200-301 Question 490
Single answerA network engineer is troubleshooting a communication issue on a serial link between two routers. The link utilizes Non-Return-to-Zero (NRZ) encoding. What is one potential issue with using NRZ for this communication?
- A
It causes high levels of electromagnetic interference (EMI).
- B
It can lead to synchronization problems during long sequences of identical bits.
- C
It requires significantly more bandwidth compared to other encoding schemes.
- D
It is incompatible with serial links and only works on Ethernet networks.
Show answer and explanation
Correct answer: B
Explanation
Non-Return-to-Zero (NRZ) encoding represents binary data using two voltage levels without any transitions to indicate bit boundaries. This can lead to synchronization issues, especially during long sequences of identical bits, because the receiver may lose track of where one bit ends and the next begins. Such issues are commonly addressed in practice by using encoding schemes like NRZI (Non-Return-to-Zero Inverted) or Manchester encoding.
- A. Incorrect.
NRZ encoding is not known to inherently cause high levels of electromagnetic interference (EMI). EMI is typically influenced by factors such as cable shielding and external noise sources, not encoding type.
- B. Correct.
NRZ encoding does not include a mechanism to indicate transitions between bits. As a result, long sequences of identical bits (e.g., multiple consecutive 0s or 1s) can make it difficult for the receiver to maintain synchronization with the sender.
- C. Incorrect.
NRZ encoding is relatively simple and does not consume more bandwidth compared to other encoding schemes like Manchester encoding. Its efficiency is one of its advantages.
- D. Incorrect.
NRZ encoding is used for both serial and parallel communication links. It is not limited to Ethernet networks and is compatible with serial connections.