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Re: [TLS] Multiple records in record limit (was: Secdir review)

Eric Rescorla <ekr@rtfm.com> Mon, 26 February 2018 16:11 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Mon, 26 Feb 2018 08:11:15 -0800
Message-ID: <CABcZeBPwV=yBnACcYYYCPkaz3kfMWPTaBUPPsKxVJDYaWDm0_Q@mail.gmail.com>
To: Alan DeKok <aland@deployingradius.com>
Cc: Martin Thomson <martin.thomson@gmail.com>, "<tls@ietf.org>" <tls@ietf.org>, Benjamin Kaduk <kaduk@mit.edu>
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Subject: Re: [TLS] Multiple records in record limit (was: Secdir review)
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On Mon, Feb 26, 2018 at 7:48 AM, Alan DeKok <aland@deployingradius.com>
wrote:

> On Feb 25, 2018, at 8:39 PM, Martin Thomson <martin.thomson@gmail.com>
> wrote:
> >
> > Out of the secdir review (thanks again Alan!), I realized that the
> > draft never actually said this:
> >
> >   PMTU governs the size of UDP datagrams, which limits the size of
> records, but
> >   does not prevent records from being smaller.  An endpoint that sends
> small
> >   records is still able to send multiple records in a single UDP
> datagram.
> >
> > I think that I should add that explanation.
> >
> > Does anyone think that this should go further and advise against
> > putting multiple records in the same datagram?
>
>   Yes.  I don't think there's any good reason for that kind of behaviour.
>

There actually are. One example is packing handshake and data records in
the same datagram.

-Ekr


>   Alan DeKok.
>
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