# Need some help understanding HFSC

• I've done a fair bit of googling, reading here and there, and well, call me stupid but I don't fully get it yet.

So we have the following fields:

Bandwidth ___
Upperlimit ___ [m1, d, m2]
Realtime ___ [m1, d, m2]

I hope someone could tell me if I got things right. Ok, I begin with the things I think I got right..

I'll keep things very minimal and simple for learning purposes..

Lets say qwanRoot = 1000KB and qlanRoot = 10000KB (usually its in bits, i wanna make calculation easier)
I have qwandef, qlandef at prio 4, bandwidth=50% and q5wan, q5lan at prio 5, bandwidth=40%
i have 2 just two simple rules set for only q5wan and q5lan, and lets say for games, meaning everything else falls under def queue.

so lets say im gonna download a 20MB movie, which falls under def queue.

if realtime.[m1=1000KB d=10 m2=500KB]

Assuming there's no other traffic, for the first 10 seconds, my rate should be 1000KB/sec. So in 10 seconds, it's 1000x10=10MB
For the rest of the time until the movie is done, itll go at 500KB/sec, which should last for another 20 seconds.

Total time = 30 seconds. Correct so far?

Or… not.......
I have set bandwidth at 50%, does this actually mean, rather than 30 seconds, it was downloading at half the speed I calculated, and hence twice the time?

Now, there's linkshare, and upperlimit. OK, even more confusion.. So I've read realtime speed is off qwanroot, so does this mean, it ignores bandwidth field? if not, what's bandwidth field for? OK, no one's playing games right now, there's a 40% there, and a 10% undefined.. How do I actually borrow bandwidth? Is it off linkshare? Now, what exactly do I do with upperlimit, can anybody give any example on how to use it?

How would one setup their shaping such that, assuming scenario is like above... a couple of people are playing games (queue priority 5), while two are watching movies, or using bulk traffic (default queue).... Games should have low latency while the two downloading movies should be allowed the maximum possible download speed without affecting the games.. (borrow if they must).. while having equal/shared/fair download speeds.

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