Also known as SDN (Software-Defined Network) and SDDN (SoftwareDefined Data Network).A digital data network service that operates much like a voice VPN or Switched 56, although the level of bandwidth provided can be much greater in support of intensive data communications, videoconferencing, or multimedia conferencing. Such a VPN creates the effect of a private, leased-line network, but without the associated issues such as design complexity and lengthy deployment. Rather than interconnecting the various sites with dedicated circuits, the carrier routes the traffic through the public switched telephone network (PSTN) facilities on a priority basis over pre-determined paths that are digital from end to end, thereby ensuring that the level of service provided is roughly equivalent to that of a true private data network. VPN services generally are interexchange, and often international, in nature, as they find their greatest application in very large multisite, national or multinational enterprises. Depending on the carrier, VPNs support bandwidth of 56/64 kbps, N.