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UDP Checksum Complement in the Network Time Protocol (NTP) (RFC7821) Disclosure Number: IPCOM000245699D
Original Publication Date: 2016-Mar-01
Included in the Prior Art Database: 2016-Mar-31
Document File: 28 page(s) / 26K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

T. Mizrahi: AUTHOR


The Network Time Protocol [NTPv4] allows clients to synchronize their clocks to a time server by exchanging NTP packets. The increasing demand for highly accurate clock synchronization motivates implementations that provide accurate timestamping.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 10% of the total text.

Internet Engineering Task Force (IETF)                        T. Mizrahi Request for Comments: 7821                                       Marvell Category: Experimental                                        March 2016 ISSN: 2070-1721

        UDP Checksum Complement in the Network Time Protocol (NTP)


   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.

Status of This Memo

   This document is not an Internet Standards Track specification; it is    published for examination, experimental implementation, and    evaluation.

   This document defines an Experimental Protocol for the Internet    community.  This document is a product of the Internet Engineering    Task Force (IETF).  It represents the consensus of the IETF    community.  It has received public review and has been approved for    publication by the Internet Engineering Steering Group (IESG).  Not    all documents approved by the IESG are a candidate for any level of    Internet Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,    and how to provide feedback on it may be obtained at

Mizrahi                       Experimental                      [Page 1]
 RFC 7821                 NTP Checksum Complement              March 2016

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