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Theory and IEEE Standardization. Presented by: Denis Surkes ID 321416505 Ran Levy ID 36679215.

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Presentation on theme: "Theory and IEEE Standardization. Presented by: Denis Surkes ID 321416505 Ran Levy ID 36679215."— Presentation transcript:

1 Theory and IEEE Standardization

2 Presented by: Denis Surkes ID Ran Levy ID

3 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.

4 The QCN Algorithm QCN CP Algorithm RP Algorithm

5 The CP Algorithm (Brief review)

6 The CP Algorithm Calculate 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

7 The RP Algorithm Two counters: byte-counter and timer Both 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/2 msec/cycle) RL 3 states – Fast recovery Active increase hyperActive increase

8 Simulation Goal Analyze 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.

9 Implementation description Network Topology

10 Switch Message Controller CP In[0] Out[0] In[1] Out[1] In[2] Out[3] Out[2] In[3] In[4] Out[4] To Host To Switch

11 Switch Description Manage 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

12 Host Description RP algrotihm is implemented here Creating the packets according to current Rate by changing the datarate channel. Distributing the packets: Uniformly Always sends through bottle neck Calculates RTT

13 Assumptions Switch is ideal, i.e routing the packets dont take time and routing tables are already configured. No delay and errors on channels Host doesnt create packets faster than the current rate. Packets are normal distributed (1000,200) Feedback messages have priority over regular messages.

14 Preventing the switch from sending feedback messages

15 QCN off Queue lengthHost datarate Queue length: Mean: Stddev: Max: Packets loss:

16 Feedback messages generated to prevent queue overload and packets lost.

17 Queue length on switch Mean: Stddev:

18 dataRates hosts 0-3 Mean: *10^9 Stddev: *10^8 Mean: *10^9 Stddev: *10^8 Mean: *10^9 Stddev: *10^7 Mean: *10^9 Stddev: *10^7

19 Host datarate zoomed

20 Feedback count Mean: Stddev:

21 Hosts - sends packets uniformly

22 Queue Length, Histogram Mean Stddev

23 Feedback counter interval 1ms Mean Stddev

24 RTT Mean e-05 Stddev e-05 Max

25 DataRate hosts 0-3 Mean: *10^9Mean: *10^9 Stddev: *10^8Stddev: *10^8 Mean: *10^9Mean: *10^9 Stddev: *10^8Stddev: *10^8

26 Host datarate zoomed

27 Hosts- sends to bottlneck Timer- set to 1ms

28 Queue length Mean Stddev

29 Datarate host0-3 Mean: *10^9 Mean: *10^9 Stddev: *10^8Stddev: *10^8 Mean: *10^9Mean: *10^9 Stddev: *10^8 Stddev: *10^8

30 Host Datarate hyperactive increase

31 Feedback counter Mean Stddev

32 RTT Mean Stddev e-05

33 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.

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