The term topology is borrowed from geometry. Network topology is the shape of the network, or the physical connectivity of the network. Network topology refers to the physical layout of various devices interconnected by transmission media, that is, the method used to connect computers and other devices in the network. The topology diagram shows the network configuration of network servers and workstations and their connections.
There are many types of network topologies, including star structure, ring structure, bus structure, distributed structure, tree structure, and mesh structure. , honeycomb structure, hybrid structure, etc.
1. Star structure
The star structure is the oldest connection method. The phones that everyone uses every day belong to this structure. Generally, network environments are designed as star topology. Star network is one of the most widely used network topology designs.
Star structure means that each workstation is connected into a network in a star manner. The network has a central node, and other nodes (workstations, servers) are directly connected to the central node. This structure is centered on the central node, so it is also called a centralized network.
2. Ring structure
The ring structure is commonly used in LAN. The transmission media in this structure goes from one end user to another until all end users are connected into a ring. Data is transmitted between nodes in one direction in the ring, and information is passed from one node to another. This structure significantly eliminates end-user communication dependence on the central system.
The characteristics of the ring structure are:
● Each end user is connected to two adjacent end users, so there is a point-to-point link, but it is always in a unidirectional manner Operation, so they are called upstream users and downstream users;
● Information flow flows in a fixed direction in the network. There is only one road between two nodes, so the control of path selection is simplified. ;
● Each node on the ring is under bootstrap control, so the control software is simple;
● Since the information source passes through each node serially in the ring, when the node in the ring When there are too many, it will inevitably affect the information transmission rate and prolong the response time of the network;
● The loop is closed and is not easy to expand;
● Reliability is low. If one node fails, it will Causes the entire network to be paralyzed;
● It is difficult to maintain and locate branch node faults.
3. Bus structure
The bus structure is a way to connect all end users using the same media or cable. That is to say, the physical media connecting the end users is All devices are shared, each workstation has an equal status, and there is no central node control. Information on the public bus is mostly transmitted serially in the form of baseband. The transmission direction always starts from the node that sends the information and spreads to both ends, just like the information transmitted by a broadcast station. The information is the same, so it is also called a broadcast computer network. When receiving information, each node performs an address check to see if it matches its own workstation address. If it matches, it will receive information from the Internet.
4. Distributed structure
A distributed structure network is a network form that interconnects computers distributed in different locations through lines. The distributed structure network has the following characteristics: due to the use of 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 shortest path algorithm for path selection in the network , so the online delay time is small, the transmission rate is high, but the control is complicated; data links can be directly established between each node, and the information process is the shortest; it facilitates resource sharing within the entire network. Disadvantages include long cables for connecting lines and high cost; complex network management software; complex packet switching, path selection, and flow control; this structure is not used in general LANs.
5. Tree structure
The tree structure is a hierarchical centralized control network. Compared with the star structure, its total length of communication lines is shorter and the cost is lower. Low, nodes are easy to expand, and finding paths is more convenient. However, in addition to leaf nodes and their connected lines, the failure of any node or its connected lines will affect the system.
6. Mesh structure
The mesh topology mainly refers to the interconnection of nodes through transmission lines, and each node is connected to at least two other nodes. Mesh topology has high reliability, but its structure is complex, expensive to implement, difficult to manage and maintain, and is not commonly used in local area networks.
7. Cellular structure
The cellular topology is a commonly used structure in wireless LAN. It uses wireless transmission media (microwave, satellite, infrared, etc.) point-to-point. It is characterized by multipoint transmission and is a wireless network suitable for city networks, campus networks, and enterprise networks.
8. Hybrid structure
A network topology that combines two or more network topologies is called a hybrid topology (some called a hybrid structure).
This network topology is a network structure that combines star structure and bus structure network. This topology can better meet the expansion of larger networks and solve the limitations of star network in transmission distance. At the same time, it solves the limitation of the number of connected users in the bus-type network. This network topology takes into account the advantages of star network and bus network, and makes up for the shortcomings to a certain extent.
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