Opaque Defined in RFC 1155 | Generated by AI
Question: What is the unknown data type defined in RFC 1155?
Answer:
In RFC 1155 (“Structure and Identification of Management Information for TCP/IP-based Internets”), which defines the Structure of Management Information (SMI) for SNMPv1, the data type defined as representing an unknown or arbitrary data type is Opaque.
Here is a breakdown of the options provided:
- Counter: A non-negative integer that increases until it reaches its maximum value ($2^{32}-1$), at which point it wraps around to zero. It cannot decrease.
- TimeTicks: A non-negative integer representing the time in hundredths of a second since some epoch.
- Gauge: A non-negative integer that can increase or decrease. It latches at its maximum value if exceeded but does not wrap around like a Counter.
- Opaque: This type is used to pass arbitrary data types that are not defined in the SMI itself. It essentially acts as an “unknown” type or a container for arbitrary octet strings, allowing for extensibility. The description in your exam question explicitly states: “Opaque: Opaque type is the unknown data type, or rather can represent any type.”
Therefore, the correct answer is D. Your selection of B (TimeTicks) was incorrect because TimeTicks is a specific type for measuring time intervals, not an unknown or arbitrary type.
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