Not my area, but it is hardware-based acceleration, pushing the trading logic to the network card with FPGA's -- for example see here
for a circa 2012 discussion, probably with quite outdated timings by now. An excerpt:
For these products, precise latency figures are application dependent and difficult to obtain. However, Accelize claims their smart NICs can turn around financial trades on the FPGA in under 2µs. This is significantly lower than the minimum latency achievable with software, as discussed earlier.