Re: [quicwg/base-drafts] Flow control for post-handshake CRYPTO messages (#1834)

Kazuho Oku <> Fri, 05 October 2018 02:30 UTC

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From: Kazuho Oku <>
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Subject: Re: [quicwg/base-drafts] Flow control for post-handshake CRYPTO messages (#1834)
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> Another incarnation of this problem is if the client receives a huge window of CRYPTO frames into the future but not the first byte, so it can't process anything yet. With STREAM frames, we have flow control. With CRYPTO frames during the handshake, we know the handshake itself is bounded. Post-handshake, we don't know a priori the server won't send lots and lots of tickets.

I agree that the problem exists.

However, in my view, the memory exhaustion issue does not get resolved just by having a window for the CRYTO frames. My understanding that most TLS stacks buffers the octets of a handshake message until it receives a complete one. That means that the TLS stack is expected to buffer at most 16MB of junk even if we introduce window to the CRYPTO frames.

Considering that, I think it would be preferable to at first discuss introducing bounds for the TLS messages in the TLS working group, then consider how to apply that to QUIC. Until then, each QUIC stacks and TLS stacks can (continue to) have their own internal limits.

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