What Is Quality of Service (QoS) in Networking?

Posted on Sep 20, 2023 by

What Is QoS?

Quality of Service (QoS) is a network mechanism used to manage quality and determine the priority of data traffic transmission on a network. It ensures that different types of data traffic, such as voice, video, and data, receive appropriate service levels. Its key objectives are to enable networks and organizations to prioritize traffic, including providing dedicated bandwidth, controlling jitter, and reducing latency. It is crucial for improving the performance of business applications, Wide Area Networks (WANs), and service provider networks. Typical services that require the use of QoS include the following.


How Does QoS Work?

QoS networking technology works by marking packets to identify service types, and then configuring routers to create separate virtual queues for each application, based on their priority. As the picture shows, packets are classified and marked as they enter the system through the ingress interface. During this process, policing mechanisms may discard some packets. Subsequently, packets are classified again based on their markings. Congestion management and congestion avoidance mechanisms assign different priorities to various types of packets so that packets with higher priorities can pass through gateways earlier in cases of network congestion. Finally, the system sends the processed packets through the egress interface using the QoS mechanism.

How Qos works

The Application Scenarios for QoS

Take the enterprise office as an example. In addition to the basic web browsing and email services, services such as Telnet-based device login, remote video conferences, real-time voice calls, FTP file upload and download, and video playback must also have their network quality guaranteed during busy hours. If services have varying network quality requirements, you can configure corresponding QoS functions or enable QoS only for some services to meet the requirements.


Network Protocols and Management Protocols (OSPF and Telnet)

These types of services require low latency and a low packet loss rate but do not have high bandwidth demands. Therefore, through QoS's priority mapping feature, packets of this type can be marked with a higher service level, allowing network devices to prioritize the forwarding of these packets.

Real-time Applications (Video Conferencing and VoIP)

Video conferencing demands high bandwidth, low latency, and low jitter. Therefore, QoS's traffic shaping feature can be utilized to provide ample bandwidth for video packets. Additionally, through QoS's priority mapping function, the priority of video packets can be appropriately increased.

VoIP refers to real-time voice calls over IP networks, requiring low packet loss, low latency, and minimal jitter. Otherwise, call quality degradation is noticeable to both parties. To address this, voice packet priorities can be adjusted to be higher than video packets. Furthermore, by using traffic shaping, maximum bandwidth can be allocated to voice packets. In the event of network congestion, this ensures that voice packets are given priority passage.

High Data Volume Services (FTP, Database Backups and File Dumping)

High data volume services involve prolonged, large-scale data transmission over the network. These types of services require the lowest possible network packet loss rate. Therefore, traffic shaping can be configured for such packets. This involves using data buffers to cache the packets to be sent from the interface, reducing the occurrence of packet loss due to congestion caused by sudden bursts of traffic.

Streaming Media (Online Audio Streaming and Video On-Demand)

Because these audio and video programs are typically pre-produced, viewers' terminals can often cache and then play them, reducing the requirements for network latency, packet loss, and jitter. If there is a need to reduce packet loss and latency for these types of services, the priority mapping function of QoS can be used to appropriately increase the priority of the corresponding packets.

Regular Services (HTML Web Browsing and Email)

These types of services have no special network requirements and are not highly critical. Administrators can keep their default settings, and there's no need to deploy additional QoS features for them.

Quality of Service in Networking

In the past, traditional business networks handled telephones and telephone conferences on one network, while laptops, desktop computers, servers, and other devices were connected to a separate network. They had limited interaction, and speed wasn't a top priority when the network only carried data. However, today, interactive applications that carry audio and video content require high-speed transmission, with no packet loss or variations in transmission speed. For any organization that wants to ensure optimal performance for critical applications and services, QoS is essential.

Unlimited Application Prioritization

QoS guarantees that businesses' mission-critical applications will always have priority and the necessary resources to achieve high performance.

Better Resource Management

QoS allows administrators to better manage an organization's internet resources, effectively reducing costs and investment requirements for link expansion.

Enhanced User Experience

The ultimate goal of QoS is to ensure high performance for critical applications, thus providing the best user experience. Employees can achieve high performance when using high-bandwidth applications, which can enhance productivity and enable them to complete tasks more quickly.

Point-to-point Traffic Management

Regardless of how traffic is delivered, network management is crucial. By using point-to-point delivery, organizations can sequentially deliver customer packets from one point to another on the Internet without packet loss.

Packet Loss Prevention

Packets are occasionally lost due to failures or inefficiencies, network congestion, router malfunctions, loose connections, or weak signals. QoS mitigates the risk of packet loss by allocating higher bandwidth to high-performance applications.

Latency Reduction

Latency is typically affected by routers taking longer to analyze information and storage delays caused by intermediate switches and bridges. QoS enables organizations to reduce latency or speed up the process of a network request by prioritizing their critical application.

Advantages of Qos


QoS is a feature of switches that allows businesses to prioritize different applications, data streams, and users, preventing packet loss for critical traffic. Switches with QoS can ensure optimal network performance.

FS provides cost-effective PoE switches with QoS support, suitable for various scenarios, such as S3150-8T2FP, S3400-24T4FP, S3260-16T4FP, etc. You can select and purchase FS switches based on your requirements.

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