Re: [quicwg/base-drafts] Endpoints MAY (not SHOULD) ignore IPv4 ICMP PTB messages (#2109)

Igor Lubashev <> Tue, 11 December 2018 03:37 UTC

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From: Igor Lubashev <>
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Subject: Re: [quicwg/base-drafts] Endpoints MAY (not SHOULD) ignore IPv4 ICMP PTB messages (#2109)
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I wholeheartedly share the desire to encourage more robust implementations.  Ironically, this is exactly why I am concerned about this SHOULD.

I see this SHOULD not as _"encourag[ing] implementations not to follow that path"_ but providing a dangerous recommendation (with no disclaimer) to implementations who already found themselves on that path for whatever reason.

We see _many_ broken PMTU discovery implementations on the Internet, because PMTUD is hard, and many implementers are not well-informed and/or under time pressure. I am worried that an implementer will implement no 8-byte-compatible validations, read this SHOULD, drop the packet, and not think too hard about it, because he is "just following the RFC recommendation".

I see that we are both approaching this with the same goal but are coming to different conclusions. Maybe it is worthwhile to take it to the list for more visibility?

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