In virtual circuit networks (e.g., X.25 or virtual circuits in frame relay/ATM), establishing a virtual connection before sending user data is most analogous to which everyday action?
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AConnecting as virtual memory
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BPhysically connecting a DTE and DCE
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CPlacing a telephone call prior to a conversation
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DPlacing a modem prior to a conversation
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ENone of the above
Answer
Correct Answer: Placing a telephone call prior to a conversation
Explanation
Introduction / Context: Virtual circuit networks set up a logical path with identifiers and state before data transfer, ensuring ordered delivery and resource expectations similar to a phone call setup.
Given Data / Assumptions:
- Virtual circuit requires a setup phase.
- After setup, data frames follow the established path.
- Teardown occurs when communication ends.
Concept / Approach: The closest analogy is dialing a telephone: a signaling exchange allocates resources and assigns a path, then conversation (data) flows. This differs from datagram networks where each packet is routed independently without prior setup.
Step-by-Step Solution:
1) Initiate call setup (signaling) → allocate a VC identifier.2) Transfer user data over the VC with guaranteed order.3) Release the VC when finished.Verification / Alternative check: Ordered delivery and fixed path semantics match the phone-call analogy far better than hardware cabling actions.
Why Other Options Are Wrong:
Virtual memory concerns OS memory, not networking.Physically connecting DTE/DCE is a hardware step, not a logical circuit setup.Placing a modem is equipment installation, not per-session signaling.“None of the above” is wrong because the telephone call analogy is correct.Common Pitfalls: Confusing logical setup with physical cabling; assuming setup implies dedicated leased lines (it does not).
Final Answer: Placing a telephone call prior to a conversation.