Some streaming protocols do not work if you have a firewall, or if your PC is behind a NAT router (either a physical router or ICS).
- Multicast is the most efficient, but is unlikely to work on a cable connection.
- UDP is the next most efficient, but:
- requires UDP ports to be opened in any firewall; and
- requires UDP port-forwarding through any NAT router.
- TCP is less efficient than UDP, but will work automatically through firewalls and NAT routers without any special configuration.
- HTTP is the least efficient, will always work, but is subject to web proxy cache degradation.
Some ISPs use Inktomi Traffic Servers to cache streaming protocol data in a similar way to how they use them as a transparent web proxy cache. The interception of streaming protocol data is meant to be transparent, but for some reasons (not understood) Real Player
does not work correctly for some sources (it appears to work for RTSP, but not for PNA protocols), and Windows Media Player
does not work correctly for some sources (MMS protocol).
To discover the default streaming media proxy under Windows
, launch a web browser, launch your player
, and launch a command window
. In the web browser, navigate to a site which contains links to clips that use the RTSP protocol (for instance, at the site http://news.bbc.co.uk/
, the links to BBC News 24
and BBC One TV news
use RTSP). While the RTSP clip is playing enter the command netstat -a
in the command window, and look for an ESTABLISHED
TCP connection to a host using a remote port other than 80
: a port often seen used is 9231
. This host will be the default streaming media proxy.