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Stochastic Fair Traffic Stochastic Fair Traffic Management for Efficient and Management for Efficient and
Robust IP NetworkingRobust IP Networking
Jae ChungAirvana Inc.
Chelmsford, MA 01824
Mark Claypool, Robert KinickiWPI Computer Science Department
Worcester, MA 01609
26th IEEE International Performance Computing and Communications Conference (IPCCC)New Orleans, Louisiana, April 11, 2007
IPCCC April 11, 20072
OutlineOutline• Introduction
• SFG Design
• Configuration
• Evaluation
• Summary
IPCCC April 11, 20073
Internet Congestion ControlInternet Congestion Control• Current Architecture
– TCP : Congestion responsive traffic sources using Additive Increase Multiplicative Decrease (AIMD)
– Drop-Tail IP Router : Implicit congestion feedback controller (packet drop congestion signal)
• Improve Congestion Feedback Control for TCP– Active Queue Management (AQM) at IP Router
• Low queuing delay• Explicit congestion notification (ECN)
• Fairness and Network Protection from non-TCP– Class-based Bandwidth Usage Control– Per-flow Bandwidth Usage Control
IPCCC April 11, 20074
Complex Light-weightScalable
Preferential-basedPacket Dropping
FQ, SFQ
Pseudo Per-flowManagement
Per-flowManagement
FRED CSFQ, RFQ RED-PD, SFB
StatisticalFlow Monitor
StatisticalPacket Filter
CHOKe
Edge-CoreArchitecture
Scheduling-basedApproaches
Per-Flow Bandwidth ControlPer-Flow Bandwidth Control
SFG
IPCCC April 11, 20075
Stochastic Fairness GuardianStochastic Fairness Guardian
SFGSFGInIn FilteredFiltered
Congestion Control
Network Protection
IP Router Queue
Drop-Tail/ AQM
Drop-Tail/ AQM
OutOut
dropdrop
TCPTCP
UDPUDP
TCPTCP
UDPUDP
UDPUDP
TCPTCP
dropdrop
TCPTCP
UDPUDP
IPCCC April 11, 20076
OutlineOutline• Introduction
• SFG Design
• Configuration
• Evaluation
• Summary
IPCCC April 11, 20077
SFG Design OverviewSFG Design Overview
………
…
p = 0.05
p (flow3) = 0.00
Level1 Level2 LevelL
Bin1
Bin2
BinN-1
BinN
p (flow2) = 0.02
p (flow1) = 0.03
…
…
…p = 0.04
p = 0.02 p = 0.00
p = 0.02
p = 0.03
p = 0.00…
LevelL-1
p = 0.06
IPCCC April 11, 20078
Multi-Level Hash Bins (1/2)Multi-Level Hash Bins (1/2)• Use multiple hash functions (L)• Each function hashes flows into N bins• Each bin is assigned an equal share (1/N) of the
outbound link capacity (C).• Every epoch (ds), update the forced packet drop
probability for each bin (prob[i][j]):
for i = 0 to L − 1 do for j = 0 to N − 1 do
prob[i][j] = (bytes[i][j] − dsC/N) / bytes[i][j];bytes[i][j] = 0; /* update drop p for all bins */
end for end for
IPCCC April 11, 20079
Multi-Level Hash Bins (2/2)Multi-Level Hash Bins (2/2)• Each packet arrival, compute the per-flow forced
drop probability (p) for the packet, and update bytes received for each hashed bins:
p = 1;for i = 0 to L − 1 do j = hash(i, packet); p = min(p, prob[i][j]); /* min drop p seen so far
*/ bytes[i][j] = bytes[i][j] + sizeof(packet);end for
• Drop the packet with the computed per-flow drop probability (p)
IPCCC April 11, 200710
OutlineOutline• Introduction
• SFG Design
• Configuration
• Evaluation
• Summary
IPCCC April 11, 200711
The Number of Hash BinsThe Number of Hash Bins• Configure maximum and minimum Congestion
Notification Probability (CNP) thresholds (mh, ml) to turn On/Off SFG
if CNP mh then Turn On SFG
if CNP ml then Turn Off SFG
• Find the number of bins (N) such that the capacity of each hash bin is equal to TCP-Friendly Rate (TTCP) at CNP = ml
N = C / TTCP (ml, RTTsys) where,
RTTsys : Estimated average system Round Trip Time
IPCCC April 11, 200712
The Number of Hash LevelsThe Number of Hash Levels
• False Positive Probability (FPP) Analysis– Given the number of hash bins (N), the number
of hash levels (L) and the estimated number of TCP-Unfriendly flows (B)
– The false positive probability (Pfp) that a TCP-Friendly flow shares all the bins with TCP-Unfriendly flows:
• Use FPP to determine the number of levels.
L
i
k
BkB
iB
ft kik
i
i
Ni
NBNLP
001
11
,,
IPCCC April 11, 200713
SFG Configuration ExampleSFG Configuration Example• Link Bandwidth = 10 Mbps, RTTsys = 300 ms• CNP Thresholds: mh = 0.02, ml = 0.01• N = 20, B = 1~10, L = ?
IPCCC April 11, 200714
Unlucky TCP-Friendly Flows?Unlucky TCP-Friendly Flows?• Problem : When hashed, an unlucky TCP-
Friendly flow can always share all the bins with TCP-Unfriendly flows.
• Solution : Use different hashing seed (increment by one) in the next measurement epoch.
