Re: Confusion about PR#3499

Ian Swett <ianswett@google.com> Mon, 11 May 2020 12:52 UTC

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From: Ian Swett <ianswett@google.com>
Date: Mon, 11 May 2020 08:52:31 -0400
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Subject: Re: Confusion about PR#3499
To: Martin Thomson <mt@lowentropy.net>
Cc: IETF QUIC WG <quic@ietf.org>
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Thanks for the improvements, I do think this is clearer now.

On Sun, May 10, 2020 at 10:06 PM Martin Thomson <mt@lowentropy.net> wrote:

> Thanks mostly to David's thoughtful comments on the PR, I've revised the
> PR.  Mostly, this is just renaming.
>
> Hopefully, this covers the two relevant examples.
>
> Simple:
>
> C->S: Initial SCID = C1, DCID = S1
> C<-S: Initial SCID = S2, DCID = C1
> ....
> C->S: Short DCID = S2
> C<-S: Short DCID = C1
>
> Client sends initial_source_connection_id = C1
> Server sends initial_source_connection_id = S2 and
> original_destination_connection_id = S1
> Each validates all of the values provided by their peer.  This includes
> verifying that retry_source_connection_id is absent.
>
> Or with a Retry:
>
> C->S: Initial SCID = C1, DCID = S1
> C<-S: Retry SCID = S2, DCID = C1
> C->S: Initial SCID = C1, DCID = S2
> C<-S: Initial SCID = S3, DCID = C1
> ....
> C->S: Short DCID = S3
> C<-S: Short DCID = C1
>
> Client sends initial_source_connection_id = C1
> Server sends initial_source_connection_id = S3, retry_source_connection_id
> = S2, and original_destination_connection_id = S1
> Each validates all of the values provided by their peer.
>
> On Sat, May 9, 2020, at 09:34, David Schinazi wrote:
> > >  Client Server
> > >
> > >  Initial [CH] SCID = C1, DCID = S1 ----------->
> > >  Initial [SH1] <---------- SCID = S2, DCID = C1
> > >  Initial [SH2] <---------- SCID = S2, DCID = C1 // LOST
> > >  Initial [ACK] SCID = C1, DCID = S2 ---------->
> > >
> > > So now we have two Initial packets with different DCIDs. Which one
> > > goes in this field? Or have I forgotten how ACKs work with Initials?
>
> I think that David's proposed changes clarify this.  The "most recent"
> thing was confusing and wrong.
>
>