[quicwg/base-drafts] congestion window increase on every ACKed packet could result in bursty sends (#3094)

[Vidhi Goel <[e-mail]>]

When an ACK arrives that acknowledges N packets (where N could be very large), QUIC will increase the congestion window by more than 1MSS per congestion window during Congestion Avoidance causing bursty send. This could also affect the slow start.

if (congestion_window < ssthresh):
       // Slow start.
       congestion_window += acked_packet.size
     else:
       // Congestion avoidance.
       congestion_window += kMaxDatagramSize * acked_packet.size / congestion_window

One could argue that QUIC ACKs every other packet, but there ACK packet could get lost or  ACK for ACK packet could get lost.

The draft is probably assuming packet pacing but not all implementations support that.

I discussed this with Jana and he thinks that we should add something in pseudo code or some specific text in the draft.

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