VSAT latency emulation



  • I'm trying to use pfSense to emulate one of our satellite connections so we can test out equipment without needing an entire installation. I've followed a lot of guides and forum posts, from here among other places, and I can achieve two things separately but not at the same time.

    Using the limiters I can limit the connection to a certain bandwidth (1534 kbps down/ kbps 1024 up in our case) and this works. In the same limiter I can also increase the latency (due to speed of light about 250 ms per leg) which also works, resulting in a ping of 500. However as long as I have the increased latency set, the bandwidth no longer reaches what I set and in fact maxes out at around 800 kbps. Reducing the latency increases the throughput and setting it to 0 gets us to the full bandwidth set. I also tried just increasing the bandwidth limits, but the throughput remains at about 800.

    From practical experience I know we can reach the full 1500 kbps throughput on the real VSAT link, so I'm assuming the satellite modem does something clever in the background, but I can't figure it out. Anyone able to help me how to decouple the latency from the bandwidth in the limiter?



  • @pieterdevries I am seeing the same thing with scheduler set to FIFO and increasing queue length to 200000 doesn't make a difference. Testing WFQ, QFQ, Round Robin and PRIO as scheduler does work with default queue length of 1000. I am not sure if something is wrong in Pfsense but you could go with PRIO as scheduler for now.


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