IPv6 increases latency under load. Bufferbloat goes from A+ to D
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I wondered if anyone can help. I've recently added IPv6 connectivity to my Netgate 2100 (pfSense+ 23.05.1). I receive a PD length of 48 and the ND prefix is 64. On the face of it, the IPv6 set up works fine. However, I've just run a bufferbloat test; with IPv4 only the grade is A+, but with IPv4 + IPv6 it is D. I'm using the Netgate recipe for bufferbloat found here. I've added a separate WAN floating rule for IPv6 traffic via the limiters.
My internet service is 65 Mbps down and ~9 Mbps up (UK based fibre-to-the-cabinet). I've set the bandwidth of the limiters at 80% of these values. When using the IPv4 only set up, latency under load increases between 0 ms and 3 ms (~50 Mbps down; 6.5 Mbps up). However, when using the IPv4 + IPv6 set up latency increases to ~350 ms (62 Mbps down; 8.5 Mbps up). It seems as though the limiters have no effect on IPv6 traffic. I've tried increasing the limiter queues without success, but I presume I've missed something more fundamental. Does anyone have any ideas on what I might be doing wrong?
Best wishes,