Podcast
Questions and Answers
In a network operating on a best-effort delivery basis, how is network traffic typically handled?
In a network operating on a best-effort delivery basis, how is network traffic typically handled?
- All traffic has equal priority and an equal chance of being delivered in a timely manner. (correct)
- Specific types of traffic are guaranteed delivery.
- Traffic is prioritized based on source.
- Traffic is dropped based on size.
What is the primary benefit of implementing QoS in a network?
What is the primary benefit of implementing QoS in a network?
- Reduced network security.
- Decreased reliability of network performance.
- Exclusive use of Layer 2 prioritization.
- More predictable network performance and more effective bandwidth utilization. (correct)
Which architecture is the QoS implementation based on?
Which architecture is the QoS implementation based on?
- The OSI model.
- The TCP/IP model.
- The Differentiated Services (Diff-Serv) architecture. (correct)
- The IEEE 802.3 standard.
Where is the classification information carried to implement QoS based on the Diff-Serv architecture?
Where is the classification information carried to implement QoS based on the Diff-Serv architecture?
How many bits from the IP Type of Service (ToS) field are used to carry classification information for QoS?
How many bits from the IP Type of Service (ToS) field are used to carry classification information for QoS?
Which field in the Layer 2 ISL frame header carries the IEEE 802.1p class of service (CoS) value?
Which field in the Layer 2 ISL frame header carries the IEEE 802.1p class of service (CoS) value?
What is the range of values for Layer 2 CoS, indicating priority levels?
What is the range of values for Layer 2 CoS, indicating priority levels?
For Layer 2 802.1Q frame headers, where are the User Priority bits located within the Tag Control Information field?
For Layer 2 802.1Q frame headers, where are the User Priority bits located within the Tag Control Information field?
Which of the following can Layer 3 IP packets carry for prioritization?
Which of the following can Layer 3 IP packets carry for prioritization?
What is the range of values for IP precedence?
What is the range of values for IP precedence?
What is the range of values for DSCP?
What is the range of values for DSCP?
Why does QoS support the use of either IP precedence or DSCP values?
Why does QoS support the use of either IP precedence or DSCP values?
On ports configured as Layer 2 802.1Q trunks, what type of traffic is not encapsulated in 802.1Q frames?
On ports configured as Layer 2 802.1Q trunks, what type of traffic is not encapsulated in 802.1Q frames?
Which of the following is NOT a direct component of implementing QoS?
Which of the following is NOT a direct component of implementing QoS?
A network engineer wants to prioritize voice traffic over other types of traffic. How can this be achieved using QoS?
A network engineer wants to prioritize voice traffic over other types of traffic. How can this be achieved using QoS?
Which of the following scenarios would benefit most from implementing QoS?
Which of the following scenarios would benefit most from implementing QoS?
Considering Layer 2 prioritization, what happens to traffic that is not encapsulated in either ISL or 802.1Q frames?
Considering Layer 2 prioritization, what happens to traffic that is not encapsulated in either ISL or 802.1Q frames?
A network administrator needs to configure QoS to ensure that video conferencing traffic is prioritized. Which of the following steps is most crucial?
A network administrator needs to configure QoS to ensure that video conferencing traffic is prioritized. Which of the following steps is most crucial?
If a network implements QoS, and a period of congestion occurs, what generally happens to lower-priority traffic?
If a network implements QoS, and a period of congestion occurs, what generally happens to lower-priority traffic?
Which of the following best describes the relationship between DSCP and IP precedence values in QoS?
Which of the following best describes the relationship between DSCP and IP precedence values in QoS?
Flashcards
Best-effort delivery
Best-effort delivery
A network operation where all traffic is treated equally, with no prioritization. In congestion, all traffic is equally likely to be dropped.
Quality of Service (QoS)
Quality of Service (QoS)
A feature that allows specific network traffic to be prioritized and managed to ensure predictable performance and efficient bandwidth utilization.
Differentiated Services (Diff-Serv)
Differentiated Services (Diff-Serv)
An architecture that classifies each packet upon entering the network, used as the basis for QoS implementation.
User field (ISL)
User field (ISL)
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Tag Control Information field
Tag Control Information field
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Layer 2 CoS values
Layer 2 CoS values
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IP Precedence values
IP Precedence values
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Differentiated Services Code Point (DSCP)
Differentiated Services Code Point (DSCP)
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Study Notes
- Networks typically operate on a best-effort delivery basis, treating all traffic equally.
- With Quality of Service (QoS), specific network traffic can be prioritized based on importance.
- QoS uses congestion management and avoidance for preferential treatment, improving predictability and bandwidth use.
- QoS implementation relies on the Differentiated Services (Diff-Serv) architecture.
- Diff-Serv classifies each packet upon network entry.
- Classification is carried in the IP packet header, using 6 bits from the deprecated IP type of service (ToS) field.
- Classification can also be carried in the Layer 2 frame.
Layer 2 Frame Prioritization
- Layer 2 Inter-Switch Link (ISL) frames use a 1-byte User field with IEEE 802.1p Class of Service (CoS) in the three least-significant bits.
- On Layer 2 ISL trunks, all traffic is in ISL frames.
- Layer 2 802.1Q frames have a 2-byte Tag Control Information field with CoS value in the three most-significant bits (User Priority bits).
- On Layer 2 802.1Q trunks, all traffic is in 802.1Q frames except for traffic in the native VLAN.
- Layer 2 CoS values range from 0 (low priority) to 7 (high priority).
Layer 3 Packet Prioritization
- Layer 3 IP packets can carry either an IP precedence value or a Differentiated Services Code Point (DSCP) value.
- DSCP values are backward-compatible with IP precedence values.
- IP precedence values range from 0 to 7.
- DSCP values range from 0 to 63.
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