Motivation for Quality of Service
This brief appendix states the motivation for, and techniques for, quality of service (QoS) in passive optical network (PON) or other systems. Very similar terminology, sometimes used interchangeably with QoS, are class of service (CoS) and quality of experience (QoE). All of these terms refer to getting packets needed by a user to that user at the time he needs them. One might argue that QoS is the broadest term, CoS refers to how it is delivered, and QoE refers to what the subscriber experiences.
In the early days, when people were just starting to deliver text files to subscribers over telephone lines, and digital audio and video were gleams in a few people’s eyes, the advantage of delivering everything ...