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Evaluation of Queue Management Algorithms. Ningning Hu, Liu Ren, Jichuan Chang 30 April 2001. Motivation. Typical queuing discipline: DropTail Active queue management: RED (93’), BLUE (99’), … FRED (97’), SFB (99’), CHOKe (2000’) Problem: How to compare them? - PowerPoint PPT Presentation
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15744 Course Project 1
Evaluation of Queue Evaluation of Queue Management AlgorithmsManagement Algorithms
Ningning Hu, Liu Ren, Jichuan Chang
30 April 2001
15744 Course Project 2
Motivation
• Typical queuing discipline: DropTail• Active queue management:
– RED (93’), BLUE (99’), …– FRED (97’), SFB (99’), CHOKe (2000’)
• Problem: How to compare them?– Metrics: Utilization, Fairness and Complexity– Method: simulation under common settings
15744 Course Project 3
Algorithms Drop Tail: drop when the queue is full RED: queue length, minth, maxth, avg
FRED: per-active-flow accounting BLUE: loss rate, link utilization, freeze_time SFB: identify flows using N * L bins CHOKe: compare incoming packet with
random selected packet in queue
15744 Course Project 4
Simulation Scenario
2Mbps
1Mbps, 40ms
2Mbps
UDP
TCP
UDP
TCP
• Topology: Dumb-bell• Metrics: throughput and queue size
source destination
router router
15744 Course Project 5
Drop Tail RED BLUE
FRED SFB CHOKe
TCP
TCP
1. # TCP Flow : # UDP Flow = 10 : 12. UDP sending rate = 2Mbps3. Buffer size = 150 packets
15744 Course Project 6
Performance Comparison
0
0.2
0.4
0.6
0.8
1
0.1 0.2 0.4 0.8 1 2 4 8 UDP Rate (Mbps)
DropTail
RED
FRED
BLUE
SFB
CHOKe
0
50
100
150
0.1 0.2 0.4 0.8 1 2 4 8 UDP Rate (Mbps)
DropTailREDFREDBLUESFBCHOKe
Figure 1. UDP Thpt (Mbps)
Figure 2. UDP Queue Size (packet)
15744 Course Project 7
ConclusionAlgorithm Link
Utilization Fairness Ease of Configuration
RED Good Unfair Hard
BLUE Good Unfair Hard
FRED Good Fair Easy (adaptive)
SFB Good Fair Easy (non-adaptive)
CHOKe Good Fair Easy (adaptive)
AlgorithmBuffer size
requirementPer-flow State Information
ComputationalOverhead
RED Large No Arrival
BLUE Small No Freeze-time
FRED Small Yes Arrival-departure
SFB Large No Freeze-time
CHOKe Small No Arrival
15744 Course Project 8
FRED• RED + Per-active-flow accounting
– protection of fragile flow– penalizing non-responsive flow– Flow type differentiation
• Key parameter: minq
– 2 or 4• Weak point:
– Compute avgq per packet
New flow?
Calculate avg & maxq
Non-adaptive?
N
Y
minth<avg<maxth
Drop
N
Y
RobustRED
avg<minth Accept
N
Drop Tail
New state
Fragile
N
15744 Course Project 9
FRED performance
00.10.20.30.40.50.60.70.80.9
1
0.1 0.2 0.4 0.8 1 2 4 8UDP rate (Mbps)
UD
P Th
pt (M
bps)
1 TCP,1 UDP10 TCP, 1 UDP10 TCP, 5 UDP
0
10
20
30
40
50
60
70
0.1 0.2 0.4 0.8 1 2 4 8UDP rate (Mbps)
UD
P Q
ueue
Siz
e (p
acke
t) 1 TCP,1 UDP10 TCP, 1 UDP10 TCP, 5 UDP
15744 Course Project 10
FRED characteristics
• Easy to configure, adaptive• Buffer size requirement
– Will degrade as DropTail with too many flows– “Two-packet-buffer” to keep fairness
0
0.25
0.5
0.75
1
10 20 40 45 50 60 70Buffer size (#Packet)
Thro
ughp
ut (M
bps)
TCP_ThptUDP_thpt
15744 Course Project 11
CHOKe
Random
Same FlowID?
CHOose and Keep for responsive flows CHOose and Kill for unresponsive flows
>maxth?minth
maxth
15744 Course Project 12
CHOKe
0
0.2
0.4
0.6
0.8
1
0.1 0.2 0.4 0.8 1 2 4 8
UDP rate (Mbps)
UD
P Th
roug
hput
(Mbp
s)
1 TCP, 1 UDP 10 TCP, 1 UDP 10 TCP, 5 UDP
15744 Course Project 13
Parameters in CHOKe
0
0.05
0.1
0.15
0.2
0.25
1 2 5 10 15Candidate Number
UD
P Fl
ow T
hrou
ghpu
t (M
bps)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
2 1.6 1 0.8UDP rate (Mbps)
UD
PFlo
wTh
roug
hput
(M
bps)
num = 1 num = 5num = 10 num = 15
15744 Course Project 14
BLUE •Main Point: Uses packet loss and link idle events instead of average queue length :
•Based on observation that RED is often forced into drop-tail mode
•Adapt to how bursty and persistent congestion is by looking at loss/idle events
15744 Course Project 15
BLUE AlgorithmPm is Blue’s packet dropping probability:
•Upon packet loss, if no update of pm in freeze_time then increase by d1
•Upon link idle, if no update of pm in freeze_time then decrease pm by d2
•d1 >> d2 •More critical to react quickly to increase in load
15744 Course Project 16
BLUE Characteristics
•More stable queue size and much better behavior with small buffers
•Good property damaged by non-responsive flows.
15744 Course Project 17
Stochastic Fair Blue(SFB)•Objective:
•Identify and penalize misbehaving flows
•Main Algorithm:
Create L hashes with N bins each
•Each bin keeps track of separate marking rate (pm)
•Rate is updated using standard technique(as BLUE)
•Flow uses minimum pm of all L bins it belongs to
•Non-misbehaving flows hopefully belong to at least one bin without a bad flow
15744 Course Project 18
SFB Characteristics
•Could effectively detect non-responsive flows and rate-limit them
•But not adaptive, the bandwidth share of non-responsive flows is controlled by a parameter(Boxtime) offered by the user.
•Boxtime is the time interval no packets from non-responsive flows can be enqueued.
15744 Course Project 19
SFB: Unfairness of Non-responsive Flows
Our solution: Randomized Boxtime a little bit.
15744 Course Project 20
Rate-limit Non-responsive flows
Time
UDP packets
Queue
Boxtime