Users Guide

Table 100. ASICs by Platform
Hardware FP CSF
S50N, S50V 2 0
S25V, S25P, S25N 1 0
As shown in the following example, you can tune buffers at three locations.
1. CSF — Output queues going from the CSF.
2. FP Uplink — Output queues going from the FP to the CSF IDP links.
3. Front-End Link — Output queues going from the FP to the front-end PHY.
All ports support eight queues, four for data traffic and four for control traffic. All eight queues are tunable.
Physical memory is organized into cells of 128 bytes. The cells are organized into two buffer pools — the dedicated buffer and the
dynamic buffer.
• Dedicated buffer — this pool is reserved memory that other interfaces cannot use on the same ASIC or by other queues on the
same interface. This buffer is always allocated, and no dynamic re-carving takes place based on changes in interface status. Dedicated
buffers introduce a trade-off. They provide each interface with a guaranteed minimum buffer to prevent an overused and congested
interface from starving all other interfaces. However, this minimum guarantee means that the buffer manager does not reallocate the
buffer to an adjacent congested interface, which means that in some cases, memory is under-used.
• Dynamic buffer — this pool is shared memory that is allocated as needed, up to a configured limit. Using dynamic buffers provides
the benefit of statistical buffer sharing. An interface requests dynamic buffers when its dedicated buffer pool is exhausted. The buffer
manager grants the request based on three conditions:
○ The number of used and available dynamic buffers.
○ The maximum number of cells that an interface can occupy.
○ Available packet pointers (2k per interface). Each packet is managed in the buffer using a unique packet pointer. Thus, each
interface can manage up to 2k packets.
You can configure dynamic buffers per port on both 1G and 10G FPs and per queue on CSFs. By default, the FP dynamic buffer allocation
is 10 times oversubscribed. For the 48-port 1G card:
• Dynamic Pool= Total Available Pool(16384 cells) — Total Dedicated Pool = 5904 cells
• Oversubscription ratio = 10
• Dynamic Cell Limit Per port = 59040/29 = 2036 cells
Debugging and Diagnostics
927