What is the Definition of QoS?

Acronyms Technology

According to abbreviationfinder, QoS stands for Quality of Service. The ability of a network to provide different levels of service to ensure different traffic profiles.


It is a set of service requirements that the network must meet in transporting a flow. It can be implemented in different situations, to manage congestion or to avoid it. It allows you to control some significant characteristics of packet transmission.

These characteristics can be specified in quantitative or statistical terms such as: bandwidth, latency, jitter, network packet loss; ensuring a pre-established degree of reliability that meets the traffic requirements, based on the profile and bandwidth for a given data flow.


The concept of quality of service (QoS) in telecommunications can have at least two common interpretations. In the first place, it refers to the capacity of certain networks and services to admit that the conditions under which communications will be carried out (dedication of resources, transmission capacities, etc.) be established in advance.

Secondly, quality of service is spoken of as a series of measurable qualities of telecommunications networks and services, such as the time it takes to make a telephone call (from the time the user dials until the telephone rings at the other end).


The motivation to apply Quality of Service in IP networks can be summarized in the following needs:

  • Prioritize certain applications on the network that require a high level of VOIP service.
  • Maximize the use of the network infrastructure, maintaining a margin of flexibility, security and growth for emerging services.
  • Improve performance for real-time services.
  • Respond to changes in the established traffic profile.
  • Provide mechanisms to prioritize traffic.

Points of view

To provide a better understanding of what QoS means, two different points of view are appreciated: the first from the point of view of the end user and the other from the point of view of network operation. For the user, it is how he perceives the receipt of a certain service, be it voice, audio or video.

For the network, it is the ability to provide a service to the user, according to the agreement between the user and the provider, for this it must be able to differentiate between the different classes of traffic and once differentiated provide the service and also be able to make differentiation in the network through priorities.

Factors that affect it

There are various causes that can threaten the proper functioning of the network or that the user has a negative perception of the service received. These factors are mostly due to the fact that the voice must travel in an environment designed for data packets, undergoing changes of packetization, fragmentation, interleaving, encoding or decoding through the network. Some of these parameters are described below.


The basic goal of traffic classes (CT) and type of service (ToS) is to achieve the necessary bandwidth and latency for a given application. Traffic classes allow the network administrator to group different packet streams, each having different latency and bandwidth requirements.

The type of service is a field in an IP header, which allows a particular class of service to take place. While the classes of service (CoS) is a classification scheme with which traffic with similar treatment requirements are grouped, to differentiate the types of traffic and therefore be able to prioritize them.


The Quality of Service levels refer to the current capacities of end-to-end connections, that is, the capacities that a determined network has to perform a service for a specific traffic. The services differ in how strict the QoS levels can be, that is, they have to be specific for a given bandwidth, jitter or packet loss. These are:

  • Best Effort level: basically these services do not offer any guarantee. It usually uses FIFO (First in First Out) techniques, which do not have any differentiation between the different flows.
  • Level for Differentiated Services (Diffserv): it is based on the division of traffic into different classes and the assignment of priorities.
  • Guaranteed Level: it is intended for applications with demanding real-time requirements. This quality ensures bandwidth, a limit on delay and no loss in queues.


There are several existing mechanisms that are implemented to guarantee an adequate Quality of Service, which are shown below:

  • Queue management: due to the nature of the transmission of multimedia applications through the network, it ensures that the amount of traffic does not exceed the speed of the connection, making several queues for the different services.
  • Packet classification: To manipulate the traffic and grant it QoS, the basic classification and prioritization procedures are used.
  • Traffic shaping and flow metering: There are many times when it is necessary to limit the amount of traffic to an application across multiple interfaces. These control capabilities are determined by the rate limit tools and the training tools.
  • High-speed queue management: it is based on the way protocols operate, in order to avoid network congestion.
  • Perceived Quality of Service Estimation Methodologies: it is the quality perceived by the user regardless of what the network transports. Measures of perceived quality can be made using objective or subjective methods.


There are multiple tools that make use of the factors that are present when it comes to ensuring that a given network has an adequate Quality of Service, among them are the PING tool (Packet Internet Groper), Traceroute or Tracert, VQManager, MyConnection server among others.

Solutions for service quality

The PlaNetS project extends current quality of service architectures in local networks to provide end-to-end quality of service. Therefore, the objective is that from the local devices that the user has to the entrance/exit of the residential environment, the UPnP QoS scheme is saved.

The specific objectives are:

  1. Design of an end-to-end QoS management mechanism, potentially from one multimedia device in a local network to another in another local network, including QoS configuration in the gateways, access network and network core.
  2. Flexibility in supporting different network technologies and peripheral devices.
  3. Development of a flexible data model that allows the integration of service quality management in heterogeneous systems, and that takes into account different aspects that influence the quality of a service.
  4. Support for quality of service with priorities and parameters.
  5. Based, as far as possible, on standard solutions.