Re: [TLS] [DTLS1.3]About the retransmission of Handshake records

Benjamin Kaduk <bkaduk@akamai.com> Mon, 02 December 2019 18:26 UTC

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Date: Mon, 2 Dec 2019 10:26:12 -0800
From: Benjamin Kaduk <bkaduk@akamai.com>
To: Xuan k <kxuanobj@gmail.com>
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Subject: Re: [TLS] [DTLS1.3]About the retransmission of Handshake records
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On Mon, Dec 02, 2019 at 07:17:32PM +0800, Xuan k wrote:
> Hi Ben,
> 
> Thanks for your reply. But we understand may not be the same.
> 
> Since ACK messages are not retransmitted, I think they should not consume
> message_seqs.
> If an ACK really use a message_seq and it is lost in network, new handshake
> records will
> always use a larger message_seq than the peer expected (next_receive_seq).
> The peer will unable to continue the handshake process.

You are correct; they should not and do not.
But in an early version of the draft the ACK messages used the same data structure
that has an associated message_seq, and as you note, that was problematic, so it was changed.

-Ben