Ethernet Not for Metropolitan Networks | Generated by AI
Question: Which of the following network technologies cannot be used for metropolitan area networks (MAN)?
A. FDDI
B. Ethernet
C. DQDB
D. ISDN
Answer:
The correct answer is B. Ethernet.
Explanation:
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FDDI (Fiber Distributed Data Interface): A high-speed token-ring network technology (100 Mbit/s) specifically designed for use in metropolitan area networks and campus backbone networks. It was commonly used in MANs in the 1990s and early 2000s. → Can be used in MAN.
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Ethernet: Traditional Ethernet standards (10 Mbps, 100 Mbps, even early Gigabit Ethernet) had significant distance limitations (usually hundreds of meters). They were designed primarily for LAN use. While modern Metro Ethernet (based on Carrier Ethernet standards such as IEEE 802.1Qay, 802.1ah, MPLS-TP, etc.) can now be used in MANs, the question is likely referring to classic Ethernet (as taught in many older textbooks), which cannot cover the distances and scale required for a true metropolitan area network. → Cannot be used in MAN (in the context of this question).
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DQDB (Distributed Queue Dual Bus): This is the technology defined in the IEEE 802.6 standard, specifically designed for Metropolitan Area Networks (MANs). It was one of the earliest standardized MAN technologies. → Can be used in MAN.
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ISDN (Integrated Services Digital Network): While ISDN is primarily a wide-area access technology (used for connecting sites over the telephone network), it was sometimes used to provide connectivity across a city/region, especially before broadband became widespread. Some textbooks classify it as usable in the MAN context for certain applications. → Can be used in MAN (in the context of this question).
Conclusion: In the context of this exam question (which appears to follow older Chinese networking textbooks), classic Ethernet is considered unsuitable for MAN due to distance and topology limitations, while the other three technologies were either designed for or practically used in metropolitan-scale networks.
Therefore, the correct choice is B. Ethernet.
References:
- None (this is based on standard networking textbook classification in many Chinese IT certification materials)