cong: removes buggy rtt estimator implementation

Author: AnoldGH

std/object/congestion/rtt_estimator.go

@@ -1,10 +1,7 @@
 package congestion
 
 import (
-	"sync"
 	"time"
-
-	"github.com/named-data/ndnd/std/log"
 )
 
 // RTTEstimator provides an interface for estimating round-trip time.
@@ -15,67 +12,4 @@ type RTTEstimator interface {
 	DeviationRTT() time.Duration	// get the deviation of RTT
 
 	AddMeasurement(sample time.Duration, retransmitted bool)	// add a new RTT measurement
-}
-
-// KarnRTTEstimator is an implementation of RTTEstimator using Karn's algorithm.
-type KarnRTTEstimator struct {
-	mutex	sync.RWMutex
-
-	estimatedRTT time.Duration		// estimated RTT
-	deviationRTT time.Duration		// deviation of RTT
-
-	alpha float64					// alpha value for exponential smoothing
-	beta  float64					// beta value for exponential smoothing
-}
-
-// NewKarnRTTEstimator creates a new KarnRTTEstimator.
-func NewKarnRTTEstimator(alpha float64, beta float64) *KarnRTTEstimator {
-	return &KarnRTTEstimator{
-		estimatedRTT: 0.0,
-		deviationRTT: 0.0,
-
-		alpha: alpha,
-		beta: beta,
-	}
-}
-
-func (rtt *KarnRTTEstimator) String() string {
-	return "karn-rtt-estimator"
-}
-
-// EstimatedRTT returns the estimated RTT.
-func (rtt *KarnRTTEstimator) EstimatedRTT() time.Duration {
-	rtt.mutex.RLock()
-	defer rtt.mutex.RUnlock()
-
-	return rtt.estimatedRTT
-}
-
-// DeviationRTT returns the deviation of RTT.
-func (rtt *KarnRTTEstimator) DeviationRTT() time.Duration {
-	rtt.mutex.RLock()
-	defer rtt.mutex.RUnlock()
-
-	return rtt.deviationRTT
-}
-
-// AddMeasurement adds a new RTT measurement.
-// For Karn's algorithm, it ignores retransmitted packets.
-func (rtt *KarnRTTEstimator) AddMeasurement(sample time.Duration, retransmitted bool) {
-	if retransmitted {
-		return	// ignore retransmitted packets
-	}
-
-	rtt.mutex.Lock()
-	defer rtt.mutex.Unlock()
-
-	// calculate new RTT using Karn's algorithm
-	newEstimatedRTT := rtt.estimatedRTT.Seconds() + rtt.alpha * (sample - rtt.estimatedRTT).Seconds()
-	newDeviationRTT := rtt.deviationRTT.Seconds() + rtt.beta * (sample - rtt.estimatedRTT).Seconds()
-
-	// update RTT
-	rtt.estimatedRTT = time.Duration(newEstimatedRTT * float64(time.Second))
-	rtt.deviationRTT = time.Duration(newDeviationRTT * float64(time.Second))
-
-	log.Debug(rtt, "new RTT", rtt.estimatedRTT.Seconds(), "new deviation", rtt.deviationRTT.Seconds())
 }