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Re: [quicwg/base-drafts] Padding ACK-only packets (#837)

Martin Thomson <notifications@github.com> Fri, 10 November 2017 00:37 UTC

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Date: Fri, 10 Nov 2017 00:36:57 +0000
From: Martin Thomson <notifications@github.com>
Reply-To: quicwg/base-drafts <reply+0166e4ab45a17368a83b7bf9c9e8ae82b4550153ce38a63092cf00000001161cb6a892a169ce0fb033e2@reply.github.com>
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Subject: Re: [quicwg/base-drafts] Padding ACK-only packets (#837)
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That sounds reasonable to me.

We should be careful though.  QUIC ACK-only packets will be larger than TCP ACKs because of all the overhead.  So we will be sending a bit more.  A minimal ACK frame is 4 octets in QUIC, which isn't bad, but the packet header (13) and AEAD expansion (16) makes it 73 octets in comparison to 40 for a basic TCP ACK.  That's nudging double the size (maybe this gets worse with SACK and extensions, so it's not a big deal).

The consequence being that we might induce congestion more easily if the congestion properties are massively asymmetric.  That's probably not worth any lost sleep, but we might add a note.

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