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A great resource for learning quality of service is the enterprise quality of service solution Reference

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Network Design Guide or a sovereign D guide.

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At the time of this recording the guide was lost updated in April 2014.

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I've added the guide below the video that you can find it by doing a search in Google for example for

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quality of service s or indeed guide.

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We are told that there is an updated version if you want to buy the latest version you'd need to purchase

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this book end to end quality of service network design that's not required for CCMA.

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So for the CCMA course I would simply use this document and the videos that I'm recording.

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This guide has been around for a long time so it was originally drafted in April 2005.

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A lot of the quality of service mechanisms that we are discussing haven't changed over the years.

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The reliance on some such as link fragmentation into leaving has been reduced as wind speeds have increased

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but a lot of the concepts remain the same.

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So if you want to study this in more detail have a look at this guide.

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But I'm going to summarize the details for you.

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And I'll do a demonstration to try and explain some of the options as required for the CCMA exam and

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I see indeed to exam in the CCMA exam if I do a search for quality of service you are expected to know

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basic quality of service concepts including marking device trust pro translation of voice video and

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data shaping policing and congestion management.

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These are quality of service mechanisms.

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The same topics are listed in the ICD two exam so the SRO and d guide starts out by looking at why is

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quality of service important.

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What are the tool sets or mechanisms available to you.

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And there's some additional information about quality of services essentially important because we need

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to prioritize some traffic at the detriment of other traffic.

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As an example if there's an emergency and an ambulance needs to take someone to hospital or reach someone

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that's injured on motorways or highways we have dedicated lanes so that an ambulance can get you to

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hospital quicker.

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We are providing a better quality of service to an ambulance than to other vehicles on the road and

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the same is true with quality of service.

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We want to provide a higher priority or better quality of service to traffic types such as voice and

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video because of the delay requirements and other requirements that those traffic types have when compared

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to other traffic tops such as FCP or HDP.

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Now the transmission quality of a network is determined by the following factors.

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Firstly loss how many packets will be lost.

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Now this is important for voice conversations voice will degrade as an example when packets are lost.

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We want to have a low loss of packets in a voice conversation for FCP loss of packets isn't as important

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because ATP uses TTP and will simply read transmit to the packets but you can't read transmit voice

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packets if voice packets are lost they are lost and it will affect the voice quality.

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Delay is the finite amount of time that it takes a packet to reach the receiving end point after being

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transmitted from the sending endpoint as an example if you're using a phone.

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It's the amount of time that it takes for me to speak till it reaches your ear.

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In other words how long does it take for the voice to travel from me to you.

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Now the round trip delay of a voice conversation needs to be less than 300 milliseconds.

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Anything greater than that is going to affect the voice quality FCP once again can tolerate much higher

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delays variable delay or so-called jitter is the difference in end to end delay between packets.

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So if the delay varies between packet arrival that is known as Jetta Jetta can once again cause problems

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in a voice conversation.