congestion.go RawHistoryFolder

1package dgram
2
3import "time"
4
5const (
6	initialCongestionPackets = 10
7	minimumCongestionPackets = 2
8	maximumCongestionBytes   = 4 << 20
9	initialPacingRTT         = 250 * time.Millisecond
10	dataBurstPackets         = 2
11)
12
13type congestionController struct {
14	mtu       int
15	cwndBytes int
16	minBytes  int
17	maxBytes  int
18	srtt      time.Duration
19}
20
21func newCongestionController(mtu int) congestionController {
22	minimum := minimumCongestionPackets * mtu
23	maximum := maximumCongestionBytes
24	if maximum < minimum {
25		maximum = minimum
26	}
27	initial := initialCongestionPackets * mtu
28	if initial > maximum {
29		initial = maximum
30	}
31	return congestionController{
32		mtu:       mtu,
33		cwndBytes: initial,
34		minBytes:  minimum,
35		maxBytes:  maximum,
36		srtt:      initialPacingRTT,
37	}
38}
39
40func (c *congestionController) onRTT(srtt time.Duration) {
41	if srtt > 0 {
42		c.srtt = srtt
43	}
44}
45
46func (c *congestionController) onACK(ackedBytes int) {
47	if ackedBytes <= 0 || c.cwndBytes >= c.maxBytes {
48		return
49	}
50	increase := int(int64(c.mtu) * int64(ackedBytes) / int64(c.cwndBytes))
51	if increase < 1 {
52		increase = 1
53	}
54	c.cwndBytes = min(c.cwndBytes+increase, c.maxBytes)
55}
56
57func (c *congestionController) onLoss() {
58	c.cwndBytes = max(c.cwndBytes/2, c.minBytes)
59}
60
61func (c congestionController) bytesPerSecond() int {
62	rtt := max(c.srtt, time.Millisecond)
63	return int(int64(c.cwndBytes) * int64(time.Second) / int64(rtt))
64}
65
66func (c congestionController) burstBytes() int {
67	return min(c.cwndBytes, dataBurstPackets*c.mtu)
68}