[Asterisk-Users] newbie questions

[Hiu Yen Onn]

i am pretty new to asterisk. hope to learn more.
i have this notice from the console. when i was doing the echo testing 
by putting the context=default. then, i called out 600 to get the echo 
test, i can hear the operator talking, but i cant really hear the playback.
i am trying to dig around from info from the log files.
what does it mean? 
RFC3389 support incomplete.  Turn off on client if possible
hope to help......thanks