109 lines
4.5 KiB
Go
109 lines
4.5 KiB
Go
package congestion
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import (
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. "github.com/onsi/ginkgo"
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. "github.com/onsi/gomega"
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"github.com/lucas-clemente/quic-go/internal/protocol"
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"github.com/lucas-clemente/quic-go/internal/utils"
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)
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var _ = Describe("PRR sender", func() {
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var (
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prr PrrSender
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)
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BeforeEach(func() {
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prr = PrrSender{}
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})
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It("single loss results in send on every other ack", func() {
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num_packets_in_flight := protocol.ByteCount(50)
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bytes_in_flight := num_packets_in_flight * protocol.DefaultTCPMSS
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ssthresh_after_loss := num_packets_in_flight / 2
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congestion_window := ssthresh_after_loss * protocol.DefaultTCPMSS
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prr.OnPacketLost(bytes_in_flight)
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// Ack a packet. PRR allows one packet to leave immediately.
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prr.OnPacketAcked(protocol.DefaultTCPMSS)
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bytes_in_flight -= protocol.DefaultTCPMSS
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Expect(prr.TimeUntilSend(congestion_window, bytes_in_flight, ssthresh_after_loss*protocol.DefaultTCPMSS)).To(BeZero())
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// Send retransmission.
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prr.OnPacketSent(protocol.DefaultTCPMSS)
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// PRR shouldn't allow sending any more packets.
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Expect(prr.TimeUntilSend(congestion_window, bytes_in_flight, ssthresh_after_loss*protocol.DefaultTCPMSS)).To(Equal(utils.InfDuration))
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// One packet is lost, and one ack was consumed above. PRR now paces
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// transmissions through the remaining 48 acks. PRR will alternatively
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// disallow and allow a packet to be sent in response to an ack.
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for i := protocol.ByteCount(0); i < ssthresh_after_loss-1; i++ {
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// Ack a packet. PRR shouldn't allow sending a packet in response.
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prr.OnPacketAcked(protocol.DefaultTCPMSS)
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bytes_in_flight -= protocol.DefaultTCPMSS
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Expect(prr.TimeUntilSend(congestion_window, bytes_in_flight, ssthresh_after_loss*protocol.DefaultTCPMSS)).To(Equal(utils.InfDuration))
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// Ack another packet. PRR should now allow sending a packet in response.
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prr.OnPacketAcked(protocol.DefaultTCPMSS)
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bytes_in_flight -= protocol.DefaultTCPMSS
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Expect(prr.TimeUntilSend(congestion_window, bytes_in_flight, ssthresh_after_loss*protocol.DefaultTCPMSS)).To(BeZero())
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// Send a packet in response.
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prr.OnPacketSent(protocol.DefaultTCPMSS)
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bytes_in_flight += protocol.DefaultTCPMSS
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}
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// Since bytes_in_flight is now equal to congestion_window, PRR now maintains
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// packet conservation, allowing one packet to be sent in response to an ack.
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Expect(bytes_in_flight).To(Equal(congestion_window))
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for i := 0; i < 10; i++ {
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// Ack a packet.
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prr.OnPacketAcked(protocol.DefaultTCPMSS)
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bytes_in_flight -= protocol.DefaultTCPMSS
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Expect(prr.TimeUntilSend(congestion_window, bytes_in_flight, ssthresh_after_loss*protocol.DefaultTCPMSS)).To(BeZero())
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// Send a packet in response, since PRR allows it.
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prr.OnPacketSent(protocol.DefaultTCPMSS)
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bytes_in_flight += protocol.DefaultTCPMSS
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// Since bytes_in_flight is equal to the congestion_window,
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// PRR disallows sending.
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Expect(bytes_in_flight).To(Equal(congestion_window))
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Expect(prr.TimeUntilSend(congestion_window, bytes_in_flight, ssthresh_after_loss*protocol.DefaultTCPMSS)).To(Equal(utils.InfDuration))
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}
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})
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It("burst loss results in slow start", func() {
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bytes_in_flight := protocol.ByteCount(20 * protocol.DefaultTCPMSS)
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const num_packets_lost = 13
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const ssthresh_after_loss = 10
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const congestion_window = ssthresh_after_loss * protocol.DefaultTCPMSS
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// Lose 13 packets.
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bytes_in_flight -= num_packets_lost * protocol.DefaultTCPMSS
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prr.OnPacketLost(bytes_in_flight)
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// PRR-SSRB will allow the following 3 acks to send up to 2 packets.
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for i := 0; i < 3; i++ {
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prr.OnPacketAcked(protocol.DefaultTCPMSS)
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bytes_in_flight -= protocol.DefaultTCPMSS
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// PRR-SSRB should allow two packets to be sent.
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for j := 0; j < 2; j++ {
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Expect(prr.TimeUntilSend(congestion_window, bytes_in_flight, ssthresh_after_loss*protocol.DefaultTCPMSS)).To(BeZero())
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// Send a packet in response.
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prr.OnPacketSent(protocol.DefaultTCPMSS)
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bytes_in_flight += protocol.DefaultTCPMSS
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}
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// PRR should allow no more than 2 packets in response to an ack.
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Expect(prr.TimeUntilSend(congestion_window, bytes_in_flight, ssthresh_after_loss*protocol.DefaultTCPMSS)).To(Equal(utils.InfDuration))
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}
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// Out of SSRB mode, PRR allows one send in response to each ack.
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for i := 0; i < 10; i++ {
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prr.OnPacketAcked(protocol.DefaultTCPMSS)
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bytes_in_flight -= protocol.DefaultTCPMSS
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Expect(prr.TimeUntilSend(congestion_window, bytes_in_flight, ssthresh_after_loss*protocol.DefaultTCPMSS)).To(BeZero())
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// Send a packet in response.
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prr.OnPacketSent(protocol.DefaultTCPMSS)
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bytes_in_flight += protocol.DefaultTCPMSS
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}
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})
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})
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