For a protocol that began life in the 1980s, DPNSS is natively a long way from VoIP. However, many of the hybrid VoIP PBXs available from manufacturer’smanufacturers world wide,worldwide provide on-board DPNSS trunk cards. Where they do not, a Protocolprotocol converter is necessary. Commercially available equipment offers the ability to convert from DPNSS to Q.Sig. Note that Itit is also possible to tunnel DPNSS and it'sits associated PCM (G711) over an IP network. This can be point to point where the IP network carries packetised voice N x 64Kbs64 Kbs speech and a separate IP signalling channel to carry the notional 64Kbs64 Kbs of DPNSS signalling. A more sophisticated solution uses intelligence on the edge of the IP network to route voice to the correct node. This is a [http://en.wikipedia.org/wiki/Voice_VPN[VoIP (voice)VPN]]
Note that this should not be confused with the pre voip-VOIP 'Voice VPN' deployed by routing calls intelligently in a TDM switching platform, often Nortel DMS100 and customers PBX nodes.