The RealServer supports three protocols.
RTSP: The Real Time Streaming Protocol (RTSP) is designed specifically for clips created and read with RealSystem G2 tools. It is an open standard protocol that supports SureStream files as well as SMIL, RealText and RealPix files.
PNA: The Progressive Networks Audio (PNA) protocol is designed and used with RealSystem versions 5.0 and earlier. RealServer supports PNA for compatibility with older versions of RealPlayer. PNA is a proprietary protocol.
HTTP: The Hyper Text Transport Protocol (HTTP) is used for metafiles that point to RealServer content, and for HTML pages that are served by RealServer (such as RealSystem Administrator). It may also be used for delivering clips to clients that are located behind firewalls.
Choosing a protocol
The protocol is determined by the type of media you are streaming and to some extent on the client's network configuration. Using the correct protocol ensures that the media will be streamed as quickly as possible. Using the wrong protocol can result in poor streaming quality.
RTSP is the best protocol for media created with RealSystem G2 tools. It supports many media styles and is open standard. Older (legacy) media developed with RealSystems 5.0 and earlier should use the PNA protocol. HTTP can be used if the client is located behind a firewall and cannot be reached by RTSP and PNA.