Port-to-port latency tests, how to?

Hello all.

we interesting where from ns developers takes.

for example:

exalink fusion

110 nanoseconds port to port latency with full layer 2 switching. The

industry's lowest latency cut-through layer 2 switch. Supports ultra-low

latency multicast and broadcast.

Latency

Measured front panel port to port:

➔ 5 ns (Layer 1 tap/patch)

➔ 95 ns (Layer 2 aggregation)

➔ 110ns (Layer 2 switching) ( !!!we interesting in this parameter )

mellanox sx1012

Lowest Latency

• 220nsec for 40/56GbE

• 250nsec for 10GbE

• Cut-through latency between ports in different speeds

but cisco got different numbers, by packet size.

http://www.cisco.com/c/en/us/products/collateral/switches/nexus-3000-series-switches/white_paper_c11-661939.html

so what are real tests for this NS?

how to make REAL compare.