Shulou(Shulou.com)11/24 Report--

I believe that many people have had this experience:

After the hit TV series, there is about to be a turning point, the characters are pressed the pause button, the scene is a little awkward or even funny.

Watching the game, the key ball has been shot, the picture suddenly trembled, so exasperating that people want to throw the phone directly.

When playing the game, it is necessary to flash and enlarge, and the network signal suddenly weakens, resulting in a successful counterattack by the other hero.

If we regard the whole network as a vast ocean, then we can access the Internet smoothly, which is the result of a ship's continuous departure and return. The ship starts from our mobile phones, shuttles through the ocean / lake / river to its destination, and then sails back to our mobile phones with new data.

The process of sailing is not plain sailing, and there will also be situations where waterways are blocked and ships get lost. Once there is a problem in data transmission, it will cause network stutter and bring us a bad network experience.

Today, let's take a look at four factors that affect the quality of the network:

01. Throughput: the width of the channel is generally described as the rate of the network. The greater the bandwidth, the greater the rate of data transmission. The bandwidth represents the width of the channel. The wider the channel, the more ships can pass through, and the smoother the data transmission process will be. The bandwidth ranges from a few Kbits to 1000 Mbps, which is the difference between a solo boat and a thousand sails.

02. Delay: the time delay (Latency) is generally used to describe the transmission time of data from the remote end to the local, and the sum of back and forth time is calculated. Time delay represents the total sailing time of a ship. The greater the delay, the more time it takes to transmit data. Generally speaking, if the delay is more than 50 ms, the network quality is not good. Once it exceeds 300 ms, the stutter of the network is more obvious.

For the size of the delay, you need to calculate the sum of the following four delays:

Processing delay: the time it takes a network device to process data. Before the departure of each ship, the dispatching center (network equipment) is required to carry out some necessary processing, such as determining the destination and determining the route to be taken during transmission.

Transmission delay: the sailing time of a ship in a data ocean river. Even if a ship loaded with data travels at the speed of light (300000 kilometers per second) and travels 40, 000 kilometers at both ends of the earth, the lowest delay is 130 ms.

Queue delay: different waterways have different widths (bandwidth). When thousands of ships want to pass through a certain section of waterway, they also need to wait in line to be processed by the dispatching center (network equipment).

Serialization delay: a ship loaded with data also has a certain length. This time also needs to be calculated from the bow (the first bit of the data) to the stern (the last bit of the data).

03. Loss: a ship that cannot reach the destination usually uses packet loss to describe the loss of data in the network. Packet loss represents the ships that can't reach the finish line. There are many reasons for packet loss, which may be due to the inability to process requests from ships due to the busy dispatching center, the excessive number of ships waiting in line for dispatch, and the closure of various waterways (links) in the route, resulting in ships making a detour or getting lost.

In the process of transmitting data at one time, it is possible to send 100 ships, and only 80 ships return smoothly after layers of tribulations, and the packet loss rate can be calculated to be 20%.

Packet loss rate is a key indicator of network quality. Generally, the packet loss rate cannot be greater than 2%, and users do not feel much impact. Once it exceeds 10%, the network quality will deteriorate rapidly, and the feeling of network stutter is more obvious.

04. Jitter: the distribution of voyage time is generally described as jitter (Jitter) to describe the maximum time difference between different data arriving at the destination. The wobble represents the difference in the return time of each ship in a fleet. The data transmission in the process of surfing the Internet is continuous, and when one ship sets out, one ship after another arrives at its destination. The delay of the first ship is 60 ms, the delay of the latter ship is 30 ms, and the jitter is 60 ms-30 ms=30 ms. Once jitter occurs in a voice conference / video conference, the sound can not be heard clearly and the image can not be seen clearly.

"if the network wants to be stable, grasp the four elements."

In different applications, bandwidth, delay, packet loss and jitter have different effects on network quality.

Voice / video conferencing, sensitive to all four factors

Online games are sensitive to bandwidth, delay and packet loss.

HTTP applications such as mailbox / news are often only sensitive to bandwidth and delay.

In order to ensure the network quality, we can try our best to ensure the bandwidth, reduce the delay and reduce the packet loss rate. Common processing methods include:

Provide differentiated bandwidth

Network devices provide different bandwidths for different applications, such as voice / video conferencing and games, which can allocate larger bandwidth, while mailboxes and news applications can allocate smaller bandwidths. In this way, the bandwidth is used efficiently and the network congestion of different applications is avoided.

Give priority to high priority applications

Different priorities are assigned to different applications, and network devices give priority to high-priority applications, which can reduce the processing delay and queue delay of these applications. On the other hand, applications with low priority in the queue can only be processed without high-priority applications.

The technology to ensure the quality of the network is still in continuous research and improvement, and the specific application is also in continuous exploration. For example, operators have provided bandwidth guarantees for "Arena of Valor" players through QoS technology, and the number of guarantees has reached 1100 per day.

It is expected that in the near future, all games and videoconferencing applications will no longer have to worry about network stutters.

This article comes from the official account of Wechat: ZTE documents (ID:ztedoc)

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