AOL Time Warner and Sun Microsystems have announced a collaboration to begin testing ways to enable the two companies’ instant messaging initiatives to communicate with each other, according to c|net. Tests will be conducted in order for Sun-owned enterprise software company iPlanet’s instant messaging service to work with AOL Instant Messenger. The collaboration is seen as a defensive maneuver against Microsoft, which is taking steps to capture a larger share of the instant messenging market by tying Windows Messenger with its Windows XP operating system.