In shared-medium networks (e.g., classic Ethernet or Wi-Fi), what condition describes the situation in which two or more stations try to transmit over the same channel at the same time?

Introduction / Context:
This question tests your grasp of access control on shared media. Multiple stations often share a common channel (wired bus, wireless spectrum). Understanding the precise term for simultaneous transmission attempts is fundamental for protocols like CSMA/CD (Ethernet) and CSMA/CA (Wi-Fi).

Given Data / Assumptions:

• A single shared channel is used by many stations.
• No centralized scheduler guarantees exclusive access per time slot.
• Stations use distributed rules to decide when to transmit.

Concept / Approach:

Contention = the condition of competition for the channel when two or more stations attempt transmission at the same instant or overlapping intervals.Collision = a possible outcome of contention when overlapping transmissions interfere, corrupting frames.Synchronous/Asynchronous = timing/formatting attributes of communication, not the access condition itself.

Step-by-Step Solution:

Verification / Alternative check:

In CSMA/CD, devices sense carrier and defer; if two devices sense idle and transmit almost simultaneously, a collision is detected. The initiating state was contention; the corrupted event is the collision.

Why Other Options Are Wrong:

Collision: Outcome of overlapping transmissions, not the general condition prompting attempts.

Synchronous: Refers to clocking/bit timing, not shared-medium access.

Asynchronous: Refers to start/stop or unslotted timing, not simultaneous-use condition.

None of the above: Incorrect because 'Contention' is the established term.

Common Pitfalls:

Equating contention and collision as synonyms. Contention can exist even when backoff prevents actual collisions.

Final Answer:

Contention