Re: [quicwg/base-drafts] Description of the use of Preferred Address is unclear (#3353)

Martin Thomson <notifications@github.com> Sun, 02 February 2020 16:53 UTC

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Subject: Re: [quicwg/base-drafts] Description of the use of Preferred Address is unclear (#3353)
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@erickinnear made me realize the nature of the hazard here.

It seems fairly natural for an server to bind connection IDs to the current socket address.  That is part of why we have new connection IDs attached to the preferred address and the forced retirement.  After all, if the server uses a different target address, the hash at a load balancer could change and cause packets to be badly routed.  Not including the target address in the hash would work, but it would force connection IDs to be bigger.

But this all assumes that you never expect the server to migrate.  If the server ever wanted to migrate, then the client is stuck with a bunch of unusable connection IDs for its own migrations.

We decided that only clients can initiate migration in this version, which might mean that we don't need to worry about this case.  We decided not to allow server migration primarily to avoid having to deal with the complex problems that ICE handles.  But it was only the lack of mechanisms, not a structural constraint.  Now it seems like we have a structural constraint that would prevent server migration.

At a minimum, it seems like we should probably acknowledge this constraint somehow.

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