Report an IPv4 delivery problem
01ICMP returns control information to the source of an IPv4 datagram.
Related RFCs and changes
“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.
DIAGRAMIntroduction ↗
RFC 792 · IntroductionEXAMPLE
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Send feedback toward the original source, not onward as payload delivery.
Send feedback toward the original source, not onward as payload delivery.
Protocol participantThreat or exceptionProtocol controlSimplified drawings · precise section references
Read the updated RFC section ↗
ICMP uses IP protocol number 1 and is carried inside an IP datagram.
- ICMP uses IP protocol number 1 and is carried inside an IP datagram.
- Feedback does not make IP reliable; ICMP errors are not sent in response to ICMP errors.
The drawing is a simplified worked example. Follow the linked RFC and its updates for implementation requirements.
Read the RFC section ↗Diagrams simplify the RFC. Read the linked sections for complete requirements.
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