Stands for Classification, Queuing, and Scheduling in reference to the steps that need to be taken in order to provide a basic level of Quality of Service for packet-based networks.
A good analogy can be found in Grenville Armitage's book Quality of Service in IP Networks of an airport check-in system:
The arrival of passengers for check-in is a bursty process, typically peaking during the the hour before a flight's departure time. Most of us are very farmiliar with the queues that build up during the sudden arrival of group of passengers...The airlines typically like to provide expedited check-in service to their premium customers (for example, first-class passengers...).
Thus, passengers are classified, queued, and scheduled for delivery in an airport check-in system. Here is a diagram of the process:
Classify Queue Schedule
Ticket First Class Check-In
o <--Holders |-----|
o ----->| | o
o -----> ()\ / |-----| \
o X \
o o -----> ()/ \ |-----| () -----> The Plane
/ ----->| | o
o Airline | | o <--- Airline Counter Person
/Agents |-----|
"May I see your Coach Check-In
ticket please?"
The steps are:
As a word of advice, do not scream "I HAVE A BOMB!" as it will adversely affect your QoS.