Maximum Delay Buffer Sizes Available to Interfaces

When you enable the large delay buffer feature on interfaces, a larger buffer is available for allocation to scheduler queues. The maximum delay buffer size that is available for an interface depends on the maximum available delay buffer time and the speed of the interface.

On channelized T1/E1 interfaces, the maximum delay buffer time varies by the number of DS0 channels configured on the interface as shown in Table 144. The default values are as follows:

• Clear-channel interface—The default delay buffer time is 500,000 microseconds (0.5 seconds).
• NxDS0 interface—The default delay buffer time is 1,200,000 microseconds (1.2 seconds).

Table 144: Maximum Available Delay Buffer Time by Channels

You can calculate the maximum delay buffer size available for an interface, with the following formula:

For example, the following maximum delay buffer sizes are available to 1xDS0 and 2xDS0 interfaces:

1xDS0—64 kilobits per second x 4 seconds = 256 kilobits (32 kilobytes)

2xDS0—128 kilobits per second x 4 seconds = 512 kilobits (64 kilobytes)

If you configure a delay buffer size larger than the new maximum, the system allows you to commit the configuration but displays a system log warning message and uses the default buffer size setting instead of the configured maximum setting.