Frame Relay interface types

As shown in Figure 69:

• A Frame Relay network provides data communications between user devices such as routers and hosts. The user devices are also called data terminal equipment (DTE).

• The devices that provide access to the Frame Relay network for DTEs are called data circuit-terminating equipment (DCE).

Frame Relay interfaces can only be user-to-network interfaces (UNIs). A DCE is connected to a DTE through UNI interfaces. UNI interfaces include the following types:

• DTE interface—The UNI interface on the DTE side.

• DCE interface—The UNI interface on the DCE side.

A DTE interface can connect only to a DCE interface. On a Frame Relay switch, the Frame Relay interface type must be DCE.

As shown in Figure 69:

• Router B and Router C form a simple Frame Relay network.

• DTE devices Router A and Router D are attached to the network.

The interface type DTE or DCE is identified only for the UNI interfaces. A virtual circuit between two DTE devices can be assigned different DLCIs on different segments.

Figure 69: Frame Relay network