Now you're not expected to know this for the CCMA exam but I'm going to demonstrate an example of quality
of service on two Cisco routers in this example.
I've got two routers running in genius three show run interface serial to slash zero shows us the configuration
these routers simply have IP addresses configured and I have no shut to the interfaces no other configuration
has been done.
Show interface several to slash zero shows us the speed of the interface which is using the default
of one point five four megabits per second so on this interface of the router we can use the command
auto cores.
Now notice we do have the discovery option where we can configure the Rada to discover traffic that
traverses that interface.
But in this example I'm simply going to enable the interface for VoIP and I'm not going to specify the
option Trust which means it's not going to trust the markings that it receives from Roorda to now typically
in the real world you would do that you would trust traffic from one writer to another unless rather
1 is a service provider and wrote it to as a customer as an example.
Now here I'm going to use order cause VoIP trust so that you can see the difference between trusting
and not trusting a neighboring router.
So rather one doesn't trust it to write it to trusts rather one based on the order cost configuration
now order quotes creates a large amount of configuration so rather than you manually typing configuration
it's done for you because write it to trusts rather one it's created a quality of service class map
that matches DCF so essentially if it to received traffic from write a one marked as E.F. it's going
to go into this order cause VoIP RTP trust CLOs that's referenced by this policy map the configuration
that you see here is an example of in QC or the modular quality of service command line interface it
consists of two main parts.
We've got class maps and we've got policy maps and policy maps then bound onto interfaces so in this
example we've got the service policy which references the policy map bound to the serial to slash the
zero interface so going back to our class maps we've got two class maps one matching DCP E.F. and one
matching either.
Notice the match any keyword class selector 3 or IP precedence 3 and assured forwarding Class 3 1 or
a 3 1 rather tooth trusting the markings that it receives from reader 1.
So it's looking for traffic that matches E.F. and that class is then matched within this policy map.
So notice the name or the quoted voice RTP trust is matched here and it's given 70 percent of the interface
bandwidth.
When there's congestion.
So in other words voice traffic match by E.F. will be given a priority bandwidth of 70 percent.
That's a priority queue.
This is an example of low latency queuing.
We've got classes of traffic but we've also got a priority key.
So this is the priority key in low latency killing of voice will be given 70 percent of the bandwidth
other traffic.
So in this case we've got a VoIP control is given 5 percent of the bandwidth notice.
This matches the class configured over here which is matching C S three and a half 31.
That's essentially called signalling protocols such as sip H3 3G 3 and skinny.
In other words those are protocols you use to set up telephone calls so notice what order quizzes done.
It's allocated 75 percent of the interface bandwidth to voice calls so the actual voice traffic the
RTP traffic gets 70 percent call signaling gets 5 percent and the remaining traffic is shared using
fake queuing.
So this is an example of waited for queuing on the default class default.
Class is going to match anything not explicitly matched so a low latency queue is actually pretty key.
Class based weighted fake queuing but that's too much of a mouthful.
So we call it low latency queuing.
There's the pretty key.
Here's an example of a class and this is an example of waited for queuing within a class low latency
queuing is pretty queuing class based waited for queuing.
And in this example we approach rising VoIP traffic over other traffic types.
70 percent of the bandwidth can be taken by voice calls.
It's a priority queue so it will be serviced first.
5 percent of the interface bandwidth could be taken by call signalling.
But this is a guaranteed minimum bandwidth not a priority.
This is a guaranteed minimum bandwidth of 70 percent of the interface bandwidth.
But it's a priority queue so voice traffic will be poor terrorized over all other traffic if voice traffic
is only using 20 percent of the interface bandwidth other traffic can use whatever is not reserved for
voice.
So this is a maximum amount of bandwidth that voice can take and voice will be policed at that level.
But in the worst case scenario other traffic will only get 25 percent of the bandwidth.
This policy is applied on the serial to slash a zero interface outbound so any traffic leaving the Rada
will be prior terrorised or cute.
Based on this configuration.