Podcast
Questions and Answers
What is the primary function of class information in network packets that traverse the Internet?
What is the primary function of class information in network packets that traverse the Internet?
- To determine the routing path based on geographical location.
- To ensure consistent forwarding treatment based on traffic class. (correct)
- To encrypt packet data for secure transmission.
- To compress packet headers for efficient bandwidth usage.
Where is the detailed examination of packets, for QoS purposes, ideally performed?
Where is the detailed examination of packets, for QoS purposes, ideally performed?
- Only at the destination host to verify data integrity.
- Randomly across the network to prevent bottlenecks.
- Closer to the edge of the network to avoid overloading core devices. (correct)
- At every router along the path to ensure consistent QoS.
What is meant by 'per-hop behavior' in the context of the DiffServ architecture?
What is meant by 'per-hop behavior' in the context of the DiffServ architecture?
- The consistent application of encryption protocols at each router.
- The monitoring of network latency at each hop for performance analysis.
- The action of an individual device when handling a specific traffic class. (correct)
- The dynamic adjustment of routing paths based on network congestion.
What is required to construct an end-to-end QoS solution using per-hop behavior?
What is required to construct an end-to-end QoS solution using per-hop behavior?
According to the basic QoS model, which function involves associating a packet with a QoS label to mark a distinct path?
According to the basic QoS model, which function involves associating a packet with a QoS label to mark a distinct path?
In the basic QoS model, what is the role of the 'policer'?
In the basic QoS model, what is the role of the 'policer'?
What does 'marking' accomplish in a QoS model?
What does 'marking' accomplish in a QoS model?
What is the primary purpose of 'queueing' in the ingress port actions of a QoS model?
What is the primary purpose of 'queueing' in the ingress port actions of a QoS model?
What role does the Weighted Tail-Drop (WTD) algorithm play in queue management?
What role does the Weighted Tail-Drop (WTD) algorithm play in queue management?
In the context of ingress port actions for QoS, what does SRR (Shaped Round Robin) control?
In the context of ingress port actions for QoS, what does SRR (Shaped Round Robin) control?
At the egress port, what factor determines which queue a packet is placed into?
At the egress port, what factor determines which queue a packet is placed into?
Why is queueing performed at the egress port in a QoS model?
Why is queueing performed at the egress port in a QoS model?
Which queue servicing strategy involves servicing one queue until it is empty before servicing others?
Which queue servicing strategy involves servicing one queue until it is empty before servicing others?
How does the complexity of implementing QoS in a network relate to network characteristics?
How does the complexity of implementing QoS in a network relate to network characteristics?
What is the main function of 'shaping' in QoS?
What is the main function of 'shaping' in QoS?
Which of the following is NOT a primary action taken at the ingress port within the basic QoS model?
Which of the following is NOT a primary action taken at the ingress port within the basic QoS model?
If a packet exceeds the configured policer rate, what action is determined by the 'marking' process?
If a packet exceeds the configured policer rate, what action is determined by the 'marking' process?
How does WTD, as a congestion-avoidance mechanism, differentiate traffic classes?
How does WTD, as a congestion-avoidance mechanism, differentiate traffic classes?
What distinguishes the expedited queue (queue 1) from other queues at the egress port?
What distinguishes the expedited queue (queue 1) from other queues at the egress port?
Which of the following is the characteristic of the QoS label?
Which of the following is the characteristic of the QoS label?
Flashcards
Forwarding Treatment
Forwarding Treatment
Treating packets with the same class information similarly and differently from packets with different class information.
Per-Hop Behavior (PHB)
Per-Hop Behavior (PHB)
The behavior of a network device when handling traffic in a DiffServ architecture.
Basic QoS Implementation
Basic QoS Implementation
Distinguishing packets, assigning labels, enforcing resource limits, and providing differentiated treatment.
Classifying (QoS)
Classifying (QoS)
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Policing (QoS)
Policing (QoS)
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Marking (QoS)
Marking (QoS)
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Queueing (QoS)
Queueing (QoS)
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Weighted Tail-Drop (WTD)
Weighted Tail-Drop (WTD)
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Scheduling (QoS)
Scheduling (QoS)
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Shaped Round Robin (SRR)
Shaped Round Robin (SRR)
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Study Notes
- Switches and routers rely on class information to provide differentiated forwarding treatment to packets.
- End hosts, switches, or routers assign class information based on policy, packet examination, or both.
- Detailed packet examination should occur closer to the edge of the network to avoid overloading core devices.
- Devices use class information to limit resource allocation per traffic class.
- Consistent per-hop behavior across devices enables end-to-end QoS solutions.
- QoS implementation varies in complexity depending on device features, traffic patterns, and control granularity.
Basic QoS Model
- The switch must classify packets, assign a QoS label, enforce resource usage limits, and provide differentiated treatment during resource contention.
- The switch ensures outbound traffic meets a specific profile.
Ingress Port Actions
- Traffic is classified by associating it with a QoS label based on CoS or DSCP values.
- The QoS label dictates subsequent QoS actions.
- Policing compares incoming traffic rate to configured limits, restricting bandwidth per traffic flow, and the result is passed to the marker.
- Marking determines action based on policer results and configuration, such as passing, marking down, or dropping packets.
- Queueing places packets into ingress queues based on QoS label and DSCP/CoS values.
- Weighted tail-drop (WTD) is used as a congestion-avoidance mechanism and drops packets if thresholds are exceeded.
- Scheduling services queues based on shaped round robin (SRR) weights and the priority queue is serviced first.
Egress Port Actions
- Queueing selects egress queues based on QoS packet label and DSCP/CoS value.
- WTD differentiates traffic classes with different thresholds.
- Scheduling services egress queues based on SRR shared or shaped weights.
- Queue 1 can be an expedited queue, serviced until empty before other queues.
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