And then one day, suddenly, the long-standing upstream inefficiency disappears; it has been the cause of so much whinging and moaning on my part. After a sizeable improvement to a sustained 1.44 Mbps upstream rate reported by speedtester2.aa.net.uk, the measured upstream rate figure is back to an all-time record high of 1.58 Mbps. The downstream is 10.66 Mbps.
Firebrick current upstream rate limiters' IP PDU tx rates (egress speeds), per-line ::
#1: 479310 bps
#2: 435106 bps
#3: 328496 bps
#4: 435106 bps
Total combined rate: 1.678018 Mbps
Fractional upstream IP PDU rate speed contributions:
#1: 28.564% [█████████████ ‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒]
#2: 25.930% [████████████ ‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒]
#3: 19.576% [█████████ ‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒]
#4: 25.930% [████████████ ‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒‒]
Current sync rates down and upstream:
#1: down 3023 kbps, up 553 kbps
#2: down 2990 kbps, up 502 kbps
#3: down 3107 kbps, up 379 kbps
#4: down 3085 kbps, up 502 kbps
and 98% modem loading factor in use on each line. So total sync rate = 1936 kbps sync
[Recap: last week: For the earlier 1.44 Mbps upstream result a day or so earlier, these were the sync rates at the time:
#1 560 kbps sync rate and 98% modem loading factor
#2 532 kbps
#3 452 kbps
#4 502 kbps
Total : 2046 kbps sync]
So amazingly, the sum of the sync rates goes down and the true measured speed goes up ! Also the slowest rate is worse and the rates are not more closely spaced. So not one single thing makes sense.
Efficiency compared to the ideal; converting IP PDU rates to TCP payload rates (TCP SDU rates):
The current sum-of-IP-PDUs-rate of 1.678018 Mbps corresponds to an IPv6 TCP with timestamps payload rate of
( 1 - ( 60 + 12 ) / 1408 ) * 1.678018 = 1.5922 Mbps TCP payload rate;
with an IP packet length assumed to be 1408 bytes, our current MTU.
Alternatively, assuming no TCP timestamps, a similar calculation
( 1 - ( 60 + 0 ) / 1408 ) * 1.678018 = 1.6065 Mbps.
So the measured result of 1.58 Mbps TCP payload rate reported by the speed tester is superb when compared with these ideal calculated figures, very efficient at 99.2% of the 1.5922 Mbps with-timestamps ideal maximum, or 98.35% of the without-timestamps case.