Re: [quicwg/base-drafts] Reword Immediate ACK Recommendation (#2424)

ianswett <notifications@github.com> Mon, 11 February 2019 19:49 UTC

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Subject: Re: [quicwg/base-drafts] Reword Immediate ACK Recommendation (#2424)
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ianswett commented on this pull request.

Suggestions

> @@ -135,6 +135,12 @@ Crypto Packets:
 : Packets containing CRYPTO data sent in Initial or Handshake
   packets.
 
+Out-of-order Packets:
+
+: Packets that do not increase the largest received packet number for its
+packet number space by exactly one. Packets usually arrive out of order

```suggestion
  packet number space by exactly one. Packets arrive out of order
```

> @@ -135,6 +135,12 @@ Crypto Packets:
 : Packets containing CRYPTO data sent in Initial or Handshake
   packets.
 
+Out-of-order Packets:
+
+: Packets that do not increase the largest received packet number for its
+packet number space by exactly one. Packets usually arrive out of order
+because earlier packets are lost or delayed.

```suggestion
  when earlier packets are lost or delayed.
```

> @@ -244,11 +250,11 @@ ack-eliciting packet. QUIC recovery algorithms do not assume the peer sends
 an ACK immediately when receiving a second ack-eliciting packet.
 
 In order to accelerate loss recovery and reduce timeouts, the receiver SHOULD
-send an immediate ACK when it receives a new packet which is not one greater
-than the largest received packet number. A receiver MAY send immediate ACKs
-for the next few ack-eliciting packets that are received, but SHOULD NOT
-send an immediate ACK for more than 1/8 RTT after receiving an out-of-order
-packet.
+send immediate ACKs for an interval after it receives an out-of-order packet.

The intent of the text is you SHOULD send one immediate ACK, but you may send more than one immediate ACK.  This new text changes that to you SHOULD send an immediate ACK for an interval, and I don't want to make that a SHOULD, only a MAY.

> @@ -244,11 +250,11 @@ ack-eliciting packet. QUIC recovery algorithms do not assume the peer sends
 an ACK immediately when receiving a second ack-eliciting packet.
 
 In order to accelerate loss recovery and reduce timeouts, the receiver SHOULD
-send an immediate ACK when it receives a new packet which is not one greater
-than the largest received packet number. A receiver MAY send immediate ACKs
-for the next few ack-eliciting packets that are received, but SHOULD NOT
-send an immediate ACK for more than 1/8 RTT after receiving an out-of-order
-packet.
+send immediate ACKs for an interval after it receives an out-of-order packet.
+This interval SHOULD NOT exceed 1/8 RTT unless more out-of-order packets arrive
+during the interval. Therefore, if out-of-order packets consistently arrive

Suggestion on an alternate clarification to Martin's question: "If every packet arrives out-of-order, then an immediate ACK will be sent for every received packet."

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