The document describes Frame Relay, a packet switching protocol used in wide-area networks. It includes 18 figures illustrating Frame Relay concepts such as its network architecture, data link connections, permanent and switched virtual circuits, congestion control using backward explicit congestion notification and forward explicit congestion notification, and the leaky bucket algorithm for traffic shaping. Frame Relay provides connection-oriented services over packet-switched networks and was commonly used for WAN connectivity in the 1990s.