Subject: [quicwg/base-drafts] minimum valid packet size is an example (#4396)

From: Kazuho Oku <[email-masked]>
Date: Thu, 19 Nov 2020 15:39:13 -0800

Minimum packet size varies between the packet types (and other things like the length of CID being used). Therefore, the sentence is merely providing an example, and should be stated as such.

Closes #4395, though I am not sure if 21 is the correct number.
You can view, comment on, or merge this pull request online at:

  https://github.com/quicwg/base-drafts/pull/4396

-- Commit Summary --

  * talk about examples, as minimum valid size differs between packet types and the CIDs being used

-- File Changes --

    M draft-ietf-quic-transport.md (6)

-- Patch Links --

https://github.com/quicwg/base-drafts/pull/4396.patch
https://github.com/quicwg/base-drafts/pull/4396.diff

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From: Nick Banks <[email-masked]>
Date: Thu, 19 Nov 2020 15:48:30 -0800

@nibanks approved this pull request.

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From: David Schinazi <[email-masked]>
Date: Thu, 19 Nov 2020 16:16:40 -0800

@DavidSchinazi commented on this pull request.

> @@ -3056,9 +3056,9 @@ An endpoint MUST NOT send a stateless reset that is three times or more larger
 than the packet it receives to avoid being used for amplification.
 {{reset-looping}} describes additional limits on stateless reset size.
 
-Endpoints MUST discard packets that are too small to be valid QUIC packets.
-With the set of AEAD functions defined in {{QUIC-TLS}}, packets that are smaller
-than 21 bytes are never valid.
+Endpoints MUST discard packets that are too small to be valid QUIC packets.  To
+give an example, with the set of AEAD functions defined in {{QUIC-TLS}}, short
+header packets that are smaller than 21 bytes are never valid.

I like this new text, but I think we need to be explicit about what the minimum length is for long headers (including VN).

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From: Martin Thomson <[email-masked]>
Date: Thu, 19 Nov 2020 16:18:20 -0800

@martinthomson approved this pull request.

Thanks Kazuho, this is great.

What I like about this is that it also implies the possibility of a higher minimum.  For instance, the limit on long headers is higher (28 for Initial, 27 for 0-RTT and handshake if I'm right, but you can also add the minimum connection ID length for receiving to that).

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From: Kazuho Oku <[email-masked]>
Date: Thu, 19 Nov 2020 16:54:47 -0800

@kazuho commented on this pull request.

I'm not sure if we can provide exact limits, because the minimum valid size of packets depend on:
* packet type
* CID being used by the endpoint
* extensions being negotiated

In practice, I'd assume that endpoints do not hard-code the numbers provided here (e.g., 21), but rather try to parse the structure of the packets, and discard if they fail. Assuming that's the way people implement, it is not important to explain what the numbers are.

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From: Jana Iyengar <[email-masked]>
Date: Fri, 20 Nov 2020 17:25:04 -0800

@janaiyengar approved this pull request.

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From: Jana Iyengar <[email-masked]>
Date: Fri, 20 Nov 2020 17:25:10 -0800

Merged #4396 into master.

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