theory and ieee standardization. presented by: denis surkes id 321416505 ran levy id 36679215
TRANSCRIPT
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Congestion Control Theory and IEEE Standardization
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Final Project Network Simulation ModelingPresented by:Denis Surkes ID 321416505Ran Levy ID 36679215
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QCN (Quantitazed Congestion Notification)The QCN Algorithm has been developed to
provide congestion control at the Ethernet layer, or at L2.
The algorithm issues a pause message to upstream buffers, when the buffer at a congested link fills up.
This action ensures packets do not get dropped due to congestion.
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The QCN Algorithm
QCN
CP Algorith
m
RP Algorith
m
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The CP Algorithm (Brief review)
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The CP AlgorithmCalculate Fb (feedback value that indicate
the level of congestion) for each income frame
Fb = (Qeq-Qlen) – w*(Qlen-Qlen_old)If Fb<0 send a congestion message back with
quantized Fb value
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The RP AlgorithmTwo counters: byte-counter and timerBoth reset by Fb < 0 signal
Byte-Counter• 5 cycles of FR (150KB/cycle)• AI cycles afterwards (75KB/cycle)
Timer• 5 cycles of FR (TIMER_PERIOD msec/cycle)• AI cycles afterwards (TIMER_PERIOD/2msec/cycle)
RL 3 states – Fast recoveryActive increasehyperActive increase
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Simulation GoalAnalyze a network with high dataRates, and a
congested links.Activate the QCN algoritm in such a network
and analayze the RTT times and stabilty of the network
Compare the behavior of congested link with and without the QCN algorithm.
Compare several parameters in the QCN algorithm itself.
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Implementation descriptionNetwork Topology
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Switch
Message Controlle
r
CP
CP
CP
CP
CP
In[0]
Out[0]
In[1]
Out[1]
In[2]
Out[3]
Out[2]
In[3]
In[4]
Out[4]
To Host
To Host
To Host
To Host
To Switch
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Switch DescriptionManage Controller – control flow of income
packets from input to CP and feedback Messages from CP to output
Manage switch routing table that configured through switch configuration file
CP (Congestion Point) - simulate output buffer and apply CP algorithm to all income packets
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Host DescriptionRP algrotihm is implemented hereCreating the packets according to current
Rate by changing the datarate channel.Distributing the packets:
UniformlyAlways sends through bottle neck
Calculates RTT
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AssumptionsSwitch is ideal, i.e routing the packets don’t
take time and routing tables are already configured.
No delay and errors on channelsHost doesn’t create packets faster than the
current rate.Packets are normal distributed (1000,200)Feedback messages have priority over
regular messages.
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QCN Off Preventing the switch from sending feedback
messages
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QCN offQueue length Host datarate
Queue length:Mean: 299.59290915772 Stddev: 3.0531562271108 Max: 300.0Packets loss: 3696354
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QCN On Feedback messages generated to prevent queue
overload and packets lost.
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Queue length on switch
Mean: 60.27619Stddev: 1.5215605
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dataRates hosts 0-3
Mean: 2.3249501*10^9Stddev: 1.1768111*10^8
Mean: 2.3903864*10^9Stddev: 1.5451428*10^8
Mean: 2.72004*10^9Stddev: 9.306672*10^7
Mean: 2.5859536*10^9
Stddev: 7.528326*10^7
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Host datarate zoomed
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Feedback count
Mean: 34.05208Stddev: 4.104861
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Uniform distribution Hosts - sends packets uniformly
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Queue Length, HistogramMean 33.4116
Stddev 24.4033
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Feedback counter interval 1ms
Mean 30.8372Stddev 11.8787
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RTT
Mean 3.92304e-05
Stddev 3.63771e-05
Max 0.000488596
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DataRate hosts 0-3
Mean:4.361909*10^9 Mean: 4.43117*10^9Stddev: 4.917516*10^8 Stddev: 4.841612*10^8
Mean: 4.6436*10^9 Mean: 4.14858*10^9Stddev: 3.271976*10^8 Stddev: 2.638262*10^8
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Host datarate zoomed
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Short timer Hosts- sends to bottlneck
Timer- set to 1ms
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Queue length
Mean 60.9034
Stddev 11.8053
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Datarate host0-3
Mean: 2.72934*10^9 Mean: 2.399835*10^9Stddev: 2.79716*10^8 Stddev: 2.22185*10^8
Mean: 2.541936*10^9 Mean: 2.392924*10^9Stddev: 1.45063*10^8 Stddev: 1.01734*10^8
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Host Datarate hyperactive increase
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Feedback counter
Mean 40.1959
Stddev 16.0076
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RTT
Mean 0.000108274
Stddev 1.45964e-05
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Conclutions The QCN algorithm is essential in data centers
because it allows the ability to transfer huge amounts of data without any loss of packets
When QCN is active there is almost no reduction In RTT.
Congested link is fully optimized while maintaining fairness to all hosts.