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RFC 7821: UDP Checksum Complement in the Network Time Protocol (NTP)

Still current, but amended. Parts of this document are changed or extended by RFC 9748. Read both.

In plain English — editorial summary, not part of the RFC

The Network Time Protocol (NTP) allows clients to synchronize to a time server using timestamped protocol messages. To facilitate accurate timestamping, some implementations use hardware-based timestamping engines that integrate the accurate transmission time into every outgoing NTP packet during transmission. Since these packets are transported over UDP, the UDP Checksum field is then updated to reflect this modification. This document proposes an extension field that includes a 2-octet Checksum Complement, allowing timestamping engines to reflect the checksum modification in the last 2 octets of the packet rather than in the UDP Checksum field. The behavior defined in this document is interoperable with existing NTP implementations.

Document record

Document ID
RFC7821
Published
March 2016
Authors
T. Mizrahi
Status
EXPERIMENTAL
Stream
IETF
Area
int
Pages
14
Also known as
—
Updated by:
RFC 9748

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The document record above — title, authors, date, status, stream, area, relationships, DOI and errata — is imported verbatim from the public RFC Editor index. The “in plain English” section is editorial: written by The metasystema editorial team, not part of the RFC. Where the two differ, the RFC text governs.

Last checked against the RFC Editor index on . RFCs are never revised after publication; changes are issued as new documents.

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canonical URL: /rfc/7821-udp-checksum-complement-in-the-network-time-protocol-ntp