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350-801 · Question #336

An administrator is developing an 8-class QoS baseline model. The CS3 standards-based marking recommendation is used for which type of class?

The correct answer is D. call signaling. In an 8-class QoS model, CS3 (Class Selector 3) is the standard recommendation for marking voice call signaling traffic, ensuring its prioritization for call setup and control.

Infrastructure and Quality of Service

Question

An administrator is developing an 8-class QoS baseline model. The CS3 standards-based marking recommendation is used for which type of class?

Options

  • AScavenger
  • Bbest effort
  • Cvoice
  • Dcall signaling

How the community answered

(34 responses)
  • B
    6% (2)
  • C
    3% (1)
  • D
    91% (31)

Why each option

In an 8-class QoS model, CS3 (Class Selector 3) is the standard recommendation for marking voice call signaling traffic, ensuring its prioritization for call setup and control.

AScavenger

Scavenger traffic is typically marked with CS1 or a custom low-priority DSCP, not CS3.

Bbest effort

Best effort traffic receives no specific QoS marking and is typically treated as default, not CS3.

Cvoice

Voice media (RTP) is typically marked with EF (Expedited Forwarding), not CS3.

Dcall signalingCorrect

CS3 (Class Selector 3) is a standards-based DiffServ Code Point (DSCP) marking typically recommended for voice call signaling traffic in an 8-class QoS model. This classification ensures that call setup, teardown, and control messages receive appropriate priority, balancing their importance with the real-time needs of voice media.

Concept tested: QoS 8-class model, CS3 marking

Source: https://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/WAN_and_MAN/QoS_SRND/QoS-SRND-Book/QoSSecurity.html#Cisco_QoS_Basics__d44e59

Topics

#QoS Marking#DSCP#Call Signaling#8-Class QoS Model

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