include the timer granularity in the advertised max_ack_delay

client.go

@@ -352,7 +352,7 @@ func (c *client) createNewTLSSession(version protocol.VersionNumber) error {
 		IdleTimeout:                    c.config.IdleTimeout,
 		MaxBidiStreams:                 uint64(c.config.MaxIncomingStreams),
 		MaxUniStreams:                  uint64(c.config.MaxIncomingUniStreams),
-		MaxAckDelay:                    protocol.MaxAckDelay,
+		MaxAckDelay:                    protocol.MaxAckDelayInclGranularity,
 		AckDelayExponent:               protocol.AckDelayExponent,
 		DisableMigration:               true,
 	}

internal/ackhandler/sent_packet_handler.go

@@ -17,8 +17,6 @@ const (
 	// Maximum reordering in time space before time based loss detection considers a packet lost.
 	// Specified as an RTT multiplier.
 	timeThreshold = 9.0 / 8
-	// Timer granularity. The timer will not be set to a value smaller than granularity.
-	granularity = time.Millisecond
 )
 
 type packetNumberSpace struct {
@@ -341,7 +339,7 @@ func (h *sentPacketHandler) detectLostPackets(
 	lossDelay := time.Duration(timeThreshold * maxRTT)
 
 	// Minimum time of granularity before packets are deemed lost.
-	lossDelay = utils.MaxDuration(lossDelay, granularity)
+	lossDelay = utils.MaxDuration(lossDelay, protocol.TimerGranularity)
 
 	var lostPackets []*Packet
 	pnSpace.history.Iterate(func(packet *Packet) (bool, error) {
@@ -616,7 +614,7 @@ func (h *sentPacketHandler) queuePacketForRetransmission(p *Packet, pnSpace *pac
 }
 
 func (h *sentPacketHandler) computeCryptoTimeout() time.Duration {
-	duration := utils.MaxDuration(2*h.rttStats.SmoothedOrInitialRTT(), granularity)
+	duration := utils.MaxDuration(2*h.rttStats.SmoothedOrInitialRTT(), protocol.TimerGranularity)
 	// exponential backoff
 	// There's an implicit limit to this set by the crypto timeout.
 	return duration << h.cryptoCount
@@ -624,7 +622,7 @@ func (h *sentPacketHandler) computeCryptoTimeout() time.Duration {
 
 func (h *sentPacketHandler) computePTOTimeout() time.Duration {
 	// TODO(#1236): include the max_ack_delay
-	duration := utils.MaxDuration(h.rttStats.SmoothedOrInitialRTT()+4*h.rttStats.MeanDeviation(), granularity)
+	duration := utils.MaxDuration(h.rttStats.SmoothedOrInitialRTT()+4*h.rttStats.MeanDeviation(), protocol.TimerGranularity)
 	return duration << h.ptoCount
 }
 

internal/ackhandler/sent_packet_handler_test.go

@@ -593,7 +593,7 @@ var _ = Describe("SentPacketHandler", func() {
 		It("uses the granularity for short RTTs", func() {
 			rtt := time.Microsecond
 			updateRTT(rtt)
-			Expect(handler.computePTOTimeout()).To(Equal(granularity))
+			Expect(handler.computePTOTimeout()).To(Equal(protocol.TimerGranularity))
 		})
 
 		It("implements exponential backoff", func() {

internal/protocol/params.go

@@ -126,5 +126,13 @@ const DefaultConnectionIDLength = 4
 // AckDelayExponent is the ack delay exponent used when sending ACKs.
 const AckDelayExponent = 3
 
+// Estimated timer granularity.
+// The loss detection timer will not be set to a value smaller than granularity.
+const TimerGranularity = time.Millisecond
+
 // MaxAckDelay is the maximum time by which we delay sending ACKs.
 const MaxAckDelay = 25 * time.Millisecond
+
+// MaxAckDelayInclGranularity is the max_ack_delay including the timer granularity.
+// This is the value that should be advertised to the peer.
+const MaxAckDelayInclGranularity = MaxAckDelay + TimerGranularity

server.go

@@ -445,7 +445,7 @@ func (s *server) createNewSession(
 		IdleTimeout:                    s.config.IdleTimeout,
 		MaxBidiStreams:                 uint64(s.config.MaxIncomingStreams),
 		MaxUniStreams:                  uint64(s.config.MaxIncomingUniStreams),
-		MaxAckDelay:                    protocol.MaxAckDelay,
+		MaxAckDelay:                    protocol.MaxAckDelayInclGranularity,
 		AckDelayExponent:               protocol.AckDelayExponent,
 		DisableMigration:               true,
 		StatelessResetToken:            &token,