Re: [quicwg/base-drafts] Equivalence of preferred_address and NEW_CONNECTION_ID (#3560)

David Schinazi <> Thu, 09 April 2020 00:23 UTC

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Date: Wed, 08 Apr 2020 17:23:31 -0700
From: David Schinazi <>
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Subject: Re: [quicwg/base-drafts] Equivalence of preferred_address and NEW_CONNECTION_ID (#3560)
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Apologies for getting to this late, but I'm not sure I agree that we should disallow this. Here's a use-case that I think makes sense: the client wants to upload a very large file to the server over HTTP/3 and it has a small MTU, making it particularly sensitive to per-packet overheads. Let's also assume that we are in the future and the server supports IPv6 and has its own /64 (shocking!). In this scenario, a good way to reduce per-packet overhead is to operate the server on a given address, and then switch each client to their own unique server IP using preferred address, and then use zero-length CIDs. I've always found this use-case a good use of preferred address, and I would rather we didn't ban it without a good reason (and making the design cleaner doesn't necessarily count as a good reason at this stage in the process).

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