[TLS] Adam Roach's Yes on draft-ietf-tls-record-limit-02: (with COMMENT)

[Adam Roach <[e-mail]>]

Adam Roach has entered the following ballot position for
draft-ietf-tls-record-limit-02: Yes

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COMMENT:
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Thanks to everyone who contributed work towards this document.

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§4:

>  MUST NOT send a value higher than the protocol-defined maximum record
>  size unless explicitly allowed by such a future version or extension.

Presumably, recipients MUST gracefully accept values higher than the maximum
record size?  That is implied by this text (and the text that follows), but
given how TLS frequently aborts connections at the first sign of any
irregularity, it's probably worth saying explicitly.

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§4:

>  a DTLS endpoint that
>  receives a record larger than its advertised limit MAY either
>  generate a fatal "record_overflow" alert or discard the record.

I'm concerned about the interaction between the option to discard the record and
protocols that perform retransmission of lost packets over DTLS (e.g., proposals
such as draft-rescorla-quic-over-dtls). In the case that an oversized packet is
simply discarded, retransmissions of that (presumably still oversized) packet
will take a while to time out (I'm not particularly well-versed in QUIC, but
assume it has characteristics similar to TCP's ~nine-minute timeout), which
would result in really bad user experiences.  Is there rationale for this optionality?
It would seem to be cleaner if the response were simply to always send a fatal
error.

If this optionality is retained, please at least consider adding text describing
the impact of discarding oversized packets when used with a reliable protocol.

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§4.1:

>  In TLS 1.2, block ciphers allow between 1 and 256 octets of padding.

nit: The formulation "between X and Y" is ambiguous as to whether X and Y are
included in the range. Consider rephrasing as "...from 1 to 256...".