i am preparing for Cisco 642-642 and now i read the "Cisco Press - IP Telephony Self-Study Cisco QOS Exam Certification Guide,Second Edition(2005)" book which is very good btw. But i'm little bit confused about how exactly QoS works in detail. Let's say that we have one router with two ethernet/fastethernet interfaces. We have one incoming and another outgoing interface:
(packet) ---> (router ingress (fa0/0) X router egress (fa0/1)) --->
In this case packet is arrived on fa0/0 interface, and here is my question. What is the order of the applied QoS mechanisms? I mean the packet has to be classified then it has to be policed, marked if we have CBQ (WFQ,CBWFQ) the packet needs to be ordered, then if we have shaper this packet have to be delayed (if it's necessarily of course). So i'm get confused of how and when packet getting queued (in order to achieve its place in fair queue), what is the sequence ? The packet first is queued and then is placed to shaping queue before it reach taildrop ? Can anyone explain me exactly (step-by-step) how the packet "rides" from end-to-end (ingress -> egress)? I'm confused of all these queues in different type of mechanisms. I mean, WFQ has it's queue, shaper manage it's own queue, we have hardware queue (TX/RX rings).. i believe that i'm getting understand all this, but i need just a little help maybe.
I'll be thankful to your answers!
Thanks in advance!