Re: [quicwg/base-drafts] Integrate QUIC text from DPLPMTUD (#3693)

Martin Thomson <> Tue, 26 May 2020 23:48 UTC

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Date: Tue, 26 May 2020 16:48:49 -0700
From: Martin Thomson <>
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Subject: Re: [quicwg/base-drafts] Integrate QUIC text from DPLPMTUD (#3693)
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@martinthomson commented on this pull request.

>  In the absence of these mechanisms, QUIC endpoints SHOULD NOT send IP packets
-larger than 1280 bytes. Assuming the minimum IP header size, this results in a
-QUIC maximum packet size of 1232 bytes for IPv6 and 1252 bytes for IPv4. A QUIC
-implementation MAY be more conservative in computing the QUIC maximum packet
-size to allow for unknown tunnel overheads or IP header options/extensions.
+larger than the minimum QUIC packet size. 
+packets other than PMTUD/DPLPMTUD probe packets SHOULD be sized to fit within the
+maximum packet size to avoid the packet being fragmented or dropped
+If a QUIC endpoint determines that the PMTU between any pair of local and remote
+IP addresses has fallen below the smallest allowed maximum packet size, it MUST immediately 

I think that Gorry's changes (recognizing the minimum on MPS in DPLPMTUD) are OK, but I would add "of 1200 bytes" for clarity.

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