Shulou(Shulou.com)06/02 Report--

This article mainly introduces the types of data exchange technology, the article is very detailed, has a certain reference value, interested friends must read it!

There are three main types of data switching technology: circuit switching, message switching and packet switching. The advantage of circuit switching technology is that data transmission is reliable and fast, data will not be lost and the original sequence will be maintained; message switching mode is suitable for non-real-time communication services, such as telegram. Packet switching can effectively improve the delay phenomenon of message transmission, and the utilization rate of network channel is high.

There are three main types of data switching technology: circuit switching, message switching and packet switching.

Correlation

Communication subnet is a network which is interconnected by several network nodes and links according to a certain topology. These switching nodes in the middle are sometimes called switching devices, which do not process the data that flows through, but simply transfer data from one switching device to another until they reach the destination. A subnet is a path that provides a complete transmission path for all data entering the subnet, and the technology to achieve this data path is called "data exchange technology".

Generally, according to the different forwarding methods of the data entering the subnet implemented by the network nodes in the communication subnet, the data exchange mode can be divided into two categories: circuit switching and store-and-forward switching. There are three commonly used switching technologies: circuit switching, message switching and packet switching.

Circuit switching

The working process of circuit switching (Circuit Switching) is similar to that of telephone switching. Before two computers exchange data through the communication subnet, it is necessary to establish an actual special physical path through the line connection between the switching devices in the communication subnet.

The switching network in this way can provide a temporary special physical path for any incoming data, which is formed by the channel transfer of each node in space or time. A straight-through and exclusive physical line is established between the source host (output) and the host (receiver). Therefore, during the path connection, no matter how long the line is, the switching network provides data communication on the point-to-point link for a pair of hosts, that is, the devices at both ends of the connection monopolize the line for data transmission until the connection is released. The switching mode of the public telephone network is circuit switching. once the two parties establish a call, they can monopolize the line until the end of the call and release the connection, then other users can use this line.

The advantage of circuit switching technology is that the data transmission is reliable and fast, the data will not be lost and the original sequence will be maintained; its disadvantage is that the channel utilization is low, even during the interval of data transmission between the two sites, the circuit is not allowed to be used by other stations. Circuit switching is suitable for real-time, large and continuous data transmission.

The most important feature of circuit switching is the establishment of a dedicated data path between a pair of hosts. The communication process includes three processes: line establishment, data transmission and line release. It takes a certain amount of time to set up the call when the channel is established. Once the path is established, there is almost no delay on each node, so it is suitable for real-time or interactive conversation communication, such as digital voice, fax and other communication services. However, because when the path is established, the line is dedicated, even if it is idle, other users can not use it, so the line utilization is not high. Because each node (switching device) in the communication subnet can not store data, can not change the data content, and does not have the ability of error control, the whole system does not have the ability to store data. unable to find and correct data errors in the process of transmission, the system efficiency is low. On the basis of circuit switching, store-and-forward switching is proposed.

Message exchange

Message switching (Message Switching) means that each node (switching device) of the network first receives and stores the whole message (Message), and then selects the appropriate link to forward to the next node. Each node stores and forwards the message and finally arrives at the destination.

In the message exchange, the intermediate device must have enough memory to store the whole message completely, and then find out the next switching node to forward the message according to the header control information of the message. If there is no free link for the time being, the message will have to be temporarily stored and waiting to be sent. Therefore, a node is often uncertain about the delay caused by a message.

The message data is transmitted completely according to the relay in the switching network. Both sides of the communication do not know in advance the transmission path through which the message will go, but each message does go through a logical path. Because it works according to the relay mode, a message only occupies the resources of one link at any time, and does not have to occupy all the link resources on the path, which improves the sharing of network resources. Although the message exchange mode does not require the call to set up the line and release the line, each node takes a long time to store and forward the message data. Message exchange is suitable for non-real-time communication services, such as Telegraph, but not suitable for real-time or interactive services, such as voice, fax and so on. In addition, because the message exchange takes the whole message as the storage and forwarding unit, when the message transmission error needs to be retransmitted, the whole message must be retransmitted.

Packet switching

Packet switching, also known as packet switching (Packet Switching), belongs to storage and forwarding switching as well as message switching. The difference between the two lies in the length of the data units involved in the exchange. In a packet-switched network, the data to be exchanged between computers is not transmitted as a whole, but is divided into many data packets of the same size, which are called "Packet". Each packet not only contains a certain length of data to be transmitted, but also includes some control information, including the destination address at which the packet will be sent. The maximum length of a packet is usually limited to 1 000 to 2 000 bit. These data packets can arrive at the same destination address successively through different routers, and the data packets can be merged and restored after arriving at the destination to ensure that the received data is completely consistent with the transmitted data as a whole.

This mode of communication is similar to the "single-page post office" mode. Assuming that a single-page post office stipulates that each letter can only use one page of paper, the writer of a long letter must number each page and put it in a different envelope; after receiving the letter, the recipient must organize and merge it in the order of the stationery in order to read the complete letter.

In packet switching, according to the difference of transmission control protocol and transmission path in the network, it can be divided into two ways: Datagram (Datagram) packet switching and virtual circuit (Virtual Circuit) packet switching.

(1) Datagram packet switching. In Datagram mode, each packet is also called Datagram. Each Datagram has to choose a path in the process of transmission, and each Datagram can reach its destination according to a different path. At the sender, the packet order of each Datagram is different from the order in which each Datagram arrives at the destination. At the receiver, these datagrams are combined into a complete message in the order of packets.

(2) Virtual circuit packet switching. The virtual circuit mode attempts to combine the Datagram mode with the circuit switching mode to give full play to the advantages of the two methods to achieve the best data exchange effect. Before the packet is sent, the connection between the sender and the receiver does not need to be established in advance, while in the virtual circuit mode, a path must be established between the sender and the receiver before sending the packet. At this point, the virtual circuit mode is the same as the circuit switching mode. The whole communication process is divided into three stages: virtual circuit establishment, data transmission and virtual circuit removal. However, unlike circuit switching, the path established in the virtual circuit establishment phase is not a dedicated physical line, but only a path. In the process of forwarding each packet along this path, it still needs to be stored when it passes through each node. and wait for the queue output. After the path is established, each packet reaches its destination by this path. Therefore, in virtual circuit switching, each packet arrives at its destination in turn according to the packet order of the sender, which is different from Datagram packet switching.

Compared with message switching, packet switching divides the whole data to be transmitted into several packets, and each packet contains a lot of transmission control information, so the communication mode of packet switching will obviously reduce the efficiency of data communication. But packet switching has the following three advantages.

① communication lines are public, and each packet will not take up too long communication line time, which is conducive to the rational allocation of communication lines and takes into account the communication requirements of each host on the network.

Errors are inevitable in ② data transmission. If some packets have transmission errors, you only need to retransmit the packet instead of retransmitting the whole data, which is conducive to rapid data error correction.

③ can effectively improve the delay phenomenon of message transmission, and the utilization rate of network channel is high.

The above is all the contents of the article "what are the types of data exchange technologies?" Thank you for reading! Hope to share the content to help you, more related knowledge, welcome to follow the industry information channel!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.