Open-Source Based Prototype for Quality of Service (QoS) Monitoring and Quality of Experience (QoE) Estimation in Telecommunication Environments

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This paper describes an implementation for monitoring the QoS and expecting the QoE of a voice communication in a Real-time Transport Protocol (RTP) based telecommunication environment. The resulting …

This paper describes an implementation for monitoring the QoS and expecting the QoE of a voice communication in a Real-time Transport Protocol (RTP) based telecommunication environment. The resulting QoS parameters are evaluated; the QoE is determined with the E-Model and processed for graphical presentation. With the use of some open-source programming libraries, the presented prototype can be a helpful alternative for expensive measurement devices and is ready to be deployed in a widespread telecom environment at low cost. Presented at NGMAST 2011 in Cardiff, UK.

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  • 1. Open-­‐‑Source  Based  Prototype  for  QoS   Monitoring  and  QoE  Estimation  in   Telecommunication  Environments   Sebastian Schumann Slovak University of Technology Bratislava, Slovakia Cardiff, UK – 15. September 2011
  • 2. Introduction •  Implementation for Quality of Service (QoS) and Experience (QoE) monitoring •  Works in Real-time Transport Protocol (RTP) based telecommunication environments •  Analysis o  QoS parameters are evaluated o  QoE is determined with the E-Model •  Output o  R-Factor, one-way delay, packet-loss probability o  Graphical representation
  • 3. Environment •  Usage of Voice over IP (VoIP) increased over the last years •  It is not always possible to enforce QoS, esp. in unmanaged networks •  Size of measured network does not matter •  Measurement system o  Measurement points (probes) are distributed o  Central reporting unit collects and evaluates the data •  Focus on widespread networks, not system components
  • 4. Motivation •  ngnlab.eu targets distributed VoIP environments and open-source based solutions •  Commercial solutions are expensive, only for operators •  Main goals o  Easy but flexible measurement design o  A non-intrusive online monitoring o  Informative results o  Ability to determine the geographical and technical source of degradations
  • 5. “Competition”
  • 6. Theory •  E-model used to determine QoE (calculated acc. several network parameters) •  Objective (i.e., calculated) value can be mapped to the subjective Mean Opinion Score (MOS) •  Impacts on speech quality are o  One-way delay o  Packet-loss probability o  Packet-loss distribution o  Speech codec •  Measurement and evaluation of values allow calculation of QoS/QoE during the call
  • 7. Correlation  between  MOS   value  and  R-­‐‑Factor
  • 8. Measured  Impairments  I •  One-way delay •  Measured by halving the Round-Trip-Time (RTT) value of the voice packets (estimation) •  Both directions possible •  RTT determination using measured values o  Time-stamp in PCAP o  Time-stamp in RTCP •  RTT1=A2-A1-D2 •  RTT2=A3-A2-D3 DLSR .. delay sender report A1 .. 1st SR passes ME A2 .. following SR D2 .. DL btw reception of SR1 and transmission of SR2
  • 9. Measured  Impairments  II •  Packet loss probability •  Determined by recording the sequence number of each RTP packet that passes the ME •  The loss probability is updated after every 100 RTP packets o  The time distance is a good balance between the applied load on the ME, the network load, and the actuality of the measurement results on the EE
  • 10. Measured  Impairments  III •  Packet loss distribution calculated acc. the patent of McGowan o  Overall packet loss probability (Ppl) o  Average length of all loss sequences •  Speech codec is determined by parsing the Session Description Protocol (SDP) during the session establishment procedure •  Knowledge is important in relation to the used compression method and its robustness against packet loss (packet loss robustness factor)
  • 11. Network  setup
  • 12. Application •  Measurement probes o  PCAP library captures packet for analysis o  Perl script extracts required information from each packet o  HTTP is used to exchange measured parameters •  Central reporting unit o  Java application o  Real-time monitoring with three detail levels (monitoring unit, call, details) o  Adjustable color indication when pre-set thresholds are reached
  • 13. GUI
  • 14. Measurement  setup
  • 15. Results  I •  Non-degraded measurement •  Normal values •  Delay in path 2+4 high due to public network
  • 16. Results  II •  Degraded measurement •  One-way delay on the Internet higher (20x) in paths 2+4 •  R-Factor decreased as well •  Knowing network and taking packet loss into account, low upload on office B is determined
  • 17. Summary •  QoS and QoE can be measured using the designed prototype •  Implementation is scalable to smaller or larger Telco networks (probes can be distributed accordingly) •  Implementation can compete with professional equipment to a certain extent •  Extensions open but easily possible o  Alarms o  Visual network status display in real-time o  Follow-up calls for neg. quality calls o  Recording of call samples possible as well
  • 18. Thank  you! Sebastian Schumann seb.schumann@gmail.com @s_schumann