The difference between UDP and TCP

When it comes to network transmission, most people probably think that TCP is the best choice.Because TCP is a reliable protocol, it can ensure the reliability and integrity of data.However, when considering UDP, some people may think that it is faster than TCP.Is this true?Under what circumstances is it slower to use UDP than TCP?In this article, we will explore this issue in depth and explain the difference between UDP and TCP.

The difference between UDP and TCP

UDP and TCP are two different protocols, both of which are used to transfer data between computers.

TCP is a connection-oriented protocol, which means that a connection must be established before sending data.This kind of connection requires a three-way handshake process, and it will take some time to establish the connection.Once the connection is established, the data will be transmitted in a reliable manner.If the data packet is lost or damaged during transmission, TCP will re-transmit the data packet to ensure the integrity and reliability of the data.However, since TCP must ensure the integrity and reliability of data, this may cause data transmission to slow down.

On the other hand, UDP is a connectionless protocol.This means that there is no need to establish a connection before sending data, so there is no need for a three-way handshake process.Since UDP does not ensure the integrity and reliability of data, it may lose some packets.However, this makes UDP faster than TCP because UDP does not need to wait for packets to be re-transmitted.

Must UDP be faster than TCP?

TCP reliability and slow speed are due to its complex mechanisms, such as retransmission mechanism, flow control mechanism, sliding window control, congestion control mechanism, etc.TCP will mark the sent message with a sequence, and the recipient will return an acknowledgment (ack) after receiving it.If the other party's confirmation is not obtained for a long time, TCP will resend the message again, which is the retransmission mechanism.

However, the performance impact of retransmission itself is relatively serious, and it is necessary to avoid retransmission as much as possible, so there is a sliding window mechanism and a flow control mechanism.Because the data sender and receiver may have different data processing capabilities, the sending and receiving windows can adjust the amount of data sent according to the capabilities of both parties. The sliding window mechanism is to dynamically adjust the size of the receiving window. TCP controls the amount of data sent according to the size of the window, thereby reducing the probability of packet loss.

Is it because there is no such complex TCP reliability mechanism that UDP is faster?Although UDP does not require a connection to be established, UDP is not always faster than TCP.The fast transmission speed of UDP depends on the type of data and the transmission load.If you need to transmit a large amount of data, TCP may be faster because it guarantees the integrity and reliability of the data, which means it can transmit data faster.

However, if you need to transmit small amounts of data or real-time data (such as video and audio), then UDP may be faster.This is because UDP can increase the transmission speed by discarding data packets, thereby transmitting data faster.And in view of the packet loss problem of UDP, in most cases, users will do some retransmission mechanisms on the application layer on the basis of UDP.UDP itself will not be segmented. If the transmitted data is too large, it will be fragmented at the IP layer.If packet loss occurs at this time, the entire large data packet needs to be retransmitted. At this time, the use of UDP will be slower than TCP.

Another factor to consider is network latency.UDP is usually faster than TCP because it does not have a process of establishing a connection, which can reduce latency.However, if your network latency is high, UDP may cause data packets to be lost or damaged, thereby affecting the integrity and reliability of the data.

Although the transmission speed of UDP is faster than that of TCP in most scenarios, it is not suitable for all scenarios.UDP is commonly used in real-time applications, such as video and audio streaming media.This is because real-time applications require fast transmission speeds and can tolerate the loss or corruption of some data packets.In addition, UDP can also be used for online games, because online games require fast transmission speed and real-time response, and can tolerate a small amount of data packet loss.

Another applicable scenario for UDP is network detection and measurement.UDP can be used to send probe packets to the network to obtain network performance information.For example, you can use UDP Ping to test network latency and packet loss rates.

How to improve the transmission efficiency of UDP and TCP?

In practical applications, we can use some technical means to improve the transmission speed and efficiency of UDP and TCP.For example, in view of the transmission characteristics of the UDP protocol, we can use the UDP protocol with other technical means to improve the transmission reliability and efficiency.For example, FEC (Forward Error Correction) technology can be used to achieve data redundancy and error correction to improve the reliability of data transmission; QoS (Quality of Service) technology can also be used to achieve bandwidth management and flow control to optimize network transmission efficiency.

In addition, in the TCP protocol, there are also some technical means that can be used to improve transmission speed and efficiency.For example, you can use TCP accelerators to speed up data transmission, and TCP BBR (Bottleneck Bandwidth and RTT) algorithms to optimize congestion control and bandwidth utilization.

In general, the transmission speed and efficiency of UDP and TCP depend on specific application scenarios and requirements, and choices and trade-offs need to be made according to the actual situation. In practical applications, we can optimize the transmission efficiency of UDP and TCP by using other technical means to better meet actual needs.

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