Cisco CCIE Collaboration: Best Practices for Priority Queue Bandwidth Allocation

Cisco Best Practice Recommendation: Priority Queue Bandwidth Allocation for Multiple Strict Priority LLQs on Router Interfaces

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Question

Which statement describes the Cisco best practice recommendation about priority queue bandwidth allocation in relationship to the total link bandwidth when multiple strict priority LLQs are configured on the same router interface?

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Explanations

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A. B. C. D. E.

D.

Cisco Technical Marketing testing has shown a significant decrease in data application response times when Real-Time traffic exceeds one-third of a link's bandwidth capacity.

Cisco IOS Software allows the abstraction (and, thus, configuration) of multiple LLQs.

Extensive testing and production-network customer deployments have shown that limiting the sum of all LLQs to 33 percent is a conservative and safe design ratio for merging real-time applications with data applications.

When configuring multiple strict priority LLQs on the same router interface, it is essential to allocate the bandwidth effectively to ensure that all traffic flows smoothly without any adverse impact on the network performance. Cisco best practice recommendation on priority queue bandwidth allocation suggests that the sum of all LLQs should be limited to one-third of the link bandwidth capacity.

The strict priority LLQ (Low Latency Queue) is used to prioritize delay-sensitive traffic, such as voice and video traffic, over other traffic types. The LLQs have a higher priority than all other traffic classes, and this priority level is applied to all traffic within the queue. When multiple LLQs are configured on the same router interface, it is important to ensure that each LLQ receives sufficient bandwidth allocation to handle its traffic effectively.

Allocating the bandwidth effectively among multiple LLQs helps ensure that no queue is starved of bandwidth, which could lead to delays or dropped packets. The recommended allocation of one-third of the link bandwidth capacity ensures that there is sufficient bandwidth available for all LLQs to function effectively. This allocation is considered the best practice for efficient bandwidth allocation when multiple LLQs are configured on the same router interface.

In contrast, allocating more bandwidth to LLQs may starve other queues of necessary bandwidth, leading to network performance degradation. For example, if the sum of all LLQs is allowed to exceed one-third of the link bandwidth capacity, there may not be enough bandwidth available to handle other traffic classes effectively. Therefore, Cisco recommends limiting the sum of all LLQs to one-third of the link bandwidth capacity as the best practice.

Option E, which suggests that Cisco does not recommend more than one strict priority LLQ per interface, is not a correct answer. Cisco does allow multiple LLQs to be configured on the same interface, but it is essential to allocate the bandwidth effectively among them, as per the best practices recommended.

To summarize, when configuring multiple strict priority LLQs on the same router interface, it is essential to allocate bandwidth effectively to ensure that all traffic flows smoothly without any adverse impact on the network performance. Cisco recommends limiting the sum of all LLQs to one-third of the link bandwidth capacity as the best practice.