Subject: [quicwg/base-drafts] Add some suggestions for RFC 4821 probe packets. (#849)

From: martinduke <[email-masked]>
Date: Mon, 09 Oct 2017 22:20:13 -0700

This is in response to #614 .
You can view, comment on, or merge this pull request online at:

  https://github.com/quicwg/base-drafts/pull/849

-- Commit Summary --

  * Add some suggestions for RFC 4821 probe packets.

-- File Changes --

    M draft-ietf-quic-transport.md (9)

-- Patch Links --

https://github.com/quicwg/base-drafts/pull/849.patch
https://github.com/quicwg/base-drafts/pull/849.diff

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From: Martin Thomson <[email-masked]>
Date: Tue, 10 Oct 2017 05:39:24 +0000 (UTC)

martinthomson commented on this pull request.

Is this intended to close #614, or just help a little?

It doesn't seem like this is much extra text.  I would need to check with RFC 4821 to determine if #614 is closed by this change, but - without reading more - it doesn't seem substantial enough.

> @@ -2403,6 +2403,15 @@ that it sends.
 Strategies and implications of the frequency of generating acknowledgments are
 discussed in more detail in {{QUIC-RECOVERY}}.
 
+# Special Considerations for Packetization Layer PMTU Discovery
+
+The PADDING frame provides a useful option for PMTU probe packets that does not
+exist in other transports. QUIC Packets with no frames other than PADDING must be
+acknowledged, but need not be retransmitted if lost. PADDING probe packets, if

We're trying to avoid talking about retransmission of packets, instead concentrating on the information content.  In this case, you could say "QUIC packets that only include PADDING frames cause the receiver to generate an acknowledgment, but PADDING frames don't contain information that needs to be reliably delivered."  Or something like that.

> @@ -2403,6 +2403,15 @@ that it sends.
 Strategies and implications of the frequency of generating acknowledgments are
 discussed in more detail in {{QUIC-RECOVERY}}.
 
+# Special Considerations for Packetization Layer PMTU Discovery
+
+The PADDING frame provides a useful option for PMTU probe packets that does not
+exist in other transports. QUIC Packets with no frames other than PADDING must be
+acknowledged, but need not be retransmitted if lost. PADDING probe packets, if
+lost, also do not delay delivery of application data. Their only impact on

I would remove the "do not delay clause" on the basis that they could consume congestion control bytes.

> @@ -2403,6 +2403,15 @@ that it sends.
 Strategies and implications of the frequency of generating acknowledgments are
 discussed in more detail in {{QUIC-RECOVERY}}.
 
+# Special Considerations for Packetization Layer PMTU Discovery
+
+The PADDING frame provides a useful option for PMTU probe packets that does not
+exist in other transports. QUIC Packets with no frames other than PADDING must be
+acknowledged, but need not be retransmitted if lost. PADDING probe packets, if
+lost, also do not delay delivery of application data. Their only impact on
+application data is the extent that they consume the congestion window and
+connection flow control credits.

Padding doesn't consume flow control (only the bytes delivered in STREAM frames do).

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From: Martin Thomson <[email-masked]>
Date: Mon, 09 Oct 2017 23:58:53 -0700

Does this address #614?  It doesn't seem to do very much (I haven't read 4821 to confirm either way).

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From: Martin Thomson <[email-masked]>
Date: Tue, 10 Oct 2017 02:09:31 -0700

This line is a tiny bit too long.

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From: martinduke <[email-masked]>
Date: Tue, 10 Oct 2017 18:02:58 +0000 (UTC)

martinduke commented on this pull request.

Perhaps poorly worded, but the subject of the setting is "the <b>loss</b> of PADDING probe packets". Sending them in the first place consumes cwnd, I'll reorder the sentences.

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From: martinduke <[email-masked]>
Date: Tue, 10 Oct 2017 18:09:30 +0000 (UTC)

@martinduke pushed 1 commit.

54c56d6  Update draft-ietf-quic-transport.md

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From: martinduke <[email-masked]>
Date: Tue, 10 Oct 2017 18:12:40 +0000 (UTC)

@martinthomson I re-read the RFC, but I've asked @gloinul to comment more on his concerns with the existing text, rather than try to guess. This PR addresses the one objection I wholeheartedly agree with.

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From: Magnus Westerlund <[email-masked]>
Date: Wed, 25 Oct 2017 12:18:29 +0000 (UTC)

gloinul approved this pull request.

I think this is a relevant start and can be accepted. 

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