[Asterisk-Users] Comfort noise support incomplete in Asterisk (RFC 3389)

[Daniel Salama]

Can anyone explain to me what this means:

Jun 14 19:46:10 NOTICE[7391]: rtp.c:331 process_rfc3389: Comfort  
noise support incomplete in Asterisk (RFC 3389). Please turn off on  
client if possible. Client IP: 66.175.1.1

When I try to make a call from certain IP phones, I see that message  
on the console.

Thanks,
Daniel