Quality of Service (QoS) for networks is an industry-wide set of standards and mechanisms for ensuring high-quality performance for critical applications. By using QoS mechanisms, network administrators can use existing resources efficiently and ensure the required level of service without reactively expanding or over-provisioning their networks.QoS is a means of providing consistent, predictable data delivery by distringuishing between packets that have strict timing requirements from those that are more tolerant of delay. Packets with strict timing requirements are given special treatment in a QoS-capable network.
The QoS module mainly consists of Access Control List (ACL), Differentiated Services (DiffServ) and Class of Service (CoS).
Access Control Lists (ACL) ensure that only authorized users have access to specific resource while blocking out any unwanted attemps to reach network resources. ACLs are used to restrict contents of routing updates, decide which types of traffic are forwarded or blocked, and, above all, provide security to the network. The switch allows classification of packets based upon Layer-2 through Layer-4 header information.
With Differentiated Services (DiffServ), network resources are apportioned based on traffic classification and priority, giving preferential treatment to data with strict timing requirements according to network management policy.
Class of Service (CoS) allows the user to directly configure device queueing and, therefore, provide the desired QoS behaviour without the complexities of DiffServ. The CoS mapping tables define the queue used to handle each enumerated type of user priority designated in either the 802.1p, IP precedence, or IP DSCP contents of a packet.
