Two main types of equipment exist on ATM networks – ATM switches, and ATM endpoints. As its name suggests, an ATM switch handles cell-switching functions across an ATM network. This includes accepting incoming cells from other ATM switches or endpoints, modifying cell header information as necessary, and then sending cells on to the next switch or end device. An ATM endpoint is a network device equipped with an ATM network interface card, such as a router, computer, LAN switch, and so forth. Cisco router models in the 5500 series are commonly equipped with ATM expansion cards for the purpose of connecting to an ATM backbone.
Special terms are used to describe the connection points between ATM equipment. – User Network Interface (UNI) and Network Node Interface (NNI). UNI represents a connection between an endpoint such as an ATM-enabled PC and an ATM switch. NNI is the term used to describe connections between ATM switches. ATM equipment and connection points are illustrated in the figure below.