commit 31c12b571ad47e11acc31be5f0bfa42bb4c104ef
author Junho Choi <1229714+junhochoi@users.noreply.github.com> Sat Mar 19 04:04:05 2022 -0700
committer GitHub <noreply@github.com> Sat Mar 19 11:04:05 2022 +0000
tree 2432c32d82e17a12ef7037d3cffc8b524c74b739
parent 6d04f006e5b3a9321381281e05d8e2d2156a965b

hystart: hystart++ draft-04 (#1195)

Update based on draft-ietf-tcpm-hystartplusplus-04.
Major change is removing LOW_CWND.

quiche/src/recovery/cubic.rs

diff --git a/quiche/src/recovery/cubic.rs b/quiche/src/recovery/cubic.rs
index 6a6ee8e..090a8f4d 100644
--- a/quiche/src/recovery/cubic.rs
+++ b/quiche/src/recovery/cubic.rs
@@ -259,14 +259,7 @@
             r.bytes_acked_sl -= r.max_datagram_size;
         }
 
-        if r.hystart.on_packet_acked(
-            epoch,
-            packet,
-            r.latest_rtt,
-            r.congestion_window,
-            now,
-            r.max_datagram_size,
-        ) {
+        if r.hystart.on_packet_acked(epoch, packet, r.latest_rtt, now) {
             // Exit to congestion avoidance if CSS ends.
             r.ssthresh = r.congestion_window;
         }

quiche/src/recovery/hystart.rs

diff --git a/quiche/src/recovery/hystart.rs b/quiche/src/recovery/hystart.rs
index dc73cdc..2285951 100644
--- a/quiche/src/recovery/hystart.rs
+++ b/quiche/src/recovery/hystart.rs
@@ -28,7 +28,7 @@
 //!
 //! This implementation is based on the following I-D:
 //!
-//! <https://datatracker.ietf.org/doc/html/draft-ietf-tcpm-hystartplusplus-03>
+//! <https://datatracker.ietf.org/doc/html/draft-ietf-tcpm-hystartplusplus-04>
 
 use std::cmp;
 use std::time::Duration;
@@ -38,8 +38,6 @@
 use crate::recovery;
 
 /// Constants from I-D.
-const LOW_CWND: usize = 16;
-
 const MIN_RTT_THRESH: Duration = Duration::from_millis(4);
 
 const MAX_RTT_THRESH: Duration = Duration::from_millis(16);
@@ -131,7 +129,7 @@
     // On receiving ACK. Returns true if need to enter Congestion Avoidance.
     pub fn on_packet_acked(
         &mut self, epoch: packet::Epoch, packet: &recovery::Acked, rtt: Duration,
-        cwnd: usize, now: Instant, max_datagram_size: usize,
+        now: Instant,
     ) -> bool {
         if !(self.enabled && epoch == packet::EPOCH_APPLICATION) {
             return false;
@@ -143,11 +141,10 @@
 
         // Slow Start.
         if self.css_start_time().is_none() {
-            if cwnd >= (LOW_CWND * max_datagram_size) &&
-                self.rtt_sample_count >= N_RTT_SAMPLE
+            if self.rtt_sample_count >= N_RTT_SAMPLE &&
+                self.current_round_min_rtt != Duration::MAX &&
+                self.last_round_min_rtt != Duration::MAX
             {
-                self.rtt_sample_count = 0;
-
                 // clamp(min_rtt_thresh, last_round_min_rtt/8,
                 // max_rtt_thresh)
                 let rtt_thresh =

quiche/src/recovery/reno.rs

diff --git a/quiche/src/recovery/reno.rs b/quiche/src/recovery/reno.rs
index 74052ad..eb8942b 100644
--- a/quiche/src/recovery/reno.rs
+++ b/quiche/src/recovery/reno.rs
@@ -88,14 +88,7 @@
             r.congestion_window += r.max_datagram_size;
         }
 
-        if r.hystart.on_packet_acked(
-            epoch,
-            packet,
-            r.latest_rtt,
-            r.congestion_window,
-            now,
-            r.max_datagram_size,
-        ) {
+        if r.hystart.on_packet_acked(epoch, packet, r.latest_rtt, now) {
             // Exit to congestion avoidance if CSS ends.
             r.ssthresh = r.congestion_window;
         }