[QoS] - Quality of Service in a nutshell

[sfx2000]

(I'm posting this as it seems to be a big forum issue at the moment, many seem to get confused about this)

QOS classifying and scheduling at a high level really comes down to this...

Queue - 3 parameters. N1, D, and N2. Where:

N1 = bandwidth needed in d time
N2 = max bandwidth for the queue
D = delay(in milliseconds)​

So we build a queue.... let's say VOIP # this is just an example, and I'm trying to make this really simple

N1 = 96oo bps (let's say EVRC voice codec)
N2 = 64,000 bps (PCM audio)
D = 80 mSec (cdma framing time)
​

This means that we want in D time, N1 traffic gets served without checking N2, and then we check N2 to see if the limit has been reached and /or continue, else, we check to see if there is more bandwidth. If there is no more bandwidth, then the Queue priority seizes the required bandwidth and moves on...

(Note - N1 can never exceed N2, FWIW, if that's not obvious)

Repeat this as needed for different traffic types...

We build many queues - based on 4 basic classifiers - VOIP, Video, Best Effort, Background - now we can tag queues based on ports (ethernet), ports (applications), even MAC/IP addresses. Queues define the priority, on a single LAN, or even across multiple LAN's, as they can be hierarchal, and we can score them accordingly...

Most QoS classifiers - even DPI and SPI, do similar things - but it's the scheduling of the Queues that is special, whether it is fq_codel, codel, hfsc, pirq, cbs, etc...

It really comes down to requested bandwidth, delay, and available bandwidth - that's why in many consumer grade routers, it's really import to set the limits on the WAN side - as the classifiers on the LAN side are pretty much asymmetric in many cases...

Notice, this is all a whitelist approach, but generally QoS is just that - reserve, not limit...

I use these four app flows for WiFi, but there are additional application flows spec'ed out across IEEE/IETF/3GPP/3GPP2...

 

[sfx2000]

Anyways - it's late, and this was a quick post - most CS majors get this, same with Communications Systems Engineers... It's not hard, just counter-intuitive..

The Quantum of Solace so to speak...

Time to get some sleep... g'nite all...

 

[cobra_shipwreck]

QOS is typically used when one has Video or Internet Telephony and one needs to guarantee the availability of the internet connection. Those are the two typical protocols that are used or referred to when one talks about QOS. QOS can also be used to limit your bandwidth hogging network users. Such as your teenage kid that keeps doing torrents of pirated materials for example. You can also use QOS to effectively block certain traffic types by making it so slow it is not usable. Windows 7 and XP have QOS support turned on by default.

 

[sfx2000]

Such as your teenage kid that keeps doing torrents of pirated materials for example. You can also use QOS to effectively block certain traffic types by making it so slow it is not usable

In QoS - we never limit - however<comma>pause... we give them guarantees that are of a specific bandwidth, and a priority queue level...

If that Queue happens to be at a low data rate and the lowest possible queue level, so be it

 

[System Error Message]

QOS is typically used when one has Video or Internet Telephony and one needs to guarantee the availability of the internet connection. Those are the two typical protocols that are used or referred to when one talks about QOS. QOS can also be used to limit your bandwidth hogging network users. Such as your teenage kid that keeps doing torrents of pirated materials for example. You can also use QOS to effectively block certain traffic types by making it so slow it is not usable. Windows 7 and XP have QOS support turned on by default.

QoS is typically used for many things and no QoS is not used to block certain traffic types, there are certain things in UDP and TCP that you can use to control the speed. How do you think your ISP controls your speed based on subscription and their F2P?

@sfx2000 if you are planning to make another tutorial/article i suggest using a router that lets you adjust the QoS algorithm and buffers, that lets you set up your own QoS in a complicated way. I know mikrotik does this but i was going to say use a linux OS so you can add various algorithms (even your own ones), do your own testing and also use graphing software and show what is really going on with the QoS process.

You dont need a physical network, just build one virtually. Heres what i mean
https://xkcd.com/350/
http://hackaday.com/2014/06/28/xkcds-virus-aquarium-made-real/
Dont forget some diagrams to help explain things and more cat pictures.