RTSP
RTSP, described in RFC 2326, controls the delivery of real-time data, such as audio and
video. It is used for large-scale broadcasts and audio- or video-on-demand streaming. It
supports applications such as Cisco IP/TV, RealNetworks RealAudio G2 Player, and Apple
QuickTime 4 software.
RTSP applications use port 554 with TCP (and rarely UDP) as a control channel. The TCP
control channel is used to negotiate the two UDP data channels that are used to transmit
audio/video traffic. RTSP does not typically deliver continuous data streams over the control
channel, usually relying on a UDP-based data transport protocol such as standard Real-Time
Transport Protocol (RTP) to open separate channels for data and for RTP Control Protocol
592 Chapter 19: IPS and Advanced Protocol Handling
(RTCP) messages. RTCP carries status and control information, and RTP carries the actual
data.
The inspect command is used for RTSP connections to let the Cisco Security Appliance do
inspection. The inspect rtsp command lets the Security Appliance dynamically create
conduits for RTSP UDP channels. For example, the standard RTSP port 554 is enabled by
the following command:
inspect rtsp