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

ianswett <notifications@github.com> Wed, 01 April 2020 14:43 UTC

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Subject: Re: [quicwg/base-drafts] Equivalence of preferred_address and NEW_CONNECTION_ID (#3560)
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I'll note that prohibiting a 0 length CID doesn't actually ensure the server's IP isn't unique, though it does remove an incentive to make it unique.

I'd like to leave the option to switch to a zero-length CID later in the connection, and I think I'd be fine with 4 if we allowed that.

An easy example is a large upload.  I mostly don't care about the CID, but if I'm uploading a 10GB file, maybe saving some bytes matters.  Also, if you're constantly filling the pipe, NAT rebinds are extremely unlikely.

Another example is an environment like a datacenter where there are no NATs and routes are very stable, unless a peer intentionally changes it, so the 5-tuple is sufficient.  In that case, the ideal operating condition is to typically use a 0 byte CID and switch to a non-0 length anytime a peer changes IP or port.  Changing port has some clear benefits in some cases, so it's in no way a threoretical use case.  @nibanks may have thoughts on this range of use case as well.

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