Đang chuẩn bị liên kết để tải về tài liệu:
Thực hiện tiếng nói qua IP (P4)

CRITERIA FOR EVALUATING VoIP SERVICE1 In this chapter, I describe a set of important criteria that can be used to perform qualitative and quantitative measurements of IP phone or POTS phone (black phone) to black phone/IP phone voice calls over an IP network. Since a legacy POTS call, with all of its robust characteristics over an IP network, is considered to be a killer application (service) by many of the proponents of VoIP, it is recommended that a private IP network or Intranet be used for measuring performance | Implementing Voice over IP. Bhumip Khasnabish Copyright 2003 John Wiley Sons Inc. ISBN 0-471-21666-6 4 CRITERIA FOR EVALUATING VoIP SERVICE1 In this chapter I describe a set of important criteria that can be used to perform qualitative and quantitative measurements of IP phone or POTS phone black phone to black phone IP phone voice calls over an IP network. Since a legacy POTS call with all of its robust characteristics over an IP network is considered to be a killer application service by many of the proponents of VoIP it is recommended that a private IP network or Intranet be used for measuring performance. This is because the network operator has better control over the entire network ingress egress routing paths and protocol and so on in such a scenario and the best possible performance can be achieved when an internal IP network instead of the public Interent is used for VoIP. The performance parameters of interest are availability of the network and dial tone call setup request processing performance call completion drop rate one-way voice transport delay or voice envelop delay voice quality during the conversation using both subjective and objective measures and so on. There is a series more than 100 of Telcordia LATA switching systems generic requirements GRs commonly known as LSSGR details can be found at www.SAIC.com 2001 which specify the reliability availability and service requirements of PSTN switch-based telephony voice calls. These specifications may need to be revised in the context of VoIP services offered using nextgeneration packet-switch-based multiservice networks. 1 The ideas and viewpoints presented here belong solely to Bhumip Khasnabish Massachusetts USA. 49 50 CRITERIA FOR EVALUATING VoIP SERVICE SERVICE REQUIREMENTS BEFORE CALL SETUP ATTEMPTS Two of the most important parameters of interest for VoIP even before a call setup attempt is made are the following Availability of the dial tone so that the users get the impression that the .