UDP Checksum Complement in the Network Time Protocol
RFC 7821, “UDP Checksum Complement in the Network Time Protocol”, is an Experimental document published in March 2016 by T. Mizrahi. It has since been updated by RFC 9748. The canonical text is published by the RFC Editor.
Abstract
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.
What “Experimental” means
Describes a specification that is part of a research or development effort, published so the community can gain experience with it.
The canonical text of RFC 7821 is hosted at rfc-editor.org. Available in TXT,HTML.
- RFC 7820 UDP Checksum Complement in the One-Way Active Measurement Protocol and Two-Way Active Measurement Protocol
- RFC 7822 Network Time Protocol Version 4 Extension Fields
- RFC 7819 Privacy Considerations for DHCP
- RFC 7823 Performance-Based Path Selection for Explicitly Routed Label Switched Paths Using TE Metric Extensions
- RFC 7818 URN Namespace for MEF Documents
- RFC 7824 Privacy Considerations for DHCPv6
- RFC 7817 Updated Transport Layer Security Server Identity Check Procedure for Email-Related Protocols
- RFC 7825 A Network Address Translator Traversal Mechanism for Media Controlled by the Real-Time Streaming Protocol