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Configuring Larger Delay Buffers

By default, T1, E1, and NxDS0 interfaces configured on Channelized IQ PICs are limited to 100,000 microseconds of delay buffer. (The default average packet size on the IQ PIC is 40 bytes.) For these interfaces, it might be necessary to configure a larger buffer size to prevent congestion and packet dropping.

To ensure traffic is queued and transmitted properly, you can configure a buffer size larger than the default maximum. Include the q-pic-large-buffer large-scale statement at the [edit chassis fpc slot-number pic pic-number] hierarchy level:



[edit chassis fpc slot-number pic pic-number]

q-pic-large-buffer {
large-scale;
}

This statement sets the maximum buffer size. (See Table 57.)

Table 57: Maximum Delay Buffer with q-pic-large-buffer Statement Enabled

Platform, PIC, or Interface Type	Maximum Buffer Size
With Large Buffer Sizes Not Enabled
T-series and M320	50,000 microseconds
Other M-series	200,000 microseconds
IQ PICs on all platforms	100,000 microseconds
Channelized T1/E1 interface on J-series Services Routers	400,000 microseconds
With Large Buffer Sizes Enabled
Channelized T3 and channelized OC3 DLCIs—Maximum sizes vary by shaping rate:
With shaping rate from 64,000 through 255,999 bps	4,000,000 microseconds
With shaping rate from 256,000 through 511,999 bps	2,000,000 microseconds
With shaping rate from 512,000 through 1,023,999 bps	1,000,000 microseconds
With shaping rate from 1,024,000 through 2,048,000 bps	500,000 microseconds
With shaping rate from 2,048,001 bps through 10 Mbps	400,000 microseconds
With shaping rate from 10,000,001 bps through 20 Mbps	300,000 microseconds
With shaping rate from 20,000,001 bps through 30 Mbps	200,000 microseconds
With shaping rate from 30,000,001 bps through 40 Mbps	150,000 microseconds
With shaping rate up to 40,000,001 bps or higher	100,000 microseconds
NxDS0 IQ Interfaces—Maximum sizes vary by channel size:
1xDSO through 3xDS0	4,000,000 microseconds
4xDSO through 7xDS0	2,000,000 microseconds
8xDSO through 15xDS0	1,000,000 microseconds
16xDSO through 32xDS0	500,000 microseconds
Other IQ interfaces	500,000 microseconds

For information on configuring the buffer size, see the JUNOS Class of Service Configuration Guide.

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