Which QoS per-hop behavior changes the value of the ToS field in the IPv4 packet header?

The correct answer is D. marking. In QoS, marking is the specific per-hop behavior that involves modifying the Type of Service (ToS) field in an IPv4 packet header.

Submitted by stefanr· Mar 5, 2026IP Services

Question

Options

Ashaping
Bclassification
Cpolicing
Dmarking

How the community answered

(52 responses)

B
4% (2)
C
2% (1)
D
94% (49)

Why each option

In QoS, marking is the specific per-hop behavior that involves modifying the Type of Service (ToS) field in an IPv4 packet header.

Ashaping

Shaping buffers and delays excess traffic to smooth the output rate, but it does not modify the packet header's ToS field.

Bclassification

Cpolicing

DmarkingCorrect

Marking is a QoS mechanism that directly alters specific fields within a packet header, such as the Differentiated Services Code Point (DSCP) within the Type of Service (ToS) field of an IPv4 packet, to indicate a particular class or desired forwarding treatment for that traffic.

Concept tested: QoS marking and packet headers

Source: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3550/software/release/12_1_13_ea1/configuration/guide/3550scg/swqos.html#wp1021481

Topics

#QoS#DSCP marking#ToS field#per-hop behavior

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