John Scudder's No Objection on draft-ietf-quic-datagram-08: (with COMMENT)

[John Scudder via Datatracker <[e-mail]>]

John Scudder has entered the following ballot position for
draft-ietf-quic-datagram-08: No Objection

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COMMENT:
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As a rank QUIC neophyte my ability to offer serious technical review of this
document is limited at best. However I do have a few questions that (in the
best case) might reveal lacunae that experts overlooked but which trip up a
neophyte, or (in the worst case) only my own ignorance.

1. In the Motivation section you write,

   *  Applications that open both a reliable TLS stream and an
      unreliable DTLS flow to the same peer can benefit by sharing a
      single handshake and authentication context between a reliable
      QUIC stream and flow of unreliable QUIC datagrams.  This can
      reduce the latency required for handshakes.

This threw me off, considering that in the previous section (Introduction) you
point to UDP/DTLS as a prior way of providing a similar service. In the
quotation above it seems as though you’re using them synonymously… or something.

TBH, I just don’t follow what the quoted text is getting at. :-( I do get (in a
general way) that QUIC makes use of (parts of?) TLS, but that doesn’t allow me
to make sense of it.

2. You’re inconsistent about whether DATAGRAM frames have a type, singular, or
types, plural. Plural seems right to me, but read on. In §3, you refer to “the
DATAGRAM frame types”, plural. But then in §4 you say that the LSB of “the
DATAGRAM frame type” (singular) “is the LEN bit”. Seems to me you should make
up your mind: either you have two types, 0x30 and 0x31, whose semantics differ
with respect to the Length field, OR you have a single type and a flag.

Really I think you have two types (witness the IANA allocation: two, not one)
and the characterization of the LSB as a flag is just a distraction, I would
remove it. Clearly that doesn’t prevent an implementor from taking advantage of
the structure if they want to, but I think it would clean up some awkwardness
in the prose.

3. Further to that, in Section 4 you say,

               The DATAGRAM frame type takes the form 0b0011000X
   (or the values 0x30 and 0x31).

It took me an embarrassingly long time to recognize that the first form you
list means “binary 0011000x, where x indicates ‘don’t care’”. I suppose maybe I
was slow because we use hex notation all the time in our document set, and
binary notation exceedingly seldom in my experience. Possibly I am the only
person who will stumble on this. But possibly not. In any case if you were to
clean up my “is it one type, or two” complaint by collapsing the waveform to
“it’s two”, this problem would also go away.

4. In Section 5 you say,

   When a QUIC endpoint receives a valid DATAGRAM frame, it SHOULD
   deliver the data to the application immediately, as long as it is
   able to process the frame and can store the contents in memory.

Isn’t the final clause in the category of “well, duh”? I mean, is there a
situation in which a QUIC endpoint is *not* able to process the frame or *not*
able to store the contents in memory, but still might be expected to deliver
the data to the application? Seems like that’d be a “no”.

I mean, the remark does no real harm, but why bother stating the obvious?