350-801 Question #385: Real Exam Question with Answer & Explanation

Question

Which DSCP class selector is necessary to mark scavenger traffic?

Options

• AAF21
• BCS1
• CAF11
• DCS2

Explanation

DSCP Class Selector 1 (CS1) is the specific marking used for scavenger or bulk traffic, indicating it should be the lowest priority and the first to be dropped during network congestion.

Approach. The DSCP Class Selector 1 (CS1), represented by a DSCP value of 001000, is the standard marking used to identify scavenger or bulk traffic. This class of traffic is explicitly designed to be given the lowest priority and should be the first to be dropped during network congestion, thereby protecting higher-priority applications.

Common mistakes.

• A. AF21 (Assured Forwarding Class 2, low drop probability) is used for business-critical but non-real-time data, indicating a higher priority than scavenger traffic.
• C. AF11 (Assured Forwarding Class 1, low drop probability) is used for business-critical but non-real-time data, implying a higher priority than scavenger traffic.
• D. CS2 (Class Selector 2) has a higher precedence than CS1 and is typically used for general low-priority data or network management traffic, not for scavenger traffic.

Concept tested. DSCP marking for scavenger traffic

Reference. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos_diffserv/configuration/xe-16/qos-diffserv-xe-16-book/qos-diffserv-xe-16-book_chapter_011.html

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