Which two statements about QoS marking are true? (Choose two)

Question

Options

• AShaping is one of the ways that packets can be remarked.
• B802.1Q/p CoS bits and IP Precedence are Layer 3 marking fields.
• CQoS marking establishes a trust boundary that scheduling tools later depend on
• DMPLS EXP and DSCP are Layer 2 marking fields
• EClass-based marking occurs after packet classification

• A
  5% (1)
• C
  95% (19)

Explanation

C is correct: QoS marking (or re-marking) at trust boundaries assigns standardized values (e.g., DSCP, CoS) that downstream QoS mechanisms-queuing, scheduling, policing-rely on to make forwarding decisions. Without consistent, trusted markings, scheduling tools cannot correctly differentiate traffic classes. E is correct: class-based marking is a two-step process-packets must first be classified (matched against ACLs, NBAR, or other criteria) before a marking action can be applied. Classification always precedes marking. The other options are incorrect: A is wrong because shaping buffers/delays traffic to enforce a rate; it does not remark packets. B is wrong because 802.1Q/p CoS bits are a Layer 2 field (Ethernet frame header), not Layer 3-only IP Precedence is Layer 3. D is wrong because DSCP is a Layer 3 field (IP header), while MPLS EXP (now called TC bits) operates at Layer 2.5 in the MPLS label stack, not strictly Layer 2.

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