Re: [quicwg/base-drafts] Compatible version upgrade (#1901)

Martin Thomson <> Fri, 26 October 2018 01:31 UTC

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From: Martin Thomson <>
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Subject: Re: [quicwg/base-drafts] Compatible version upgrade (#1901)
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Good questions.  

> Does the version number included in the packet header need to appear in supported_versions?

Yes.  We want this under integrity protection.  We want the union of both lists to include every version the client supports and the client won't ever attempt to connect with a version that it just put in unsupported_versions.

> Is the server allowed to perform a compatible version upgrade against a version included in unsupported_versions?

Yes, and we should allow that to happen.  The client won't care.  It is only splitting the versions into two lists for purposes of detecting a downgrade attack.  This should make the upgrade process easier.  I will call this out explicitly.

Having just written up the text for upgrades, I think that the 

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