Second-generation VoIP networks have achieved a fair degree of commercial success. Companies are using the technology to save money on trunking costs and for functional enhancements such as mobility, presence-related functions and unified messaging. VoIP networks are beginning to support roaming from Ethernet-based phones to cellular service.

Why is IPv6 well-suited for VoIP than IPv4? For starters, IPv6 eliminates the need for network address translation, which disrupts end-to-end connectivity that VoIP was really designed for. Secondly, QoS (or quality of service) is assured in IPv6 because it's easy to mark or group VoIP traffic and be given priority on the network.