[quicwg/base-drafts] Add caution when using IW10 and fragmentation (#3243)

Jana Iyengar <notifications@github.com> Sun, 17 November 2019 04:24 UTC

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Subject: [quicwg/base-drafts] Add caution when using IW10 and fragmentation (#3243)
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Gorry notes correctly that fragmentation can play poorly with using IW10. If a sender uses a large max_datagram_size, and if the network fragments, then IW10 can result in substantially larger amplification than 10x.

A simple fix here is to say that if the endpoint uses max_datagram_size larger than 1280 bytes (this is what the transport spec limits it to in the absence of DPLPMTUD), then the endpoint MUST set DF on outgoing packets.

This is a problem with RFC 6928 as well, but we should be clear about it for QUIC.

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