What is the name of the layer 2 protocol characterized by a frame structure often used in WAN links?

The layer 2 protocol that is characterized by a frame structure and is commonly utilized in WAN (Wide Area Network) links is HDLC, which stands for High-Level Data Link Control. HDLC is a bit-oriented synchronous data link layer protocol that encapsulates data into frames for transmission over various types of physical media. It is particularly known for its ability to provide reliable and efficient communication over point-to-point and point-to-multipoint links.

HDLC frames consist of a specific header and trailer structure, including fields for addressing and control information, which enables it to manage different types of data flows and provide error detection capabilities. This makes HDLC suitable for a range of applications in WAN environments, where data integrity and frame synchronization are critical.

The other choices represent different concepts or layers in networking:

• Packet refers to a unit of data at the network layer (Layer 3) and does not specifically address Layer 2 protocols or frame structures.

• Datagram is also a networking term related to Layer 3, often associated with connectionless protocol data units, particularly in the context of IP networks.

• Message is a more generic term that can refer to any unit of communication in networking, without being specific to a layer or protocol.

Thus, HDLC stands