Compared with asynchronous protocols, synchronous data link protocols typically provide what performance characteristic during transmission on serial links?

Introduction:
Serial communications can be organized as asynchronous or synchronous. The distinction affects framing overhead, timing recovery, and achievable throughput. This question asks which performance characteristic is typically associated with synchronous protocols.

Given Data / Assumptions:

• Synchronous links share a common clock or embed timing so characters/frames do not need per-character start/stop bits.
• Asynchronous links add start/stop bits to each character and do not depend on a shared clock.
• We compare typical throughput under similar line conditions.

Concept / Approach:
Synchronous protocols (e.g., HDLC/SDLC) frame blocks of data with minimal per-character overhead. Clocking is continuous or recovered, so the line can be used efficiently with fewer overhead bits per payload bit. Asynchronous protocols add start and stop bits to every character (often 10 bits per 8-bit character), reducing efficiency and limiting maximum useful throughput on the same physical line. Hence, for a given signaling rate, synchronous protocols usually achieve higher effective data rates.

Step-by-Step Solution:
Identify overhead differences: async adds start/stop per character; sync does not.Relate overhead to efficiency: fewer overhead bits → higher throughput.Map to the offered choices: “allow faster transmission than asynchronous protocols do.”Select that as the correct statement.

Verification / Alternative check:
Line efficiency calculations show typical async 8N1 uses 10 bits per byte (80% efficiency before other overhead), whereas sync frames can approach near 100% efficiency for large blocks.

Why Other Options Are Wrong:

• Transmit characters one at a time (A): describes asynchronous character framing, not synchronous block/frame transfer.
• Generally used by personal computers (C): both types are used; not a defining truth.
• Are more reliable (D): reliability depends on error control, not strictly sync vs. async.
• None of the above (E): invalid because option B is correct.

Common Pitfalls:
Equating “synchronous” with “parallel” or assuming reliability is intrinsic rather than a function of framing and error control.

Final Answer:
allow faster transmission than asynchronous protocols do