Frame Relays are a telecommunication service designed for cost-efficient data
transmission for intermittent traffic between local area networks LAN and between end-points in a wide area network (WAN.
Frame relay puts data in a variable-size unit called frame and leaves any necessary error correction (retransmission of
data) up to the end-points, which speeds up overall data transmission. For most services, the network provides a
permanent virtual circuit (PVC which means that the customer sees a continuous, dedicated connection without having to
pay for a full-time leased line, while the service provider figures out the route each frame
travels to its destination and can charge based on usage. An enterprise can select a level of service quality - prioritizing
some frames and making others less important. Frame relay is offered by a number of service providers, including AT&T. Frame
relay is provided on T-carrier system carriers. Frame relay complements and provides a mid-range service between ISDN which offers speeds
at 128 Kbps, and Asynchronous Transfer Mode, which operates in somewhat similar fashion to frame relay but at
speeds from 155.520 Mbps or 622.080 Mbps. (ISDN is similar to a modem but does not accept analog signals and thus cannot accept dial-up signals which are analog).
Frame Relay is based on the older X.25 packet-switching technology which was designed for transmitting analog
data such as voice conversations. Unlike X.25 which was designed for analog signals, frame relay is a fast packet technology which means that the protocol does not attempt to correct
errors. When an error is detected in a frame, it is simply "dropped." (thrown away). The end points are responsible for
detecting and retransmitting dropped frames. (However, the incidence of error in digital networks is extraordinarily small relative to analog networks.)
Frame Relay is often used to connect local area networks with major backbones as well as on public wide area networks and also
in private network environments with leased lines over T-1 lines. It requires a dedicated connection during the
transmission period. It's not ideally suited for voice or video transmission, which requires a steady flow of transmissions.
However, under certain circumstances, it is used for voice and video transmission.
Frame Relay relays packets at the data link layer of the Open Systems Interconnection model rather than at the
Network layer. A frame can incorporate packets from different protocols such as X.25. It is variable in size and can be as large as a thousand bytes