On each WAN connection, data is encapsulated into frames before it crosses the WAN link. The following are typical WAN protocols:
1. High-level Data Link Control (HDLC): The Cisco default encapsulation type on point-to-point connections, dedicated links, and circuit-switches connections.
2. PPP: Provides router-to-router and host-to-network connections over synchronous and asynchronous circuits. PPP was designed to work with several network layer protocols, including IP.
3. Frame-relay: A successor to X.25. This protocol is an industry-standard, switchesdata-link layer protocol that handles multiple virtual circuits