Three Ways of Data Transmission--Computer Network

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Three ways of data transmission

There are three main ways of data transmission in the network.

1. Circuit Switching
2. Message Switching
3. Packet Switching

1. Circuit Switching (Circuit Switching)

Circuit switching is often used in the telephone network. One party requests to establish a connection with the other party through the phone. After the other party agrees, the system will allocate a dedicated line to both parties for data exchange. After the data exchange is over, the connection is closed and resources are released. So The biggest difference between electrical switching and the following two switching methods is line exclusive

The circuit switching steps are as follows:

1. Establish connections and allocate circuit resources
2. transfer data
3. Close connection and release circuit resources

1.1 Advantages of circuit switching

• Small communication delay, strong real-time performance (both parties have dedicated data channels)
• Orderly transmission (same as above)
• No conflict (same as above)
• Wide range of applications (both analog signals and digital signals can be transmitted)
• Simple control

1.2 Disadvantages of circuit switching

• Long connection time
• Low use efficiency (the line is exclusive, after the connection is established, even if the line is idle, it cannot be used by other users)
• Poor flexibility and low fault tolerance (If there is a problem at a certain point in the dedicated channel, the connection needs to be re-established)
• Difficult to standardize (different types and specifications of terminals are difficult to establish a connection)

2. Message Switching

In the message exchange, the data is in the unit of the message, and the message contains the original address and the target address, etc., and can be sent by the host without connection, and then finally reach the target address through the storage and forwarding of the switch (router) . It was widely used in telegraph communication in the last century.

The message exchange steps are as follows:

1. Convert the source data into a message and send it
2. The router stores the message and forwards it to the next unit according to the message information ( store and forward )

2.1 Advantages of message exchange

1. No need to establish a connection
2. Dynamic allocation (when a message is transmitted to the switch and stored, the switch will select an idle line to send out)
3. High line reliability (when a line is damaged, it will not affect the data transmission)
4. Improved line utilization
5. Provide multi-target services (a message can be sent to multiple users)

2.2 Disadvantages of message exchange

1. There is a forwarding delay (because the switch has a store-and-forward process during the forwarding process and there is no dedicated line for transmission)
2. Message exchange only applies to digital signals
3. The nodes in the network are required to have a larger buffer (because the length of the message is not limited, and the intermediate node must receive the message completely and store it)
4. Need to transmit extra information (the message adds a lot of information compared to the original data)

3. Packet Switching

Packet switching can be regarded as an upgraded version of message switching. In fact, there is basically no message switching. The data exchange in the network is mostly packet switching. Packet switching divides the message into packets of equal length. , And call a header in front of each packet data , the header contains information about the destination address and the original address.

The packet switching steps are as follows:

1. Divide the message into individual packets and send
2. After the router receives the packet, it stores it and selects the appropriate line for forwarding according to the header
3. The receiving node restores each packet to the original data

3.1 Advantages of packet switching

Packet switching has almost all the advantages of message exchange, and it has the following advantages compared to message exchange

1. Simplified storage management (because the packet length of packet switching is equal, the corresponding buffer size is also equal, which simplifies storage)
2. Accelerated transmission (the transmission between packets does not affect each other, so you can better use resources to accelerate transmission)
3. Reduce the probability of errors and the amount of retransmitted data (because the data is divided into many packets, only part of the data needs to be retransmitted even if the transmission of a certain packet fails)

3.2 Disadvantages of packet switching

Compared with packet exchange, packet switching has no shortcomings of buffer . But it also adds several shortcomings.

1. Need to transmit additional information (each packet has a header)
2. Operation is troublesome (it is troublesome to restore the original message when the packet reaches the destination node)

4. Summary and comparison diagram of the three circuit switching