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101 · Question #682
101 Question #682: Real Exam Question with Answer & Explanation
The correct answer is B: Application. DNS SERVFAIL, HTTP 404, and SMTP 550 are protocol-specific error codes generated by Application layer (OSI Layer 7) services, classifying them as application errors.
Question
Comment calculator DNS error SERVFAL. HTTP 404 and SMTP error 550 are all examples of which type of error?
Options
- AService
- BApplication
- CNetwork
- DSession
Explanation
DNS SERVFAIL, HTTP 404, and SMTP 550 are protocol-specific error codes generated by Application layer (OSI Layer 7) services, classifying them as application errors.
Common mistakes.
- A. 'Service' is not a recognized OSI error classification layer; application protocol errors such as these are correctly categorized at the Application layer, not a generic service category.
- C. Network-layer errors involve packet routing and delivery failures such as ICMP unreachable messages or TTL expiration, not protocol-specific response codes returned by application services.
- D. Session-layer errors (OSI Layer 5) relate to session establishment, maintenance, and termination failures, not to status codes returned by application protocols like HTTP or SMTP.
Concept tested. OSI Application layer protocol error code classification
Reference. https://www.rfc-editor.org/rfc/rfc9110#section-15
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