The fixup protocol rtsp command lets PIX Firewall pass Real Time Streaming Protocol (RTSP) packets. RTSP is used by RealAudio, RealNetworks, Apple QuickTime 4, RealPlayer, and Cisco IP/TV connections. PIX Firewall does not support multicast RTSP. If you are using Cisco IP/TV, use RTSP TCP port 554 and TCP 8554:
fixup protocol rtsp 554
fixup protocol rtsp 8554