This is WIZnet Ethernet Interface using Hardware TCP/IP chip, W5500, W5200 and W5100. One of them can be selected by enabling it in wiznet.h.
for only W5500 / WIZ550io user, you could use
This is the Interface library for WIZnet W5500 chip which forked of EthernetInterfaceW5500, WIZnetInterface and WIZ550ioInterface. This library has simple name as "W5500Interface". and can be used for Wiz550io users also.