C. Queuing would be the process of managing packets in different queues, often based on their markings, before transmitting them, which may be what is occurring here.
In the normal sense, DSCP value AF31 has higher priority than AF21 and AF11.
From the figure, the packet with DSCP value AF11 was delivered first. This means that the IP precedence value of the DSCP values has been modified such that the lowest DSCP value has the highest priority.
This is done through QOS marking.
dscp values only have the priority that the router recognizes, the dscp values were not changed (marked) in your interpretation, the order they are sent out in technically does not have anything to do with the dscp value at that point, but more, "what queue was the packet placed in" and "what is the priority of that queue"
of course in normal circumstances, you would want to go with "generally" recognized best practices. but since you were thinking so deep about it, i thought that i would too. :)
per-hop behavior (PHB) for QoS such as classification, marking, queuing, congestion, policing, shaping
■ “Classification and Marking” is about the marking of packets and the definition of trust
boundaries.
■ “Queuing” describes the scheduling of packets to give one type of packet priority over
another.
■ “Shaping and Policing” explains these two tools together because they are often used on
opposite ends of a link.
■ “Congestion Avoidance” addresses how to manage the packet loss that occurs when network devices get too busy.
from p232 OCG volume 2
By definition, choose C
I guess marking makes the most sense?
They're not being sent out in an order that corresponds to their priority. They're not being queued because the default queue is FIFO, which doesn't correspond to the diagram. Neither does CBWFQ or PQ because their order doesn't correspond to their priority levels.
But, if it's marking, it's not made clear since the priority numbers don't change, just their order. I'm not sure if the 1, 2, and 3 are supposed to correspond to the order in which the arrive? I assume it is, but then why not just show them in a chain like on the other side?
It kinda feels like something is missing here.
After revisiting this, I think queuing is probably the most appropriate:
1. The packets arrive simultaneously on G0/0.
2. The packets are placed into individual queues.
3. The packets are removed from their queues, in an order dictated by the underlying queue mechanism, which *isn't necessarily dependent on their priority*.
For example:
"WFQ places packets of the various conversations in the fair queues before transmission. The order of removal from the fair queues is determined by the virtual time of the delivery of the last bit of each arriving packet. "
https://content.cisco.com/chapter.sjs?uri=/searchable/chapter/content/en/us/td/docs/ios-xml/ios/qos_conmgt/configuration/xe-17/qos-conmgt-xe-17-book/qos-conmgt-oview.html.xml
So it's probably C, queuing.
Marking: This is the process of setting a marking or tag on a packet, indicating its priority level or class. Marking is typically done at the edge of the network and is used by the network devices to make QoS decisions.
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