wip change ledbat and start cubic

CMakeLists.txt

@@ -25,6 +25,8 @@ add_library(solanaceae_ngcft1
 	./solanaceae/ngc_ft1/cca.hpp
 	./solanaceae/ngc_ft1/ledbat.hpp
 	./solanaceae/ngc_ft1/ledbat.cpp
+	./solanaceae/ngc_ft1/cubic.hpp
+	./solanaceae/ngc_ft1/cubic.cpp
 
 	./solanaceae/ngc_ft1/rcv_buf.hpp
 	./solanaceae/ngc_ft1/rcv_buf.cpp

solanaceae/ngc_ft1/cca.hpp

@@ -3,6 +3,16 @@
 #include <vector>
 #include <cstdint>
 
+// TODO: refactor, more state tracking in ccai and seperate into flow and congestion algos
+inline bool isSkipSeqID(const std::pair<uint8_t, uint16_t>& a, const std::pair<uint8_t, uint16_t>& b) {
+	// this is not perfect, would need more ft id based history
+	if (a.first != b.first) {
+		return false; // we dont know
+	} else {
+		return a.second+1 != b.second;
+	}
+}
+
 struct CCAI {
 	public: // config
 		using SeqIDType = std::pair<uint8_t, uint16_t>; // tf_id, seq_id

solanaceae/ngc_ft1/cubic.cpp

@@ -0,0 +1,49 @@
+#include "./cubic.hpp"
+
+#include <cmath>
+#include <iostream>
+
+float CUBIC::getCWnD(void) const {
+	const double K = cbrt(
+		(_window_max * (1. - BETA)) / SCALING_CONSTANT
+	);
+
+	const double TK = _time_since_reduction - K;
+
+	const double cwnd =
+		SCALING_CONSTANT
+		* TK * TK * TK // TK^3
+		+ _window_max
+	;
+
+	std::cout << "K:" << K << " TK:" << TK << " cwnd:" << cwnd << " rtt:" << getCurrentDelay() << "\n";
+
+	return cwnd;
+}
+
+float CUBIC::getCurrentDelay(void) const {
+	return _rtt_ema;
+}
+
+void CUBIC::addRTT(float new_delay) {
+	// lerp(new_delay, rtt_ema, 0.1)
+	_rtt_ema = RTT_EMA_ALPHA * new_delay + (1.f - RTT_EMA_ALPHA) * _rtt_ema;
+}
+
+size_t CUBIC::canSend(void) const {
+	return 0;
+}
+
+std::vector<CUBIC::SeqIDType> CUBIC::getTimeouts(void) const {
+	return {};
+}
+
+void CUBIC::onSent(SeqIDType seq, size_t data_size) {
+}
+
+void CUBIC::onAck(std::vector<SeqIDType> seqs) {
+}
+
+void CUBIC::onLoss(SeqIDType seq, bool discard) {
+}
+

solanaceae/ngc_ft1/cubic.hpp

@@ -0,0 +1,64 @@
+#pragma once
+
+#include "./cca.hpp"
+
+#include <chrono>
+
+struct CUBIC : public CCAI {
+	using clock = std::chrono::steady_clock;
+
+	public: // config
+		static constexpr float BETA {0.7f};
+		static constexpr float SCALING_CONSTANT {0.4f};
+		static constexpr float RTT_EMA_ALPHA = 0.1f; // 0.1 is very smooth, might need more
+
+	private:
+		// window size before last reduciton
+		double _window_max {2.f * MAXIMUM_SEGMENT_SIZE}; // start with mss*2
+		double _window_last_max {2.f * MAXIMUM_SEGMENT_SIZE};
+		double _time_since_reduction {0.};
+
+		// initialize to low value, will get corrected very fast
+		float _fwnd {0.01f * max_byterate_allowed}; // in bytes
+
+		// rtt exponental moving average
+		float _rtt_ema {0.5f};
+
+		clock::time_point _time_start_offset;
+
+	private:
+		float getCWnD(void) const;
+
+		// make values relative to algo start for readability (and precision)
+		// get timestamp in seconds
+		float getTimeNow(void) const {
+			return std::chrono::duration<float>{clock::now() - _time_start_offset}.count();
+		}
+
+		// moving avg over the last few delay samples
+		// VERY sensitive to bundling acks
+		float getCurrentDelay(void) const;
+
+		void addRTT(float new_delay);
+
+	public: // api
+		CUBIC(size_t maximum_segment_data_size) : CCAI(maximum_segment_data_size) {}
+
+		// TODO: api for how much data we should send
+		// take time since last sent into account
+		// respect max_byterate_allowed
+		size_t canSend(void) const override;
+
+		// get the list of timed out seq_ids
+		std::vector<SeqIDType> getTimeouts(void) const override;
+
+	public: // callbacks
+		// data size is without overhead
+		void onSent(SeqIDType seq, size_t data_size) override;
+
+		void onAck(std::vector<SeqIDType> seqs) override;
+
+		// if discard, not resent, not inflight
+		void onLoss(SeqIDType seq, bool discard) override;
+};
+

solanaceae/ngc_ft1/ledbat.cpp

@@ -1,4 +1,5 @@
 #include "./ledbat.hpp"
+#include "solanaceae/ngc_ft1/cca.hpp"
 
