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Request: increase default udp payload size buffer to recommended 1232 bytes #142

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realbiz21 opened this issue Jul 1, 2024 · 2 comments · Fixed by #143
Closed

Request: increase default udp payload size buffer to recommended 1232 bytes #142

realbiz21 opened this issue Jul 1, 2024 · 2 comments · Fixed by #143

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@realbiz21
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Latest guidance[1] suggests using buffer sizes of 1232 bytes, which is optimized to reduce IP fragmentation as well as the need to switch to TCP. The default udpPayloadSize in minidns is 1024 bytes.

For example, a DNSSEC-validated DNSKEY record for <Root> will return UDP truncation with a buffer size of 1024 bytes. At present, the DNS payload is 1139 bytes.

dig +dnssec +bufsize=1024 DNSKEY .

Is there any opposition to increasing minidns' default size from 1024 to 1232?

[1]: https://www.dnsflagday.net/2020/#action-dns-software-vendors reads:

It is important for DNS software vendors to comply with DNS standards, and to use a default EDNS buffer size (1232 bytes) that will not cause fragmentation on typical network links. Relevant standards include RFC 7766, RFC 6891 section 6.2.3. and RFC 6891 section 6.2.4.. The motivation for this effort is described in IETF draft intarea-frag-fragile section 6.1 and IETF draft iab-protocol-maintenance.
@Flowdalic
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Is there any opposition to increasing minidns' default size from 1024 to 1232?

None at all, PRs welcome. Please also include the reference to the URL in the commit message.

realbiz21 added a commit to realbiz21/minidns that referenced this issue Jul 2, 2024
@realbiz21
[client] use 1232 byte udp payload size buffer by default
85ca1ea 
DNS flag day of 2020 addressed optimum DNS message sizes to avoid IP fragmentation and minimize the usage of TCP. The recommendation for DNS software vendors was to "use a default EDNS buffer size" of 1232 bytes.

Fixes MiniDNS#142.
    
Reference: https://www.dnsflagday.net/2020/#action-dns-software-vendors
Reference: https://blog.cloudflare.com/dns-flag-day-2020/
@realbiz21 realbiz21 mentioned this issue Jul 2, 2024
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@realbiz21
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@Flowdalic - is PR #143 sufficient or did you have an alternate approach in mind?

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[client] use 1232 byte udp payload size buffer by default realbiz21/minidns
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@Flowdalic @realbiz21