So in a situation like this the phone has to indicate to the switch that its traffic is important so
it needs a mechanism or a way to tell switch one that its traffic is more important than the P.C. traffic.
Now there are two main ways to do this.
We either mock at Layer 2 or mock at least three.
So in the same way that FedEx or DHL will mock a parcel.
In other words they put a sticker or a barcode on the puzzle to indicate that the parcel is of great
importance and should be delivered the next day.
The phone will mark the packets that it sends to the switch either at least to what Layer 3 to indicate
that the packets are important.
Assuming that switch one accepts those markings it will send the packets to switch to with the relevant
markings markings are important in packets because when they arrive at a switch such as Switch two it
needs to make a decision which class does the packet belong to.
In other words is it platinum is it gold is it silver is it bronze.
Or to use a airline analogy is it first class or business class or economy class.
Packets within a class will be treated the same way.
So the switch needs to determine which class the packets go into.
So again platinum gold silver and so forth.
And then it will treat those packets accordingly.
So how does a phone or a switch indicate to another switch or rather the level of importance of packets.
Not to use the airline analogy again.
This is very similar to a ticket that you get.
So does your ticket indicate that you're a first class passenger or business class or economy class.
Think of the markings as a ticket.
The ticket is an indicator of the service that you'll receive.
So when the phone sends a voice packets to the switch it's going to mock them at least to using an attitude
of one queue marking.
I'll show you the details of the markings when I do a y shock capture in a moment but for now understand
that when you speak into a phone.
So let's assume these are your voice waves a phone transfer codes that into a digital signal of zeros
and ones that are put into UDP packets that are encapsulated in IP which are in turn encapsulated in
Ethernet and are sent to the switch.
So layer two we have an attitude of one queue head.
The reason why is that Ethernet doesn't have these additional markings.
As an example if using ethernet too it has no way to indicate the importance of a packet.
So when we capture the frame you'll see in a moment that we have a destination address.
We'll have a source address and then we'll have an edited one Q header and then the actual voice within
the packet.
So the editor the one Q header has a priority field to this is three bits in size also called costs
or class of service or S.O.S.
It's three bits in size.
So the binary values go from 0 0 0 all the way to triple 1.