Which of the following statements are TRUE when discussing self-generated traffic QoS? (Choose two)

Question

Options

• AIn order to mark Layer 2 traffic, sgt-qos will set various ToS bits.
• BDSCP bits can be set per application, per routing instance.
• CThe DSCP marking stays nc1 for all applications. Only the internal FC is manipulated across
• DIn order to mark Layer 2 self-generated traffic, network interfaces must be set to dot1Q.
• EThe internal forwarding class for self-generated traffic is set once and applied to the base router

• A
  13% (4)
• B
  78% (25)
• C
  6% (2)
• E
  3% (1)

Explanation

B is correct because Nokia SR OS self-generated traffic QoS (sgt-qos) provides granular control - DSCP values can be assigned per application (BGP, OSPF, LDP, etc.) and per routing instance (base router or VPRNs), allowing fine-tuned marking of control-plane traffic. D is correct because Layer 2 self-generated traffic relies on 802.1p bits inside a VLAN tag, which only exists when dot1Q encapsulation is configured on the interface - without it, there's no tag field available to carry the CoS marking.

A is wrong because ToS bits are a Layer 3 construct; Layer 2 marking uses 802.1p (dot1Q CoS bits), not ToS. C is wrong because it contradicts B - DSCP is not locked to nc1 for all applications; sgt-qos exists precisely to customize DSCP per app/instance. E is wrong because the forwarding class is not a single global setting applied only to the base router - it too can be configured per application and per routing instance.

Memory tip: Think "Big Dot" - B for "DSCP is flexible per application/instance" and D for "Dot1Q is required for L2 marking." If there's no dot, there's no tag; if there's no tag, there's no L2 QoS.

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