Subject: [tsvwg] Comments on draft-ietf-tsvwg-datagram-plpmtud-06

From: Martin Duke <[email-masked]>
Date: Mon, 26 Nov 2018 20:17:34 -0800

Thanks for updating this document. As an active QUIC WG participant I
thought I'd offer a few comments on Section 6.4.

1. s/illict/elicit
2. QUIC is meant to give up if the MTU proves to below the IPv6 minimum of
1280 bytes, so that is probably a better value for BASE_PMTU and MIN_PMTU
3. 1200 bytes is the minimum size of the UDP payload that contains the
initial packet. It is not equivalent to a full IP-layer PMTU. I don't
remember the full story here, but I believe it is meant to provide some
wiggle room below 1280 for tunneling and other phenomena, as a dropped
Initial packet is an overloaded signal.
4. "Padding only frames enable probing the without affecting the transfer
of other QUIC frames. " This is mostly true, except that the probe packet
does count against congestion control, with effects that I think we all
understand.

As a related question, is it the opinion of the tsvwg that transports no
longer have to deal with RFC 792 routers that include only 8 bytes of
transport header in their ICMP messages? Validating these messages is
something we dedicated a fair amount of text to, but you don't mention it
at all in your draft.

Thanks,
Martin

.

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From: Martin Duke <[email-masked]>
Date: Mon, 26 Nov 2018 20:33:06 -0800

Reading more carefully, I see that the answer to my question is in Section
1.1.

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From: Derek Fawcus <[email-masked]>
Date: Tue, 27 Nov 2018 09:34:09 +0000

> something we dedicated a fair amount of text to, but you don't mention it

One particularly large router vendor still had such code 4 years ago.
So their installed base up until then still did the truncate at 8.
I rather doubt they've changed in the mean time; but that would be
easily tested.

DF