Understand the development history of Data Exchange Technology

The data exchange technology plays an important role in the exchange technology. Here we mainly introduce the development history of the Data Exchange Technology. As an important implementation of human information interaction, switch devices play a role in Intercommunication. The development of data exchange technology is always dependent on the development of human information needs, formats and technologies for transmitting information, and control technology.

From telephone exchange to today's data exchange and integrated business digital exchange, data exchange technology has gone through the process of manual exchange to automatic exchange. The demand for broadband services such as videophone, visual text, image communication, and multimedia will also greatly promote asynchronous transmission technology (ATM) and Synchronous Digital series (SDH) and Broadband User Access Network Technology is constantly improving and widely used. From the development history of data exchange technology, data exchange has gone through the development process of circuit exchange, Packet Exchange, group exchange and integrated business digital exchange.

I. Circuit Switching

Since Bell invented the telephone in 1876, with the increasing social demand and the continuous development of communication technology, circuit switching technology started from the initial manual connection mode, with the transformation of electromechanical and electronic automatic switching, storage Program Control Simulation and digital switching, third-party programmable switching, and other technologies, the integrated multimedia format communication Softswitch technology is being developed.

With the rapid development of electronic technology, especially semiconductor technology, electronic technology is introduced into switches. Such switches are called electronic switches. Initially, electronic technology was introduced into the control part of the vswitch, while mechanical contacts were still used in the traffic part, resulting in "semi-electronic switches" and "quasi-electronic switches ". Only after the further development of micro-electronics and digital technology has the rapid development of all electronic switches started.

The birth of the first electronic computer in and has had a huge impact on the development of exchange technology. In the late 1960s S, the pulse coding modulation (PCM) technology was successfully applied in communication transmission systems, which has brought great benefits to the quality of calls and cost reduction of line equipment. With the rapid development and wide application of digital communication and p c m technology, the idea of directly exchanging p c m information has emerged. In 1970, France first successfully opened the world's first program-controlled digital exchange system in Lanion, marking the entry of exchange technology from traditional analog exchange to the digital exchange era. The program-controlled digital exchange technology uses PCM Digital Transmission and digital exchange, which is very suitable for digital information applications, in addition to ordinary telephone communication, it also provides favorable conditions for enabling non-telephone services such as user telegraph and data transmission. Currently, all the circuit switches used in the telecom network are programmable digital switches, which can provide users with fixed telephone services, mobile phone services, and narrowband ISDN services.

Ii. Packet Exchange

The unit of data transmission in the message exchange mode is the message, and the message is the data block to be sent at one time by the site. Its length is unlimited and variable. When a station sends a message, it attaches a destination address to the message. The network node sends the packet to the next node based on the destination address information, it is always forwarded to the target node one by one.

After each node receives the entire packet and checks whether the packet is correct, it stores the packet, uses the route information to find the address of the next node, and then transmits the entire packet to the next node. Therefore, you do not need to call the client to establish a connection. The delay time of a message on each node is the sum of the time required for receiving the message plus the queuing delay time required for forwarding to the next node.

Iii. group exchange

Group Exchange is an important achievement in the development of data exchange technology and represents the future evolution of the network. The Group switching method has the advantages of packet switching and line switching. Grouping switching technology uses statistical multiplexing, which greatly improves bandwidth utilization compared with circuit switching. This requires the use of storage and forwarding on the switch node, resulting in leeching. Therefore, the concept of unfixed latency is introduced in group switching. The Group switching network consists of two main methods: connection-oriented and connectionless. The Group network consists of three functional areas: data plane, control plane, and management plane. The data area is responsible for grouping and forwarding, so high performance is required. Currently, the main packet exchange networks include connection-oriented X.25, frame relay, ATM, MPLS, and connectionless Ethernet and CP/IP networks.

The group exchange network has two main forms: connection-oriented and connectionless. For Grouping data exchange technology, connection-oriented networks are similar to circuit switches, and resources need to be allocated in Switches during connection establishment. However, because of the reuse of statistics, the allocated resources are represented by logical labels. Since the emergence of the group data exchange technology, there have been a variety of group exchange network investors. China Telecom first proposed the X.2 5 network, but because of its complicated protocol and limited speed, it is gradually replaced by a network with better performance, such as frame relay. The frame relay network can be considered an improved version of X.2, which simplifies the Protocol to improve processing efficiency. A focus in the computer field is the local area network (LAN), which is a small-scale network used to interconnect computers in the office. Currently, Ethernet has become the dominant LAN technology.

In the middle and late S, the Internet was greatly developed and its scale continued to expand, and the requirements for core router throughput were also increasing. The route table query is complex when the router forwards the I P group, and the forwarding speed is limited. As mentioned above, it is very fast to use logical sub-channel labels for forwarding table search for connection networks. Combining the advantages of the ATM technology, we propose to change the core network to a vswitch similar to the ATM, and only use the IP address data exchange technology of the vro on the edge network, it eventually evolved into Multi-Protocol Label Switching (MPlS ). However, in the following years, a variety of practical high-speed routing search methods have been proposed, making it no longer a bottleneck.