Datagram Packetization Layer Path MTU Discovery for UDP Options
RFC 9869, “Datagram Packetization Layer Path MTU Discovery for UDP Options”, is a Proposed Standard document published in October 2025 by G. Fairhurst, T. Jones. The canonical text is published by the RFC Editor.
Abstract
This document specifies how a UDP Options sender implements Datagram Packetization Layer Path MTU Discovery (DPLPMTUD) as a robust method for Path MTU Discovery (PMTUD). This method uses the UDP Options packetization layer. It allows an application to discover the largest size of datagram that can be sent across a network path. It also provides a way to allow the application to periodically verify the current Maximum Packet Size (MPS) supported by a path and to update this when required.
What “Proposed Standard” means
An entry-level standards-track specification: stable, peer-reviewed and a solid basis for implementation, though it may still evolve before becoming an Internet Standard.
The canonical text of RFC 9869 is hosted at rfc-editor.org. Available in HTML,TXT,PDF,XML.
- RFC 9868 Transport Options for UDP
- RFC 9870 Export of UDP Options Information in IP Flow Information Export
- RFC 9867 Mixing Preshared Keys in the IKE_INTERMEDIATE and CREATE_CHILD_SA Exchanges of the Internet Key Exchange Protocol Version 2 for Post-Quantum Security
- RFC 9871 BGP Color-Aware Routing
- RFC 9866 Root Node Failure Detector : Fast Detection of Border Router Crashes in the Routing Protocol for Low-Power and Lossy Networks
- RFC 9872 Recommendations for Discovering IPv6 Prefix Used for IPv6 Address Synthesis
- RFC 9865 Cursor-Based Pagination of System of Cross-domain Identity Management Resources
- RFC 9873 Additional Email Address Extension for the Extensible Provisioning Protocol