QoS Quiz: Test Your Knowledge
Quiz
Question 1
Which field in the 802.1q VLAN tag is used to implement Layer 2 Quality of Service?
a) Type of Service (ToS)
b) Priority Code Point (PCP)
c) Differentiated Services Code Point (DSCP)
d) EtherType
Question 2
In the standard DSCP mapping, which value is typically assigned to VoIP media (Voice) traffic to ensure the lowest latency?
a) CS3 (24)
b) AF41 (34)
c) EF (46)
d) CS1 (8)
Question 3
Why is Layer 2 CoS marking typically lost when a packet moves between different subnets?
a) TTL expiration clears the CoS bits
b) Routers do not support 3-bit priority fields
c) The 802.1q header is stripped by the router at the layer 3 boundary
d) Encryption hides the CoS bits from the next hop
Question 4
In a Wi-Fi Multimedia (WMM) environment, which Access Category would be mapped to a packet with a DSCP value of 34 (AF41)?
a) AC_BE (Best Effort)
b) AC_VO (Voice)
c) AC_BK (Background)
d) AC_VI (Video)
Question 5
Which of the following describes 'Jitter' in a network context?
a) The percentage of packets that fail to reach their destination
b) The total time it takes for a packet to travel from source to destination
c) The maximum amount of data that can be sent over a link
d) The variation in the delay of received packets
Question 6
You observe a CoS value of 1. According to standard QoS logic, how is this traffic treated compared to CoS 0 (Best Effort)?
a) It is prioritised above CoS 0 traffic
b) It is prioritised above all traffic
c) It is treated as the lowest priority
d) It is dropped automatically
Question 7
Which DSCP value is mathematically equivalent to the 'Class Selector 1' (CS1) scavenger class?
a) 8
b) 46
c) 16
d) 0
Question 8
On a switch you run 'show interface queues' and see 'Dropped Packets' in Queue 3, but 0 drops in Queue 7. What does this indicate?
a) The switch is failing a needs replacing
b) There is a loop in the network
c) The 'Trust' setting is disabled on all ports
d) QoS is working
Question 9
Which traffic would typically be tagged as DSCP priority 46?
a) Video Conferencing
b) VOIP
c) Database
d) Call Signalling (SIP)
Question 10
What is a trust boundary in QoS?
a) The physical edge of the network
b) The software defined limit that prevents a single application consuming more than 50% of an interface
c) The points in a network where QoS markings are accepted from an external source
d) The logical separation between a Guest Wi-Fi network and a Corporate LAN to prevent VLAN hopping
Answers
Question 1
Which field in the 802.1q VLAN tag is used to implement Layer 2 Quality of Service?
a) Type of Service (ToS)
b) Priority Code Point (PCP)
c) Differentiated Services Code Point (DSCP)
d) EtherType
Question 2
In the standard DSCP mapping, which value is typically assigned to VoIP media (Voice) traffic to ensure the lowest latency?
a) CS3 (24)
b) AF41 (34)
c) EF (46)
d) CS1 (8)
Question 3
Why is Layer 2 CoS marking typically lost when a packet moves between different subnets?
a) TTL expiration clears the CoS bits
b) Routers do not support 3-bit priority fields
c) The 802.1q header is stripped by the router at the layer 3 boundary
d) Encryption hides the CoS bits from the next hop
Question 4
In a Wi-Fi Multimedia (WMM) environment, which Access Category would be mapped to a packet with a DSCP value of 34 (AF41)?
a) AC_BE (Best Effort)
b) AC_VO (Voice)
c) AC_BK (Background)
d) AC_VI (Video)
Question 5
Which of the following describes 'Jitter' in a network context?
a) The percentage of packets that fail to reach their destination
b) The total time it takes for a packet to travel from source to destination
c) The maximum amount of data that can be sent over a link
d) The variation in the delay of received packets
Question 6
You observe a CoS value of 1. According to standard QoS logic, how is this traffic treated compared to CoS 0 (Best Effort)?
a) It is prioritised above CoS 0 traffic
b) It is prioritised above all traffic
c) It is treated as the lowest priority
d) It is dropped automatically
Question 7
Which DSCP value is mathematically equivalent to the 'Class Selector 1' (CS1) scavenger class?
a) 8
b) 46
c) 16
d) 0
Question 8
On a switch you run 'show interface queues' and see 'Dropped Packets' in Queue 3, but 0 drops in Queue 7. What does this indicate?
a) The switch is failing a needs replacing
b) There is a loop in the network
c) The 'Trust' setting is disabled on all ports
d) QoS is working
Question 9
Which traffic would typically be tagged as DSCP priority 46?
a) Video Conferencing
b) VOIP
c) Database
d) Call Signalling (SIP)
Question 10
What is a trust boundary in QoS?
a) The physical edge of the network
b) The software defined limit that prevents a single application consuming more than 50% of an interface
c) The points in a network where QoS markings are accepted from an external source
d) The logical separation between a Guest Wi-Fi network and a Corporate LAN to prevent VLAN hopping
