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Testing Quality of Service
Comprehensive QoS validation requires a large scale of mixed traffic of different classes and types. The Agilent N2X simplifies QoS testing with per field statistics and scalable traffic generation.
In the context of networking, quality of service (QoS) refers to various technologies in which traffic flows are classified and given forwarding preference on the basis of assigned priority levels.
QoS strategies create better utilization of network resources by giving delay-sensitive and mission critical applications precedence over lower-priority streams during periods of network congestion. QoS priority information is carried at Layer-2 in the VLAN tag’s user priority field and at Layer-3 in the IP packet header’s IP Precedence or differentiated services Code Point (DSCP) field. Using six bits, the DSCP field is capable of defining 64 service levels. Each service level corresponds to a Per-Hop-Behavior (PHB) that defines the relative priority and QoS parameters that a packet should be given by each node in a Differentiated Services (DS) domain. As differentiated services marks each packet with specific service-level requirements, routing decisions can be made on per-packet rather than per-session basis. This application note describes how to use the N2X test system to test the SUT’s implementation of Layer-3 QoS based on different DSCP service levels.
QoS testing based on VLAN traffic with different priority levels is described in a separate application note “Testing Quality of Service with the RouterTester900 Application”.