Guidelines for Defining Packet Timestamps
RFC 8877
Internet Engineering Task Force (IETF) T. Mizrahi
Request for Comments: 8877 Huawei
Category: Informational J. Fabini
ISSN: 2070-1721 TU Wien
A. Morton
AT&T Labs
September 2020
Guidelines for Defining Packet Timestamps
Abstract
Various network protocols make use of binary-encoded timestamps that
are incorporated in the protocol packet format, referred to as
"packet timestamps" for short. This document specifies guidelines
for defining packet timestamp formats in networking protocols at
various layers. It also presents three recommended timestamp
formats. The target audience of this document includes network
protocol designers. It is expected that a new network protocol that
requires a packet timestamp will, in most cases, use one of the
recommended timestamp formats. If none of the recommended formats
fits the protocol requirements, the new protocol specification should
specify the format of the packet timestamp according to the
guidelines in this document.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
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 candidates for any level of Internet
Standard; see Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8877.
Copyright Notice
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Table of Contents
1. Introduction
1.1. Background
1.2. Scope of this Document
1.3. How to Use This Document
2. Terminology
2.1. Requirements Language
2.2. Abbreviations
2.3. Terms Used in This Document
3. Packet Timestamp Specification Template
4. Recommended Timestamp Formats
4.1. Using a Recommended Timestamp Format
4.2. NTP Timestamp Formats
4.2.1. NTP 64-Bit Timestamp Format
4.2.2. NTP 32-Bit Timestamp Format
4.3. The PTP Truncated Timestamp Format
5. Synchronization Aspects
6. Timestamp Use Cases
6.1. Example 1
6.2. Example 2
7. Packet Timestamp Control Field
7.1. High-Level Control Field Requirements
8. IANA Considerations
9. Security Considerations
10. References
10.1. Normative References
10.2. Informative References
Acknowledgments
Authors' Addresses
1. Introduction
1.1. Background
Timestamps are widely used in network protocols for various purposes:
for logging or reporting the time of an event, for messages in delay
measurement and clock synchronization protocols, and as part of a
value that is unlikely to repeat (nonce) in security protocols.
Timestamps are represented in the RFC series in one of two forms:
text-based timestamps and packet timestamps. Text-based timestamps
[RFC3339] are represented as user-friendly strings and are widely
used in the RFC series -- for example, in information objects and
data models, e.g., [RFC5646], [RFC6991], and [RFC7493]. Packet
timestamps, on the other hand, are represented by a compact binary
field that has a fixed size and are not intended to have a human-
friendly format. Packet timestamps are also very common in the RFC
series and are used, for example, for measuring delay and for
synchronizing clocks, e.g., [RFC5905], [RFC4656], and [RFC7323].
1.2. Scope of this Document
This document presents guidelines for defining a packet timestamp
format in network protocols. Three recommended timestamp formats are
presented. It is expected that a new network protocol that requires
a packet timestamp will, in most cases, use one of these recommended
timestamp formats. In some cases, a network protocol may use more
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