Advanced Topics: Call Redirection
Olivier Hersent · 2010
There is no question that the ability of VoIP to redirect calls without tromboning media is the major breakthrough of the technology. This chapter discusses in detail the various implementation choices for call redirection services, the difficulties that appear in the context of public networks, and how these challenges can be addressed. PSTN residential services frequently provide the call forward service. The service is implemented in the last-hop class 5 switch. The chapter describes many heterogeneous PBX networks use that call transfer by the PBX method. However, this method is not optimal as call media are ‘tromboned’ through the redirecting PBX, and this uses more bandwidth on the corporate intersite communications lines. If all PBXs are from the same brand, or if they support the QSIG extensions of ISDN (about one-third of PBXs are QSIG capable), there is a possibility to optimize the call flow. Controlled Vocabulary Terms computer networks; Internet telephony; ISDN; Voice over internet protocol