Classification is necessary as a first step so that traffic in need of management can be identified.
For classification of traffic, SonicOS uses:
This provides fine controls using combinations of Address Object, Service Object, and Schedule Object elements, allowing for classification criteria as general as all HTTP traffic and as specific as SSH traffic from host A to server B on Wednesdays at 2:12am.
SonicWall network security appliances have the ability to recognize, map, modify, and generate the industry-standard external CoS (Class of Service) designators, DSCP (Differentiated Services Code Point) and 802.1p. For more information, refer to 802.1p and DSCP QoS.
When identified or classified, traffic can be managed. Management can be performed internally by SonicOS Bandwidth Management (BWM), which is effective as long as the network is a fully contained autonomous system. Once external or intermediate elements are introduced such as foreign network infrastructures with unknown configurations or other hosts contending for bandwidth (for example, the Internet), the ability to offer guarantee and predictability are diminished. In other words, as long as the endpoints of the network and everything in between are within your management, BWM works exactly as configured. Once external entities are introduced, the precision and efficacy of BWM configurations can begin to degrade.
But all is not lost. After SonicOS classifies the traffic, it can tag the traffic to communicate this classification to certain external systems that are capable of abiding by CoS tags, thus they too can participate in providing QoS.