A new Link Layer interface such as DUAL is useless unless it can be easily integrated into an existing system. Fortunately, most existing amateur packet stations use Terminal Node Controllers (TNCs) with KISS functionality [K3MC \& KA9Q 85].
All TNCs provides a LLC, MAC and one or more Physical layers, giving the user AX.25 virtual circuit connectivity. TNCs which have KISS support give access directly to the Medium Access Control (MAC) layer, allowing a new LLC layer to be added to the system.
Our implementation of DUAL, described earlier in this paper, encapsulates DUAL packets in KISS format, see figure 17. The computer, which contains the network layers from DUAL up to the applications, can be connected to a TNC in KISS mode, which provides the MAC and Physical layers.
Figure : DUAL packets encapsulated in KISS format