Which of the following are characteristics of DSCP? (Choose two)

Question

Options

• ADSCP is part of the Layer 3 header.
• BDSCP is a 6-bit field.
• CDSCP specifies eight different priorities.
• DDSCP specifies four precedence levels.
• EDSCP is part of the Layer 2 header
• FDSCP specifies 128 different per-hop behaviors.

• A
  86% (43)
• C
  2% (1)
• E
  4% (2)
• F
  8% (4)

Explanation

DSCP (Differentiated Services Code Point) resides in the IP header, making it a Layer 3 QoS marking mechanism - this is why A is correct. It occupies 6 bits of the ToS (Type of Service) field in IPv4 or the Traffic Class field in IPv6, yielding 2⁶ = 64 possible values (PHBs), confirming B is correct.

Why the distractors are wrong:

• C (eight priorities) describes 802.1p/CoS, a Layer 2 mechanism using a 3-bit field (2³ = 8 values) - not DSCP.
• D (four precedence levels) is simply inaccurate for any standard QoS scheme; the older IP Precedence used 3 bits for 8 levels.
• E (Layer 2 header) is the opposite of A - Layer 2 QoS uses 802.1Q tags with CoS bits, not DSCP.
• F (128 PHBs) would require 7 bits; DSCP's 6 bits only support 64 per-hop behaviors.

Memory tip: Think "DSCP = D3-6" - Differentiated services, L3 header, 6-bit field. If an answer says Layer 2 or 128 values, it's wrong by one layer or doubled the math.

No community discussion yet for this question.