Within the OSI model, which layer is responsible for creating and recognizing frame boundaries (i.e., framing) on a link between adjacent nodes?

Introduction / Context:
The OSI model separates networking responsibilities into seven layers. Framing—the process of packaging bits into identifiable units with headers, trailers, and delimiters so that neighbors can detect beginnings and ends—is essential to reliable link-local communication. Knowing which layer performs framing helps distinguish physical signaling from logical link control.

Given Data / Assumptions:

• We are focused on communication between directly connected nodes (adjacent).
• Framing is about defining frame boundaries and associated control information.
• Error detection (e.g., CRC) is often part of the same layer’s responsibilities.

Concept / Approach:
The Data Link layer (Layer 2) handles framing. It encapsulates higher-layer packets into frames with headers and trailers, includes an FCS/CRC for error detection, and manages media access control (MAC). The Physical layer (Layer 1) is responsible for transmitting raw bits as electrical/optical/radio signals but does not define where frames start or end. Network and Transport layers operate on packets/segments above the link level, not on raw frames between adjacent nodes.

Step-by-Step Solution:

Verification / Alternative check:
Examples include Ethernet frames with preamble/SFD, headers, payload, and FCS; HDLC/PPP frames with flags and FCS. All are standardized Data Link layer constructs for framing on point-to-point or shared media.

Why Other Options Are Wrong:

• Physical: no framing; only signal levels, modulation, and timing.
• Network: routing and logical addressing, not frame delimitation.
• Transport: reliability and flow control between endpoints, not neighbors.
• Session: dialog control above Transport; not link framing.

Common Pitfalls:
Attributing CRC solely to Physical layer; mixing the concept of packets (L3) with frames (L2). Also, assuming preamble is a Physical construct—while transmitted at Layer 1, its framing meaning belongs to Layer 2.

Final Answer:
Data link layer