Fit packets to the path
04Every IPv6 link supports at least a 1280-octet packet, directly or through lower-layer fragmentation.
Related RFCs and changes
“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.
DIAGRAM§ 5 ↗
RFC 8200 · § 5EXAMPLE
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03
Send a packet that fits.
The source lowers its size to fit the reported path MTU.
Protocol participantThreat or exceptionProtocol controlSimplified drawings · precise section references
Read the updated RFC section ↗
The smallest link MTU constrains the path.
- Path MTU is the minimum link MTU along the route.
- IPv6 routers do not fragment packets; source nodes adapt or fragment.
- Path MTU Discovery is recommended; a minimal implementation can restrict packets to at most 1280 octets.
An ICMPv6 Packet Too Big message can inform the source about a smaller path limit. Discovery details are in RFC 8201.
Read the RFC section ↗Diagrams simplify the RFC. Read the linked sections for complete requirements.
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