 #include <algorithm>
 #include <chrono>
@@ -68,6 +69,11 @@ void LEDBAT::onSent(SeqIDType seq, size_t data_size) {
 }
 
 void LEDBAT::onAck(std::vector<SeqIDType> seqs) {
+	if (seqs.empty()) {
+		assert(false && "got empty list of acks???");
+		return;
+	}
+
 	// only take the smallest value
 	float most_recent {-std::numeric_limits<float>::infinity()};
 
@@ -75,6 +81,23 @@ void LEDBAT::onAck(std::vector<SeqIDType> seqs) {
 
 	const auto now {getTimeNow()};
 
+	{ // skip in ack is congestion event
+		// 1. look at primary ack of packet
+		auto it = std::find_if(_in_flight.begin(), _in_flight.end(), [seq = seqs.front()](const auto& v) -> bool {
+			return std::get<0>(v) == seq;
+		});
+		if (it != _in_flight.end()) {
+			if (isSkipSeqID(_last_ack_got, std::get<0>(*it))) {
+				if (getTimeNow() >= _last_congestion_event + _last_congestion_rtt) {
+					_recently_lost_data = true;
+					_last_congestion_event = getTimeNow();
+					_last_congestion_rtt = getCurrentDelay();
+				}
+			}
+			// TODO: only if newer, triggers double event otherwise (without a timer)
+			_last_ack_got = std::get<0>(*it);
+		}
+	}
 	for (const auto& seq : seqs) {
 		auto it = std::find_if(_in_flight.begin(), _in_flight.end(), [seq](const auto& v) -> bool {
 			return std::get<0>(v) == seq;
@@ -124,15 +147,17 @@ void LEDBAT::onLoss(SeqIDType seq, bool discard) {
 	}
 	// TODO: reset timestamp?
 
+#if 0 // temporarily disable ce for timeout
 	// at most once per rtt?
 	// TODO: use delay at event instead
 	if (getTimeNow() >= _last_congestion_event + _last_congestion_rtt) {
 		_recently_lost_data = true;
 		_last_congestion_event = getTimeNow();
 		_last_congestion_rtt = getCurrentDelay();
+	}
+#endif
 
 	updateWindows();
-	}
 }
 
 float LEDBAT::getCurrentDelay(void) const {
@@ -205,7 +230,7 @@ void LEDBAT::updateWindows(void) {
 
 		if (_recently_lost_data) {
 			_cwnd = std::clamp(
-				_cwnd / 2.f,
+				_cwnd * 0.7f,
 				//_cwnd / 1.6f,
 				2.f * MAXIMUM_SEGMENT_SIZE,
 				_cwnd
@@ -213,7 +238,7 @@ void LEDBAT::updateWindows(void) {
 		} else {
 			// LEDBAT++ (the Rethinking the LEDBAT Protocol paper)
 			// "Multiplicative decrease"
-			const float constant {2.f}; // spec recs 1
+			const float constant {1.f}; // spec recs 1
 			if (queuing_delay < target_delay) {
 				_cwnd = std::min(
 					_cwnd + gain,

solanaceae/ngc_ft1/ledbat.hpp

@@ -123,6 +123,8 @@ struct LEDBAT : public CCAI{
 
 		int64_t _in_flight_bytes {0};
 
+		SeqIDType _last_ack_got {0xff, 0xffff}; // some default
+
 	private: // helper
 		clock::time_point _time_start_offset;
 };

solanaceae/ngc_ft1_sha1/sha1_ngcft1.cpp

@@ -826,6 +826,7 @@ bool SHA1_NGCFT1::onEvent(const Events::NGCFT1_send_data& e) {
 	}
 
 	auto& transfer = peer.at(e.transfer_id);
+	transfer.time_since_activity = 0.f;
 	if (std::holds_alternative<SendingTransfer::Info>(transfer.v)) {
 		auto& info_transfer = std::get<SendingTransfer::Info>(transfer.v);
 		for (size_t i = 0; i < e.data_size && (i + e.data_offset) < info_transfer.info_data.size(); i++) {
@@ -859,8 +860,6 @@ bool SHA1_NGCFT1::onEvent(const Events::NGCFT1_send_data& e) {
 		assert(false && "not implemented?");
 	}
 
-	transfer.time_since_activity = 0.f;
-
 	return true;
 }