Why should you implement Quality of Service (QoS) in your network?

Quality of Service (QoS) is a set of tools and techniques used in IP networks to manage and optimize the distribution of resources according to the varying needs of different applications, users, and services. This ensures that applications requiring special conditions (such as voice and video) receive them, even in congestion scenarios (i.e., when the infrastructure is overloaded due to high traffic demand).

This has become increasingly necessary because IP networks were originally designed to provide a best-effort service, meaning that all packet traffic is treated the same way and sent in a FIFO (First In, First Out) manner: the first to arrive is the first to leave.

What is Quality of Service (QoS)?

Quality of Service gives the network the ability to provide adequate performance and availability for each application or service running on it, while ensuring certain quality criteria. For example:

• Bandwidth: the amount of data that a network can transmit over a specified period of time.

• Latency: the time it takes for a packet to travel from its source to its destination.

• Jitter: the variation in latency.

• Packet loss.

These quality criteria are important since each application has different requirements.

For example, an application like Zoom or Teams (Microsoft) requires the network to provide sufficient bandwidth to transmit high-quality video and voice in real-time, low latency to enhance the user experience and prevent delays in image or audio, and low packet loss to avoid interruptions in transmission. On the other hand, an email application is not as dependent on latency, as long as it has low packet loss and sufficient bandwidth to send messages.

How can it be implemented?

There are several mechanisms that allow differentiating the treatment given to the generated traffic according to its needs:

Traffic classification/tagging

Although this does not define the quality of service itself, it is an important part of its implementation, as it allows the network to identify packets as belonging to a specific type of traffic and thus ensure they receive the most appropriate treatment.

It can be done in different ways, depending on the network's characteristics. For example, by using the DSCP code in IP packets or the IEEE 802.1p standard to implement it at the data link layer (Layer 2).

Bandwidth management

Different types of traffic have various bandwidth requirements. Once the traffic is identified, based on a tag, as belonging to a specific application or type, that traffic can be guaranteed a bandwidth that meets its needs.

For example, high-quality video and audio traffic should be guaranteed more bandwidth than email or instant messaging application traffic.

Behavior in the face of congestion

This is crucial, as the bandwidth of a path in a network is limited (considering cost or investment optimization). By prioritizing sensitive traffic over less critical traffic, the proper functioning of important applications is ensured, even in congestion scenarios.

The "guaranteed" and "peak" bandwidths can be set for different types of traffic, thus keeping the network operational even when it is at full capacity.

Policing y shaping

These are technologies that allow controlling network traffic. Policing is used to limit network traffic to a specified bandwidth level (or packets per second), while shaping imposes restrictions on network traffic to prevent it from exceeding set limits; for example, in the case of providing differentiated services to customers who subscribe to different plans.

The use of these tools in all their possible combinations constitutes the implementation of quality of service, which will depend on the specific objectives and needs of each network.

A technique that adds value to network services.

In an era where networks are becoming increasingly important, their ability to dynamically adapt to the needs of different applications with the shortest possible response time is a highly valuable characteristic.

The market is relentless, and users are becoming more demanding, so the design and implementation of an appropriate quality of service policy to ensure the reliability and optimal performance of the infrastructure can make the difference between poor service and a better user experience.

By:

Andrés Burel, Engineering Leader de Telco & Smart Cities.

Andrés is a Telecommunications engineer from the University ORT (Uruguay). He has more than 10 years of experience in telecommunications and has worked for vendors and service providers.