What Are the Different Ways to Control Water Flow?

Traffic control has different meanings in different fields. Such as aviation flow control, network flow control, etc.

Network traffic control is a measure that uses software or hardware to control network data traffic.

Chinese name: flow control

Foreign name: traffic control

Flow control

Network traffic control (Network traffic control) is a software or hardware approach to control computer network traffic. Its main method is to introduce the concept of QoS. From marking different types of network data packets, the priority order of data packets is determined. ^[1]

There is a big difference between DTE and DCE speeds. In the process of data transmission and reception, it is likely that the receiver has too late to receive it. At this time, the sender needs to be controlled to avoid data loss.

It is used to control the data flow between the modem and the computer, and prevents data loss caused by the mismatch in the communication processing speed between the computer and the modem. There are usually hardware flow control (RTS / CTS) and software flow control (XON / XOFF) control. ^[1]

DCE: Data Circuit-terminal Equipment, a device that is directly connected to a channel. When the channel is an analog channel, DCE is Modern. When the channel is a digital channel, the DCE is a bridge, switch, router, etc. ^[1]

DTE: Data Terminal Equipment) Speed refers to the transmission speed from the local computer to the modem. If the telephone line transmission rate (DCE speed) is 56000bps, the modem decompresses 56000 × 4 according to the V.42 bis protocol after receiving the data. = 115200bps, and then transmitted to the computer at this rate, which shows that the DTE speed of 56K cats (using V.42bis) should ideally reach 115200bps. ^[1]

Flow control flow mechanism

flow control

Definition: Flow control is used to prevent dropped frames when the port is blocked. This method is implemented by sending a blocking signal back to the source address when the send or receive buffers begin to overflow. Flow control can effectively prevent the impact of a large amount of data in the network on the network and ensure the efficient and stable operation of the user network. ^[1]

Two ways to control traffic:

1. In the half-duplex mode, the flow control is achieved by backpressure, which is what we usually call back pressure counting. This kind of counting makes the information source reduce the sending speed by sending jamming signals to the sending source. ^[1]

2. In full-duplex mode, the flow control generally follows the IEEE 802.3X standard. The switch sends a "pause" frame to the information source to make it pause. ^[1]

Some switches' flow control will block the input of the entire LAN, which greatly reduces the network performance; high-performance switches only block the ports that input frames to the switch's congested ports. Flow control is used to control the data flow between transmitting and receiving nodes, which can prevent data packet loss. ^[1]

Flow control flight flow

Air traffic control (English: Airtrafficcontrol, abbreviation: ATC) refers to the coordination and guidance of air traffic controllers on the ground to guide the navigation routes and flight modes of different aircraft in the airspace or airport to prevent accidents on the ground or in the air. Make sure they all work smoothly and for maximum efficiency. In addition, the air traffic control system will also provide information such as weather, air traffic flow, NOTAM, and special airport arrangements to assist pilots and airlines in making corresponding arrangements. Into the 21st century, with the increase of terrorist attacks related to aviation activities, the air traffic control system also plays the role of airspace defense and homeland security. In some countries, the air traffic control system (such as the Brazilian Air Force) is operated by the air force. The aircraft can still fly without air traffic control, but the existence of control can effectively ensure the safety of the aircraft in flight. ^[2]

Referred to as flow control. Flow control refers to maintaining a safe air flow by limiting the number of aircraft entering an air traffic control node per unit time. It is the aircraft waiting in line for a take-off or landing instruction on the apron or in the air. Just like when you check in, for flight safety, you need to queue up one by one to go through security in turn. ^[2]

Reason: In order to ensure the safety of flight, passenger life and property, the weather at the take-off airport, the en route, the destination airport may be bad (such as thunderstorms in summer, typhoons, snow and ice in winter), or military exercises in the area, or An unexpected event, or flight flow limitation due to too many aircraft takeoffs and landings in this airspace within a certain period of time (unlike ground traffic jams, the air can be stopped and stopped, and the aircraft cannot stay in the air, so once the flight number exceeds A certain number of measures that must be taken for safety). ^[2]

Purpose: Flight safety, passenger life and property safety, smooth flight, etc. ^[2]

Flow control data flow

It can also be understood as a type of traffic shaping, which is a network traffic management technology of a computer network, so as to delay some or all of the data packets and make them conform to the network traffic rules and rate limiting. ^[1]

Network flow control is used to optimize or guarantee performance, improve latency, and / or increase the available bandwidth for certain types of packet delays to meet certain conditions. If a certain link approaches the saturation point, the network delay may increase significantly. Therefore, network flow control can be used to prevent this from happening and to maintain latency checks. ^[1]

Network flow control provides a means to control the amount of data that is sent to the network within a specified time (bandwidth limitation), or the maximum rate of data traffic sent. There are many ways this control can be implemented, but usually, network flow control is always implemented by delaying packet sending. It is generally applied at the edge of the network to control the traffic entering the network, but it can also be directly applied to data sources (such as , Computer or network card), or an element of a network. ^[3]

Flow control network flow control

Flow control control implementation

With the rapid development of network technology, network-based applications are becoming more and more complex. A wide variety of applications are eating up more and more network resources. As a new media carrier, the network is also being hit by the media. In particular, the infiltration of media such as online video, personal media, and traditional television into the Internet has caused a sharp increase in traffic on the network, which has significantly increased the operating and management costs of operators. Operators can use the current-limiting method to control network traffic, but this also limits the development of network media and ultimately is not conducive to the further development of the Internet. So developing a new technology to control network traffic has become a research hotspot. ^[1]

At this stage, traffic on the Internet is mainly generated by P2P and HTTP. It is estimated that these two types of traffic have accounted for more than 70% of the total traffic, and they are still on the rise. Therefore, the focus of flow control is P2P and HTTP. Reducing the traffic generated by these two protocols will effectively reduce the overall network traffic. By comparing multiple network flow control systems, an optimal system is then adopted. The system is deployed at the network exit to cache P2P and HTTP traffic, and subsequent requests for the same resource will be cached to respond, thereby reducing network traffic, saving bandwidth and improving the user experience. ^[1]

Flow control characteristics

(1) Session identification based on content. Through high-speed deep protocol analysis, the application to which each network session belongs can be intercepted or a corresponding bandwidth allocation policy can be formulated for a certain protocol. Traditional network devices such as routers and firewalls only Can identify the first level according to the port. ^[1]

(2) The intelligent bandwidth adjustment function can intelligently adjust the terminal bandwidth allocation method in the network according to the network load. For example, if the network load is heavy, then the terminal with a large amount of traffic is automatically restricted to ensure that most users' network applications can function normally and quickly When the network load is light, a loose bandwidth processing strategy is adopted so that the bandwidth of the network can be fully utilized. ^[1]

(3) Terminal-based resource control only needs to set a rule to limit the bandwidth usage limit of each terminal, and can set the number of sessions per terminal to prevent the exhaustion of network resources caused by a virus and other prisoners , ^[1]

(4) On-demand dynamic allocation of bandwidth Since the HTTD bandwidth management system can understand the network from the second to the seventh protocol layers and even the association between sessions, it can automatically distinguish the deep rate control of various protocols, services and applications Technology (DeeperRateControl), which can distinguish this information flow from other information flows based on basic characteristics such as 1P address, subnet, server location, protocol, application port, application type, and application correlation analysis, and then give appropriate according to different needs Or due bandwidth level (Privilege) and bandwidth policy (Policy), the bandwidth level and bandwidth policy can be divided by intervals, the implementation method is rigid or flexible, according to different flexible implementation, can ensure that the WAN limited resources are dynamically allocated on demand . ^[1]