Quality of Service refers to the assertions a vendor makes, and are then agreed upon by the vendor and buyer, on the performance of the software or service.
During the sales cycle when a service or resource is purchased, the provider and user enter a contract. The software licensing agreements or service-level agreements (SLAs) for technology products of these kinds spell out their end-to-end measurable performance properties. The properties speak to the service at hand and generally include tolerable or expected latency, (transit delay), bandwidth (throughput), error rates, various kinds of losses or turbulence, and more.
Were it not for the two parties agreeing on quality of service beforehand, it would be impossible and unreasonable for the vendor to provide the software or service in a manner that is satisfactory to the customer’s application requirements.
Example:
“An authentication solution’s quality of service is paramount. How users access a service is a critical path — without the enabling way to enter the service, there is no service for the user. Some enterprises have zero appetite for downtime or even latency since it affects their bottom line, down to the minute.”
