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In this test, we set up a linear topology, and create two hosts in the first and the last two switches, and then analyze the datapath build time between this two hosts.If the time is more than 5 minutes, then it was deemed to can't support so many switches.
This test will create multiple switches connected to one controller. Datapath depends on the flow tables needed, through some triggering means (such as ping) will trigger the flows download, when all the switches have these flow table entries, datapath can be setup successfully.
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Suggestions
- The topo of the switches
Linear topology can show the datapath performance best. Mabe there's no linear topology in your IXIA tester version, create a ring topology first and then transformed into a linear topology. - The trigger mode
Through the topology in the first and last two hosts to do the operation of ping can trigger the flow download.
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Test steps
1. Config IxNetwork with one switch switches (first with 100) with linear topology and two hosts . Set the packet_ in messages of the switch, the interval is 50ms, total 1000000 packets, using ICMP or ARP packetsfirst and last switch.
2. Start the controller with the features install.
3. Start the OF protocol of the switch.
4. Wait until the channel is established and Echo message interaction started.
5. Start the capture of IxNetwork.
6. Enable packet_inthe traffic between this two hosts, wait until all of the packet_in messages are sent and no packet_out messages receivethe hosts can ping through each other.
7. Stop the capture, analyse the messages captured. First verify Write down the number of packet_out message N, N should be equal to 1 million, if N is less than 1 million, restart this test with smaller packet_in rate. Second, calculate the time difference between the time of the first packet_out in message T1 and the time of the last packet_out message T, the packet_out rate can be calculated by N/T. Third, calculate the time delay of each packet_in-packet_out pair as t1、t2、t3 ... ... , of course this can be caculate by decentralized way(select ten sets of pairs), at last calculate the latency by t1+t2+t3 ... ... /N.flow mod message T2. Caculate the time of Datapath seted up T=T2-T1
8. Clean the configuration of controllers and IxNetwork.
9. Repeat test step 1-9 8 for five three times.
10. Restart the test with another packet_in ratenumber of switches.
Test Results
Datapath Setup Time
switches First (ms) Second (ms) Third (ms) Avg (ms) 100 1200 1169 1164 1178 200 1809 1745 1659 1738 300 3100 3363 3357 3273 400 5478 7171 7177 6609 500 10983 12946 10624 11518 600 30633 32603 46932 36723 700 69950 68673 58760 65794 800 131691 122576 142910 132392
After 800 switches, datapath can't setup in 5 minutes so we conclude that the maximum number is 800 switches.
- Histogram of Datapath Setup Time
As the histogram shown, the time increases significantly with the number of switches.