Measures against cache poisoning attacks using IP fragmentation in DNS

Document Type Expired Internet-Draft (individual)
Author Kazunori Fujiwara 
Last updated 2019-09-02 (latest revision 2019-03-01)
Stream (None)
Intended RFC status (None)
Expired & archived
pdf htmlized bibtex
Stream Stream state (No stream defined)
Consensus Boilerplate Unknown
RFC Editor Note (None)
IESG IESG state Expired
Telechat date
Responsible AD (None)
Send notices to (None)

This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


Researchers proposed practical DNS cache poisoning attacks using IP fragmentation. This document shows feasible and adequate measures at full-service resolvers and authoritative servers against these attacks. To protect resolvers from these attacks, avoid fragmentation (limit requestor's UDP payload size to 1220/1232), drop fragmented UDP DNS responses and use TCP at resolver side. To make a domain name robust against these attacks, limit EDNS0 Responder's maximum payload size to 1220, set DONTFRAG option to DNS response packets and use good random fragmentation ID at authoritative server side.


Kazunori Fujiwara (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)