Re: [quicwg/base-drafts] Cleaning up Loss Detection overview (#536)

[ianswett <[e-mail]>]

ianswett commented on this pull request.



>  QUIC uses a combination of ack information and alarms to detect lost packets.
 An unacknowledged QUIC packet is marked as lost in one of the following ways:
 
-  * A packet is marked as lost if at least one packet that was sent a threshold
-    number of packets (kReorderingThreshold) after it has been
-    acknowledged. This indicates that the unacknowledged packet is either lost
-    or reordered beyond the specified threshold. This mechanism combines both
-    TCP's FastRetransmit and FACK mechanisms.
-
-  * If a packet is near the tail, where fewer than kReorderingThreshold packets
-    are sent after it, the sender cannot expect to detect loss based on the
-    previous mechanism. In this case, a sender uses both ack information and an
-    alarm to detect loss. Specifically, when the last sent packet is
-    acknowledged, the sender waits a short period of time to allow for
-    reordering and then marks any unacknowledged packets as lost. This mechanism
+  * When at least one packet that was sent a threshold number of packets

I agree it's a bit hard to read.  Packet number skipping doesn't matter, because the sender knows it skipped packets.  It does introduce extra work in that case, but it's easily solvable.

>  
-  * Instead of a packet threshold to tolerate reordering, a QUIC sender may use
-    a time threshold. This allows for senders to be tolerant of short periods of
-    significant reordering. In this mechanism, a QUIC sender marks a packet as
-    lost when a packet larger than it is acknowledged and a threshold amount of
-    time has passed since the packet was sent.
+The above mechanisms use a packet threshold to tolerate
+reordering. Alternatively, a QUIC sender may use a time threshold. This allows

I tend to agree.

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