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Thực hiện tiếng nói qua IP (P5)

A TESTBED FOR EVALUATING VoIP SERVICE1 A new service must be prototyped and tested in a laboratory environment before massive deployment. This allows objective and subjective evaluation of the service in question. In addition, the findings can be used for tuning the network operations and performance control parameters, as required for maintaining acceptable QoS (as discussed in Chapter 4). The testbed presented in this chapter consists of a variety of PSTN and IP domain network elements [1]. These elements are required to emulate PSTN and IP networks, IP network impairments, and elements of SS7 networks like SCP and STP | Implementing Voice over IP. Bhumip Khasnabish Copyright 2003 John Wiley Sons Inc. ISBN 0-471-21666-6 5 A TESTBED FOR EVALUATING VoIP SERVICE1 A new service must be prototyped and tested in a laboratory environment before massive deployment. This allows objective and subjective evaluation of the service in question. In addition the findings can be used for tuning the network operations and performance control parameters as required for maintaining acceptable QoS as discussed in Chapter 4 . The testbed presented in this chapter consists of a variety of PSTN and IP domain network elements 1 . These elements are required to emulate PSTN and IP networks IP network impairments and elements of SS7 networks like SCP and STP. Other network elements include a the network timing server b software- and hardware-based IP and SIP phones c analog and digital including ISDN BRI circuit or PSTN phones and d test equipment to emulate and analyze single and bulk phone calls. This testbed is used for a variety of VoIP tests and measurements as described in Appendixes A B and C. Appendix A discusses how this testbed can be used to measure call progress time in IP telephony. A multistage call setup method is proposed and its implementation using a set of scripts written in Hammer visual basic HVB language www.hammer.com www.empirix.com 2001 is described. Appendix B presents techniques to determine the bulk-call-setup requesthandling performance of IP-PSTN GWs. To achieve this both call burst size and intercall burst time gap must be determined so that the call setup requests are properly processed. These are implemented using HVB language for testing some commercially available IP telephony GWs. 1 The ideas and viewpoints presented here belong solely to Bhumip Khasnabish Massachusetts USA. 59 60 A TESTBED FOR EVALUATING VoIP SERVICE Finally Appendix C shows how this testbed can be utilized to evaluate the impact of various IP network impairments such as delay jitter packet loss and .