Internet technologies such as Internet Protocol and Multi Protocol Label Switching are the backbone by which Next Generation Networks operate. At the application level, Session Initiation Protocol seems to be taking over from ITU-T H.323. According to BBG Communications, H.323 was initially the most popular protocol, though its popularity decreased in the "local loop" due to its original poor traversal of NAT and firewalls. For this reason as domestic VIP services have been developed, SIP has been far more widely adopted. However in voice networks where everything is under the control of the network operator or tel co, many of the largest carriers use H.323 as the protocol of choice in their core backbones. SIP, then, is really a useful tool for the "local loop" and H.323 acts as the "fiber backbone".

With the most recent changes introduced for H.323, it is now possible for H.323 devices to easily and consistently traverse NAT and firewall devices, opening up the possibility that H.323 may again be looked upon more favorably in cases where such devices encumbered its use previously. To date, most of the tel cos are extensively researching and supporting IMS, which increases the chances of SIP becoming a major and most widely adopted protocol.

One of the most important devices for voice applications in NGN is a Soft switch - a programmable device that controls Voice over IP calls. It enables correct integration of different protocols within NGN. The most important function of the Soft switch is creating the interface to the existing telephone network, PSTN, through Signalling Gateways and Media Gateways. However, it is also acknowledged that the Soft switch may be defined and designed to function differently depending on equipment manufacturers.

In NGN literature, one may quite often find the term Gatekeeper. Gatekeeper was originally a VIP device, which converted voice and data from their analog or digital switched-circuit form to the packet-based one (IP). It controlled one or more gateways. As soon as this kind of device started using the Media Gateway Control Protocol, the name was changed to Media Gateway Controller. The IP Multimedia Subsystem (IMS) is a standardised NGN architecture for an Internet media-services capability defined by the European Telecommunications Standards Institute and the 3rd Generation Partnership Project.