Voip Think- Voice over IP - Asterisk and SER - SIP IAX and H323

3CX VoIP Phone System, IP PBX for Windows
3CX PBX and Phone System for Windows
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  • VoIP Protocols

  • Telephones

  • QoS (Quality of Service)

  • Codecs

  • Asterisk

  • 3CX PBX

  • SER (Sip Express Router)

  • More information


      QoS - Quality of Service  

        Introduction   Jitter   Latency   Latency   Packet Loss   Test   Bandwidth  



    Jitter is a typical problem of the connectionless networks or packet switched networks. Due to the information is divided into packets each packet can travel by a different path from the emitter to the receiver.

    Jitter is technically the measure of the variability over time of the latency across a network

    Real time communications (for example VoIP) usually have quality problems due to this effect. In general, it is a problem in slow-speed links or with congestion. It is hoped that the increase of QoS (quality of the service) mechanisms like priority buffers, bandwidth reservation or high-speed connections (100Mb Ethernet, E3/T3, SDH) can reduce jitter problem in the future although it will keep on being a problem for a long time.


    Jitter between the starting and final point of the communication should be less than 100 ms. If jitter value is smaller than 100 ms it can be solved. If not must be reduced.


    - The best solution is to use jitter buffers. A jitter buffer is basically to assign a small buffer to receive the packets and give it to the receiver with a small delay. If some packet is not in the buffer (it is lost or it has still not arrived) when it is necessary it is not taking into account. Usually in IP telephones (hardware and software) buffer lengths can be modified. If jitter buffer is increased turns out in less packet loss but more delay. A reduction turns out in less delay but more packet loss.


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