A Network Termination Interface (NTI) is a gateway device that sits at the boundary between the Wide Area Network (WAN) or Metropolitan Area Network (MAN) and the end user (subscriber's) Local Area Network (LAN). This interface device converts the network providers delivery network into a delivered network format usable by the subscriber. For our purposes the delivered network is an Internet Protocol (IP) network.

In the residential cable and DSL marketplace it has become ubiquitous to refer to the NTI as a modem even though it is not. A modem is a modulator/de-modulator that converts digital signals to analog wave forms for transmission over analog voice channels. Since most consumers were used to dial up modems it was simply easier to refer to the newer consumer digital termination units as modems to avoid confusion on the part of the consumer.

We are now seeing a return to the more proper term "gateway" with the newest technology being delivered by the cellular broadband manufacturers to further differentiate themselves as being set apart from the older "modem" technology provided by cable and DSL.

The subscriber will generally get very little choice in the selection of the NTI as it is generally a bundled product with the subscription. The NTI is generally capable of reporting back to the service provider some level of problem determination information and subscriber security verification.