iproute is a package used for TrafficShaping and as an interface to NetEm typically through the use of the program tc. /sbin/ip is one of the applications in this package and it uses LinuxNetlinkSockets
The home page for this is at http://developer.osdl.org/dev/iproute2/
See also iproute(7) or much better ip(8)
Part of NetworkingUtilities
3 pages link to IpRoute: