Question about bytes_in_flight & prior_bytes_inlight in OnPacketSent & OnCongestionEvent

[李锤子]

hello,

    Lastes I'm using bbr code in my project. When watching params in OnPacketSent & OnCongestionEvent, I find sth Puzzled.

First, origin code is:

void OnCongestionEvent(bool rtt_updated, QuicByteCount prior_in_flight, QuicTime event_time,

const AckedPacketVector& acked_packets, const LostPacketVector& lost_packets) override;

void OnPacketSent(QuicTime sent_time, QuicByteCount bytes_in_flight, QuicPacketNumber packet_number,

QuicByteCount bytes, HasRetransmittableData is_retransmittable) override;

As above, we can concluede in OnCongestionEvent, we use prior( before process ack&loss packets). However in OnPacketSent we use just the bytes_flight(already been calc when sending, as in Quic-BBR bbr2_simulation_test.cc file).

But when I see codes in BandwidthSampler::OnPacketSent, I see this "connection_state_map_.Emplace(packet_number, sent_time, bytes,

bytes_in_flight + bytes, *this);

So I get confused, bytes_in_flight in OnPacketSent shouldn't be prior_bytes_inflight, why use (bytes_in_flight + bytes)

Sincerely.

Carlos Li

[ians...@google.com]

bytes_in_fight in OnPacketSent() is bytes_in_flight prior to the packet being sent.  If you look at QuicSentPacketManager::OnPacketSent(), you'll notice the call to the congestion controller is before the call add the packet to unacked_packets_AddSentPacket.

Ian