JN0-102 · Question #356
When is the BA Classifier engaged for identifying the forwarding class of traffic in a Juniper router?
The correct answer is C. prior to ingress policing of traffic. The BA Classifier is engaged early in the packet processing pipeline on a Juniper router, specifically before any ingress policing is applied, to identify the forwarding class of incoming traffic.
Question
When is the BA Classifier engaged for identifying the forwarding class of traffic in a Juniper router?
Options
- Aafter a packet is identified by a multifield classifier
- Bafter the traffic passes though a shaper
- Cprior to ingress policing of traffic
- Dwhile the packet is stored in the switching fabric of the router
How the community answered
(45 responses)- A2% (1)
- B4% (2)
- C91% (41)
- D2% (1)
Why each option
The BA Classifier is engaged early in the packet processing pipeline on a Juniper router, specifically before any ingress policing is applied, to identify the forwarding class of incoming traffic.
Multifield classifiers are generally more granular and can be applied after BA classifiers, or in their place, if more complex matching is needed.
Shapers are applied much later in the QoS process to limit the output rate of traffic, long after initial classification.
Behavior Aggregate (BA) classifiers are applied at the ingress interface and are among the first Quality of Service (QoS) mechanisms to identify traffic forwarding classes, based on fields like DSCP or CoS bits. This classification occurs prior to subsequent QoS actions such as ingress policing, shaping, and queuing.
Packet classification primarily occurs at the ingress physical interface, before the packet is stored and processed within the switching fabric of the router.
Concept tested: Junos BA classifier placement in QoS
Source: https://www.juniper.net/documentation/us/en/software/junos/qos/topics/topic-map/cos-understanding-interfaces-ingress-egress.html
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