The functions of Quality of service (QoS) are of great importance for the successful operation of the long-distance voice provider. Without QoS, the network load can have a very unfavorable effect on voice quality. This data shows the results of the tests, during which the impact of QoS on the quality of voice communication was assessed when the volumes of network traffic fluctuated. In the case of “Quality without QoS” there will be a decrease in the quality of voice communication in every case of overloads in the network. Another case of “Quality with QoS” shows that the quality of voice communication is always high, as soon as the use of QoS methods begins on the network.
Different methods that give priority to voice packets, allow stabilizing the quality of voice communication in spite of fluctuations in network load. Priority processing of voice packets is achieved using different QoS standards.
The Following QoS Protocols Are Supported (Based On Cisco IOS):
WFQ is the Weighted Fair Queuing protocol. This is a data flow sequence algorithm that simultaneously solves two problems: places interactive traffic in the head of the queue, thereby shortening the response time, and evenly distributes the remaining bandwidth between broadband streams. WFQ provides predictability of services. Small data streams, which constitute the majority of the traffic, are served on a priority basis, which allows the timely transfer of all the information contained in them. Large traffic flows evenly share the remaining part of the bandwidth. The WFQ protocol is sensitive to IP-priority (IP Precedence). This means that it recognizes high-priority tags that are placed on packets during data transfer, and processes these packets faster than low-priority ones. This reduces the response time for priority traffic.
Priority Queuing and Custom Queuing. This protocol creates flexible mechanisms for prioritizing VoIP services. The Priority queue feature allows network administrators to prioritize traffic by creating filters that respond to packet characteristics. These filters divide traffic into four queues. The queue with the highest priority level is always serviced first. The regular queue function (bandwidth allocation function) reserves part of the bandwidth for each type of traffic. Traffic is distributed by queues, and then it is transferred in turn, so that each queue receives a band allocated for it.
WRED – Weighted Random Early Detection protocol. This protocol allows anticipating and avoiding overflow of the network by means of priority processing of priority traffic packets recognized by the IP Precedence labels. At times when the first signs of overflow appear on the interface, this protocol can selectively reject low priority packets. In addition, WRED can provide support for different performance indicators for different classes of service.
While choosing the provider pay attention, if the equipment supports QoS specifications for IP and ATM protocols and provides a comprehensive quality of service over the entire length of the channel. In ATM networks, various persistent virtual channels (PVCs) can have different quality of service characteristics (for example, they may have different buffer and overload thresholds). The IP Precedence parameters are assigned by the gateway and superimposed on the corresponding ATM traffic classes.
Tag Switching / Multiprotocol Label Switching (MPLS) allows Internet Service Providers to differentiate tariffs depending on the class of service (CoS). So, for example, a subscriber can subscribe to a service for the first class, business class or economy class. The traffic of this subscriber will receive labels corresponding to the subscription class. The gatekeeper can choose different routes for traffic transmission with different classes of services.