Re: Closing on CONNECTION_CLOSE

[Ian Swett <[e-mail]>]

Nice summary.  As you implied, I favor the RST-like model.

And as you stated, it'd be very helpful to specify something soon, since
it's about to become an implementation blocker.

On Thu, Jul 27, 2017 at 9:47 AM, Eric Rescorla <[e-mail]> wrote:

> There have been a number of issues raised about the exact semantics of
> CONNECTION_CLOSE [0], but we have never really closed on them. As Ryan
> says, one might have think that CONNECTION_CLOSE is like TCP FIN or
> like TCP RST.
>
>
> In the FIN-like model:
> - The closing side sends a CONNECTION_CLOSE
> - The non-closing side ACKs it
> - The closing side keeps retransmitting until it gets an ACK or it
>   times out.
>
>
> In the RST-like model:
> - The closing side sends a CONNECTION_CLOSE
> - The non-closing side just terminates the connection
> - The closing side responds to new packets from the non-closing side
>   with a retransmitted CONNECTION_CLOSE (perhaps just a stored packet)
>   for some time.
>
> The specification seems kind of vague on this point (there is a big
> TODO for TIME_WAIT) and in places suggests retransmission [1] I had
> previously assumed the FIN-like model but after talking to Ian this
> morning I think the RST-like model is better. It's easier to implement
> because you don't need to manage a post-close state machine on either
> side. The only downside I'm really aware of is that the closing side
> has to keep state for something like 2MSL (so that it can properly
> respond to late packets), rather than being able to clean up on
> receiving an ACK. However, this isn't that big a deal, because as
> noted above, you can throw away the connection and just send a stored
> packet, or alternately, just send public reset (or just go silent).
>
> Given that ID1 does include CONNECTION_CLOSE, albeit with limited
> semantics, it would be good to resolve this soon. Are there people who
> want to argue in favor of the FIN-like model?
>
> -Ekr
>
>
> [0] https://github.com/quicwg/base-drafts/issues/330
> https://github.com/quicwg/base-drafts/issues/328
>
> [1] See also the spec for ID1 which says:
> "The packet containing a connection close does not need to be
> retransmitted."
>
>