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Introduction
The evolution of the data networks evolution entails an increase in the volume of the transmitted traffic, which requires the usage of the quality of service policy usage. The implementation of the policy implementation will allow classifying the classification of the network traffic and distributing the distribution of the network resources between different traffic classes.
Terminology
- QoS (Quality of Service) - technology that allows to classify a data stream and to prioritize the each stream's transmission in accordance with its class.
- QoS policy - document describing the principles of traffic streams stream classification and the resource requirements for each class.
- Traffic stream - data the data of one service transmitted between two nodes.
- Service - process running on end nodes which data need to be transmitted between nodes. Data of one . The data of a service is distinguished by a unique set of service field values and within the network packets packet's structure. IP telephony, web, and video surveillance are the examples of services.
- Responsibility area - a network segment which whose effective operation is lays in the responsibility of a certain subject. A subject can be either a specific person or an organization.
- DS domain (Differentiated Services domain) - a logical area having uniform traffic classification rules, defined by a QoS policy. Usually the DS domain coincides with the responsibility area.
- CIR - Committed Information Rate. The system guarantees must guarantee the resources resource allocation in compliance with the CIR for of the service.
- MIR - Maximum Information Rate. In case that the CIR is ensured, the additional resources may be allocated to the services. Additional The additional resources cannot exceed the MIR threshold and their allocation is not guaranteed.
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Packet distribution scheme
In packet networks traffic is transmitted from the sending node to the receiving node through communication channels and intermediate devices. Generally a data packet is processed by each intermediate device independently. Let's look at the example of a data packet processing by an intermediate network device (Figure 1):
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