A great resource for learning quality of service is the enterprise quality of service solution Reference
Network Design Guide or a sovereign D guide.
At the time of this recording the guide was lost updated in April 2014.
I've added the guide below the video that you can find it by doing a search in Google for example for
quality of service s or indeed guide.
We are told that there is an updated version if you want to buy the latest version you'd need to purchase
this book end to end quality of service network design that's not required for CCMA.
So for the CCMA course I would simply use this document and the videos that I'm recording.
This guide has been around for a long time so it was originally drafted in April 2005.
A lot of the quality of service mechanisms that we are discussing haven't changed over the years.
The reliance on some such as link fragmentation into leaving has been reduced as wind speeds have increased
but a lot of the concepts remain the same.
So if you want to study this in more detail have a look at this guide.
But I'm going to summarize the details for you.
And I'll do a demonstration to try and explain some of the options as required for the CCMA exam and
I see indeed to exam in the CCMA exam if I do a search for quality of service you are expected to know
basic quality of service concepts including marking device trust pro translation of voice video and
data shaping policing and congestion management.
These are quality of service mechanisms.
The same topics are listed in the ICD two exam so the SRO and d guide starts out by looking at why is
quality of service important.
What are the tool sets or mechanisms available to you.
And there's some additional information about quality of services essentially important because we need
to prioritize some traffic at the detriment of other traffic.
As an example if there's an emergency and an ambulance needs to take someone to hospital or reach someone
that's injured on motorways or highways we have dedicated lanes so that an ambulance can get you to
hospital quicker.
We are providing a better quality of service to an ambulance than to other vehicles on the road and
the same is true with quality of service.
We want to provide a higher priority or better quality of service to traffic types such as voice and
video because of the delay requirements and other requirements that those traffic types have when compared
to other traffic tops such as FCP or HDP.
Now the transmission quality of a network is determined by the following factors.
Firstly loss how many packets will be lost.
Now this is important for voice conversations voice will degrade as an example when packets are lost.
We want to have a low loss of packets in a voice conversation for FCP loss of packets isn't as important
because ATP uses TTP and will simply read transmit to the packets but you can't read transmit voice
packets if voice packets are lost they are lost and it will affect the voice quality.
Delay is the finite amount of time that it takes a packet to reach the receiving end point after being
transmitted from the sending endpoint as an example if you're using a phone.
It's the amount of time that it takes for me to speak till it reaches your ear.
In other words how long does it take for the voice to travel from me to you.
Now the round trip delay of a voice conversation needs to be less than 300 milliseconds.
Anything greater than that is going to affect the voice quality FCP once again can tolerate much higher
delays variable delay or so-called jitter is the difference in end to end delay between packets.
So if the delay varies between packet arrival that is known as Jetta Jetta can once again cause problems
in a voice conversation.