Killer 2100 gaming network card
The Flexible Network Architecture is a framework used to create and run Flexible Network Applications. These applications run on the embedded Linux operating system, and are accessed through a driver interface within the host computer's OS. Aside from that, they use a very little of the computers resources, instead handling processing on the cards CPU. Bigfoot Networks has released a Software Development Kit that allows third party developers to create their own applications. Bigfoot also publishes some of their own applications; these include a firewall, torrent client, FTP application, and Telnet service that allows access to the Killer NIC's OS. This was considered a breakthrough at the time  as independent reviews verified that gaming and downloading would proceed without interfering with each other.
Programs that download files often use the USB port to transfer data to external storage, making the Killer NIC useful as a NAS albeit at the generally higher power draw of a desktop PC, compared to a device like a NSLU2.
More typically applications that benefit from low latency, such as Skype or SIP or older VoIP using USB devices (NetTalk, MagicJack) may benefit. As these increasingly use Ethernet directly to routers, however, which would generally be a much lower latency than using a PC and USB connection.
However, FNA is not widely supported as of 2012 and interfaces with more typical router operating systems like DD-WRT, OpenWRT, NetBSD, FreeBSD, OpenBSD, or with proprietary router OS, have not generally been updated.
The successor technology Game Networking DNA now supported by Qualcomm Atheros  remains a Microsoft Windows-only solution  making it effectively useless for network applications other than gaming.