Dell Networking S6000 Uživatelský manuál stáhnout pdf (Strana 285)

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Dynamic ingress buffering enables the sending of pause frames at different thresholds based on the

number of ports that experience congestion at a time. This behavior impacts the total buffer size used by

a particular lossless priority on an interface. The pause and resume thresholds can also be configured

dynamically. You can configure a buffer size, pause threshold, ingress shared threshold weight, and

resume threshold to control and manage the total amount of buffers that are to be used in your network

environment.

All the PFC-related settings such as the DCB input and output policies or DCB maps are saved in the DCB

application and the Differentiated Services Manager (DSM) application. All of these configurations can be

modified only for interfaces that are enabled for DCB. The DCB buffer configurations are also saved in the

DCB and DSM databases.

Buffer Sizes for Lossless or PFC Packets

You can configure up to a maximum of 4 lossless (PFC) queues. By configuring 4 lossless queues, you

can configure 4 different priorities and assign a particular priority to each application that your network is

used to process. For example, you can assign a higher priority for time-sensitive applications and a lower

priority for other services, such as file transfers. You can configure the amount of buffer space to be

allocated for each priority and the pause or resume thresholds for the buffer. This method of

configuration enables you to effectively manage and administer the behavior of lossless queues.

Although the system contains 9 MB of space for shared buffers, a minimum guaranteed buffer is provided

to all the internal and external ports in the system for both unicast and multicast traffic. This minimum

guaranteed buffer reduces the total available shared buffer to 7,787 KB. This shared buffer can be used for

lossy and lossless traffic.

The default behavior causes up to a maximum of 6.6 MB to be used for PFC-related traffic. The remaining

approximate space of 1 MB can be used by lossy traffic. You can allocate all the remaining 1 MB to

lossless PFC queues. If you allocate in such a way, the performance of lossy traffic is reduced and

degraded. Although you can allocate a maximum buffer size, it is used only if a PFC priority is configured

and applied on the interface.

The number of lossless queues supported on the system is dependent on the availability of total buffers

for PFC. The default configuration in the system guarantees a minimum of 52 KB per queue if all the 128

queues are congested. However, modifying the buffer allocation per queue impacts this default behavior.

By default the total available buffer for PFC is 6.6 MB and when you configure dynamic ingress buffering,

a minimum of least 52 KB per queue is used when all ports are congested. By default, the system enables

a maximum of 1 lossless queue on the S6000 platform.

This default behavior is impacted if you modify the total buffer available for PFC or assign static buffer

configurations to the individual PFC queues.

Interworking of DCB Map With DCB Buffer Threshold

Settings

DCB map functionality is supported on the S6000 platform.

The dcb-input and dcb-output configuration commands are deprecated. You must use the dcp-map

command to create a DCB map to configure priority flow control (PFC) and enhanced transmission

selection (ETS) on Ethernet ports that support converged Ethernet traffic.

Data Center Bridging (DCB)

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