Hello everyone!
Today, we learn about data communication.
What is Data Communication？
According to the communication protocol, data is transferred between functional units by using the transmission technology, so as to realize the information exchange between computers, between computers and terminals, and between other data terminal devices.
A data communication network is a network formed to provide data communication services, and Access Network is a part of the data communication network.
To help you understand the implementation mechanism of network interconnection, you can compare the examples in life to understand the data communication process on the network.
As shown in the following figure, two computers are directly connected through a network cable to form the simplest network. The two computers can communicate with each other through this network. The two computers can transmit information, such as texts, pictures, and videos, to each other.
A complete data communication system should be composed of five parts: message, sender, receiver, medium, and protocol.
Message
A packet is a data block in communication. Information such as texts, numbers, pictures, audio, and videos is encoded and then transmitted in packets.
Sender
The sender refers to the device that sends data packets. It can be a computer, workstation, server, mobile phone, etc.
Receiver
The receiver refers to the device that receives packets. It can be a computer, workstation, server, mobile phone, TV, etc.
Medium
Transmission media: It refers to the carrier for signal transmission. Common transmission media in LANs include optical fibers, coaxial cables, and twisted pairs.
Protocol
A protocol is a set of rules that govern data communications. It represents a set of conventions between communication devices. Without a protocol, even if the two devices are physically connected, they cannot communicate. For example, a person who can only speak Chinese cannot be understood by a person who can only speak English.
Understanding the Data Communication Process
The data communication process is similar to the real-life article express service. The process can be compared and understood.
Step | Goods Express | Data communication |
1 | The mailer prepares and packs the items properly. For large items, split them into separate parts and pack them separately. | The sender prepares the packets to be transmitted. If the file is large, split it into small data segments. |
2 | The express company packs the mailed items. Fill in the sender's name and address, and the recipient's name and address. | Encapsulates data fragments into data packets. The data packet contains information about the sender and receiver. |
3 | By searching the address and name of the recipient, determine the express delivery path and transit node. Transfer goods between transit nodes by means of sea, land, and air. | Search for the address information of the receiver and determine the data forwarding path. Forwarding data packets on forwarding nodes using media such as network cables |
4 | The recipient receives the mail, unpacks and packs the mail. If it is a large item, reassemble it. | The destination computer receives the data packet. If the packet is fragmented, reassemble the fragmented packet and restore the packet. |
Characteristics of Data Communication
1. Connectionless: No independent link exists between the two communication systems.
2. Packet switching: Each packet has the destination address, source address, and error control information, and can find its own destination.
Connectionless packet switching uses packet switching to encapsulate user information into packets for switching. Each packet has a packet header, which is used for routing, error control, and flow control. The length and interval of each packet can be changed. Therefore, packet switching supports multiple rates.
In connectionless packet switching, routing information is carried in each packet header. A switching device checks the address information in each packet header, selects a route based on the network status, and sends packets to the next-level network device. Therefore, different packets of the same service pass through different paths on the network.
In connectionless packet switching, packets occupy network resources only when they are transmitted. Network resources can be shared by services.
Transmission Mode
Simplex
In simplex mode, the communication is unidirectional. Only one of the two devices can send packets, and the other can only receive packets.
Keyboards and displays are simplex communication devices. The keyboard can only be used for input, and the monitor can only receive output.
Half-duplex
In half-duplex mode, each device can send and receive packets, but cannot send and receive packets at the same time. When one device sends packets, the other device can only receive packets and vice versa.
The walkie-talkie is a typical example of a half-duplex system.
Full-duplex
In full-duplex mode, both communication parties can receive and transmit data simultaneously.
The telephone network is a typical example of full-duplex.
Standardization Organizations
Currently, the main standardization organizations are:
International Organization for Standardization (ISO)
Institute of Electrical and Electronics Engineers (IEEE)
American National Standards Agency (ANSI)
Electronic Industry Association (EIA/TIA)
International Telecommunication Union (ITU)
Internet Architecture Board (IAB)
Thank you for reading!
