Which of the following can be used as classifiers of customer traffic? (Choose three)

Question

Options

• ADSCP value
• B802.1p value
• CIP DF bit
• DTCP/UDP port numbers
• EHTML version number

• A
  87% (13)
• C
  7% (1)
• E
  7% (1)

Explanation

DSCP (A), 802.1p (B), and TCP/UDP port numbers (D) are all standard QoS traffic classifiers used by network devices to identify and prioritize traffic flows. DSCP marks Layer 3 IP packets with a 6-bit value in the ToS field, 802.1p marks Layer 2 Ethernet frames with a 3-bit CoS value in the 802.1Q VLAN tag, and TCP/UDP port numbers identify specific applications or services (e.g., port 80 = HTTP, port 5060 = SIP) allowing policy-based classification.

C (IP DF bit) is a fragmentation control flag ("Don't Fragment") - it tells routers whether a packet can be fragmented, but carries no QoS or traffic-type information, so it cannot classify traffic. E (HTML version number) is an application-layer concept embedded in HTTP payload content; network devices performing QoS classification operate at Layers 2–4 and do not inspect HTML content.

Memory tip: Think "Two layers, one app" - you need L2 marking (802.1p), L3 marking (DSCP), and L4 application identity (port numbers) to classify traffic end-to-end. DF bit and HTML version are outliers that serve entirely different purposes (fragmentation and web standards).

No community discussion yet for this question.