Re: [TLS] John Scudder's No Objection on draft-ietf-tls-dtls-connection-id-11: (with COMMENT)

Hannes Tschofenig <Hannes.Tschofenig@arm.com> Wed, 21 April 2021 07:16 UTC

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From: Hannes Tschofenig <Hannes.Tschofenig@arm.com>
To: John Scudder <jgs@juniper.net>, Eric Rescorla <ekr@rtfm.com>
CC: The IESG <iesg@ietf.org>, "draft-ietf-tls-dtls-connection-id@ietf.org" <draft-ietf-tls-dtls-connection-id@ietf.org>, tls-chairs <tls-chairs@ietf.org>, "tls@ietf.org" <tls@ietf.org>, Joseph Salowey <joe@salowey.net>
Thread-Topic: John Scudder's No Objection on draft-ietf-tls-dtls-connection-id-11: (with COMMENT)
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Date: Wed, 21 Apr 2021 07:15:41 +0000
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Archived-At: <https://mailarchive.ietf.org/arch/msg/tls/zHUN_gJIkLpKy74eYJ8UKO-UF6o>
Subject: Re: [TLS] John Scudder's No Objection on draft-ietf-tls-dtls-connection-id-11: (with COMMENT)
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Hi John,


[*] By the way, why not just use “255” in the text instead of “2^8-1”? Eschew
obfuscation!

Which one of these is clearer seems like a question of taste, I should think.
It's worth noting that because the length prefix is determined by the ceiling,
arguably 2^8-1 is clearer.

I don’t follow your point, but suit yourself.

[Hannes] As mentioned by Ekr it is a matter of taste how to describe the payloads. We follow the style used in previous TLS specifications.
In any case, for an implementer it is important to know the length of each data item.

For example, if you have a ceiling of 2^16-1 for a data item you know that two bytes have to be written (or parsed). Here is a copy-and-paste from the Mbed TLS code to show an example:

    *p++ = (unsigned char)( ( MBEDTLS_TLS_EXT_SERVERNAME >> 8 ) & 0xFF );
    *p++ = (unsigned char)( ( MBEDTLS_TLS_EXT_SERVERNAME ) & 0xFF );

Ciao
Hannes

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