Quality of Service (QoS) - 10 : Types of QoS

The concept of QoS is covered in detail in the following 3 playlists:
1 - #QoS - Explains how the quality of service (QoS) provides different levels of priority to traffic crossing the network. Discusses the need for and advantages of QoS.

2 - #Hard QoS - Discusses the advantages and disadvantages of hard QoS, which provides guaranteed levels of service to network traffic.

3 - #Soft QoS - Discusses the advantages and disadvantages of soft QoS, which provides priority levels (rather than guarantees) to network traffic.

There are many types of QoS and many different related protocols. However, QoS always falls under one of two categories : hard QoS or soft QoS.
Hard QoS offers QoS guarantees to the network data. ATM and Frame Relay networks support hard QoS.

Soft QoS, on the other hand, is really more a priority than a guaranteed service. Soft QoS gives some data priority over other data, but it does not guarantee a specific level of service. Ethernet and token ring networks use soft QoS.

So, while hard QoS guarantees a certain throughput level for an application, soft QoS just gives traffic a priority, but no guarantee. Sometimes hard QoS is necessary, but sometimes soft QoS is good enough. If this seems confusing, don't worry - we will explore hard and soft QoS further in the next two lessons.