In data communications, the error-detecting code field inserted into a frame before transmission is called what?

Introduction / Context:
At the data link layer, frames include a dedicated field used to detect accidental bit errors introduced by noise, attenuation, or interference. This field lets the receiver verify integrity before passing data up the stack or requesting a retransmission. Knowing the correct term used in standards and textbooks prevents confusion with related ideas such as checksums and general error-control concepts.

Given Data / Assumptions:

• The question asks for the name of the specific field placed in a frame to detect errors.
• We are at the data link (layer 2) level, dealing with frames, not packets or segments.
• Typical LAN/WAN technologies include Ethernet, PPP, and HDLC-like links.

Concept / Approach:
Most layer-2 protocols append a field called the Frame Check Sequence (FCS). The FCS is the container that carries check bits computed over the frame—commonly using a Cyclic Redundancy Check (CRC) polynomial. While the underlying math might be CRC, the on-the-wire field in the frame trailer is formally named FCS in many standards (for example, IEEE 802 LANs).

Step-by-Step Solution:
Identify the OSI layer and unit: layer 2 and “frame.”Recall the standardized trailer field name: Frame Check Sequence.Understand that the FCS usually contains CRC bits used to detect errors.Therefore, the field inserted for error detection is the Frame Check Sequence.

Verification / Alternative check:
In Ethernet, the 32-bit CRC value is placed in the FCS field at the end of each frame. PPP and HDLC use a Frame Check Sequence of configurable length (often 16 or 32 bits) to provide similar integrity checks.

Why Other Options Are Wrong:
Error-detecting code: A generic phrase; the field’s standardized name is FCS.

Checksum: Another integrity mechanism, but Ethernet and many L2 links use CRC in an FCS, not a simple checksum.

Flow control: Regulates sending rate/windowing; not error detection.

Cyclic Redundancy Check field: Describes the math, but the proper frame-field name is FCS in common standards.

Common Pitfalls:
Mixing the algorithm (CRC) with the frame field name (FCS). Also, confusing higher-layer checksums (e.g., TCP checksum) with link-layer FCS.

Final Answer:
Frame Check Sequence