Re: [quicwg/base-drafts] Don't retransmit lost packets that are acked later (#3957)

[Jana Iyengar <[e-mail]>]

@janaiyengar commented on this pull request.

I've rewritten the long sentence based on feedback

> @@ -3804,6 +3804,14 @@ number length, connection ID length, and path MTU.  A receiver MUST accept
 packets containing an outdated frame, such as a MAX_DATA frame carrying a
 smaller maximum data than one found in an older packet.
 
+When a sender declares a packet as lost and either retransmits the contained
+frames or marks them for retransmission, the sender SHOULD avoid subsequent
+retransmission of this information if it later receives an acknowledgement for
+that packet. Doing so requires senders to retain information about packets after
+they are declared lost. A sender can discard this information after a period of
+time elapses, such as three times the PTO (Section 6.2 of {{QUIC-RECOVERY}}), or

The PTO is the period of time that you expect the ack back by, not RTT. 

It's true that 3 PTO is a conservative value, but, it's only on lost packets. When that's the uncommon case, it won't consume a lot of memory. When it's the common case, you're not sending a lot of packets anymore because the sender is in congestion, so it shouldn't also cause memory exhaustion.

Either way, this is a suggestion, not a recommendation.

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