Sadly, not just SCTP. Anything not-tcp, not-udp, not-icmp (are there others in common use?) tends to get nuked by firewalls. Great fun if you try to run IPSEC with GRE for example. Really sad to have a protocol number in the IP header, only to have firewalls dropping anything but a few whitelisted ones... :-/

On another note... does anyone know if RDP[1] has seen any use lately? I'm guessing it's pretty redundant vis-a-vis TCP in practice?

[1] http://tools.ietf.org/html/rfc908