Frame - a unit of data exchanged within a network or subnetwork. PVC's save bandwidth associated with establishment and teardown in situations where certain virtual circuits must exist all the time. A data communications network that serves users across a broad geographic area and often uses transmission devices provided by common carriers. The DTE is typically a router, and the DCE is a Frame Relay switch. This allows packets of various sizes to be switched and transported over the frame relay network.
Encapsulation involves adding a header and a trailer to the existing packet to create the new frame.
A frame relay frame consists of a header, and information field and a trailer. The header contains a flag to identify the start of the frame, and an address field for routing the frame to its destination. The information field contains the original data from the sender. The following diagram outlines each of these components. Frame Relay vs. X.25 Services Frame Relay is a modified form of packet-switching X.25 networks that perform error recovery and flow control between nodes.