Subject: [DNSOP] I-D Action: draft-ietf-dnsop-avoid-fragmentation-05.txt

From: [email-masked]
Date: Wed, 23 Jun 2021 02:00:55 -0700

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the Domain Name System Operations WG of the IETF.

        Title           : Fragmentation Avoidance in DNS
        Authors         : Kazunori Fujiwara
                          Paul Vixie
	Filename        : draft-ietf-dnsop-avoid-fragmentation-05.txt
	Pages           : 12
	Date            : 2021-06-23

Abstract:
   EDNS0 enables a DNS server to send large responses using UDP and is
   widely deployed.  Path MTU discovery remains widely undeployed due to
   security issues, and IP fragmentation has exposed weaknesses in
   application protocols.  Currently, DNS is known to be the largest
   user of IP fragmentation.  It is possible to avoid IP fragmentation
   in DNS by limiting response size where possible, and signaling the
   need to upgrade from UDP to TCP transport where necessary.  This
   document proposes to avoid IP fragmentation in DNS.

The IETF datatracker status page for this draft is:
https://datatracker.ietf.org/doc/draft-ietf-dnsop-avoid-fragmentation/

There is also an htmlized version available at:
https://datatracker.ietf.org/doc/html/draft-ietf-dnsop-avoid-fragmentation-05

A diff from the previous version is available at:
https://www.ietf.org/rfcdiff?url2=draft-ietf-dnsop-avoid-fragmentation-05

Internet-Drafts are also available by anonymous FTP at:
ftp://ftp.ietf.org/internet-drafts/

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From: [email-masked]
Date: Thu, 24 Jun 2021 19:07:53 +0900 (JST)

Paul Vixie and I submitted draft-ietf-dnsop-avoid-fragmentation-05.

Please review it.

Major changes are the following:

 1. Moved some text from Introduction to Appendix A. Weaknesses of IP
    fragmentation.

 2. Section 3.3 Default Maximum DNS/UDP payload size

    Generated Table 1 Default maximum DNS/UDP payload size

    1400 as "Authors' recommendation".

    Moved details to Appendix B.  Details of maximum DNS/UDP payload
    size discussions.

    Changed texts about " operators of DNS servers SHOULD measure
    their path MTU to UDP payload size.  the Internet at setting up
    DNS servers"

 3. added "IP_DONTFRAG option" definition in Terminology section.

    IP_DONTFRAG option is not defined by any RFCs. It is similar to
    IPV6_DONTFRAG option defined in [RFC3542].  IP_DONTFRAG option is
    used on BSD systems to set the Don't Fragment bit [RFC0791] when
    sending IPv4 packets.  On Linux systems this is done via
    IP_MTU_DISCOVER and IP_PMTUDISC_DO.

#   IP_DONTFRAG is a macro used in BSD socket API.
#   IPV6_DONTFRAG is defined by RFC 3452, but it is BSD's IPv6 API.
#   Then, 
#   We may need to change "IP_DONTFRAG" to "DF" bit. ([RFC0791])
#   We may need to change "IPV6_DONTFRAG" to "Sending without Fragmentation".
#   (Good texts required.)
#   IPv6 experts, please advice.

 4. Appendix sections reordered.

    Appendix A.  Weaknesses of IP fragmentation
    Appendix B.  Details of maximum DNS/UDP payload size discussions
    Appendix C.  How to retrieve path MTU value to a destination from
  	     	 applications
    Appendix D.  How to retrieve minimal MTU value to a destination
    Appendix E.  Minimal-responses

  5. Added some names in Acknowledgeent section

--
Kazunori Fujiwara, JPRS <[email-masked]>