Onboard SDRAM Split

Stateful Flow Management

Platform
Napatech SmartNIC
Content Type
User Guide
Capture Software Version
Link™ Capture Software 12.9

The SmartNIC SDRAM memory split between frame buffering and flow management is configurable using the SDRAMSplit parameter.

SDRAMSplit parameter

Onboard SDRAM of SmartNICs running on a flow management image is used for storing the flow table and for frame buffering. The SDRAM memory split between frame buffering and flow management is configurable using the SDRAMSplit parameter in the ntservice.ini file. By default, it is configured to have limited frame buffering / a lot of flows. The following is the default configuration in the ntservice.ini file.
SDRAMSplit=[Buffer=12.5, Flowtable=87.5]
By default, 10.5 Gbytes (87.5% of 12 Gbytes) are reserved for the flow table and 1.5 Gbytes (12.5% of 12 Gbytes) are reserved for frame buffering on the NT200A02. By default, 7 Gbytes (87.5% of 8 Gbytes) are reserved for the flow table and 1 Gbyte (12.5% of 8 Gbytes) is reserved for frame buffering on the NT100A01. If received frames are dropped due to traffic burst, it is recommended to adjust the SDRAMSplit values to have larger frame buffering / less flows.

Buffering time and flow table capacity

The table below shows expected buffering time at full line rate and expected flow table capacity based on the onboard SDRAM split configuration examples for the NT200A02.
SDRAMSplit values in ntservice.ini Frame buffering Flow table
SDRAM size in Gbytes Buffering in milliseconds at 100 Gbit/s SDRAM size in Gbytes Number of flows
[Buffer=12.5, Flowtable=87.5] 1.5 130 10.5 140 M
[Buffer=50, Flowtable=50] 6.0 510 6.0 80 M
[Buffer=75, Flowtable=25] 9.0 770 3.0 40 M
[Buffer=87.5, Flowtable=12.5] 10.5 900 1.5 20 M
The table below shows expected buffering time at full line rate and expected flow table capacity based on the onboard SDRAM split configuration examples for the NT100A01.
SDRAMSplit values in ntservice.ini Frame buffering Flow table
SDRAM size in Gbytes Buffering in milliseconds at 100 Gbit/s SDRAM size in Gbytes Number of flows
[Buffer=12.5, Flowtable=87.5] 1.0 90 7.0 93 M
[Buffer=50, Flowtable=50] 4.0 350 4.0 53 M
[Buffer=68.75, Flowtable=31.25] 5.5 500 2.5 33 M
[Buffer=87.5, Flowtable=12.5] 7.0 600 1.0 13 M
See DN-0449 for more information about the SDRAMSplit parameter in the ntservice.ini file.