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Hi Andrei POPOV,I answer on the OpenSAND mailing list as it can be useful for other users, if you need more details, please continue writing on it. If you are not registered, you can join us following this link : https://launchpad.net/~opensand/+join
The OpenSAND bottleneck and queuing are not handled in the input virtual interface but in the OpenSAND software. In the OpenSAND terminals, we implement MAC queues that receive all the incoming traffic but they only output the authorized amount of traffic, which creates the bottleneck. The queue size can be modified in the advanced configuration. In the configuration tab on manager, click advanced, then under stX you can access the queue in the dvb_rcs_tal tab and modify size_max parameters. While running OpenSAND, you can also display the queue sizes under the probes' tab; select program stX and the queue you want to display (BE if IP packets are not tagged) under Terminal_queue_size. Be sure you are running opensand-collector on the platform to receive the statistics.
In the OpenSAND source code, you can look for macSchedule functions in OpenSAND DAMA agent.
If required, you can also perform layer 3 bandwidth limitation outside OpenSAND with traffic shaping software as tc (Traffic Control).
best regards, -- Julien BERNARD Viveris Technologies 05 61 00 31 84
Dear Julien BERNARD, I have a question related to bottleneck in OpenSand. As we now, emulated satellite network creates a bottleneck of RTT=600 ms and Throughput= 1 Mbps. It means that when the traffic coming from workstation connected to ST with the speed rate of 1 Gbps or 100 Mbps it faces the bottleneck of 1 Mbps on outgoing "opensand" virtual interface. So besides that the emulated network is limited to 1 Mbps, the incoming traffic has to be somehow queued in the buffer of this virtual opensand interface. My first question is I don't really understand how the bottleneck of 1 Mbps is created. When I display, for example, the link speed of the virtual opensand interface using ethtool - I see the speed link equal to 10Mbps. And the second question is about queuing. Is there a queue on the outgoing opensand virtual interface? What is its maximum size before the packets get dropped and whether it's possible somehow to display the current queue size when traffic passes through the interface? Which source files of the OpenSand components would you recommend me to look at in order to understand these mechanisms? Best regards, Andrei POPOV
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