two adjacent end users, so there is a point-to-point link, which operates in a one-way manner, and is divided into upstream end users and downstream end users. User n is the upstream end user of user n+1, and n+1 is the downstream end user of n. If the n+1 end needs to send data to the n end, it will take almost a circle to reach the n end.
4. Hybrid topology The
hybrid topology is a network structure that combines a star structure or a ring structure and a bus structure. Such a topology can better meet the expansion of a larger network and solve the problem of the transmission distance of the star network. At the same time, it solves the limitation of the number of connected users in the bus-type network.
5. Distributed structure The
distributed structure of the network connects computers distributed in different locations through wires. Each device in the network has a point-to-point link connection. The distributed network structure has the following characteristics: Using decentralized control, even if a certain part of the entire network fails, it will not affect the operation of the entire network, so it has high reliability; the path selection adopts the shortest path algorithm, so the network delay time is small, and the transmission rate is high. The control is complicated; each node can directly establish a data link, and the information flow is the shortest; it is convenient for resource sharing within the entire network. The shortcomings are the long cables used for the connection lines and high cost; complex network management software; complex packet switching, path selection, and flow control; this structure is not used in general local area networks.
6. Tree structure network The
tree structure is a hierarchical centralized control network. Compared with the star type, its communication line is short in total length, lower in cost, easy to expand, and it is more convenient to find a path, but except for leaf nodes and their Outside the connected line, any node or its connected line failure will affect the system.
7. Cellular topology The
cellular topology is a commonly used structure in wireless local area networks. It is characterized by point-to-point and multi-point transmission of wireless transmission media (microwave, satellite, infrared, etc.). It is a wireless network suitable for city networks, campus networks, and enterprise networks.
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