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Voice packet telephony is a reality today, although, as an industry, there still is a lot of work ahead. The larger incumbent carriers are starting the migration to packet telephony on the trunk side first (Class-4 tandem) and will eventually migrate to the access side (Class 5). This migration model is similar to the migration from analog switches to digital switches, which started in the late 1970s, and offers a proven path for migration to new technologies. The full migration to packet-based Class 5 systems will happen when the inner network becomes packet-based and when differentiated Class-5 services become available. And the services must go beyond currently available PSTN–based services for packet telephony to become truly compelling. On this journey, the debates over VoIP and VoATM will continue. While VoATM makes sense today for some carriers, especially the larger incumbents, VoIP is the longer-term goal especially with MPLS–based QoS becoming available. For some carriers, VoIP is the answer today as the consumer benefits are persuasive.
Service providers looking to deploy VoP will be best served if they choose a solution that addresses the issues of interoperability, call control and signaling, voice encoding, delay, echo, reliability, density, and performance of all the elements that make up the switching platform. And they should look for solutions that deal with these issues for TDM switching, as well as VoIP and VoATM.
