Configuration Examples - Configuration Examples - 2.0 English - PG468

This section provides two example configurations along with their lookup rate and latency for different DRAM types.

ACL Example

An example of Access Controlled List (ACL) using a Five-Tuple key with range matching. The table has 512 K entries with each 64 B in size. The lookup keys used in this example generates an average of 17 reads per lookup. The lookup rate is 6 Mlps, and update rate is 10000 per second; the lookup read bandwidth value is calculated as follows:

Lookup Read Bandwidth = DRAM Reads × 64 B = 17 × 6E6 x 64 B = 6.08 GB/s

DRAM Write Latency = 500E-9 x UPDATE_RATE = 500E-9 x 10E3 = 5 ms

DRAM Bandwidth = 1/(1 - DRAM Write Latency) x Lookup Read Bandwidth = 1/(1 - 5E-3 × 6.1G) = 6.11 GB/s

A TDM Factor = 64 is used for more efficient filter implementation. The RAM_FREQ must be least 64 × 6 M + 2 × 10 K = 385 MHz. Single clock mode is used so that the Lookup Interface Frequency is also 385 MHz.

LPM Example

An example of Longest Prefix Matching (LPM) where, table size is 512 K × 64 B with storage capacity of up to 4 M prefixes, target lookup rate is 150 Mlps, and update rate is 10000 per second; Lookup Read bandwidth is calculated as follows:

Lookup Read Bandwidth = DRAM Bandwidth × 64 B = Lookup Rate × 64 B = 150E6 x 64 B = 8.94 GB/s

DRAM Write Latency = 500E-9 x UPDATE_RATE = 500E-9 x 10E3 = 5 ms

DRAM Bandwidth = 1/(1 - DRAM Write Latency) x Lookup Read Bandwidth = 1/(1 - 5E-3 × 8.94G) = 8.98 GB/s

A TDM Factor = 2 is used for more efficient implementation. This requires the RAM Frequency to be at least 2 × 150 M + 2 × 10 K = 301 MHz. Additionally, HBM imposes a requirement on the RAM Frequency to be at least 350 MHz. In this example, the same RAM Frequency is used for all memory types. Single clock mode is used so that the Lookup Interface Frequency is also 350 MHz.