route/vendor/github.com/lucas-clemente/quic-go/congestion/prr_sender_test.go

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2017-12-12 02:51:45 +00:00
package congestion
import (
. "github.com/onsi/ginkgo"
. "github.com/onsi/gomega"
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"github.com/lucas-clemente/quic-go/internal/protocol"
"github.com/lucas-clemente/quic-go/internal/utils"
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)
var _ = Describe("PRR sender", func() {
var (
prr PrrSender
)
BeforeEach(func() {
prr = PrrSender{}
})
It("single loss results in send on every other ack", func() {
num_packets_in_flight := protocol.ByteCount(50)
bytes_in_flight := num_packets_in_flight * protocol.DefaultTCPMSS
ssthresh_after_loss := num_packets_in_flight / 2
congestion_window := ssthresh_after_loss * protocol.DefaultTCPMSS
prr.OnPacketLost(bytes_in_flight)
// Ack a packet. PRR allows one packet to leave immediately.
prr.OnPacketAcked(protocol.DefaultTCPMSS)
bytes_in_flight -= protocol.DefaultTCPMSS
Expect(prr.TimeUntilSend(congestion_window, bytes_in_flight, ssthresh_after_loss*protocol.DefaultTCPMSS)).To(BeZero())
// Send retransmission.
prr.OnPacketSent(protocol.DefaultTCPMSS)
// PRR shouldn't allow sending any more packets.
Expect(prr.TimeUntilSend(congestion_window, bytes_in_flight, ssthresh_after_loss*protocol.DefaultTCPMSS)).To(Equal(utils.InfDuration))
// One packet is lost, and one ack was consumed above. PRR now paces
// transmissions through the remaining 48 acks. PRR will alternatively
// disallow and allow a packet to be sent in response to an ack.
for i := protocol.ByteCount(0); i < ssthresh_after_loss-1; i++ {
// Ack a packet. PRR shouldn't allow sending a packet in response.
prr.OnPacketAcked(protocol.DefaultTCPMSS)
bytes_in_flight -= protocol.DefaultTCPMSS
Expect(prr.TimeUntilSend(congestion_window, bytes_in_flight, ssthresh_after_loss*protocol.DefaultTCPMSS)).To(Equal(utils.InfDuration))
// Ack another packet. PRR should now allow sending a packet in response.
prr.OnPacketAcked(protocol.DefaultTCPMSS)
bytes_in_flight -= protocol.DefaultTCPMSS
Expect(prr.TimeUntilSend(congestion_window, bytes_in_flight, ssthresh_after_loss*protocol.DefaultTCPMSS)).To(BeZero())
// Send a packet in response.
prr.OnPacketSent(protocol.DefaultTCPMSS)
bytes_in_flight += protocol.DefaultTCPMSS
}
// Since bytes_in_flight is now equal to congestion_window, PRR now maintains
// packet conservation, allowing one packet to be sent in response to an ack.
Expect(bytes_in_flight).To(Equal(congestion_window))
for i := 0; i < 10; i++ {
// Ack a packet.
prr.OnPacketAcked(protocol.DefaultTCPMSS)
bytes_in_flight -= protocol.DefaultTCPMSS
Expect(prr.TimeUntilSend(congestion_window, bytes_in_flight, ssthresh_after_loss*protocol.DefaultTCPMSS)).To(BeZero())
// Send a packet in response, since PRR allows it.
prr.OnPacketSent(protocol.DefaultTCPMSS)
bytes_in_flight += protocol.DefaultTCPMSS
// Since bytes_in_flight is equal to the congestion_window,
// PRR disallows sending.
Expect(bytes_in_flight).To(Equal(congestion_window))
Expect(prr.TimeUntilSend(congestion_window, bytes_in_flight, ssthresh_after_loss*protocol.DefaultTCPMSS)).To(Equal(utils.InfDuration))
}
})
It("burst loss results in slow start", func() {
bytes_in_flight := protocol.ByteCount(20 * protocol.DefaultTCPMSS)
const num_packets_lost = 13
const ssthresh_after_loss = 10
const congestion_window = ssthresh_after_loss * protocol.DefaultTCPMSS
// Lose 13 packets.
bytes_in_flight -= num_packets_lost * protocol.DefaultTCPMSS
prr.OnPacketLost(bytes_in_flight)
// PRR-SSRB will allow the following 3 acks to send up to 2 packets.
for i := 0; i < 3; i++ {
prr.OnPacketAcked(protocol.DefaultTCPMSS)
bytes_in_flight -= protocol.DefaultTCPMSS
// PRR-SSRB should allow two packets to be sent.
for j := 0; j < 2; j++ {
Expect(prr.TimeUntilSend(congestion_window, bytes_in_flight, ssthresh_after_loss*protocol.DefaultTCPMSS)).To(BeZero())
// Send a packet in response.
prr.OnPacketSent(protocol.DefaultTCPMSS)
bytes_in_flight += protocol.DefaultTCPMSS
}
// PRR should allow no more than 2 packets in response to an ack.
Expect(prr.TimeUntilSend(congestion_window, bytes_in_flight, ssthresh_after_loss*protocol.DefaultTCPMSS)).To(Equal(utils.InfDuration))
}
// Out of SSRB mode, PRR allows one send in response to each ack.
for i := 0; i < 10; i++ {
prr.OnPacketAcked(protocol.DefaultTCPMSS)
bytes_in_flight -= protocol.DefaultTCPMSS
Expect(prr.TimeUntilSend(congestion_window, bytes_in_flight, ssthresh_after_loss*protocol.DefaultTCPMSS)).To(BeZero())
// Send a packet in response.
prr.OnPacketSent(protocol.DefaultTCPMSS)
bytes_in_flight += protocol.DefaultTCPMSS
}
})
})