QoS and QoS Policies
32
Quality of Service Guide
3HE 11014 AAAC TQZZA Edition: 01
• 7705 SAR-W Ethernet ports
• 7705 SAR-Wx Ethernet ports
• 7705 SAR-M Ethernet ports
• 7705 SAR-H Ethernet ports
• 7705 SAR-Hc Ethernet ports
• 7705 SAR-X Ethernet ports
3.1.6 Buffering
Buffer space is allocated to queues based on the committed buffer space (CBS), the
maximum buffer space (MBS) and availability of the resources, and the total amount
of buffer space. The CBS and the MBS define the queue depth for a particular queue.
The MBS represents the maximum buffer space that is allocated to a particular
queue. Whether that much space can actually be allocated depends on buffer usage
(that is, the number of other queues and their sizes).
Memory allocation is optimized to guarantee the CBS for each queue. The allocated
queue space beyond the CBS is limited by the MBS and depends on the use of buffer
space and the guarantees accorded to queues as configured in the CBS.
This section contains information on the following topics:
• Buffer Pools
• CBS and MBS Configuration
• Buffer Unit Allocation and Buffer Chaining
3.1.6.1 Buffer Pools
The 7705 SAR supports two types of buffer pools that allocate memory as follows:
• reserved pool—represents the CBS that is guaranteed for all queues. The
reserved pool is limited to a maximum of 75% of the total buffer space.
• shared pool—represents the buffer space that remains after the reserved pool
has been allocated. The shared pool always has at least 25% of the total buffer
space.
Both buffer pools can be displayed in the CLI using the show pools command.
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