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Now, you're not expected to know this for the CCNA exam, but I'm going to demonstrate an example of

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quality of service on two Cisco routers.

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In this example, I've got two routers running in genius three show run interface, serial, 2/0.

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Shows us the configuration.

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These routers simply have IP addresses configured and I have no shut the interfaces.

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No other configuration has been done.

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Show Interface Serial 2/0 shows us the speed of the interface, which is using the default of 1.54 megabits

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per second.

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So on this interface of the router we can use the command auto quoz.

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Now notice we do have the discovery option where we can configure the rider to discover traffic that

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traverses that interface.

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But in this example, I'm simply going to enable the interface for VoIP, and I'm not going to specify

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the option trust, which means it's not going to trust the markings that it receives from rather to.

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Not typically in the real world you would do that.

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You would trust traffic from one router to another unless router one is a service provider and router

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two is a customer as an example.

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Now here I'm going to use order VoIP trust so that you can see the difference between trusting and not

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trusting a neighboring router.

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So rather one doesn't trust router two rather two trusts router one based on the order configuration.

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Now order cause creates.

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A large amount of configuration.

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So rather than you manually typing configuration.

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It's done for you because rather to trusts rather one, it's created a quality of service class map

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that matches DCP f.

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So essentially, if rather two receives traffic from rather one marked as F, it's going to go into

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this order.

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Quoz VoIP RTP Trust class.

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That's referenced by this policy map.

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The configuration that you see here is an example of moxie or the modular quality of service command

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line interface.

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It consists of two main parts.

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We've got class maps and we've got policy maps.

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And policy maps are then bound onto interfaces.

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So in this example.

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We've got the service policy which references the policy map bound to the serial 2/0 interface.

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So going back to our class maps.

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We've got two class maps, one matching DCP f.

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And one matching either notice the match any key word clause selector three or IP precedence three and

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assured forwarding class three one or AF three one.

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Now, rather to trusting the markings that it receives from rather one.

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So it's looking for traffic that matches F and that class is then matched within this policy map.

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So notice the name order quasi VoIP trust is matched here and it's given 70% of the interface bandwidth

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when there's congestion.

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So in other words, voice traffic matched by F will be given a priority bandwidth of 70%.

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That's a priority queue.

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This is an example of low latency queuing.

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We've got classes of traffic, but we've also got a priority queue.

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So this is the priority queue in low latency queuing.

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A voice will be given 70% of the bandwidth, other traffic.

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So in this case, we've got VoIP control is given 5% of the bandwidth.

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Notice this matches the class configured over here, which is matching CS3 and AF 31.

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That's essentially call signaling protocols such as CIP, H three, D three and skinny.

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In other words, those are protocols you use to set up telephone calls.

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So notice what Audioquest has done.

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It's allocated 75% of the interface bandwidth to voice calls.

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So the actual voice traffic, the HTTP traffic gets 70%, call signaling gets 5%, and the remaining

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traffic is shared using fare queuing.

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So this is an example of waited for queuing on the default clause.

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Default clause is going to match anything not explicitly matched.

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So a low latency cue is actually priority queue.

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Class based weighted.

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Fair queuing.

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But that's too much of a mouthful.

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So we call it low latency queuing.

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There's the priority queue.

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He has an example of a class.

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And this is an example of waiting for queuing within a class.

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Low latency queuing is part of queuing.

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Class based waited for queuing.

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And in this example, we are prioritizing VoIP traffic over other traffic types.

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70% of the bandwidth can be taken by voice calls.

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It's a priority queue, so it will be serviced first.

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5% of the interface bandwidth could be taken by call signaling, but this is a guaranteed minimum bandwidth,

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not a priority.

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This is a guaranteed minimum bandwidth of 70% of the interface bandwidth, but it's a priority queue.

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So voice traffic will be prioritized over all other traffic.

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If voice traffic is only using 20% of the interface bandwidth, other traffic can use whatever is not

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reserved for voice.

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So this is a maximum amount of bandwidth that voice can take and voice will be policed at that level.

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But in the worst case scenario, other traffic will only get 25% of the bandwidth.

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This policy is applied on the serial to zero interface outbound.

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So any traffic leaving the rudder will be prioritized or cued based on this configuration.