Latency - Latency - 5.0 English - PG319

Variable Rate

Lookup latency is not constant for variable rate STCAM. The latency value shown in the GUI represents the minimum lookup latency.

Latency varies depending on how many entries match the lookup key. If more than MAX(2, TDM_FACTOR) rules match, the lookup request cannot finish at the defined lookup rate, and the latency increases. The latency further increases if there are consecutive lookup requests with more than MAX(2, TDM_FACTOR) matches. The latency decreases if there are lookup requests with less than MAX(2, TDM_FACTOR) matches.

LPM Mode

Lookup latency varies in LPM mode.

Fixed Rate

The STCAM lookup latency depends on the size of the STCAM, the TDM factor and memory type. The lookup latency is constant for fixed rate STCAM, and some examples are shown in the following table.