Frame relay is a packet-switching telecommunication service designed for interconnecting enterprise LANs. It is layer2 non-broadcast multiaccess (NBMA) WAN technology. It allows for a single serial interface on the router to connect multiple remote sites with the help of permanent virtual circuits (PVCs) or switched virtual circuit (SVCs).

PVCs have dedicated connection without having to pay for a full-time leased line, but the service provider can monitor each frame travels to its destination and can charge based on usage. PVCs can bring both voice and data traffic between a source and destination, and support data rates up to 4 Mb/s, with some providers offering higher data speed. A customer can select a level of service quality, for example, they can prioritize some traffic and can make some traffic less important. Frame relay create switched virtual circuit (SVCs) when data is available for sending and then close these SVCs when there is no more data available for sending.

Data-link Connection Identifier (DLCI)

Data-link connection identifier (DLCI) is used to uniquely identify the frame relay PVCs. PVC and DLCI both are responsible for bidirectional communication from DTE to another device. DLCI may be the router configured with frame relay or provided by the service provider in both cases, the endpoints are configured as DLCI number to identify uniquely. DLCI number is necessary on both sides of frame relay as the source and destination.

Frame Relay Devices

It is used, Data Terminal Equipment (DTE) and Data Circuit terminating Equipment (DCE) for data transmission. DTEs is usually the customer’s side equipment and can include routers, bridges and personal computers. DCEs are service provider side equipment providing switching and associated services.