In Nokia's Service Router Operating System (SR OS), a queue's access to buffer space is controlled by two main parameters: the Committed Burst Size (CBS) and the Maximum Burst Size (MBS). The CBS reserves a dedicated amount of buffer space for the queue. The MBS defines the absolute maximum buffer space the queue can occupy, including both its committed portion and a portion drawn from a shared buffer pool.

The amount of shared buffer space a queue is allowed to contend for is calculated as (MBS - CBS). To prevent a queue from using any shared buffer space, its maximum allowable burst (MBS) must be set equal to its committed burst (CBS). This makes the potential allocation from the shared pool zero.

A. Set the CBS to 0: This configuration provides no dedicated buffer space, forcing the queue to rely exclusively on the shared buffer pool.

C. Set the high-priority-only equal to the MBS: The high-priority-only parameter defines a threshold within the shared buffer portion for preferential packet admission; it does not prevent its use.

D. Set the MBS to 0: This would prevent the queue from buffering any packets, effectively disabling it, which is not the goal.

E. Set the high-priority-only to 0: This removes preferential treatment for high-priority packets within the shared buffer but does not stop the queue from accessing it.

1. Nokia 7750 SR OS Quality of Service Guide, Release 22.10.R1, Document Part Number: 3HE 18148 AAAB TQZZA, Section: "Queue Buffer Management".

In the subsection "Committed and Maximum Burst Size", the guide states: "The difference between the MBS and the CBS is the amount of buffer space that the queue can contend for from the shared portion of the buffer pool... If the MBS and CBS are equal, the queue can only use its committed buffer allocation and cannot contend for shared buffers." This directly supports the correct answer.

2. Nokia 7450 ESS, 7750 SR, 7950 XRS, and VSR Quality of Service Guide, Release 19.10.R1, Document Part Number: 3HE 15084 AAAC TQZZA 01, Section: "Queue Parameters".

The section on "Maximum Burst Size (MBS)" explains: "The MBS parameter is the maximum queue depth for a queue. The queue’s shared buffer allocation is the queue’s MBS minus its CBS. To prevent a queue from using the shared buffer pool, the MBS should be configured to be equal to the CBS." This confirms that setting MBS equal to CBS is the correct procedure.