• Note : This solution also relaxes the low False Positive Probability (FPP) requirement for long-lived flows (i.e. large file transfer).
IPCCC April 11, 200715
Measurement Epoch LengthMeasurement Epoch Length• The epoch length should be
– Large enough to avoid control error due to insufficient control data acquisition
– Larger than the effective congestion feedback control system response time to minimize congestion control interference.
• We recommend two seconds for SFG epoch– Approximately twice the upper-bound average
RTT seen on the Internet (1 second) [Choi, INFOCOM 2004]
– The large epoch length, hence slow response time, is acceptable considering the long flow lifetimes of potentially misbehaving flows.
IPCCC April 11, 200716
OutlineOutline• Introduction
• SFG Design
• Configuration
• Evaluation
• Summary
IPCCC April 11, 200717
Evaluation OverviewEvaluation Overview• Evaluation Subjects
– Drop-Tail Queue (Baseline)– PI Controller (Hollot+, INFOCOM 2001)– RED-PD (Mahajan+, ICNP 2001),– SFB (Feng+, INFOCOM 2001)– CHOKe (Mitra+, INFOCOM 2000)– SFG, SFG-PI
• Evaluation Objectives– TCP performance– Protection performance– Queuing delay and jitter– Web performance
IPCCC April 11, 200718
Network Topology and ScenarioNetwork Topology and Scenario
• C = 10 Mbps• Q = 500 Kbytes• RTLD = [60, 1000] ms• Nweb = 300 (Loadoffered = 0.25)
– Web session setting (H-Campos+, MASCOTS 2003)
Sizeavg= 5KB, Shape = 1.2, Tavg_think = 7sec (expo distribution)
• Nftp_bw = 50• Nftp_fw = 10 50 100 200 400 (every 200 sec)
400 200 100 50 10 (every 200 sec)• Ncbr = 5
– 2 Mbps CBR (1.2 Mbps VBR) from 100 to 1700 sec
• Simulation time = 2000 sec
r1 r2
s
s
s
s
d
d
d
d
Q = 500 pkts
C = 10 Mbps
IPCCC April 11, 200719
Queue Configurations (1/2)Queue Configurations (1/2)
• RED-PD– RED : qmin = 50, qmax = 300, pmax = 0.15, wq =
0.002
– PD : RTTtarget = 100 ms, Windowflow_monitor_history = 5,
Tflow_unmonitor = 15 sec, Ratedrop_threshold = 0.005,
pmax_inc_step = 0.05
• CHOKe– RED : Same as above – Packet Filter : Divide RED’s queue threshold range
(qmax - qmin) into 5 even sub-regions and apply 2i+1 drop comparisons for an incoming packet, where i = {0, 1, 2 ,3, 4} is the sub-region ID.
IPCCC April 11, 200720
Queue Configurations (2/2)Queue Configurations (2/2)
• SFB– BLUE (inside each SFB bin) :
pinc_step = 0.005, pdec_step = 0.001, Tfreeze = 100 ms
– Flow Monitor :
L = 3, N = 20, punresp_detect = 0.98,
Tpenalty_box = 15 ms, Thash_switch = 20 sec
• SFG-PI– PI : KP = 0.71× 10−5, KI = 2.8116 × 10−5
– SFG : L = 3, N = 20, mh = 0.02, ml = 0.01, ds = 2 sec
IPCCC April 11, 200721
System ThroughputSystem Throughput
Offered Load1.2 1.4 1.7 1.4 1.21.11.0 1.01.1
# of FTP 100 200 400 200 100 50 1010 50 400
1.7
IPCCC April 11, 200722
Unresponsive CBR ThroughputUnresponsive CBR Throughput
Offered Load1.2 1.4 1.7 1.4 1.21.11.0 1.01.1
# of FTP 100 200 400 200 100 50 1010 50 400
1.7
IPCCC April 11, 200723
Queuing Delay and JitterQueuing Delay and JitterOffered Load 1.2 1.4 1.7 1.4 1.21.11.0 1.01.1
# of FTP 100 200 400 200 100 50 1010 50 400
1.7
IPCCC April 11, 200724
Web Object Service TimeWeb Object Service Time
Offered Load1.2 1.4 1.7 1.4 1.21.11.0 1.01.1
# of FTP 100 200 400 200 100 50 1010 50 400
1.7
IPCCC April 11, 200725
OutlineOutline• Introduction
• SFG Design
• Configuration
• Evaluation
• Summary
IPCCC April 11, 200726
SummarySummary• IP Router Queue Management Taxonomy
• Stochastic Fairness Guardian (SFG)– A lightweight Statistical Packet Filter– Flexible deployment with Drop-Tail or AQM– Practical configuration guidelines– Performs comparable to or better than complex
flow monitoring mechanisms (RED-PD, SFB).
IPCCC April 11, 200727
Additional ContributionAdditional Contribution
• Confirms [Le+, SIGCOMM 2003] result that ECN degrades Web service time at a high offered load (1.2). This is because the congestion notification probability (CNP) is significantly higher than that of packet drop congestion notification system, causing more TCP SYN packet drops.
Stochastic Fair Traffic Stochastic Fair Traffic Management for Efficient and Management for Efficient and
Robust IP NetworkingRobust IP Networking
Jae ChungAirvana Inc.
Chelmsford, MA 01824
Mark Claypool, Robert KinickiWPI Computer Science Department
Worcester, MA 01609
26th IEEE International Performance Computing and Communications Conference (IPCCC)New Orleans, Louisiana, April 11, 2007