I prefer the truth.
I'm not quite sure if that means you don't fully understand Plusnet's traffic management strategy and you're still trying to get to grips with it, you're pretty sure you do understand it and your understanding is different from what has been said here by others, or you believe the explanation of it given by Plusnet is different from what it really does. Have I missed any possibilities?
Here's my version of the truth (bearing in mind the PN prioritisation scheme has no impact on upstream traffic apart from downstream ACKs affecting upstream flow control):
1. Traffic to the line is well below its capacity (IP profile):
There's virtually no difference at all between "standard" Plusnet traffic prioritisation, Pro prioritisation and no prioritisation. There might be some
very slight instantaneous differences in latency between different traffic types, since traffic flows are statistical and there will be very short, instantaneous peaks in utilisation that require data buffering in PN's gateway router before the traffic can be shipped off down the line. But in practice, this effect will be imperceptible.
2. Traffic to the line is near (or at) its capacity:
With "standard" prioritisation, lower priority traffic types will see increased latency and high priority types will experience very little increase in latency. The change in latency increases with decreasing priority. With the Pro add on there are only 2 priority classes. Traffic in the lower class will experience increased latency, traffic in the higher class will be little affected. With no prioritisation, all traffic will see an increase in latency.
3. Traffic to the line exceeds its capacity:
As for case 2, but in addition some packets need to be dropped to match the throughput of the IP profile and to flow control the traffic sources. I guess this is what would be called "throttling". With "standard" prioritisation, some traffic in the lower priority classes will be dropped, that in the higher priority classes will not (unless the line is severely congested). The lower the priority, the more likely the traffic will be dropped. With the Pro add on, again there are only 2 classes, so the lower priority class traffic gets dropped first. With no prioritisation, traffic is dropped randomly, affecting all types of traffic fairly equally (or at least, in proportion to the volume of traffic of each type).
But... In practice the connection is rarely in one of these 3 "states" for long, but is switching between them continuously.
All networks experience "throttling" when demand exceeds capacity for long enough. Assuming the same sized buffers, all networks will drop pretty much the same amount of traffic. Plusnet just tries to manage this in a way which probably helps the majority of its customers, by managing latency and "throttling" lower priority traffic in preference to higher priority traffic. And you get a choice of 2 priority schemes: standard and Pro. Standard offers finer grained control based on use of more priority levels (so is really more sophisticated than Pro!). If your traffic levels rarely exceed your line capacity, you're unlikely to see any difference between the 2 Plusnet schemes and "no prioritisation".
Anyway, I think you know all this already
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