att/ryu — pull request #35 by powerist (2014-02-28 02:26:13+00:00)
Title: Eliminate ARP broadcast:

No ARP broadcast in the network at all.
The controller is supposed to collect
hosts' info through gratuitous ARP, when
hosts boot.
If an ARP request finds no matching entry
in the ip_to_mac dictionary, either the
requested host does not exist, or the
gratuitous arp has not arrived at the
controller. The requesting host should
try later.