QOS (Quality of Service) refers to the ability of a network to use various basic technologies to provide better service capabilities for designated network communications. It is a network security mechanism and a technology used to solve problems such as network delay and congestion. QOSguarantee is very important for networks with limited capacity, especially for streaming multimedia applications, such as VoIP and IPTV, because these applications often require a fixed transmission rate and are sensitive to delay.
Traditional IP networks treat all packets indiscriminately. The network equipment adopts a first in first out FIFO (First In First Out) strategy to process packets, which allocates the resources needed for forwarding according to the sequence of message arrival time. All messages share the bandwidth and other resources of the network and equipment. However, the amount of resources finally obtained depends entirely on the time of message arrival. FIFO tries its best to send the message to the destination, but it does not provide any commitment and guarantee for the delay, jitter, packet loss rate and reliability of the message, so it cannot guarantee the communication quality of some key services (such as voice, video, etc.).
With the continuous emergence of new applications on the IP network, new requirements are put forward for the quality of service of the IP network. For example, real-time services such as VoIP put forward higher requirements for the transmission delay of messages. If the message transmission delay is too long, users will not accept it (relatively speaking, E-Mail and FTP services are not sensitive to time delays). In order to support voice, video, data and other services with different service requirements, the network is required to distinguish different communications and provide corresponding services. The best effort service of traditional IP network can not identify and distinguish various communication types in the network, and the ability to distinguish communication types is the premise of providing different services for different communications. Therefore, the best effort service mode of traditional network can no longer meet the needs of applications.
When the network is congested, all data flows may be discarded; In order to meet users’ requirements for different quality of service for different applications, the network needs to be able to allocate and schedule resources according to users’ requirements and provide different quality of service for different data streams: for real-time and important datagrams, QOS technology is committed to solving this problem.
For ordinary data packets with poor real-time performance, it provides lower processing priority and even discards them when the network is congested. QOS came into being. Devices that support QOS functions can provide QOS services; For a certain type of data flow, you can assign it a certain level of transmission priority to identify its relative importance, and use various priority forwarding strategies, congestion avoidance and other mechanisms provided by the device to provide special transmission services for these data flows. The network environment configured with QOS increases the predictability of network performance, effectively allocates network bandwidth, and makes more reasonable use of network resources.
Starting from the QOS service model, describe some of the most used and mature QOS technologies one by one. The reasonable use of these technologies in a specific environment can effectively improve the quality of service. Generally, QOS provides the following three service models: Best Effort service model, Integrated service model (Int Serv for short), and Differentiated service model (Diff Serv for short) https://cciedump.spoto.net
