Network Time Protocol Best Current Practices
RFC 8633
Document | Type |
RFC - Best Current Practice
(July 2019; No errata)
Also known as BCP 223
Was draft-ietf-ntp-bcp (ntp WG)
|
|
---|---|---|---|
Authors | Denis Reilly , Harlan Stenn , Dieter Sibold | ||
Last updated | 2019-07-18 | ||
Replaces | draft-reilly-ntp-bcp | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Reviews | |||
Stream | WG state | Submitted to IESG for Publication | |
Document shepherd | Karen O'Donoghue | ||
Shepherd write-up | Show (last changed 2018-12-13) | ||
IESG | IESG state | RFC 8633 (Best Current Practice) | |
Action Holders |
(None)
|
||
Consensus Boilerplate | Yes | ||
Telechat date | |||
Responsible AD | Suresh Krishnan | ||
Send notices to | Karen O'Donoghue <odonoghue@isoc.org> | ||
IANA | IANA review state | Version Changed - Review Needed | |
IANA action state | No IANA Actions |
Internet Engineering Task Force (IETF) D. Reilly, Ed. Request for Comments: 8633 Orolia USA BCP: 223 H. Stenn Category: Best Current Practice Network Time Foundation ISSN: 2070-1721 D. Sibold PTB July 2019 Network Time Protocol Best Current Practices Abstract The Network Time Protocol (NTP) is one of the oldest protocols on the Internet and has been widely used since its initial publication. This document is a collection of best practices for the general operation of NTP servers and clients on the Internet. It includes recommendations for the stable, accurate, and secure operation of NTP infrastructure. This document is targeted at NTP version 4 as described in RFC 5905. Status of This Memo This memo documents an Internet Best Current Practice. 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). Further information on BCPs is available in 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/rfc8633. Reilly, et al. Best Current Practice [Page 1] RFC 8633 Network Time Protocol BCP July 2019 Copyright Notice Copyright (c) 2019 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Reilly, et al. Best Current Practice [Page 2] RFC 8633 Network Time Protocol BCP July 2019 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 2. General Network Security Best Practices . . . . . . . . . . . 4 2.1. BCP 38 . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. NTP Configuration Best Practices . . . . . . . . . . . . . . 5 3.1. Keeping NTP Up to Date . . . . . . . . . . . . . . . . . 5 3.2. Using Enough Time Sources . . . . . . . . . . . . . . . . 5 3.3. Using a Diversity of Reference Clocks . . . . . . . . . . 6 3.4. Control Messages . . . . . . . . . . . . . . . . . . . . 7 3.5. Monitoring . . . . . . . . . . . . . . . . . . . . . . . 7 3.6. Using Pool Servers . . . . . . . . . . . . . . . . . . . 8 3.7. Leap-Second Handling . . . . . . . . . . . . . . . . . . 8 3.7.1. Leap Smearing . . . . . . . . . . . . . . . . . . . . 9 4. NTP Security Mechanisms . . . . . . . . . . . . . . . . . . . 10 4.1. Pre-Shared Key Approach . . . . . . . . . . . . . . . . . 11 4.2. Autokey . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.3. Network Time Security . . . . . . . . . . . . . . . . . . 11 4.4. External Security Protocols . . . . . . . . . . . . . . . 12 5. NTP Security Best Practices . . . . . . . . . . . . . . . . . 12 5.1. Minimizing Information Leakage . . . . . . . . . . . . . 12 5.2. Avoiding Daemon Restart Attacks . . . . . . . . . . . . . 13 5.3. Detection of Attacks through Monitoring . . . . . . . . . 14 5.4. Kiss-o'-Death Packets . . . . . . . . . . . . . . . . . . 15 5.5. Broadcast Mode Only on Trusted Networks . . . . . . . . . 15 5.6. Symmetric Mode Only with Trusted Peers . . . . . . . . . 16 6. NTP in Embedded Devices . . . . . . . . . . . . . . . . . . . 16 6.1. Updating Embedded Devices . . . . . . . . . . . . . . . . 16 6.2. Server Configuration . . . . . . . . . . . . . . . . . . 17 7. NTP over Anycast . . . . . . . . . . . . . . . . . . . . . . 17 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 9. Security Considerations . . . . . . . . . . . . . . . . . . . 19 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 19Show full document text