conclusion about my sctp experiment was that after i got sctp activated in the proxy and tried to forward a request out using sctp transport, nothing happened. wireshark didn't show any packet going out after proxy printed
Dec 23 13:18:08 sars /usr/sbin/sip-proxy[30485]: INFO: Routing INVITE sip:XXXXX@X.X.X.X:8000;transport=sctp
and called t_relay.
-- juha